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Positional cloning and characterization of a paired box- and homeobox-containing gene from the aniridia region

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Abstract

Based on the map location of the aniridia (AN) locus in human chromosomal band 11p13, we have cloned a candidate AN cDNA (D11S812E) that is completely or partially deleted in two patients with AN. The less than 70 kb smallest region of overlap between the two deletions encompasses the 3' coding region of the cDNA. This cDNA, which spans over 50 kb of genomic DNA, detects a 2.7 kb message specifically within all tissues affected in AN. The predicted polypeptide product possesses a paired domain, a homeodomain, and a serine/threonine-rich carboxy-terminal domain, structural motifs characteristic of certain transcription factors. The concordance between expression and pathology, map location, structure, and predicted function argues that the cDNA corresponds to the AN gene.

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... It has been 30 years since Pax6/PAX6 was identified as a gene responsible for congenital anomalies of the eye in mice and humans [1,2]. The gene turned out to be a member of a paired box (Pax) family encoding transcriptional factors that also work in brain development [3]. ...
... The human PAX6 gene was discovered during the search for the gene responsible for WAGR (Wilms tumor, aniridia, genital ridge defects, mental retardation) syndrome; patients with the syndrome often show a deletion in chromosome region 11p13 [145]. PAX6 was originally identified as AN2 (aniridia type II protein) [2] and found to be a homolog of the causative gene in Sey/Sey mice [1], as mentioned above. Another aniridia gene AN1 was previously mapped to chromosome two, although this mapping was disproven in 1992 [146]. ...
Article
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Pax6 is a sequence-specific DNA binding transcription factor that positively and negatively regulates transcription and is expressed in multiple cell types in the developing and adult central nervous system (CNS). As indicated by the morphological and functional abnormalities in spontaneous Pax6 mutant rodents, Pax6 plays pivotal roles in various biological processes in the CNS. At the initial stage of CNS development, Pax6 is responsible for brain patterning along the anteroposterior and dorsoventral axes of the telencephalon. Regarding the anteroposterior axis, Pax6 is expressed inversely to Emx2 and Coup-TF1, and Pax6 mutant mice exhibit a rostral shift, resulting in an alteration of the size of certain cortical areas. Pax6 and its downstream genes play important roles in balancing the proliferation and differentiation of neural stem cells. The Pax6 gene was originally identified in mice and humans 30 years ago via genetic analyses of the eye phenotypes. The human PAX6 gene was discovered in patients who suffer from WAGR syndrome (i.e., Wilms tumor, aniridia, genital ridge defects, mental retardation). Mutations of the human PAX6 gene have also been reported to be associated with autism spectrum disorder (ASD) and intellectual disability. Rodents that lack the Pax6 gene exhibit diverse neural phenotypes, which might lead to a better understanding of human pathology and neurodevelopmental disorders. This review describes the expression and function of Pax6 during brain development, and their implications for neuropathology.
... 50 Linkage analyses have demonstrated that autosomal dominant cases are caused by mutations in paired box gene-6 (PAX6) on chromosome 11p13. 29,30 90% of all aniridia cases are caused by PAX6 mutations, including sporadic cases. 31 Individuals with WAGR syndrome also have a deletion of the neighbouring Wilms Tumour 1 (WT1) gene in addition to PAX6. ...
... 31 Individuals with WAGR syndrome also have a deletion of the neighbouring Wilms Tumour 1 (WT1) gene in addition to PAX6. 29,51 The PAX6 gene encodes a transcription factor that plays a critical role in activating genes involved in eye, nose, central nervous system and pancreatic development in the embryonal period. 32 Heterozygous mouse models demonstrate aniridia-like iris abnormalities. ...
Article
Glaucoma refers to a heterogenous group of disorders characterised by progressive loss of retinal ganglion cells and associated visual field loss. Both early-onset and adult-onset forms of the disease have a strong genetic component. Here, we summarise the known genetic associations for various forms of glaucoma and the possible functional roles for these genes in disease pathogenesis. We also discuss efforts to translate genetic knowledge into clinical practice, including gene-based tests for disease diagnosis and risk-stratification as well as gene-based therapies.
... Human PAX6 is located on the 11p13 chromosome segment (Ton et al., 1991) and controls many aspects of eye development during early embryogenesis (Terzic and Saraga-Babic, 1999) and after birth (Collinson et al., 2004;Koroma et al., 1997;Quinn et al., 1996;Ton et al., 1991;Hanson et al., 1994;Glaser et al., 1992;Ramaesh et al., 2003;Baulmann et al., 2002. It has been reported that 90% of heterozygous mutations in the PAX6 gene lead to aniridia (Tzoulaki et al., 2005;Lima Cunha et al., 2019). ...
... Human PAX6 is located on the 11p13 chromosome segment (Ton et al., 1991) and controls many aspects of eye development during early embryogenesis (Terzic and Saraga-Babic, 1999) and after birth (Collinson et al., 2004;Koroma et al., 1997;Quinn et al., 1996;Ton et al., 1991;Hanson et al., 1994;Glaser et al., 1992;Ramaesh et al., 2003;Baulmann et al., 2002. It has been reported that 90% of heterozygous mutations in the PAX6 gene lead to aniridia (Tzoulaki et al., 2005;Lima Cunha et al., 2019). ...
Article
PAX6 haploinsufficiency related aniridia is characterized by disorder of limbal epithelial cells (LECs) and aniridia related keratopathy. In the limbal epithelial cells of aniridia patients, deregulated retinoic acid (RA) signaling components were identified. We aimed to visualize differentiation marker and RA signaling component expression in LECs, combining a differentiation triggering growth condition with a small interfering RNA (siRNA) based aniridia cell model (PAX6 knock down). Primary LECs were isolated from corneoscleral rims of healthy donors and cultured in serum free low Ca²⁺ medium (KSFM) and in KSFM supplemented with 0.9 mmol/L Ca²⁺. In addition, LECs were treated with siRNA against PAX6. DSG1, PAX6, KRT12, KRT 3, ADH7, RDH10, ALDH1A1, ALDH3A1, STRA6, CYP1B1, RBP1, CRABP2, FABP5, PPARG, VEGFA and ELOVL7 expression was determined using qPCR and western blot. DSG1, FABP5, ADH7, ALDH1A1, RBP1, CRABP2 and PAX6 mRNA and FABP5 protein expression increased (p ≤ 0.03), PPARG, CYP1B1 mRNA expression decreased (p ≤ 0.0003) and DSG1 protein expression was only visible after Ca²⁺ supplementation. After PAX6 knock down and Ca²⁺ supplementation, ADH7 and ALDH1A1 mRNA and DSG1 and FABP5 protein expression decreased (p ≤ 0.04), compared to Ca²⁺ supplementation alone. Using our cell model, with Ca²⁺ supplementation and PAX6 knockdown with siRNA treatment against PAX6, we provide evidence that haploinsufficiency of the master regulatory gene PAX6 contributes to differentiation defect in the corneal epithelium through alterations of RA signalling. Upon PAX6 knockdown, DSG1 differentiation marker and FABP5 RA signaling component mRNA expression decreases. A similar effect becomes apparent at protein level though differentiation triggering Ca²⁺ supplementation in the siRNA-based aniridia cell model. Expression data from this cell model and from our siRNA aniridia cell model strongly indicate that FABP5 expression is PAX6 dependent. These new findings may lead to a better understanding of differentiation processes in LECs and are able to explain the insufficient cell function in AAK.
... The PAX6 gene, located on chromosome 11p13, encodes a highly conserved transcriptional regulatory protein that is expressed in the developing eye, brain, spinal cord, and pancreas [4,5]. The protein consists of two DNA binding domains-a paired domain (PD) and a homeodomain (HD) separated by a 79-amino acid linker peptide (LNK)-and a proline, serine, and threonine-rich (PST) transcriptional transactivation domain [4,5]. ...
... The PAX6 gene, located on chromosome 11p13, encodes a highly conserved transcriptional regulatory protein that is expressed in the developing eye, brain, spinal cord, and pancreas [4,5]. The protein consists of two DNA binding domains-a paired domain (PD) and a homeodomain (HD) separated by a 79-amino acid linker peptide (LNK)-and a proline, serine, and threonine-rich (PST) transcriptional transactivation domain [4,5]. Thus far, more than 400 distinct PAX6 variants have been reported based on the Human PAX6 Mutation Database) [6]. ...
Article
Purpose: Aniridia is a rare congenital panocular disease caused by mutations in PAX6. The purposes of this study were to clarify the mutation features of PAX6 in a cohort of Chinese patients with aniridia and to describe their clinical characteristics. Methods: We recruited 95 patients from 65 unrelated families clinically diagnosed with aniridia. All patients underwent ophthalmic examinations. Sanger sequencing and multiplex ligation probe amplification of PAX6 were performed to detect intragenic variants and copy number variations (CNVs). Results: We identified 58 disease-causing mutations in PAX6 in 63 families; the detection rate was 96.9%. The 58 mutations included frameshift indels (27.6%), splice site changes (25.9%), nonsense mutations (20.7%), CNVs (19.0%), missense mutations (3.4%), run-on mutations (1.7%), and a synonymous mutation (1.7%). Clinical examinations revealed that 71 patients had complete or almost complete iris loss, 16 patients showed partial iris loss, and six patients had a full iris but with an abnormal structure. Conclusions: The results confirmed that mutations in PAX6 are the predominant cause of aniridia, and the majority are loss-of-function mutations that usually result in classical aniridia. In contrast, missense mutations, run-on mutations, and small numbers of splicing mutations mostly lead to atypical aniridia and an intrafamilial phenotypic variability of iris hypoplasia.
... There are N600 kinds of hereditary eye diseases and systemic hereditary diseases with ocular manifestations. The involved parts include the cornea, iris, lens and the vitreous, retina, optic nerve of the posterior segment of the eye, which can cause various retina diseases such as Meesmann epithelial corneal dystrophy (MECD) [38], congenital aniridia [39], congenital cataract [40,41], retinitis pigmentosa (RP) [42] and Leber hereditary opticneuropathy (LHON) [43]. Most of the ophthalmic diseases are not fully elucidated and there is no effective treatment, thus seriously affecting the patient's vision and quality of life. ...
... Congenital ocular coloboma (COC) is one of the main causes of visual impairment and blindness in children [44]. Studies have shown that mutations in the paired-box gene 6 (PAX6) are associated with COC [45], and PAX6 is a congenital adia-free pathogenic gene [39]. Nakayama et al. constructed the Xenopuslaevis PAX6 mutant strain using TALENs technology, and they used it to study the effects of PAX6 gene on early development stage of the eye and pathological changes of no iris malformation [46]. ...
Article
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Genome editing technology is a technique for targeted genetic modifications, enabling the knockout and addition of specific DNA fragments. This technology has been widely used in various types of biomedical research, clinics and agriculture. In terms of disease research, constructing appropriate animal models is necessary. Combining reproductive technology with genome editing, many animal disease models have been generated for basic and clinical research. In addition, precisely targeted modifications allow genome editing to flourish in the field of gene therapy. Many mutations refractory to traditional gene therapy could be permanently corrected at the DNA level. Thus, genome editing is undoubtedly a promising technology for gene therapy. In this review, we mainly introduce the applications of genome editing in constructing animal disease models and gene therapies, as well as its future prospects and challenges.
... Aniridia is inherited as an autosomal dominant trait in two thirds of patients; the rest of cases appear to be sporadic caused by variants occurring de novo (Prosser and van Heyningen, 1998;Samant et al., 2016). The disease is known to be caused by sequence variants in the paired box 6 (PAX6) gene, which encodes a transcriptional regulator involved in oculogenesis and other developmental processes of the brain, olfactory system and pancreas (Grindley et al., 1995;Hanson and Van Heyningen, 1995;Ton et al., 1991;Robinson et al., 2008). Classical aniridia is caused by PAX6 haploinsufficiency, i.e., loss of function of one allele, resulting in a 50% reduction of overall activity (Prosser and van Heyningen, 1998). ...
... A possible association of PAX6 variants and cognitive deficiency has been reported (Ton et al., 1991;Chien et al., 2009). Two individuals from our series were found to have severe learning difficulties. ...
