Prader-Willi and Angelman syndromes: sister imprinted disorders.
ABSTRACT Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are clinically distinct complex disorders mapped to chromosome 15q11-q13. They both have characteristic neurologic, developmental, and behavioral phenotypes plus other structural and functional abnormalities. However, the cognitive and neurologic impairment is more severe in AS, including seizures and ataxia. The behavioral and endocrine disorders are more severe in PWS, including obsessive-compulsive symptoms and hypothalamic insufficiency. Both disorders can result from microdeletion, uniparental disomy, or an imprinting center defect in 15q11-q13, although the abnormality is on the paternally derived chromosome 15 for PWS and the maternally derived 15 for AS because of genomic imprinting. Although the same gene may control imprinting for both disorders, the gene(s) causing their phenotypes differ. AS results from underexpression of a single gene, UBE3A, which codes for E6-AP, a protein that functions to transfer small ubiquitin molecules to certain target proteins, to enable their degradation. The genes responsible for PWS are not determined, although several maternally imprinted genes in 15q11-q13 are known. The most likely candidate is SNRPN, which codes for a small nuclear ribonucleoprotein, a ribosome-associated protein that controls gene splicing and thus synthesis of critical proteins in the brain. Animal models exist for both disorders. The genetic relationship between PWS and AS makes them unique and potentially highly instructive disorders that contribute substantially to the population burden of cognitive impairment.
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ABSTRACT: Sperm cryopreservation is widely used in clinic for insemination, in vitro fertilization and other procedures such as intracytoplasmic sperm injection. The assessment after freezing/thawing of spermatozoa viability, motility and sometimes DNA integrity (mainly using fragmentation assays) has been considered enough to guarantee the safety and effectiveness of the technique. However, it is known that, even when fragmentation is absent, a significant DNA damage could be detected in some genome regions. This is particularly important considering that, during the last years, several studies have pointed out the importance of key paternal genes in early embryo development. In this study, using normozoospermic donors, we present a candidate gene approach in which we quantify the number of lesions produced by freezing/thawing over key genes (PRM1, BIK, FSHB, PEG1/MEST, ADD1, ARNT, UBE3A, SNORD116/PWSAS) using quantitative PCR. Our results demonstrated that the cryopreservation protocol used, which is routinely employed in clinic, produced DNA lesions. The genes studied are differentially affected by the process, and genome regions related to Prader-Willi and Angelman syndromes were among the most damaged: SNORD116/PWSAS (4.56 ± 1.84 lesions/10 kb) and UBE3A (2.22 ± 1.3 lesions/10 kb). To check if vitrification protocols could reduce these lesions, another experiment was carried out studying some of those genes with higher differences in the first study (FSHB, ADD1, ARNT and SNORD116/PWSAS). The number of lesions was not significantly reduced compared to cryopreservation. These results could be relevant for the selection of the most adequate available cryopreservation protocol in terms of the number of lesions that produced over key genes, when no differences with other traditional techniques for DNA assessment could be detected.Andrology 09/2013; 1(5):723-30. DOI:10.1111/j.2047-2927.2013.00116.x
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ABSTRACT: Prader-Willi syndrome (PWS), a neurodevelopmental disorder primarily characterized by hyperphagia and food preoccupations, is caused by the absence of expression of the paternally active genes in the proximal arm of chromosome 15. Although maladaptive behavior and the cognitive profile in PWS have been well characterized, social functioning has only more recently been systematically examined. Findings to date indicate the social impairment exhibited may reflect specific difficulty interpreting and using social information effectively. In addition, evidence suggests that there is an increased risk of social deficits in people with the maternally-derived uniparental disomy (mUPD) subtype of PWS in comparison to those with 15q11-13 paternal deletion (DEL). Using the Social Responsiveness Scale (SRS) and the Social Competence Inventory, our goal was to compare social functioning in PWS to individuals with autism spectrum disorder (ASD). Participants with mUPD scored similarly to the ASD group across most SRS domains. All groups had difficulty with social competence, although the DEL group scored highest on prosocial behavior. Findings suggest further characterization of social behavior in PWS is necessary to aid in advancing the understanding of the contributions of genes in the 15q11-13 critical region to ASD susceptibility, particularly with respect to the overexpression of maternally expressed genes in this region, as well as aiding in awareness and development/implementation of interventions.Journal of Autism and Developmental Disorders 05/2012; DOI:10.1007/s10803-012-1547-3
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ABSTRACT: Trisomy causes mental retardation, pregnancy loss, IVF failure, uniparental disomy and several other pathologies, and its accurate detection is thus clinically essential. Most trisomies arise at meiosis I and are associated with increasing maternal age and reduction or alteration in recombination patterns. Investigations into the relationship between trisomy and meiotic recombination have used short tandem repeat markers; however, this approach is limited by the resolution with which the position of crossovers can identified. As cytogenetics enters the post-genomic era, recent work has used array comparative genomic hybridisation (aCGH) to screen for trisomy of all 24 chromosomes, determining chromosome copy number by dosage analysis. However, aCGH has a fundamental drawback for studying the aetiology of trisomy since neither the parent and phase of origin nor uniparental disomy can be ascertained. The development of SNP microarrays has made it possible to analyse multiple loci for sequence variation, and the proprietary software provided can determine the presence of aneuploidy by algorithms based on fluorescence intensity. To the best of our knowledge, however, such software is not equipped to determine the phase of origin of the error or the position of any chiasmata. In this study, therefore, we present an algorithm to determine the parent of origin, the phase of origin and the location of chiasmata in a series of nine "trisomy triplets" (i.e. samples derived from father, mother and their trisomic foetus). Novel adaptations of well-established principles are applied along with a simple algorithm written in Microsoft Excel for visualisation of the results. Such analysis has a range of applications in preimplantation and prenatal diagnosis.Chromosome Research 02/2011; 19(2):155-63. DOI:10.1007/s10577-010-9181-4