1/14. Familial interstitial 570 kbp deletion of the UBE3A gene region causing Angelman syndrome but not prader-willi syndrome.angelman syndrome (AS) is a disorder of psychomotor development caused by loss of function of the imprinted UBE3A gene. Since the paternal UBE3A copy is regularly silent, only mutations inactivating the maternal copy cause AS. Among 1,272 patients suspected of AS, we found one with an isolated deletion of the UBE3A gene on the maternally inherited chromosome. Initial dna methylation testing at the SNURF-SNRPN locus in the patient revealed a normal pattern. The deletion was only detected through allelic loss at microsatellite loci D15S1506, D15S122, and D15S210, and confirmed with fluorescence in situ hybridization (FISH) using bacterial artificial chromosome (BAC) probes derived from the loci. It extends approximately 570 kilobase pairs (kbp), encompassing the UBE3A locus, and is flanked by loci PAR/SN and D15S986. The deletion is familial, and haplotype studies suggest that a great grandfather of the index patient already carried this deletion, and that it causes AS when inherited through the female germline but not prader-willi syndrome (PWS) when paternally inherited. Our findings support the hypothesis that the functional loss of maternal UBE3A gene activity is sufficient to cause AS and that the deleted region does not contain genes or other structures that are involved in PWS. Finally, this case highlights that methylation tests can fail to detect some familial AS cases with a recurrence risk of 50%.- - - - - - - - - - ranking = 1keywords = mutation (Clic here for more details about this article) |
2/14. Maternal but not paternal transmission of 15q11-13-linked nondeletion angelman syndrome leads to phenotypic expression.angelman syndrome (AS) may result from either maternally inherited deletions of chromosome 15q11-13 or from paternal uniparental disomy for chromosome 15. This is in contrast to prader-willi syndrome (PWS), which is caused by either paternal deletion of this region or maternal disomy for chromosome 15. However, 40% of AS patients inherit an apparently intact copy of chromosome 15 from each parent. We now describe a family in which three sisters have given birth to four AS offspring who have no evidence of deletion or paternal disomy. We show that AS in this family is caused by a mutation in 15q11-13 that results in AS when transmitted from mother to child, but no phenotype when transmitted paternally. These results suggest that the loci responsible for AS and PWS, although closely linked, are distinct.- - - - - - - - - - ranking = 1keywords = mutation (Clic here for more details about this article) |
3/14. Fetal phenotype of prader-willi syndrome due to maternal disomy for chromosome 15.prader-willi syndrome (PWS) results from either paternal deletion of 15q11-q13, or maternal uniparental disomy (UPD) of chromosome 15 or imprinting center mutation. prenatal diagnosis of PWS is currently indicated for chromosomal parental translocation involving chromosome 15 and for decreased fetal movements during the third trimester of gestation. Here we present the prenatal diagnosis of PWS during the first trimester of gestation and autopsy findings. Chorionic villus sampling (CVS) was performed for advanced maternal age at 13 weeks' gestation. CVS showed mosaicism including cells with a normal karyotype and cells with trisomy 15. amniocentesis showed cells with a normal karyotype. Molecular analysis demonstrated that the fetus had a typical PWS abnormal methylation profile and maternal disomy for chromosome 15. Fetal ultrasound examination showed slightly enlarged lateral ventricles and hypoplasic male external genitalia without intra-uterine growth retardation. The autopsy showed a eutrophic male fetus with facial dysmorphy, hypoplasic genitalia, abnormal position of both feet and posterior hypoplasia of the corpus callosum. This report points out that in a karyotypically normal fetus with ambiguous male external genitalia and cerebral anomalies, extensive cytogenetic and molecular biology studies are strongly recommended because of risk of PWS.- - - - - - - - - - ranking = 1keywords = mutation (Clic here for more details about this article) |
4/14. prader-willi syndrome with a karyotype 47,XY, min(15)(pter->q11.1:) and maternal UPD 15--case report plus review of similar cases.Prader-Willi (PWS) and Angelman (AS) are syndromes of developmental impairment that can result either from a 15q11-q13 deletion, paternal uniparental disomy (UPD), imprinting, or UBE3A mutations. A small cytogenetic subset of PWS and AS patients are carriers of a so-called small supernumerary marker chromosome (sSMC). Here, we report on an previously unreported PWS case with a karyotype 47,XY, min(15)(pter->q11.1:) plus maternal heterodisomic UPD 15. A review of the literature revealed, that for both, PWS and AS patients, cases with (1) a sSMC plus microdeletion of the PWS/AS critical region, (2) inv dup(15) plus uniparental disomy (UPD) 15 and (3) cases without exclusion of a microdeletion an UBE3A mutation or UPD are described. The present case as well as the review of similar cases provides further evidence for the necessity to test UPD in prenatal cases with a de novo sSMC and in postnatal cases with otherwise unexplainable clinical phenotype.- - - - - - - - - - ranking = 2keywords = mutation (Clic here for more details about this article) |
