Novel mutations of FOXC1 and PITX2 in patients with Axenfeld-Rieger malformations

Molecular Genetics Laboratory, University Eye Hospital, Tübingen, Germany.
Investigative Ophthalmology &amp Visual Science (Impact Factor: 3.66). 10/2006; 47(9):3846-52. DOI: 10.1167/iovs.06-0343
Source: PubMed

ABSTRACT To determine the prevalence of FOXC1 and PITX2 mutations and to assess clinical phenotypes in a cohort of German patients with Axenfeld-Rieger malformations.
All coding exons of the FOXC1 and PITX2 genes were amplified by PCR from genomic DNA and subjected to direct DNA sequencing. Analysis of mutations in control subjects was performed by restriction fragment length polymorphism (RFLP) analysis.
Sequence variants were identified by DNA sequencing in 15 of 19 cases. Mutation screening identified four potentially pathogenic FOXC1 mutations causing amino acid substitutions (P79R, Y115S, G149D, and M161V) that were not present in 100 control subjects. In addition, two different 1-bp deletions causing a frameshift and subsequent premature stop codon were identified in two subjects. One patient harbored a FOXC1 nonsense mutation (S48X). Mutation screening also identified two potentially pathogenic PITX2 mutations (P64L and P64R) in two index patients that were excluded in 100 healthy control subjects.
The findings in the present study clearly demonstrate that FOXC1 and PITX2 mutations are responsible for a significant proportion of Axenfeld-Rieger malformations in Germany.