Article
The aim of this study was to report PAX6 disease-causing variants in six Czech families, to describe the associated phenotypes, and to perform functional assessment of the splice site variants. Detailed ophthalmic examination was performed. The PAX6 coding region was directly sequenced in three probands. Two probands were analysed by exome sequencing and one by genome sequencing. The effect of two variants on pre-mRNA splicing was evaluated using an exon trapping assay. Six different heterozygous PAX6 variants were identified, with c.111_120del and c.1183+1G˃T being novel. Both c.1183+1G˃T and c.1032+1G>A were proved to cause aberrant splicing with exon skipping and subsequent frameshift. The phenotypic features were variable between and within families. One individual, aged 31 years, presented with mild unilateral ptosis accompanied by aniridia in the right eye, partial aniridia in the left eye, and bilateral congenital cataracts, without marked foveal hypoplasia. Bilateral microcornea, partial aniridia, congenital cataracts, and a large posterior segment coloboma were found in another proband, aged 32 years. One child, aged 8 years, had bilateral high myopia, optic nerve colobomas, anterior polar cataracts, but no iris defects. Another individual, aged 46 years, had bilateral congenital ptosis, iris hypoplasia, keratopathy with marked fibrovascular pannus, anterior polar cataract, and foveal hypoplasia combined with impaired glucose tolerance. However, his daughter, aged 11 years, showed classical features of aniridia. Our study extends the genetic spectrum of PAX6 disease-causing variants and confirms that the associated phenotypic features may be very broad and different to the 'classical' aniridia.
... NFT4 is also involved in the postnatal survival of retinal neurons during development and degeneration [170]. In the literature data, the role of NTF4 in POAG pathogenesis remains controversial, whereas NTF4 has not been identified as a POAG-causing gene in several studies [171,172] PAX6 gene is located on 11p13 region on chromosome 11 [173]. PAX6 protein belongs to the paired box family of transcription factors. ...
Article
Full-text available
Glaucoma is a heterogenous, chronic, progressive group of eye diseases, which results in irreversible loss of vision. There are several types of glaucoma, whereas the primary open-angle glaucoma (POAG) constitutes the most common type of glaucoma, accounting for three-quarters of all glaucoma cases. The pathological mechanisms leading to POAG pathogenesis are multifactorial and still poorly understood, but it is commonly known that significantly elevated intraocular pressure (IOP) plays a crucial role in POAG pathogenesis. Besides, genetic predisposition and aggregation of abrogated proteins within the endoplasmic reticulum (ER) lumen and subsequent activation of the protein kinase RNA-like endoplasmic reticulum kinase (PERK)-dependent unfolded protein response (UPR) signaling pathway may also constitute important factors for POAG pathogenesis at the molecular level. Glaucoma is commonly known as a ‘silent thief of sight’, as it remains asymptomatic until later stages, and thus its diagnosis is frequently delayed. Thereby, detailed knowledge about the glaucoma pathophysiology is necessary to develop both biochemical and genetic tests to improve its early diagnosis as well as develop a novel, ground-breaking treatment strategy, as currently used medical therapies against glaucoma are limited and may evoke numerous adverse side-effects in patients.
... By analyzing a Chinese family with a history of congenital aniridia,we herein identi ed a novel hybrid mutation(C.114_119delinsAATTTCC:p.Pro39fs)in the PAX6 gene.This mutation consisted of a 6 bp deletion and a 7 bp insertion that resulted in the premature truncation of the PAX6 protein.The affected brother and sister patients exhibited shared ophthalmic abnormalities including cataracts,nystagmus,glaucoma,aniridia,and macular fovea hypoplasia.The PAX6 gene was rst characterized by Ton et al.in 1991 [6] ,and is found on chromosome 11p13.PAX6 encodes a transcriptional regulator that is important for the development of organs and tissues including the eyes.PAX6 expression is detectable in the iris,lens,optic disc,corneal epithelium,ciliary body,retinal neuroepithelium,and retinal pigment epithelium.In 2005,Tzoulaki et al.characterized human PAX6 mutations and found that mutations throughout this gene were associated with aniridia and related phenotypes [7] .In an additional study of 95 Chinese patients with aniridia,You et al.found that PAX6 loss-of-function mutations were the most common cause of aniridia [8] .The identi ed PAX6 mutation in these siblings(c.114_119delinsAATTTCC:p.Pro39fs)resulted in a frameshift from the 39th codon of this gene,resulting in the premature generation of a stop codon.In light of prior studies,we hypothesized that this mutation was likely to be the primary cause of aniridia and other observed ophthalmic abnormalities in these siblings. ...
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Background Aniridia is a congenital,panocular disease affecting the cornea,anterior chamber angle,iris,lens,retina and optic nerve.PAX6 loss-of-function mutations were the most common cause of aniridia.Mutations throughout the PAX6 gene have been linked to a range of ophthalmic abnormalities,with distinct mutations at a given site within this gene leading to distinct phenotypic findings.This study aimed to characterize genetic mutations associated with congenital aniridia in a Chinese family. Methods The proband and the proband’s brother of this family underwent comprehensive ophthalmologic examinations as well as exome sequencing,with Next Generation Sequencing being used to confirm these results. Results A novel mutation(c.114_119delinsAATTTCC:p.Pro39fs)in the PAX6 gene was identified in subjects III-2 and III-3 in these family,and both of these subjects exhibited complete aniridia,cataracts,glaucoma,high myopia,and foveal hypoplasia. Conclusions We identified a novel PAX6 frameshift heterozygous deletion mutation in a Chinese family and determined that this mutation was a probable cause of various eye abnormalities in carriers.
... The syndrome is determined by chromosomal deletion in the 11p13 region. Clinical features are determined by loss of individual genes: deletion of WT1 is responsible for Wilms tumors [34], while PAX6 deletion is responsible for aniridia [35]. Larger deletion of this region account for the full WAGR syndrome. ...
Article
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Identifying patients with a genetic predisposition for developing malignant tumors has a significant impact on both the patient and family. Recognition of genetic predisposition, before diagnosing a malignant pathology, may lead to early diagnosis of a neoplasia. Recognition of a genetic predisposition syndrome after the diagnosis of neoplasia can result in a change of treatment plan, a specific follow-up of adverse treatment effects and, of course, a long-term follow-up focusing on the early detection of a second neoplasia. Responsible for genetic syndromes that predispose individuals to malignant pathology are germline mutations. These mutations are present in all cellsof conception, they can be inherited or can occur de novo. Several mechanisms of inheritance are described: Mendelian autosomal dominant, Mendelian autosomal recessive, X-linked patterns, constitutional chromosomal abnormality and non-Mendelian inheritance. In the following review we will present the most important genetic syndromes in pediatric oncology.
... Since the 1980s, chromosomal microdeletions have been associated with DDs, for example the 22q11 deletion with DiGeorge syndrome, and the 17p11 deletion with Smith-Magenis syndrome (Watson et al., 2014). In the 1990s, it became evident that DDs are often caused by HI of TF genes, such as aniridia caused by PAX6 HI (Ton et al., 1991) or Waardenburg syndrome caused by PAX3 HI (Tassabehji et al., 1992;Baldwin et al., 1992). In fact, for many microdeletion syndromes, HI of a specific transcriptional regulator gene could later be pinpointed as the causal factor for most of the characteristic features, for example TBX1 HI in DiGeorge syndrome (Yagi et al., 2003) and RAI1 HI in Smith-Magenis syndrome (Slager et al., 2003). ...
Article
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Many human birth defects and neurodevelopmental disorders are caused by loss-of-function mutations in a single copy of transcription factor (TF) and chromatin regulator genes. Although this dosage sensitivity has long been known, how and why haploinsufficiency (HI) of transcriptional regulators leads to developmental disorders (DDs) is unclear. Here I propose the hypothesis that such DDs result from defects in cell fate determination that are based on disrupted bistability in the underlying gene regulatory network (GRN). Bistability, a crucial systems biology concept to model binary choices such as cell fate decisions, requires both positive feedback and ultrasensitivity, the latter often achieved through TF cooperativity. The hypothesis explains why dosage sensitivity of transcriptional regulators is an inherent property of fate decisions, and why disruption of either positive feedback or cooperativity in the underlying GRN is sufficient to cause disease. I present empirical and theoretical evidence in support of this hypothesis and discuss several issues for which it increases our understanding of disease, such as incomplete penetrance. The proposed framework provides a mechanistic, systems-level explanation of HI of transcriptional regulators, thus unifying existing theories, and offers new insights into outstanding issues of human disease. This article has an associated Future Leader to Watch interview with the author of the paper.
... 1,2 Heterozygous mutations within the PAX6 gene (paired box gene 6; OMIM # 607108) or associated regulatory regions are the most common cause of aniridia. [3][4][5][6] These mutations reduce the expression of the PAX6 gene and lead to a shortage of functional PAX6 protein, which, among other effects, disrupts eye development. 7 This can lead to a spectrum of ocular anomalies, including incomplete development of the iris, fovea, and optic nerve; severely impaired vision; and nystagmus. ...
Article
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Purpose: To investigate the association between PAX6 genotype and macular morphology in congenital aniridia. Methods: The study included 37 participants (15 males) with congenital aniridia (aged 10-72 years) and 58 age-matched normal controls (18 males). DNA was isolated from saliva samples. PAX6 exons, intron/exon junctions, and known regulatory regions were amplified in PCR and sequenced. Multiplex ligation-dependent probe amplification (MLPA) was performed to detect larger deletions or duplications in PAX6 or known cis-regulatory regions. Spectral-domain optical coherence tomography images were acquired and segmented semiautomatically. Mean thicknesses were calculated for inner and outer retinal layers within the macula along nasal and temporal meridians. Results: Mutations in PAX6 or regulatory regions were found in 97% of the participants with aniridia. Foveal hypoplasia was observed in all who had a mutation within the PAX6 gene. Aniridic eyes had thinner outer retinal layers than controls, but with large between-individual variation (mean ± SD, 156.3 ± 32.3 µm vs 210.8 ± 12.3 µm, P < 0.001). Parafoveal and perifoveal inner and outer retinal layers were thinner in aniridia. Participants with mutations in noncoding PAX6 regions had thicker foveal outer retinal layers than those with mutations in the PAX6 coding regions (P = 0.04) and showed signs of postnatal development and maturation. Mutations outside the PAX6 gene were associated with the mildest retinal phenotypes. Conclusions: PAX6 mutations are associated with significant thinning of macular inner and outer retinal layers, consistent with misdirected retinal development resulting in abnormal foveal formation and reduced number of neurons in the macula, with mutations in PAX6 coding regions giving the worst outcome.
... PAX6 (OMIM 607108), paired box gene 6, is a member of the paired box gene family which encodes a transcriptional regulator involved in oculogenesis and other developmental processes [11]. This transcription factor has shown functional conservation in developmental pathways. ...
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Background: Aniridia is a kind of congenital human panocular anomaly, which is related to PAX6 commonly. Methods: A Chinese Aniridia pedigree underwent ophthalmic examinations, including visual acuity, slit lamp and fundoscopy examination. The targeted next-generation sequencing of Aniridia genes was used to identify the causative mutation. Results: A novel heterozygous PAX6 nonsense mutation c.619A>T (p.K207*) was identified in the Chinese autosomal dominant family with aniridia. Phenotypes related to the novel mutation include nystagmus, iris defect, cataract and absence of macular fovea. Conclusion: The novel nonsense mutation in PAX6 was responsible for aniridia phenotype in the family. which expands the spectrum of the PAX6 mutation and its associated phenotype.
... The first large aniridia cohort was reported approximately 60 years ago (Shaw et al., 1960), but a genetic cause was not identified until the cloning of a candidate cDNA that was deleted in two patients with aniridia (Ton et al., 1991). The first sequence variant within the PAX6 gene was reported the following year (Jordan et al., 1992). ...
Article
Pathogenic variants within PAX6 are most often associated with aniridia, but have been linked with other phenotypes such as nystagmus, cataracts and foveal hypoplasia. Data are presented from a large cohort of 434 probands referred for PAX6 diagnostic testing. This analysis identified a wide range of pathogenic variants (n = 145) in 254 probands (including 61 novel variants). Excluding missense variants predicted to affect splicing, all 29 of the remaining missense variants were located within the paired (n = 27) or homeobox (n = 2) domains of the PAX6 protein, providing further evidence that these domains are critical to normal PAX6 function. Genotype-phenotype evidence suggests that while aniridia is associated with most variant types, a much broader clinical spectrum is seen in patients harbouring a missense variant, or a frameshift or run-on variant that results in an elongated or extended PAX6 protein.