5/14. A new case of interstitial 6q16.2 deletion in a patient with Prader-Willi-like phenotype and investigation of SIM1 gene deletion in 87 patients with syndromic obesity.The association of obesity, phenotypic abnormalities and mental retardation characterizes syndromic obesity. Its most common form is the prader-willi syndrome (PWS-- neonatal hypotonia, poor sucking, delayed psychomotor development, hyperphagia, severe obesity, short stature, small hands and feet, hypogonadism, mild to moderate mental retardation and behavioral disorders). A PWS-like phenotype has been described in patients with chromosome abnormalities involving the chromosome region 6q16.2 that includes the SIM1 gene. Herein we report cytogenetic and gene studies including a screening for the SIM1 gene deletion, performed on 87 patients with PWS-like phenotype, and describe the fifth case of syndromic obesity with an interstitial deletion of the chromosome segment 6q16-q21 and suggest that mutational analysis and further studies of the parental origin of chromosome alterations of 6q16.2 in patients with and without PWS-like phenotype are needed to evaluate possible imprinting effects of SIM1 gene and establish the contribution that alterations in this gene makes to the etiology of syndromic and non-syndromic obesity.- - - - - - - - - - ranking = 1keywords = mutation (Clic here for more details about this article) |
6/14. Prader-Willi-like phenotype in fragile x syndrome.A 3-year-old boy was referred to the pediatric department because of unexplained extreme obesity. Height and occipitofrontal circumference were just above the 90th centile. Endocrine studies failed to show any significant abnormality. Motor and speech development were generally delayed. On clinical-cytogenetic-molecular grounds, prader-willi syndrome was excluded. fragile x syndrome was diagnosed by the presence of the classical FMR-1 mutation and confirmed by cytogenetic studies, revealing 20% fragile X positive cells. We compare the clinical features in the present patient with the nine reported patients with fra(X) syndrome and extreme obesity. In pathogenesis, hypothalamic dysregulation is hypothesized. In differential diagnosis of prader-willi syndrome, fragile X has to be considered, especially when laboratory workup for prader-willi syndrome is negative. Clinical behavior can be of help.- - - - - - - - - - ranking = 1keywords = mutation (Clic here for more details about this article) |
7/14. Mutations of the P gene in oculocutaneous albinism, ocular albinism, and prader-willi syndrome plus albinism.BACKGROUND. Type II (tyrosinase-positive) oculocutaneous albinism is an autosomal recessive disorder that has recently been mapped to chromosome segment 15q11-q13. The frequency of this disorder is greatly increased in patients with Prader-Willi or angelman syndrome, both of which involve deletions of chromosome 15q. The P protein is a transmembrane polypeptide that may transport small molecules such as tyrosine, the precursor of melanin. The P gene is located in chromosome segment 15q11-q13. methods. We studied the tyrosinase and P genes in three patients with type II oculocutaneous albinism, one of whom also had prader-willi syndrome, and in one patient with a milder syndrome known as autosomal recessive ocular albinism. Individual exons of these genes were amplified from the DNA of each patient by the polymerase chain reaction and screened for mutations by simultaneous analyses of single-stranded conformation polymorphisms and heteroduplexes and subsequent DNA sequencing. RESULTS. Mutations of the P gene were identified in all four patients. These included one frame shift, three missense mutations that result in amino acid substitutions, and one mutation that affects rna splicing. The patient with prader-willi syndrome plus albinism had a typical deletion of the paternal chromosome 15, rendering him hemizygous for a maternally inherited mutant allele of the P gene. The child with ocular albinism was heterozygous for two different mutations in the P gene. CONCLUSIONS. Abnormalities of the P gene are associated with a wide range of clinical phenotypes, including type II oculocutaneous albinism, albinism associated with the prader-willi syndrome, and at least some cases of autosomal recessive ocular albinism.- - - - - - - - - - ranking = 4keywords = mutation (Clic here for more details about this article) |