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    • "GH deficiency (Feingold et al. 1969, Sadeghi-Nejad & Senior 1974) and short stature (Brooks et al. 1989) have also been reported in several cases, with an enlarged sella turcica and combined GH/TSH or GH/ACTH deficiency (Polomeno et al. 1980). A broad range of PITX2 mutations have been described, with missense mutations usually affecting the homeodomain and leading, in some cases, to a dominantnegative mutant form (Semina et al. 1996, Alward et al. 1998, Kulak et al. 1998, Perveen et al. 2000, Priston et al. 2001, Phillips 2002, Xia et al. 2004, Idrees et al. 2006, Kniestedt et al. 2006, Vieira et al. 2006, Weisschuh et al. 2006). Splice-site (Semina et al. 1996, Doward et al. 1999, Perveen et al. 2000, Maciolek et al. 2006), frameshift, and nonsense mutations have been found throughout the gene and may result in truncated proteins (Semina et al. 1996, Perveen et al. 2000, Priston et al. 2001, Wang et al. 2003, Brooks et al. 2004, Lines et al. 2004, Saadi et al. 2006, Vieira et al. 2006). "
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    ABSTRACT: The bicoid-like transcription factor PITX2 has been previously described to interact with the pituitary-specific POU homeodomain factor POU1F1 (human ortholog of PIT-1) to achieve cell-specific expression of prolactin (PRL) and GH in pituitary somatolactotroph cells. In this work, we have investigated the functional properties of three PITX2 mutants reported in Axenfeld-Rieger syndrome patients relative to the regulation of these genes, using reporter genes under the control of human PRL (hPRL), hGH, or POU1F1 promoters transfected in nonpituitary and pituitary cell lines. Among the three mutations studied, Y167X and E101X introduce a premature stop codon, and F104L leads to an amino acid substitution. While PITX2(E101X) is not expressed in the cells following transfection, and PITX2(F104L) is functionally inactive, the PITX2(Y167X) mutant keeps its DNA-binding capacity and displays a markedly enhanced activation of the hPRL and POU1F1 promoters, but not of the hGH promoter. Y167X is the first mutation of PITX2 described to result in a differential effect on the activation of its different physiological targets, hPRL and POU1F1 on one hand and hGH on the other hand. The differential effect of the Y167X mutation might be linked to an interaction of PITX2 with different transcription factors or cofactors when bound to the hPRL and POU1F1 or the hGH promoters. These results might form the basis for the identification of the PITX2 protein complex necessary for the differential GH or PRL expression.
    Journal of Molecular Endocrinology 10/2010; 46(1):9-19. DOI:10.1677/JME-10-0063 · 3.62 Impact Factor
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    • "Pitx2 encodes a homeodomain transcription factor which plays an essential role during ocular anterior segment patterning and development (Gage et al., 1999; Hjalt et al., 2000; Gage et al., 2005). Heterozygous mutations in human PITX2 results in Axenfeld-Rieger syndrome characterized by anterior segment dysgenesis and high risk of developing glaucoma (Semina et al., 1996; Mears et al., 1998; Kozlowski and Walter, 2000; Vieira et al., 2006; Weisschuh et al., 2006). Global and neural crest specific Pitx2 knockout mice exhibit a similar eye phenotype including abnormal anterior segment differentiation, vasculogenesis, eyelid defects and coloboma (Gage et al., 1999; Kitamura et al., 1999; Lu et al., 1999; Evans and Gage, 2005). "
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    ABSTRACT: Morphogenesis during eye development requires retinoic acid (RA) receptors plus RA-synthesizing enzymes, and loss of RA signaling leads to ocular disorders associated with loss of Pitx2 expression in perioptic mesenchyme. Several Wnt signaling components are expressed in ocular tissues during eye development including Dkk2, encoding an inhibitor of Wnt/beta-catenin signaling, which was previously shown to be induced by Pitx2 in the perioptic mesenchyme. Here, we investigated potential cross-talk between RA and Wnt signaling during ocular development. Genetic studies using Raldh1/Raldh3 double null mice deficient for ocular RA synthesis demonstrated that Pitx2 and Dkk2 were both down-regulated in perioptic mesenchyme. Chromatin immunoprecipitation and gel mobility shift studies demonstrated the existence of a DR5 RA response element upstream of Pitx2 that binds all three RA receptors in embryonic eye. Axin2, an endogenous readout of Wnt/beta-catenin signaling, was up-regulated in cornea and perioptic mesenchyme of RA deficient embryos. Also, expression of Wnt5a was expanded in perioptic mesenchyme of RA deficient eyes. Our findings demonstrate excessive activation of Wnt signaling in the perioptic mesenchyme of RA deficient mice which may be responsible for abnormal development leading to defective optic cup, cornea, and eyelid morphogenesis.
    Developmental Biology 04/2010; 340(1):67-74. DOI:10.1016/j.ydbio.2010.01.027 · 3.64 Impact Factor
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    • "A three-generation pedigree of the family members was constructed (Figure 1). All four patients were screened for mutations in PITX2 and FOXC1 by direct DNA sequencing [7]. "
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    ABSTRACT: Axenfeld-Rieger syndrome (ARS) (OMIM Nr.: 180500) is a rare autosomal dominant disorder (1 : 200000) with genetic and morphologic variability. Glaucoma is associated in 50% of the patients. Craniofacial and dental anomalies are frequently reported with ARS. The present study was designed as a multidisciplinary analysis of orthodontic, ophthalmologic, and genotypical features. A three-generation pedigree was ascertained through a family with ARS. Clinically, radiographic and genetic analyses were performed. Despite an identical genotype in all patients, the phenotype varies in expressivity of craniofacial and dental morphology. Screening for PITX2 and FOXC1 mutations by direct DNA-sequencing revealed a P64L missense mutation in PITX2 in all family members, supporting earlier reports that PITX2 is an essential factor in morphogenesis of teeth and craniofacial skeleton. Despite the fact that the family members had identical mutations, morphologic differences were evident. The concomitant occurrence of rare dental and craniofacial anomalies may be early diagnostic indications of ARS. Early detection of ARS and elevated intraocular pressure (IOP) helps to prevent visual field loss.
    Case Reports in Medicine 03/2010; 2010:621984. DOI:10.1155/2010/621984
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