... The human paired box 6, as coded by the PAX6 gene, is a member of the PAX family of transcription factors, which are evolutionarily highly conserved among metazoans and are characterized by the presence of a conserved DNA-binding domain, the paired domain [1]. Positional cloning identified it in the early 1990s [2]. At the same time, murine Pax6 was also identified by the screening of mouse embryonic expression libraries [3] and associated as the causal gene of an heterozygous Sey mouse strain (Sey +/− ) [4], which presented with microphthalmia, iris hypoplasia, cataracts, and corneal opacifications, resembling human developmental eye disorder aniridia [5]. ...
Article
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The transcription factor PAX6 is essential in ocular development in vertebrates, being considered the master regulator of the eye. During eye development, it is essential for the correct patterning and formation of the multi-layered optic cup and it is involved in the developing lens and corneal epithelium. In adulthood, it is mostly expressed in cornea, iris, and lens. PAX6 is a dosage-sensitive gene and it is highly regulated by several elements located upstream, downstream, and within the gene. There are more than 500 different mutations described to affect PAX6 and its regulatory regions, the majority of which lead to PAX6 haploinsufficiency, causing several ocular and systemic abnormalities. Aniridia is an autosomal dominant disorder that is marked by the complete or partial absence of the iris, foveal hypoplasia, and nystagmus, and is caused by heterozygous PAX6 mutations. Other ocular abnormalities have also been associated with PAX6 changes, and genotype-phenotype correlations are emerging. This review will cover recent advancements in PAX6 regulation, particularly the role of several enhancers that are known to regulate PAX6 during eye development and disease. We will also present an updated overview of the mutation spectrum, where an increasing number of mutations in the non-coding regions have been reported. Novel genotype-phenotype correlations will also be discussed.
... Similarly there is considerable evidence that the human congenital disorder aniridia is homologous to the Small-eye mutation (Sey) in mouse which has been shown to result from mutations in the paired-box gene Fax-6 [Van der Meer-deJong et al., 1990;Hill et al., 1991;Ton et al., 1991]. ...
Thesis
Craniosynostosis or premature closure of the cranial sutures is a common abnormality occuring in about 1 m 2000 children. There is evidence of Mendelian inheritance in some 20% of cases. A number of autosomal dominant craniosynostosis syndromes exist in which craniosynostosis occurs in association with various limb anomalies. Although relatively rare, this group of monogenic craniodigital syndromes provides a way of mapping, by molecular genetic methods, genes important in craniofacial and limb development. The aims of the present work were to determine the chromosomal location of the mutations responsible for some of the human craniodigital syndromes. Chromosome 7 was chosen as a suitable starting point as premature sutural fusion is a relatively uncommon finding in patients with chromosome anomalies but has been reported in at least 10 patients with a variety of structural alterations of 7p. Craniosynostosis appears to be consistently associated with deletion of one of two specific and separate regions, either deletion of part of band 7p21/proximal 7p22 or deletion of 7p13-p14. Many of the patients with deletions of the more proximal region 7p13-7p14 have features of the Greig cephalopolysyndactyly syndrome (GCPS), whereas those with more distal deletions have features reminiscent of the non-Apert acrocephalosyndactylies. The karyotypic findings in these cases suggest that two or more genes responsible for craniosynostosis and limb anomalies may be situated on chromosome 7p. The localisation, identification and characterisation of one or more of the genes responsible for such autosomal dominant craniodigital syndromes will help lead to determination of the genetic elements involved in the complex process of normal craniofacial and limb formation and the consequences of mutation in these developmental genes. The results of clinical and molecular genetic studies undertaken to investigate the possible localisation of GCPS and the non-Apert acrocephalosyndactyly syndromes to chromosome 7p are reported. It is demonstrated that GCPS maps to 7p13 whilst the gene responsible for Saethre-Chotzen syndrome is localised to 7p21-22. Evidence to show that GCPS and the acrocallosal syndrome are not allelic disorders is also provided. The outcome of a clinical study of the non-Apert acrocephalosyndactylies is presented in detail. This helps to define the degree of variability within and between families and the question of genetic heterogeneity in this group of conditions is addressed.
... PAX6 is known as a master gene for the eye. Previous articles [43][44][45][46][47] showed that ectopic expression of PAX6 can generate functional eyes at various sites in the body and homozygous PAX6-depleted embryos have no eye formation. In the ocular surface, the boundary between PAX6expressing and PAX6-non-expressing cells is precisely defined at the edge of the eyelid, wherein PAX6-expressing cells located on the inside of the eyelid develop into ocular surface cells, and PAX6-non-expressing cells found on the outside of the eyelid differentiate into epidermal cells. ...
Article
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In its early stages, an embryo polarizes to form cell subpopulations that subsequently produce specific organ cell types. These cell subpopulations are defined by transcription factors (TFs) that activate or repress specific genes. Although an embryo comprises thousands of TFs, surprisingly few are needed to determine the fate of a given cell. The ectoderm divides into the neuroectoderm and surface ectoderm, the latter of which gives rise to epidermal keratinocytes and corneal epithelial cells (CECs). Meanwhile, neuroectoderm cells give rise to other parts of the eye such as the corneal endothelium and retina. To investigate the regulatory role of TFs in CECs, we overexpressed the "core TFs" (PAX6, OVOL2, and KLF4) in human fibroblasts and found that the cells adopted a CEC-like quality. OVOL2 overexpression was even able to directly induce cells with a neuroectoderm fate toward a surface ectoderm fate, designated "direct reprogramming." Conversely, suppression of OVOL2 or PAX6 expression induced CECs to show qualities consistent with neural lineage cells or epidermal keratinocytes, respectively. This suggests that these core TFs can maintain the CEC phenotype through reciprocal gene regulation. Direct reprogramming has important implications for cell therapies. The potential benefits of cells derived by direct reprogramming compared with induced pluripotent stem cells include the fact that it requires less time than reprogramming a cell back to the pluripotent state and then to another cell type. Further understanding of the reciprocally repressive mechanism of action for core TFs could lead to alternative treatments for regenerative medicine not requiring cell transplantation.
... PAX6, a paired-box and homeobox domain gene is one of the principal regulators in eye development, first described as a candidate for human aniridia [11]. PAX6 plays an important role in the early development of the lens including the interaction between the embryonic surface ectoderm and the budding optic vesicle. ...
Article
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Background Lens development is orchestrated by transcription factors. Disease-causing variants in transcription factors and their developmental target genes are associated with congenital cataracts and other eye anomalies. Methods Using whole exome sequencing, we identified disease-causing variants in two large British families and one isolated case with autosomal dominant congenital cataract. Bioinformatics analysis confirmed these disease-causing mutations as rare or novel variants, with a moderate to damaging pathogenicity score, with testing for segregation within the families using direct Sanger sequencing. Results Family A had a missense variant (c.184 G>A; p.V62M) in PAX6 and affected individuals presented with nuclear cataract. Family B had a frameshift variant (c.470–477dup; p.A160R*) in PITX3 that was also associated with nuclear cataract. A recurrent missense variant in HSF4 (c.341 T>C; p.L114P) was associated with congenital cataract in a single isolated case. Conclusions We have therefore identified novel variants in PAX6 and PITX3 that cause autosomal dominant congenital cataract.
... There was some rivalry, but even more sharing of data and resources. Eventually the gene for Wilms' tumour, the four zinc-finger tumour suppressor WT1 was cloned in 1990 at Harvard , and for aniridia, the iconic PAX6 gene was identified in Houston, Texas (Ton et al. 1991). In both cases, we were offered the cDNA clones immediately and for PAX6 we co-authored the initial paper. ...
Article
The development of genome sequencing technologies has revolutionized the biological sciences in ways which could not have been imagined at the time. This article sets out to document the dawning of the age of genomics and to consider the impact of this revolution on biological investigation, our understanding of life, and the relationship between science and society.
... Since then, at least 491 mutations in the PAX6 gene have been reported in the Leiden Open Variation Database (PAX6-LOVD). As both copies of PAX6 are essential for eye development, silencing of one of the two copies leads to a PAX6 haploinsufficiency disease mechanism [15,16]. In most cases, the disease is caused by the loss of function of PAX6 that results from either intragenic mutations or chromosomal rearrangements at 11p13. ...
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Purpose: Congenital iris abnormality is a feature of several genetic conditions, such as aniridia syndrome and anterior segment degeneration (ASD) disorders. Aniridia syndrome is caused by mutations in the PAX6 gene or its regulatory elements in the locus 11p13 or deletions of contiguous genes, while ASDs are the result of mutations in various genes, such as PAX6, FOXC1, PITX2, and CYP1B1. This study aims to identify pathogenic mutations in Vietnamese individuals with congenital anomalies of the iris. Methods: Genomic DNA was extracted from peripheral blood of 24 patients belonging to 15 unrelated families and their available family members. Multiplex ligation-dependent probe amplification (MLPA) was used to detect the deletions or duplications in the 11p13–14 region, including the PAX6 gene and its neighboring genes. Direct PCR sequencing was used to screen mutations in 13 exons and flanking sequences of the PAX6 gene. The patients without mutation in the PAX6 locus were further analyzed with whole exome sequencing (WES). Identified mutations were tested with segregation analysis in proband family members. Results: We identified a total of 8 novel and 4 recurrent mutations in 20 of 24 affected individuals from 12 families. Among these mutations, one large deletion of the whole PAX6 gene and another deletion of the PAX6 downstream region containing the DCDC1 and ELP4 genes were identified. Eight mutations were detected in PAX6, including four nonsense, three frameshift, and one splice site. In addition, two point mutations were identified in the FOXC1 and PITX2 genes in patients without mutation in PAX6. Some of the mutations segregated in an autosomal dominant pattern where family members were available. Conclusions: This study provides new data on causative mutations in individuals with abnormal development of iris tissue in Vietnam. These results contribute to clinical management and genetic counseling for affected people and their families.
... Second, the presence of several PAX6 binding sites upstream of the TMPRSS2 gene suggests direct inhibitory PAX6/TMPRSS2 gene interactions, a possibility with relevance for potentially cell-protective mechanisms of resistance to SARS-CoV2 tropism of additional developmental and adult PAX6-expressing tissues (such as, for example, the brain [36]), and for potentially enhanced susceptibility to SARS-CoV2 tropism of individuals suffering from genetic syndromes associated with impaired PAX6 function (such as, for example, Aniridia and Gillespie syndrome [37]). Our findings warrant further investigation of such potential vulnerabilities. ...
Article
Purpose: Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). While the ocular surface is considered one of the major SARS-CoV2 transmission routes, the specific cellular tropism of SARS-CoV2 is not fully understood. In the current study, we evaluated the expression and regulation of two SARS-CoV2 viral entry proteins, TMPRSS2 and ACE2, in human ocular epithelial cells and stem cells. Methods: TMPRSS2 and ACE2 expression in ABCB5-positive limbal stem cells (LSCs) were assessed by RNAseq, flow cytometry and immunohistochemistry. PAX6, TMPRSS2, and ACE2 mRNA expression values were obtained from the GSE135455 and DRA002960 RNA-seq datasets. siRNA-mediated PAX6 knockdown (KD) was performed in limbal and conjunctival epithelial cells. TMPRSS2 and ACE2 expression in the PAX6 KD cells was analyzed by qRT-PCR and Western blot. Results: We found that ABCB5-positive LSCs express high levels of TMPRSS2 and ACE2 compared to ABCB5-negative limbal epithelial cells. Mechanistically, gene knockout and overexpression models revealed that the eye transcription factor PAX6 negatively regulates TMPRSS2 expression. Therefore, low levels of PAX6 in ABCB5-positive LSCs promote TMPRSS2 expression, and high levels of TMPRSS2 and ACE2 expression by LSCs indicate enhanced susceptibility to SARS-CoV2 infection in this stem cell population. Conclusions: Our study points to a need for COVID-19 testing of LSCs derived from donor corneas before transplantation to patients with limbal stem cell deficiency. Furthermore, our findings suggest that expandable human ABCB5+ LSC cultures might represent a relevant novel model system for studying cellular SARS-CoV2 viral entry mechanisms and evaluating related targeting strategies.