8/14. Clinical and molecular studies in fragile X patients with a Prader-Willi-like phenotype.A special subphenotype of the fragile x syndrome is reported which is characterised by extreme obesity with a full, round face, small, broad hands/feet, and regional skin hyperpigmentation. It resembles the prader-willi syndrome (PWS) and might therefore be named 'Prader-Willi-like'. Unlike the PWS, these PW-like fragile X patients lack the neonatal hypotonia with feeding problems during infancy followed by hyperphagia from toddlerhood. We describe five new fragile X patients and present a clinical update of three previously described patients with the PW-like phenotype. In one family, segregation of either the classical Martin-Bell or the PW-like phenotype was observed and in another family there was repeated transmission of the PW-like phenotype. Previously, one of the patients had been misdiagnosed as having classical PWS, based on clinical findings. Molecular studies of the FMR-1 gene showed the typical full mutations as seen in fragile x syndrome males. Molecular analysis of the 15q11-13 region, which is deleted in the majority of classical PWS patients, did not show any detectable abnormalities. In a group of 26 patients with suspected prader-willi syndrome but without detectable molecular abnormalities of chromosome 15, one fragile X patient was found. These clinical and molecular findings illustrate the necessity to perform DNA analysis of the FMR-1 gene in mentally retarded patients presenting with a PW phenotype but without the PWS specific cytogenetic/molecular abnormalities of chromosome 15.- - - - - - - - - - ranking = 1keywords = mutation (Clic here for more details about this article) |
9/14. Exclusion of SNRPN as a major determinant of prader-willi syndrome by a translocation breakpoint.The predominant genetic defects in prader-willi syndrome (PWS) are 15q11-q13 deletions of paternal origin and maternal chromosome 15 uniparental disomy (UPD). In contrast, maternal deletions and paternal chromosome 15 UPD are associated with a different neurogenetic disorder, angelman syndrome (AS). In both disorders, these mutations are associated with parent-of-origin specific methylation at several 15q11-q13 loci. The critical PWS region has been narrowed to a approximately 320-kb region between D15S63 and D15S174, encoding several imprinted transcripts, including PAR5, IPW, PAR1 (refs 7,8) and SNRPN, which has so far been considered a strong candidate for the PWS gene. A few PWS-associated microdeletions involving a putative imprinting centre (IC) proximal to SNRPN have also been observed. We have mapped the breakpoint of a balanced translocation (9;15)pat associated with most of the PWS features between SNRPN and IPWIPAR1. Methylation and expression studies indicate that the paternal SNRPN allele is unaffected by the translocation, while IPW and PAR1 are unexpressed. This focuses the attention on genes distal to the breakpoint as the main candidate for PWS genes, and is consistent with a cis action of the putative IC, and suggests that further studies of translocational disruption of the imprinted region may establish genotype-phenotype relationships in this presumptive contiguous gene syndrome.- - - - - - - - - - ranking = 1keywords = mutation (Clic here for more details about this article) |
10/14. A 5-year-old white girl with prader-willi syndrome and a submicroscopic deletion of chromosome 15q11q13.We report on a 5-year-old white girl with prader-willi syndrome (PWS) and a submicroscopic deletion of 15q11q13 of approximately 100-200 kb in size. High resolution chromosome analysis was normal but fluorescence in situ hybridization (FISH), Southern hybridization, and microsatellite data from the 15q11q13 region demonstrated that the deletion was paternal in origin and included the SNRPN, PAR-5, and PAR-7 genes from the proximal to distal boundaries of the deletion segment. SNRPN and PW71B methylation studies showed an abnormal pattern consistent with the diagnosis of PWS and supported the presence of a paternal deletion of 15q11q13 or an imprinting mutation. Biparental (normal) inheritance of PW71B (D15S63 locus) and a deletion of the SNRPN gene were observed by microsatellite, quantitative Southern hybridization, and/or FISH analyses. Our patient met the diagnostic criteria for PWS, but has no reported behavior problems, hyperphagia, or hypopigmentation. Our patient further supports SNRPN and possibly other genomic sequences which are deleted as the cause of the phenotype recognized in PWS patients.- - - - - - - - - - ranking = 1keywords = mutation (Clic here for more details about this article) |
| | Next -> |