... Approximately 80% congenital aniridia cases are caused by the gene mutation of human paired box-6 (PAX6) [7][8][9]. The Human PAX6 Allelic Variant Database (http:// lsdb.hgu.mrc.ac.uk/home.php?select_db=PAX6) has recorded over 400 PAX6 mutations, to date [10]. ...
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Background This study aims to investigate the clinical characterization and causative genetic defect of a four-generation Chinese family with autosomal dominant aniridia. Methods The recruited family members underwent comprehensive routine and ophthalmic examinations, and Sanger sequencing was performed to screen the mutation in PAX6. Results A novel heterozygous PAX6 deletion c.435_445delTAGCGAAAAGC (p.Ser146ThrfsX9) in exon 7 was identified in all affected individuals, but this was absent in any of the unaffected family members and in the 200 unrelated controls. Conclusion A novel deletion in the PAX6 gene was identified in a Chinese family associated with aniridia, which expands the spectrum of the PAX6 mutation and its associated phenotype.
Article
Purpose: Aniridia is a rare congenital eye disease, characterized by a constellation of symptoms including hypoplastic irides, foveal hypoplasia, early cataract, corneal stem cell deficiency, and glaucoma. Large chromosomal deletions spanning the PAX6 gene cause WAGR syndrome (Wilms tumor, anirida, genitourinary anomalies, and intellectual disability [formerly called mental retardation]). We describe clinical and genetic studies of a three-generation pedigree with aniridia along with additional systemic conditions (morbid obesity, diabetes) suggesting the possibility of a contiguous-gene syndrome like WAGR. Methods: Clinical records were obtained and DNA was prepared from blood samples from three of the four patients and tested for mutations in the coding sequences of the PAX6 gene. The index patient also had cardiomyopathy and was tested for known cardiomyopathy genetic mutations using a next-generation DNA sequencing assay. Results: We discovered a novel intragenic PAX6 mutation, a 16 bp heterozygous deletion c.203delCCAGGGCAATCGGTGG, with Sanger sequencing that is the likely cause of autosomal dominant aniridia in this pedigree. This PAX6 deletion causes a frameshift in predicted protein translation and a subsequent premature termination, p.Pro68Leufs*6. The PAX6 deletion was detected in all three available family members with aniridia, the index patient, his mother, and his maternal aunt but was not observed in the Exome Aggregation Consortium (ExAC) database. Targeted sequencing of known cardiomyopathy genes in the index patient identified a second mutation, a 1.7 Mp deletion that spans the MYBPC3 gene Conclusions: We report a pedigree with aniridia and other systemic abnormalities that were initially suspicious for a contiguous gene syndrome like WAGR. However, genetic analysis of the pedigree revealed two independent genetic abnormalities on chromosome 11p: 1) a novel PAX6 mutation, and 2) a large chromosome deletion spanning MYBPC3, a known cardiomyopathy gene. It is unclear if morbid obesity and type II diabetes mellitus have a related genetic cause.
Article
This case report presents a rare association of a complete aniridia with lenticular and choroidal coloboma. An 8-year-old female patient was referred to our glaucoma clinic with aniridia, nystagmus and bilateral corneal opacity with right eye being phthisical. Ultrasonography of the phthisical eye revealed the presence of an old closed funnel retinal detachment. Further examination under anaesthesia revealed lens coloboma in the inferonasal quadrant and presence of a choroidal coloboma in the left eye. The intraocular pressure was 28 mmHg with a central corneal thickness of 693 µm. A macula sparing laser barrage around the colobomatous area was done in the left eye and topical ocular hypotensives were started.
Article
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Mutations in human PAX6 gene are associated with various congenital eye malformations including aniridia, foveal hypoplasia, and congenital nystagmus. These various phenotypes may depend on the mutation spectrums that can affect DNA-binding affinity, although this hypothesis is debatable. We screened PAX6 mutations in two unrelated patients with congenital nystagmus, and measured DNA-binding affinity through isothermal titration calorimetry (ITC). To elucidate phenotypic differences according to DNA-binding affinity, we also compared DNA-binding affinity among the previously reported PAX6 missense mutations within the linker region between two subdomains of the paired domain (PD). We identified two novel mutations of PAX6 gene: c.214 G > T (p.Gly72Cys) and c.249_250delinsCGC (p.Val84Alafs*8). Both were located within the linker region between the two subdomains of the PD. ITC measurement revealed that the mutation p.Val84Alafs*8 had no DNA-binding affinity, while the p.Gly72Cys mutation showed a decreased binding affinity (Kd = 0.58 μM) by approximately 1.4 times compared to the wild type-PAX6 (Kd = 0.41 μM). We also found that there was no close relationship between DNA-binding affinity and phenotypic differences. Our results suggest that the DNA-binding affinity alone might be insufficient to determine PAX6-related phenotypes, and that other modifier genes or environmental factors might affect phenotypes of the PAX6 gene.
Article
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Background: Congenital aniridia is a severe ocular abnormality characterized by incomplete formation of the iris and many other ocular complications. Most cases are caused by the paired box 6 (PAX6) gene mutations generating premature termination codons (PTCs). Methods: Ophthalmic examination was performed on a Chinese pedigree with congenital aniridia. The mutation was identified by targeted next-generation sequencing. Nonsense suppression therapy was applied on patient-derived lymphocytes. The PAX6 expression was assayed by real-time polymerase chain reaction and Western blot. Results: Complete aniridia was complicated with horizontal nystagmus, contract, foveal hypoplasia, and microphthalmia. A novel heterozygous c.702_703delinsAT (p.Tyr234*) mutation was found in exon 9 of PAX6, generating a PTC at the homeodomain. There were about 50% reductions of both full-length PAX6 protein and PAX6 mRNA in patient-derived lymphocytes, indicating haploinsufficiency due to nonsense-mediated mRNA decay. Ataluren (PTC124) and geneticin (G418) could induce about 30%-40% translational readthrough. Nonsense suppression therapy restored PAX6 protein to about 65%-70% of unaffected family controls. Conclusion: Our data expanded the genetic and phenotypic variations of congenital aniridia, and showed the therapeutic effect of nonsense suppression on this disease using patient-derived cells.
Article
Purpose: Congenital aniridia is a kind of panocular disorder characterized by the absence of iris in both eyes. Paired box 6 (PAX6) gene mutation has been identified to be the most common cause of congenital aniridia. The aim of this study was to reveal the genetic defect in PAX6 in a Chinese family with congenital aniridia. Methods: Twelve individuals from a three-generation Chinese family were recruited. All the family members underwent comprehensive ophthalmologic examinations. The entire coding region of PAX6 was amplified by polymerase chain reaction, followed by direct Sanger sequencing. Possible structural and functional changes of the protein were predicted by bioinformatic analysis using SIFT and Polyohen-2. Results: Among all the 12 members, four were clinically diagnosed with congenital aniridia. A novel heterozygous mutation c.275G>A (p.R92Q) in exon 6 of PAX6 was identified in all the patients, but not in the unaffected individuals or 1186 healthy subjects. This missense mutation is a G-A transition, converting Arginine (R) to Glutamine (Q) at amino acid 92. The substitution of amino acid in the PAX6 protein changed the local charge density and was predicted to damage the normal protein function. Conclusions: Our study identified a novel mutation of PAX6 responsible for congenital aniridia in a Chinese family, which may contribute to understanding the molecular basis and clinical diagnosis of congenital aniridia.
Chapter
A majesty of evolution encompasses in diversity of the types of eyes known today. Out of all organisms, only a bit over 30 different phyla possess sophisticated eyes. Stating that, rest of the animals are not blind. There could be camera type, or compound eyes, or mirror-like eyes, all different from one another in several aspects, still performing more or less the same function. Even though there are several differences, there are striking similarities as well in all diverse animal life forms. After Ramon y Cajal observed striking similarities between vertebrate and insect retinas, over a century ago, newer research keeps adding to the account with the help of cutting edge technology. Today, we know for the fact that there are more similarities than one can think into visual systems of insects and vertebrates. Of all invertebrate model systems, Drosophila melanogaster stands apart; for, it shares a high degree of genetic conservation and less redundancy. Shorter life span, ease of culture, and availability of wide variety of genetic tools are other benefits which make Drosophila melanogaster a great model system. In this chapter, we shall be providing a comparative account on the compound eye of Drosophila melanogaster with that of camera type eye of vertebrates, in terms of development, structure, and physiology.
Article
Purpose: Pax-6 is a master regulator for eye and brain development. Previous studies including ours have shown that Pax-6 exists in 4 major isoforms. According to their sizes, they are named p48, p46, p43 and p32 with the corresponding molecular weight of 48, 46, 43 and 32 kd, respectively. While p48 and p46 is derived from alternative splicing, p32 Pax-6 is generated through an internal translation initiation site. As for 43 kd Pax-6, two resources have been reported. In bird, it was found that an alternative splicing can generate a p43 Pax-6. In human and mouse, we reported that the p43 kd Pax-6 is derived from sumoylation: addition of a 11 kd polypeptide SUMO1 into the p32 Pax-6 at the K91 residue. Whether other Pax-6 isoforms can be sumoylated or not remains to be explored. Methods: The 5 major ocular cell lines were cultured in Dulbecco's modified Eagle's medium (DMEM) containing fetal bovine serum (FBS) or rabbit serum (RBS) and 1% Penicillin- Streptomycin. The mRNA levels were analysed with qRT-PCR. The protein levels were determined with western blot analysis and quantitated with Image J. Results: Both non-sumoylated and sumoylated isoforms of Pax-6 exist in 6 major types of ocular cells among which five are lens epithelial cells, and one is retinal pigment epithelial cell. Our results revealed that the most abundant isoforms of Pax-6 are the p32 and p46 Pax-6. These two major isoforms can be sumoylated to generate p43 (mono-sumoylated p32 Pax-6), p57 and p68 Pax-6 (mono- and di-sumoylated p46 Pax-6). In addition, the splicing-generated p48 Pax-6 is also readily detected. Conclusion: Our results for the first time, have determined the relative isoform abundance and also the sumoylation patterns of pax-6 in 6 major ocular cell lines.
Chapter
Making of an eye requires commitment of cells to adopt an eye tissue fate by the process of retinal specification and determination. Basic molecular mechanisms to form an eye depend upon evolutionarily conserved processes and are controlled by a gene regulatory network called retinal determination network (RDN). The compound eye of the fruit fly, Drosophila melanogaster, has been widely used as an excellent experimental system to understand the genetic mechanisms occurring during eye specification and patterning. In Drosophila, the RDN not only controls eye field determination and patterning of visual anlage in the embryo but also regulates cell proliferation and retinal cell specification from eye-antennal disc at different larval stages. This chapter will highlight mechanisms of early eye specification and determination and will explain how each member of RDN and their genetic interactions guide early eye specification process. This chapter will also emphasize on how RDN controls extraretinal photoreceptor development in the Drosophila larval eye and adult ocelli and will draw attention to our understanding of how early eye fate is determined.
Article
Aniridia and Axenfeld-Rieger Syndrome are related, human ocular disorders that are typically inherited in an autosomal dominant manner. Both result from incorrect development of the eye and have, as their most serious consequences, elevated risk to develop the blinding condition glaucoma. This review will focus on describing the clinical presentations of Aniridia and Axenfeld-Rieger Syndrome as well as the molecular genetics and current and emerging therapies used to treat patients.
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Background: Aniridia is a congenital,panocular disease affecting the cornea,anterior chamber angle,iris,lens,retina and optic nerve.PAX6 loss-of-function mutations were the most common cause of aniridia.Mutations throughout the PAX6 gene have been linked to a range of ophthalmic abnormalities,with distinct mutations at a given site within this gene leading to distinct phenotypic findings.This study aimed to characterize genetic mutations associated with congenital aniridia in a Chinese family. Methods:The proband and the proband’s brother of this family underwent comprehensive ophthalmologic examinations as well as exome sequencing,with Next Generation Sequencing being used to confirm these results. Results: A novel mutation(c.114_119delinsAATTTCC:p.Pro39fs)in the PAX6 gene was identified in subjects III-2 and III-3 in these family,and both of these subjects exhibited complete aniridia,cataracts,glaucoma,high myopia,and foveal hypoplasia. Conclusions: We identified a novel PAX6 frameshift heterozygous deletion mutation in a Chinese family and determined that this mutation was a probable cause of various eye abnormalities in carriers.
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Background: Aniridia is a kind of congenital human panocular anomaly, which is related to PAX6 commonly. Methods: The ophthalmic examinations including visual acuity, slit lamp and fundoscopy examination were preformed in a Chinese aniridia pedigree. The targeted next-generation sequencing of Aniridia genes was used to identify the causative mutation. Results: A novel heterozygous PAX6 nonsense mutation c.619A>T (p.K207*) was identified in the Chinese autosomal dominant family with aniridia. Phenotypes related to the novel mutation include nystagmus, iris defect, cataract and absence of macular fovea. Conclusion: The novel nonsense variation in PAX6 was the cause of aniridia in this family, which expands the spectrum of the PAX6 mutation and its associated phenotype.
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The conversion of mesenchyme to epithelium during the embryonic development of the mammalian kidney requires reciprocal inductive interactions between the ureter and the responding metanephric mesenchyme. The Pax-2 gene is activated in the mesenchyme in response to induction and is subsequently down-regulated in more differentiated cells derived from the mesenchyme. Pax-2 belongs to a family of genes, at least three of which encode morphogenetic regulatory transcription factors. In order to determine the role of Pax-2 during kidney development, we have generated a loss- of-function phenotype using antisense oligonucleotides in mouse kidney organ cultures. These oligonucleotides can specifically inhibit Pax-2 protein accumulation in kidney mesenchyme cells, where the intracellular concentrations are maximal. The kidney organ cultures were stained with uvomurulin and laminin antibodies as markers for epithelium formation. With significantly reduced Pax-2 protein levels, kidney mesenchyme cells fail to aggregate and do not undergo the sequential morphological changes characteristic of epithelial cell formation. The data demonstrate that Pax-2 function is required for the earliest phase of mesenchyme-to-epithelium conversion.
Article
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Background Aniridia is a congenital, panocular disease that can affect the cornea, anterior chamber angle, iris, lens, retina and optic nerve. PAX6 loss-of-function variants are the most common cause of aniridia, and variants throughout the gene have been linked to a range of ophthalmic abnormalities. Furthermore, particular variants at a given site in PAX6 lead to distinct phenotypes. This study aimed to characterize genetic variants associated with congenital aniridia in a Chinese family. Methods The proband and family underwent ophthalmologic examinations. DNA was sampled from the peripheral blood of all 6 individuals, and whole-exome sequencing was performed. Sanger sequencing was used to verify the variant in this family members. Results A novel variant (c.114_119delinsAATTTCC: p.Pro39llefsTer17) in the PAX6 gene was identified in subjects II-1, III-1 and III-2, who exhibited complete aniridia and cataracts. The proband and the proband’s brother also had glaucoma, high myopia, and foveal hypoplasia. Conclusions We identified that a novel PAX6 frameshift heterozygous deletion variant is the predominant cause of aniridia in this Chinese family. Trial registration We did not perform any health-related interventions for the participants.
Article
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Monogenic syndromic disorders frequently feature ocular manifestations, one of which is glaucoma. In many cases, glaucoma in children may go undetected, especially in those that have other severe systemic conditions that affect other parts of the eye and the body. Similarly, glaucoma may be the first presenting sign of a systemic syndrome. Awareness of syndromes associated with glaucoma is thus critical both for medical geneticists and ophthalmologists. In this review, we highlight six categories of disorders that feature glaucoma and other ocular or systemic manifestations: anterior segment dysgenesis syndromes, aniridia, metabolic disorders, collagen/vascular disorders, immunogenetic disorders, and nanophthalmos. The genetics, ocular and systemic features, and current and future treatment strategies are discussed. Findings from rare diseases also uncover important genes and pathways that may be involved in more common forms of glaucoma, and potential novel therapeutic strategies to target these pathways.
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We are presenting the case of a 6-year-old male patient with progeroid phenotype and severe developmental delay referred to Genetic clinic. Given the complex phenotype an extensive metabolic and genetic evaluation was performed including a whole exome sequencing analysis that showed genetic variants in TTR, RELN, MYH6, PHIP, and SYNE2 genes. Patients' mother and brother were analyzed for the genetic variants in MYH6, PHIP and RELN. Both had same variants on PHIP and RELN as our patient, with no apparent phenotypical consequences. Physical examination was remarkable for dysmorphism including plagiocephaly, low set and abnormally shaped ears, up slanted palpebral fissures, hypoplastic alae nasi, and a head circumference two standard deviations below the 3rd percentile (microcephaly). Other characteristics include wrinkled skin, a broad forehead, sparse eyelashes in lower eyelid, short palpebral fissures, upturned nares, thick lips, right occipital plagiocephaly, overfolded helix and prominent anti-helix, protuberant chest, scaphoid abdomen, digitalized thumbs, and kyphosis due to low muscle tone. The patient presented abnormal EEG with evidence of epileptic discharges. A temporal bone CT showed plagiocephaly with flattening of the right occipital bone. Brain MRI showed callosal agenesis with bilateral colpocephaly with temporal horn dilatation, parahippocampal atrophy, lissencephaly and midbrain hypoplasia. The combination of de novo gene variants mentioned above has never been reported nor correlated as the result of haploinsufficiency mechanisms. Thus, we propose haploinsufficiency and loss of heterozygosity as etiological reasons for this patient phenotype. Further proteomic studies are needed to allocate the extense of genetic influence within the clinical manifestations.
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Purpose We aimed to reveal the underlying genetic defect in a multigenerational Chinese family with autosomal dominant concomitant strabismus complicated by multiple ocular developmental abnormalities. Methods Comprehensive ophthalmic examinations were performed in 14 patients and 24 healthy family members. Whole exome sequencing was performed, and Sanger sequencing was used to confirm the probable mutation in all the family members. Results Concomitant strabismus was the predominant phenotype in the affected family members, although the patients also exhibited variable phenotypes, including nystagmus, mild iris abnormalities, myopia, cataract, and coloboma. An R208W mutation in PAX6 was identified as the pathogenic mutation in the affected family members. Conclusions We recommend considering PAX6 as a candidate gene in the diagnostic screen for familial concomitant strabismus in order to avoid missed diagnosis of the mild ocular abnormalities. Careful examinations of mild ocular phenotypes are necessary for an accurate diagnosis of varied ocular abnormalities in the families with the PAX6 mutation, and proper diagnosis can facilitate genetic and clinical counseling for affected patients.
Article
The abundance of crystallins (> 80% of the soluble protein) in the ocular lens provides advantageous markers for selective gene expression during cellular differentiation. Here we show by functional and protein-DNA binding experiments that the chicken alpha A-crystallin gene is regulated by at least five control elements located at sites A (-148 to -139), B (-138 to -132), C (-128 to -101), D (-102 to -93), and E (-56 to -41). Factors interacting with these sites were characterized immunologically and by gel mobility shift experiments. The results are interpreted with the following model. Site A binds USF and is part of a composite element with site B. Site B binds CREB and/or CREM to enhance expression in the lens and binds an AP-1 complex including CREB, Fra2 and/or JunD which interacts with USF on site A to repress expression in fibroblasts. Sites C and E (which is conserved across species) bind Pax-6 in the lens to stimulate alpha A-crystallin promoter activity. These experiments provide the first direct data that Pax-6 contributes to the lens-specific expression of a crystallin gene. Site D (-104 to -93) binds USF and is a negative element. Thus, the data indicate that USF, CREB and/or CREM (or AP-1 factors), and Pax-6 bind a complex array of positive and negative cis-acting elements of the chicken alpha A-crystallin gene to control high expression in the lens and repression in fibroblasts.
Article
Pax-8, a member of the paired box-containing gene family, was shown to be coexpressed with Pax-2 in several human kidney carcinoma cell lines. Four different Pax-8 mRNA isoforms, a to d, were cloned from one of these cell lines by polymerase chain reaction amplification, and the Pax-8 gene was isolated from a human cosmid library. Analysis of the exon-intron structure of Pax-8 revealed that the four mRNA isoforms arise by alternative splicing, resulting in inclusion or exclusion of exon 7 and/or exon 8 sequences. All four Pax-8 proteins retain the paired domain as their DNA-binding motif and recognize DNA in the same manner as do the closely related Pax-2 and BSAP (Pax-5) proteins. The Pax-8a and Pax-8b isoforms end in a serine/threonine/tyrosine-rich sequence, while the C terminus of Pax-8c and Pax-8d is translated in a different, proline-rich reading frame. Transient transfection experiments revealed that Pax-8 isoforms a and b, but not c and d, strongly stimulate transcription from a promoter containing six copies of a paired-domain recognition sequence. The same four mRNA variants were also detected by RNase protection analysis in the mouse embryo and adult kidney, thus indicating evolutionary conservation of Pax-8 mRNA splicing. A different splice pattern was observed in the developing placenta, which expresses two new variants, Pax-8e and Pax-8f, instead of transcripts b to d. Expression of these mRNAs is high at embryonic day 9.5 and is gradually reduced until Pax-8a is the predominant transcript in the 12.5-day placenta. In the embryo, however, the synthesis of mRNAs b to d is initially low and then increases relative to that of Pax-8a. Hence, alternative splicing of Pax-8 gene transcripts not only generates six different Pax-8 variants but is also temporally and spatially regulated during early mouse development.
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Background: Aniridia is a congenital, panocular disease which could affect cornea, anterior chamber angle, iris, lens, retina and optic nerve. PAX6 loss-of-function mutations were the most common cause of aniridia. Mutations throughout the PAX6 gene have been linked to a range of ophthalmic abnormalities. Distinct mutations at a given site in PAX6 lead to distinctive phenotypic findings. This study aimed to characterize genetic mutations associated with congenital aniridia in a Chinese family. Methods: The proband and family underwent ophthalmologic examinations as well as exome sequencing. Results have been confirmed by Next Generation Sequencing. Results: A novel mutation(c.114_119delinsAATTTCC:p.Pro39llefsTer17)in the PAX6 gene was identified in subjectsⅡ-1, III-1 and III-2 in these family who exhibited complete aniridia and cataract. Proband and the proband’s brother also exhibited glaucoma, high myopia, and foveal hypoplasia. Conclusions: We identified a novel PAX6 frameshift heterozygous deletion mutation in a Chinese family and infered this mutation a probable cause of various eye abnormalities in carriers. Trial registration:We did not do any health-related interventions on the participants.
Article
During gestation, the paired box-containing gene Pax2 is expressed in the mid-hindbrain area, developing eye and inner ear. We generated Pax2 null mutant mice, which show the requirement of Pax2 for the establishment of axonal pathways along the optic stalks and ventral diencephalon. In mutant brains, the optic tracts remain totally ipsilateral due to agenesis of the optic chiasma. Furthermore, Pax2 mutants show extension of the pigmented retina into the optic stalks and failure of the optic fissure to close resulting in coloboma. In the inner ear, Pax2 mutants show agenesis of the cochlea and the spiral ganglion, i.e., the parts of the organ responsible for auditory function and in whose primordium Pax2 is expressed. Our results identify Pax2 as a major regulator of patterning during organogenesis of the eye and inner ear and indicate its function in morphogenetic events required for closure of the optic fissure and neural tube.
Thesis
L’aniridie est une pathologie rare principalement due à des mutations hétérozygotes sur PAX6, le gène contrôlant le développement oculaire et le maintien de l’homéostasie cornéenne. Elle est caractérisée par une hypo/aplasie de l’iris, des atteintes de la rétine et du cristallin. La totalité des patients atteints développe aussi une kératopathie associée à l’aniridie (KAA), conduisant à une opacification progressive de leur cornée. La KAA a pour origine un déficit en cellules souches limbiques et diverses perturbations de l’épithélium et du stroma cornéens. Actuellement, il n’existe ni traitement pour soulager efficacement les patients, ni modèle cellulaire pour cette pathologie. Afin de pallier ces manques, le système CRISPR/Cas9 a été utilisé pour intégrer une mutation hétérozygote non-sens dans le gène PAX6 de cellules épithéliales limbiques immortalisées. Les cellules mutées présentent une expression réduite de PAX6 et une modulation de celle de ses gènes cibles, un ralentissement de la prolifération, de la clonogénicité et de la migration ainsi qu’une adhésion accrue. De plus, nous avons montré qu’un traitement de ces cellules avec une protéine recombinante PAX6, portant un peptide de pénétration cellulaire, permet une induction de l’expression endogène de PAX6 et également une restauration partielle du phénotype décrit précédemment. Cette réversion phénotypique valide le modèle d’haploinsuffisance développé et suggère l’implication de PAX6 dans les différentes fonctions restaurées. Les cellules mutées peuvent maintenant être utilisées pour le criblage d’outils thérapeutiques potentiels pour la KAA et pour d’autres défauts liés à une diminution du dosage de PAX6.
Article
Pax-6 genes have been identified from a broad range of invertebrate and vertebrate animals and shown to be always involved in early eye development. Therefore, it has been proposed that the various types of eyes evolved from a single eye prototype, by a Pax-6-dependent mechanism. Here we describe the characterization of a cephalochordate Pax-6 gene. The single amphioxus Pax-6 gene (AmphiPax-6) can produce several alternatively spliced transcripts, resulting in proteins with markedly different amino and carboxy termini. The amphioxus Pax-6 proteins are 92% identical to mammalian Pax-6 proteins in the paired domain and 100% identical in the homeodomain. Expression of AmphiPax-6 in the anterior epidermis of embryos may be related to development of an olfactory epithelium. Expression is also detectable in Hatschek's left diverticulum as it forms the preoral ciliated pit, part of which gives rise to the homolog of the vertebrate anterior pituitary. A zone of expression in the anterior neural plate of early embryos is carried into the cerebral vesicle (a probable diencephalic homolog) during neurulation. This zone includes cells that will differentiate into the lamellar body, a presumed homolog of the vertebrate pineal eye. In neurulae, AmphiPax-6 is also expressed in ventral cells at the anterior tip of the nerve cord; these cells are precursors of the photoreceptive neurons of the frontal eye, the presumed homolog of the vertebrate paired eyes. However, AmphiPax-6 expression was not detected in two additional types of photoreceptors, the Joseph cells or the organs of Hesse, which are evidently relatively recent adaptations (ganglionic photoreceptors) and appear to be rare exceptions to the general rule that animal photoreceptors develop from a genetic program triggered by Pax-6.
Article
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Congenital aniridia is a rare genetic eye disorder with total or partial absence of the iris from birth. In most cases the genetic origin of aniridia is a mutation in the PAX6 gene, leading to involvement of most eye structures. Hypoplasia of the fovea is usually present and is associated with reduced visual acuity and nystagmus. Aniridia-associated keratopathy, glaucoma, and cataract are serious and progressive complications that can further reduce visual function. Treatment of the ocular complications of aniridia is challenging and has a high risk of side effects. New approaches such as stem cell therapy may, however, offer better prognosis. We describe the various ocular manifestations of aniridia, with a special focus on conditions that commonly require treatment. We also review the growing literature reporting systemic manifestations of the disease.
Article
Background: Retinol binding protein 1 (Rbp1) acts as an intracellular regulator of vitamin A metabolism and retinoid transport. In mice, Rbp1 deficiency decreases the capacity of hepatic stellate cells to take up all-trans retinol and sustain retinyl ester stores. Furthermore, Rbp1 is crucial for visual capacity. Although the function of Rbp1 has been studied in the mature eye, its role during early anterior neural development has not yet been investigated in detail. Results: We showed that rbp1 is expressed in the eye, anterior neural crest cells (NCCs) and prosencephalon of the South African clawed frog Xenopus laevis. Rbp1 knockdown led to defects in eye formation, including microphthalmia and disorganized retinal lamination, and to disturbed induction and differentiation of the eye field, as shown by decreased rax and pax6 expression. Furthermore, it resulted in reduced rax expression in the prosencephalon and affected cranial cartilage. Rbp1 inhibition also interfered with neural crest induction and migration, as shown by twist and slug. Moreover, it led to a significant reduction of the all-trans retinoic acid target gene pitx2 in NCC-derived periocular mesenchyme. The Rbp1 knockdown phenotypes were rescued by pitx2 RNA co-injection. Conclusion: Rbp1 is crucial for the development of the anterior neural tissue. This article is protected by copyright. All rights reserved.
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Background: Aniridia is a congenital,panocular disease affecting the cornea,anterior chamber angle,iris,lens,retina and optic nerve.PAX6 loss-of-function mutations were the most common cause of aniridia.Mutations throughout the PAX6 gene have been linked to a range of ophthalmic abnormalities,with distinct mutations at a given site within this gene leading to distinct phenotypic findings.This study aimed to characterize genetic mutations associated with congenital aniridia in a Chinese family. Methods: The proband and the proband’s brother of this family underwent comprehensive ophthalmologic examinations as well as exome sequencing,with Next Generation Sequencing being used to confirm these results. Results: A novel mutation(c.114_119delinsAATTTCC:p.Pro39fs)in the PAX6 gene was identified in subjects III-2 and III-3 in these family,and both of these subjects exhibited complete aniridia,cataracts,glaucoma,high myopia,and foveal hypoplasia. Conclusions We identified a novel PAX6 frameshift heterozygous deletion mutation in a Chinese family and determined that this mutation was a probable cause of various eye abnormalities in carriers.
Article
In autosomal dominant conditions with haploinsufficiency, a single functional allele cannot maintain sufficient dosage for normal function. We hypothesized that pharmacologic induction of the wild-type allele could lead to gene dosage compensation and mitigation of the disease manifestations. The paired box 6 ( PAX6 ) gene is crucial in tissue development and maintenance particularly in eye, brain, and pancreas. Aniridia is a panocular condition with impaired eye development and limited vision due to PAX6 haploinsufficiency. To test our hypothesis, we performed a chemical screen and found mitogen-activated protein kinase kinase (MEK) inhibitors to induce PAX6 expression in normal and mutant corneal cells. Treatment of newborn Pax6 -deficient mice ( Pax6 Sey-Neu/+ ) with topical or systemic MEK inhibitor PD0325901 led to increased corneal PAX6 expression, improved corneal morphology, reduced corneal opacity, and enhanced ocular function. These results suggest that induction of the wild-type allele by drug repurposing is a potential therapeutic strategy for haploinsufficiencies, which is not limited to specific mutations.
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Background: Aniridia is a congenital, panocular disease affecting the cornea, anterior chamber angle, iris, lens, retina and optic nerve. PAX6 loss-of-function mutations were the most common cause of aniridia .Mutations throughout the PAX6 gene have been linked to a range of ophthalmic abnormalities, with distinct mutations at a given site within this gene leading to distinct phenotypic findings.This s tudy aimed to characterize genetic mutations associated with congenital aniridia in a Chinese family. Methods: The proband and the proband’s brother of this family underwent comprehensive ophthalmologic examinations as well as exome sequencing, with Next Generation Sequencing being used to confirm these results. Results: A novel mutation (c.114_119delinsAATTTCC:p.Pro39fs) in the PAX6 gene was identified in subjects III-2 and III-3 in these family, and both of these subjects exhibited complete aniridia, cataracts, glaucoma, high myopia, and foveal hypoplasia. Conclusions: We identified a novel PAX6 frameshift heterozygous deletion mutation in a Chinese family and determined that this mutation was a probable cause of various eye abnormalities in carriers.
Article
A previously published table of ocular genetic disorders and inherited systemic conditions with eye findings has been updated with a comprehensive review of world literature. This tabulation of conditions is designed to provide a useful desk reference for practitioners and medical scientists. The summary will serve again as a benchmark of the significant advances that have occurred in the past few years.
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The fruit fly Drosophila melanogaster has served as an excellent model to study and understand the genetics of many human diseases from cancer to neurodegeneration. Studying the regulation of growth, determination and differentiation of the compound eyes of this fly, in particular, have provided key insights into a wide range of diseases. Here we review the regulation of the development of fly eyes in light of shared aspects with human eye development. We also show how understanding conserved regulatory pathways in eye development together with the application of tools for genetic screening and functional analyses makes Drosophila a powerful model to diagnose and characterize the genetics underlying many human eye conditions, such as aniridia and retinitis pigmentosa. This further emphasizes the importance and vast potential of basic research to underpin applied research including identifying and treating the genetic basis of human diseases.
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We have cloned the paired gene of Drosophila melanogaster, a pair-rule gene required for the establishment of proper segmentation. The transcriptional pattern in young embryos shows developmental polarities along the antero-posterior and dorso-ventral axes. Transcripts, initially expressed with a double-segment periodicity, switch to a single-segment repeat during syncytial blastoderm.
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Maximum likelihood analysis for linkage between autosomal dominant aniridia and 12 biochemical and serological markers in a single large family showed a probable linkage between autosomal dominant aniridia and the enzyme acid phosphatase-1. The presence of an autosomal dominant aniridia gene linked to acid phosphatase-1 on chromosome arm 2p and the existence of an aniridia syndrome resulting from deletion of band 13 of the short arm of chromosome 11 establishes a chromosome basis for genetic heterogeneity of aniridia phenotypes.
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The mouse Hox-7.1 gene has previously been shown to be related to the Drosophila Msh homeobox-containing gene. Here we report the isolation of a new member of this family which resides at an unlinked chromosomal location and has been designated Hox-8.1. Both Hox-7.1 and Hox-8.1 are expressed in the mouse embryo during the early stages of eye development in a distinct spatial and temporal relationship. Hox-8.1 is expressed in the surface ectoderm and in the optic vesicle before invagination occurs in regions corresponding to the prospective corneal epithelium and neural retina, respectively. Hox-7.1 is expressed after formation of the optic cup, marking the domain that will give rise to the ciliary body. The activity of these genes indicates that the inner layer of the optic cup is differentiated into three distinct compartments before overt cellular differentiation occurs. Our results suggest that these genes are involved in defining the region that gives rise to the inner layer of the optic cup and in patterning this tissue to define the iris, ciliary body and retina.
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A common chromosomal abnormality in childhood T-cell acute leukemia is a translocation, t(10;14) (q24;q11), that together with the variant t(7;10)(q35;q24) is present in up to 7% of this tumor type. The gene adjacent to the 10q24 region is transcriptionally activated after translocation to either TCRD (14q11) or TCRB (7q35). It encodes a homeobox gene closely related to the developmentally regulated homeotic genes of flies and mammals. The coding capacity of this activated gene, designated HOX11, is undisturbed in a T-cell line carrying the translocation t(7;10)(q35;q24). Therefore, the HOX11 homeobox gene seems to be involved in T-cell tumorigenesis.
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Several mouse genes designated 'Pax genes' contain a highly conserved DNA sequence homologous to the paired box of Drosophila. Here we describe the isolation of Pax8, a novel paired box containing clone from an 8.5 day p.c. mouse embryo cDNA library. An open reading frame of 457 amino acids (aa) contains the 128 aa paired domain near the amino terminus. Another conserved region present in some other paired box genes, the octapeptide Tyr-Ser-Ile-Asn-Gly-Leu-Leu-Gly, is located 43 aa C-terminal to the paired domain. Using an interspecies backcross system, we have mapped the Pax8 gene within the proximal portion of mouse chromosome 2 in a close linkage to the surf locus. Several developmental mutations are located in this region. In situ hybridization was used to determine the pattern of Pax8 expression during mouse embryogenesis. Pax8 is expressed transiently between 11.5 and 12.5 days of gestation along the rostrocaudal axis extending from the myelencephalon throughout the length of the neural tube, predominantly in two parallel regions on either side of the basal plate. We also detected Pax8 expression in the developing thyroid gland beginning at 10.5 days of gestation, during the thyroid evagination. In the mesonephros and metanephros the expression of Pax8 was localized to the mesenchymal condensations, which are induced by the nephric duct and ureter, respectively. These condensations develop to functional units, the nephrons, of the kidney. These data are consistent with a role for Pax8 in the induction of kidney epithelium. The embryonic expression pattern of Pax8 is compared with that of Pax2, another recently described paired box gene expressed in the developing excretory system.
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The murine genome contains multiple genes with protein domains homologous to the Drosophila paired box, present in certain segmentation genes. At least one of these murine paired box (Pax) genes is associated with a developmental mutation. This report, in conjunction with the accompanying paper, describes a second member of this gene family, Pax2, that is also expressed during embryogenesis. Two overlapping cDNA clones were isolated and sequenced. At least two forms of the Pax2 protein can be deduced from the cDNA sequence. In addition to the highly conserved paired domain, an octapeptide sequence is located downstream. Expression of Pax2 is primarily restricted to the developing embryo in the excretory and central nervous systems. The transient nature of Pax2 expression during kidney organogenesis correlates with polarization and induction of epithelial structures and may indicate an important morphogenetic role for this gene.
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Deletion of chromosome 11p13 in humans produces the WAGR syndrome, consisting of aniridia (an absence or malformation of the iris), Wilms tumor (nephroblastoma), genitourinary malformations, and mental retardation. An interspecies backcross between Mus musculus/domesticus and Mus spretus was made in order to map the homologous chromosomal region in the mouse genome and to define an animal model of this syndrome. Nine evolutionarily conserved DNA clones from proximal human 11p were localized on mouse chromosome 2 near Small-eyes (Sey), a semidominant mutation that is phenotypically similar to aniridia. Analysis of Dickie's Small-eye (SeyDey), a poorly viable allele that has pleiotropic effects, revealed the deletion of three clones, f3, f8, and k13, which encompass the aniridia (AN2) and Wilms tumor susceptibility genes in man. Unlike their human counterparts, SeyDey/+ mice do not develop nephroblastomas. These findings suggest that the Small-eye defect is genetically equivalent to human aniridia, but that loss of the murine homolog of the Wilms tumor gene is not sufficient for tumor initiation. A comparison among Sey alleles suggests that the AN2 gene product is required for induction of the lens and nasal placodes.
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Sequences homologous to the paired domain of Drosophila melanogaster have been conserved in species as distantly related as nematodes, sea urchins, or man. In particular, paired domains of three human genes, HuP1, HuP2 and HuP48, have been isolated and sequenced. Together with four Drosophila paired domains, they fall into two separate paired domain classes named according to their Drosophila members, paired--gooseberry and P29 class. The P29 class includes the mouse Pax 1 and the human HuP48 gene which are nearly identical in their sequenced portions and hence might be true homologues. In addition to the paired domain, the two human genes HuP1 and HuP2 share the highly conserved octapeptide HSIAGILG with the two gooseberry genes of Drosophila. Possible functions of the paired domain are discussed in the light of a predicted helix-turn-helix structure in its carboxy-terminal portion.
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The octamer motif ATGCAAAT is recognized indistinguishably by two mammalian transcription factors: one that is expressed ubiquitously and referred to here as Oct-1, and another, Oct-2, that is expressed in lymphoid cells. We report the cDNA cloning of the human oct-1 gene, which encodes Oct-1, by screening lambda gt11 recombinant phage in situ for octamer motif-specific DNA binding. One lambda gt11 recombinant expressed a beta-galactosidase-octamer-binding fusion protein with a DNA-binding specificity indistinguishable from human HeLa cell Oct-1 protein. As expected for a ubiquitously expressed protein, Oct-1 mRNA is expressed in all five human and two mouse cell lines tested. Polyclonal rabbit antiserum raised against the beta-galactosidase fusion protein shows that the DNA-binding domains of Oct-1 and Oct-2 proteins are related antigenically. Deletion analysis of the 743-amino-acid-long oct-1 open reading frame shows that the DNA-binding activity lies within a central highly charged domain of 160 amino acids. Comparison of the Oct-1 and Oct-2 sequences reveals that this domain is nearly identical between the two proteins. Highly similar domains are also present in the pituitary-specific transcription factor Pit-1 and the Caenorhabditis elegans unc-86 cell lineage gene product (see Herr et al. 1988). Within this shared POU (Pit-1, Oct-1 and Oct-2, unc-86) domain (pronounced 'pow') lie two subdomains: a POU-related homeo box and a POU-specific box. The Oct-1 protein is unique among the POU-related proteins and other homeo box proteins because it is expressed ubiquitously.
Article
It is indeed a pleasure to write a foreword for this spectacular book which represents a landmark in the history of ocular pathology. Not since the three volumes of the Henke-Lubarsch handbook appeared forty years ago has anything like this come on the market. This book represents a compre hensive, thorough and up-to-date clinically oriented textbook on ocular pathology. We are all indebted to the senior author, who is now professor of ophthal mology at the University of Erlangen, who presents us here with the fruit of decades of industrious endeavors. We also have to be grateful to the American ophthalmic pathologist, Dr. David Apple, who, as one of the main collaborators of the German edition, has now provided us with the English translation. The book has a twofold purpose: First, it is meant to be a source of instruction for ophthalmologists and pathologists. For that purpose it is beautifully illustrated both by clinical pictures and by excellent photomicro graphs and electromicroscopic pictures. Most valuable from a didactic point of view are the colored schematic drawings and the many tables. These two features are practically unique and should help any neophyte in grasp ing the principles of ocular pathology."
Article
Purpose: Our purpose was to analyze the various ocular manifestations, treatment options, and the possible outcome of congenital aniridia (CA) a rare and severe developmental disorder.Methods: 52 eyes of 26 patients were regularly checked with full eye examination including anterior segment photography. Electrophysiology, OCT, UBM, and glaucoma testing was done if appropriate. The mean age at the last examination was 17.6 years (range: 2 months – 72 years).Results: The best corrected visual acuity was: 0.2 (ranging from no light perception to 0.6). 20 cases were sporadic and 6 cases showed autosomal dominant inheritance in 3 families. A deletion including band p13 of the short arm of chromosome 11 was found in one familial and one sporadic case.Associated ocular signs were nystagmus (88.5%), congenital cataract (61.5%), and ectopia lentis (3.8%). 14 eyes of 10 cases needed cataract surgery. Secondary glaucoma occurred in 24 eyes of 12 patients, with severe outcome in 15 eyes of 8 patients despite treatment. Aniridic keratopathy occurred in 23 eyes of 12 patients; in 3 cases keratoplasty was performed. One patient had aniridia on one eye, and iris coloboma on the fellow eye confirming the common origin of the two diseases. Interestingly, no Wilms tumor occurred in our series, but mental deficits were found in 4 patients.Conclusions: Secondary glaucoma is the most severe complication of CA. It can appear in relatively young age, is relatively resistant to treatment, and the earlier the onset, the worse the prognosis. Risk factors for vision loss included eye surgeries at young age. Moreover, the outcome of cataract-surgery is limited by foveal hypoplasia and the progression of glaucoma.
Article
A simple method for generating cDNA libraries from submicrogram quantities of mRNA is describe. It combines classical first-stand synthesis with the novel RNase H-DNA polymerase I-mediated second-strand synthesis [Okayama, H., and Berg, P., Mol. Cell. Biol. 2 (1982) 161–170]. Neiher the elaborate vector-primer system nor the classical hairpin loop cleavage by S1 nuclease are used. cDNA thus made can be tailed and cloned without further purification or sizing. Cloning efficiencies can be as high as 106 recombinants generated per μg mRNA, a considerable improvement over earlier methods. Using the fully sequenced1300 nucleotide-long bovine preproenkephalin mRNA, we have established by sequencing that the method yields faithful full-length transcripts. This procedure considerably simplifies the establishment of cDNA libraries and thus the cloning of low-abundance mRNAs.
Article
The mammalian genome contains at least 30 sequences related to the Drosophila Antennapedia (Antp) homeo-box (see references below). Most, if not all, of these sequences are present in the coding regions of actively transcribed genes (1–23) and thus define a homeo-gene family of as yet unknown function. It is supposed, by analogy with similar genes in insects (24, 25 and refs. therein), and by structural comparisons with prokaryotic DNA-binding domains (26), that such homeo-genes are involved in a regulatory network during ontogenesis through a DNA-binding activity. This gene family might therefore be of considerable importance in vertebrate morphogenesis, pattern formation and the specification of cell lineages. In this paper, we present some aspects of the structure of the homeo-gene family and homeo-genes themselves. Organisational features apparent at both levels may provide insight into their evolution, phylogenetic relationships, and possible modes of action. These aspects will be considered separately and exemplified by the situation as it is known in the house mouse.
Article
A new semidominant mutation in the laboratory mouse, Dickie's small eye (Dey), is described. It is localized on chromosome 2. Heterozygotes show reduced body size, small eyes with coloboma, small or lacking lens with cataract, abnormal folding of the retina and reduction of the pigment layer. The anterior chamber is usually missing. Homozygotes apparently die early in pregnancy.
Article
The triad of aniridia, ambiguous genitalia, and mental retardation (AGR triad) is the characteristic clinical feature of three unrelated patients with previously unreported chromosome 11 short arm interstitial deletions. A Wilms' tumor in one patient establishes one cause for the aniridia-Wilms' tumor association. The genetic heterogeneity of aniridia, the AGR triad, and Wilms' tumor are demonstrated, and Wilms' tumor is indicated to be a neoplastic birth defect which can result from a variety of embryologic insults, some of which may be chromosomal or heritable.
Article
A 7-year-old boy with aniridia, Wilms' tumor, and mental retardation, previously reported as having an interstitial deletion of the short arm of chromosome 8 resulting from a t(8p+;11q-) translocation (Ladda et al., 1974), has been restudied using high-resolution trypsin-Giemsa banding of prometaphase chromsomes. The results revealed a complex rearrangement with four break points in 8p, 11p, and 11q, leading to a net loss of an interstitial segment of 11p (region p1407 yields p1304) but not of 8p. His red blood cells contained normal activities of glutathione reductase (gene on 8p) and lactate dehydrogeanse A (gene on 11p12), indicating a gene dosage consistent with the chromosomal findings. The revised interpretation of this case agrees with seven others reported as having aniridia and interstitial 11p deletions in establishing the distal half of band 11p13 as the site of gene(s) which lead to aniridia and predispose to Wilms' tumor if present in a hemizygous state. Possible relationships between heterozygous deletion of specific chromosomal bands 11p13 and 13q14 and the autosomal dominant disorders aniridia, Wilms' tumor, and retinoblastoma, respectively, are discussed.
Article
A new method for determining nucleotide sequences in DNA is described. It is similar to the "plus and minus" method [Sanger, F. & Coulson, A. R. (1975) J. Mol. Biol. 94, 441-448] but makes use of the 2',3'-dideoxy and arabinonucleoside analogues of the normal deoxynucleoside triphosphates, which act as specific chain-terminating inhibitors of DNA polymerase. The technique has been applied to the DNA of bacteriophage varphiX174 and is more rapid and more accurate than either the plus or the minus method.
Article
A clone panel containing various segments of human chromosome 11 has been selected and use for regional assignment of the gene for human lysosomal acid phosphatase (ACP2) to the short arm of chromosome 11, in the region 11p11 leads to 11p12. Further evidence has also been presented to update the regional assignment of the gene for lactate dehydrogenase A (LDHA) to 11p12 leads to 11p13, and to support a previous assignment of the genes for the two components of the human cell-surface antigens of the SA11 (previously designated AL) group, SA11-1 and SA11-3 (previously designated AL-a1 and AL-a3), to 11pter leads to 11p13. This regional clone panel will be useful for rapid regional mapping of other genes assigned to chromosome 11.
Article
This paper describes a method of transferring fragments of DNA from agarose gels to cellulose nitrate filters. The fragments can then be hybridized to radioactive RNA and hybrids detected by radioautography or fluorography. The method is illustrated by analyses of restriction fragments complementary to ribosomal RNAs from Escherichia coli and Xenopus laevis, and from several mammals.
Article
The homeo box, which encodes the DNA-binding homeo domain, is a DNA sequence motif present in several Drosophila developmental genes; it has been used to identify many homologous genes involved in mammalian development. The paired box is another conserved sequence motif, first identified in the paired (prd) and gooseberry (gsb) Drosophila homeo domain genes. It encodes a 128-amino-acid domain, the paired domain, which has since been found in other fly and mouse gene products, in association with the homeo domain or in its absence. We show that the paired box of the prd gene encodes a DNA-binding activity, independent of the DNA-binding activity of the Paired (Prd) homeo domain and with a different sequence specificity. The amino-terminal region of the paired domain, including one of the three predicted alpha-helices, is necessary and sufficient for binding. We investigate the binding of the Prd protein to two sites in the even-skipped promoter, which are composed of overlapping sequences bound by the homeo domain and by the paired domain. We also show that a mutation in the paired box of Prd, corresponding to the mutation in the paired box of the mouse Pax-1 gene thought to cause the undulated skeletal phenotype, destroys the ability of the Prd protein to bind to the paired domain-specific site. This supports the view that the undulated phenotype results from the inactivation of the DNA-binding activity of the paired domain of Pax-1.
Article
We review here old experiments that defined the existence of morphogenetic gradient fields in vertebrate embryos. The rather abstract idea of cell fields of organ-forming potential has become less popular among modern developmental and molecular biologists. Results obtained with antibodies directed against homeodomain proteins suggest that gradient fields may indeed be visualized at the level of individual regulatory molecules in vertebrate embryos.
Article
Various strategies have been used to isolate genes that participate in the regulation of mouse development. Gene families that have been identified on the basis of their homology to motifs within Drosophila control genes or human transcription factor genes, namely homeobox (Hox), paired-box (Pax), and POU genes, can be compared with respect to gene organization, structure, and expression patterns. The functions of these genes can be analyzed molecularly in vitro and in vivo with the use of available mouse mutants or transgenic mice. In addition, it has been possible to generate gain- or loss-of-function mutations by random or targeted introduction of transgenes. Models derived from these studies can reveal the successive steps of developmental control on a genetic level.
Article
The homeobox is a evolutionarily conserved 183 bp DNA sequence motif first found in genes that control the morphogenesis of Drosophila melanogaster .In this article,the key questions are,to what degree do different homeodomain proteins control different target genes,and how is the specificity of action of the protein attained ?
Article
Eight murine paired box-containing (Pax) genes have been isolated so far. The gene described here, Pax7, contains not only a paired box, but also an octapeptide and a paired-type homeobox. As shown by Northern and in situ analysis, Pax7 is expressed from day 8 to 17 p.c. during embryogenesis. At early stages Pax7 transcripts are present in a subset of cells throughout the entire brain, but later in development expression is limited to the mesencephalon. In the developing neural tube Pax7 is restricted to the dorsal ventricular zone along the entire antero-posterior axis, suggesting a role for Pax7 in the formation of certain parts of the CNS. Additionally Pax7 expression can be followed during myogenesis from the dermamyotome of the somites to the skeletal muscle tissues.
Article
A complete physical map of the 11p13 region containing the Wilms' tumor locus has been developed and used to localize a candidate Wilms' tumor gene. Our strategy to construct the map combined the use of pulsed-field gel electrophoresis and irradiation-reduced somatic cell hybrids. These hybrids, which contain limited segments of human chromosome 11 segregated from the remainder of the human genome, permit direct visualization of restriction fragments located in 11p13 using human interspersed repeated DNA sequences as hybridization probes. The physical map has provided a framework to identify the sites of genes responsible for the complex of disorders associated with hemizygous 11p13 deletion: Wilms' tumor, aniridia, genitourinary abnormalities, and mental retardation. The Wilms' tumor locus has been limited to a region of less than 345 kb, and a transcript with many of the characteristics expected for the Wilms' tumor gene has been localized to this region.
Article
Recognition of an AUG initiator codon in a suboptimal context improves when a modest amount of secondary structure is introduced near the beginning of the protein-coding sequence. This facilitating effect depends on the position of the downstream stem-loop (hairpin) structure. The strongest facilitation is seen when the hairpin is separated from the preceding AUG codon by 14 nucleotides. Because 14 nucleotides corresponds to the approximate distance between the leading edge of the ribosome and its AUG-recognition center as measured by ribonuclease protection experiments, a likely explanation for the enhancing effect of a downstream hairpin is that secondary structure slows scanning, thereby providing more time for recognition of the AUG codon, and the facilitation is greatest when the 40S ribosome stalls with its AUG-recognition center directly over the AUG. The variable ability of mammalian ribosomes to initiate at non-AUG codons in vitro is also explicable by the presence or absence of a stem-loop structure just downstream from the alternative initiator codon. This may be relevant to recent reports of adventitious upstream initiation events at non-AUG codons in some vertebrate mRNAs that have structure-prone, G + C-rich leader sequences.
Article
Using an interspecific backcross, we have mapped the gene involved in the mouse Small eye mutation (SeyMH) relative to six cloned markers on chromosome 2 (Hox-5.1, Cas-1, Fshb, Bmp-2a, and ld) and the agouti locus. The results suggest that the Sey gene maps between Fshb and Cas-1. Human mapping studies have shown that the aniridia (AN2) gene, which is part of the Wilms tumor susceptibility, aniridia, genitourinary abnormalities, and mental retardation (WAGR) complex, is also between FSHB and CAT on human chromosome 11. The conserved linkage of the cloned markers and the similarity of the Sey/+ and AN2/+ phenotypes suggest that the gene involved in the Sey mutation is the mouse homolog of the human AN2 gene.
Article
It is likely that most vertebrate genes are associated with 'HTF islands'--DNA sequences in which CpG is abundant and non-methylated. Highly tissue-specific genes, though, usually lack islands. The contrast between islands and the remainder of the genome may identify sequences that are to be constantly available in the nucleus. DNA methylation appears to be involved in this function, rather than with activation of tissue specific genes.
Article
Only a small proportion of the vertebrate genome codes for proteins. It would therefore be useful if genes, and in particular the sites at which transcription begins, could be identified in libraries of cloned DNA. Since many known vertebrate genes have distinctive sequences (HTF-islands) surrounding their transcription start sites, we wished to be able to select these sequences easily and to find out how diagnostic they are for genes. HTF-islands contain a high density of non-methylated CpG (ref. 2) and can be detected in chromosomal DNA as clustered sites for certain rare-cutting (C-G) restriction enzymes. Identification of islands in chromosomal DNA is aided by methylation which blocks C-G enzyme sites in non-island DNA. This advantage is lost in cloned DNA, where CpG methylation is absent. We have calculated, however, that even in cloned DNA most sites for certain C-G enzymes should occur in HTF-islands. We tested this prediction using the enzyme SacII and found that four out of four sites in separate cosmids from the human X chromosome were located in HTF-islands. Hybridization to Northern blots provided preliminary evidence that three of the islands were associated with genes.
Article
The pattern of protein synthesis in 8-, 9- and 10-day post coitum (p.c.) mouse embryos was examined by 2-D gel electrophoresis of [35S]methionine-labelled proteins. Of the 600-800 polypeptides detected only one, a 14 X 10(3) Mr (14K) protein, was found to accumulate over this period. To isolate cDNA clones that potentially encode this protein, 32P-labelled cDNA was synthesized from 9 and 10 days p.c. embryo poly(A) +RNA, and used for the differential screening of an 8.5-day p.c. mouse embryo cDNA library cloned in lambda gt10. Six clones that hybridized strongly to the 10-day probe were purified and their inserts subcloned into plasmid vectors. Cross hybridization and restriction mapping of these inserts indicate that they fall into four distinct groups. Each of these hybridize with transcripts of approximately 600 nucleotides, which accumulate in the embryo from 9 to 10 days p.c. Expression was barely detectable in adult tissues and restricted to liver and spleen. Expression of one of these clones, 10.1, was examined by in situ hybridization of 35S-labelled RNA probes to 8.5-12.5 day p.c. embryo sections. Strong hybridization was observed in yolk sac blood islands, fetal liver and embryonic erythrocytes, suggesting that 10.1A encodes an erythrocyte-specific protein. DNA sequence analysis indicates that the four classes of cDNA were derived from transcripts of the alpha 1, zeta, beta h1 and epsilon globin genes. Labelling of 10-day p.c. erythrocyte proteins with [35S]methionine, followed by 2-D gel electrophoresis, clearly demonstrates that the most abundant polypeptide migrates to the same position as the 14K protein which accumulates from 8 to 10 days p.c. Thus the only abundant transcripts and corresponding proteins that change over a period of profound morphogenetic change correspond to globins of the newly established blood system.
Article
'Walking' using traditional methods (see this volume) is a timeconsuming procedure. We have designed new cosmic vectors to expedite many of the steps involved in genomic walking, particularly the preparation of end-specific hybridization probes and the determination of restriction endonuclease maps of the cloned DNA. This series of vectors designated pWE (for 'walking easily'), is based on the pJB8 cosmid vector containing the Co1E1 origin of replication with the addition of bacteriophage promoter sequences on either side of the cloning site. The most useful pWE vectors, pWE15 and pWE16, contain bacteriophage T3 and T7 promoters flanking a unique BamHI cloning site. By using the cosmid DNA containing a genomic insert as a template for either T3 or T7 polymerase, directional 'walking' probes can be synthesized and used to screen genomic cosmid libraries.
Article
The mouse genome contains at least three copies of sequences homologous to the "paired box", a conserved domain in several Drosophila segmentation genes of the pair-rule and segment polarity classes. Overlapping phages were isolated from two different genomic libraries using the Drosophila gooseberry distal paired box as a probe. The hybridizing sequences are highly homologous to the conserved Drosophila paired box sequences. A single 3.1 kb Pax 1 (paired box gene) transcript was detected during embryonic development, whereas no transcripts were detected in adult tissues. Detailed in situ hybridization analyses with frozen embryonic sections demonstrated Pax 1 transcripts in the perichordal zone of the developing vertebral column. The expression pattern suggests a role for this gene in the formation of segmented structures of the mouse embryo.
Article
Chromosome translocations involving 11p13 have been associated with familial aniridia in two kindreds highlighting the chromosomal localization of the AN2 locus. This locus is also part of the WAGR complex (Wilms tumor, aniridia, genitourinary abnormalities, and mental retardation). In one kindred, the translocation is associated with a deletion, and probes for this region were used to identify and clone the breakpoints of the translocation in the second kindred. Comparison of phage restriction maps exclude the presence of any sizable deletion in this case. Sequences at the chromosome 11 breakpoint are conserved in multiple species, suggesting that the translocation falls within the AN2 gene.
Article
Using two random DNA markers, and pulsed field gel electrophoresis, a 1.5-Mb physical map surrounding the 11p13 aniridia locus (AN2) has been assembled. The map was constructed using a combination of single- and double-restriction digests on DNA from normal controls and a patient transmitting familial aniridia. The aniridia patient has a chromosome translocation and the two DNA markers flank the breakpoint. This 11p13 breakpoint lies no further than 100 kb from the DNA marker 1104 (D11S95), located on the centromeric side of the breakpoint. Two CpG islands, separated by 550 kb and flanking the translocation, suggest an upper limit to the size of the gene.
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The bicoid (bcd) protein is expressed in an anteroposterior gradient in early Drosophila embryos and controls the zygotic activation of the segmentation gene hunchback (hb) in a broad but precisely bounded anterior domain. Here we show that the hb gene contains multiple regulatory elements that mediate transcriptional activation in response to bcd protein. Further, we demonstrate that the resulting patterns of expression in vivo depend critically on both the bcd gradient profile and the number and quality of these hb elements. Finally, we show that these same elements mediate bcd-dependent transcriptional activation in yeast and that this interaction requires distinct DNA binding and activating regions in the bcd protein. Our results argue that bcd protein normally binds and activates the hb gene in a concentration-dependent fashion, thereby allowing the gradient of bcd protein to dictate where the hb gene is initially turned on in early embryos. They also suggest that the bcd gradient has the instructive capacity to activate other subordinate control genes by the same mechanism, each in a distinct spatial domain according to its affinity for bcd protein.
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A long-range restriction map of part of the short arm of chromosome 11 including the WAGR region has been constructed using pulsed-field gel electrophoresis and a number of infrequently cutting restriction enzymes. A total of 15.4 Mbp has been mapped in detail, extending from proximal 11p14 to the distal part of 11p12. The map localizes 35 different DNA probes and reveals at least nine areas with features characteristic of HTF islands, some of which may be candidates for the different loci underlying the phenotype of the WAGR syndrome. This map will furthermore allow screening of DNA from individuals with WAGR-related phenotypes and from Wilms tumors for associated chromosomal rearrangements.