RESUMEN
The Beckwith-Wiedemann syndrome (BWS) is a growth disorder for which an increased frequency of monozygotic (MZ) twinning has been reported. With few exceptions, these twins are discordant for BWS and for females. Here, we describe the molecular and phenotypic analysis of 12 BWS twins and a triplet; seven twins are MZ, monochorionic and diamniotic, three twins are MZ, dichorionic and diamniotic and three twins are dizygotic. Twelve twins are female. In the majority of the twin pairs (11 of 13), the defect on chromosome 11p15 was hypomethylation of the paternal allele of DMR2. In 5 of 10 twins, there was additional hypomethylation of imprinted loci; in most cases, the loci affected were maternally methylated, but in two cases, hypomethylation of the paternally methylated DLK1 and H19 DMRs was detected, a novel finding in BWS. In buccal swabs of the MZ twins who share a placenta, the defect was present only in the affected twin; comparable hypomethylation in lymphocytes was detected in both the twins. The level of hypomethylation reached levels below 25%. The exchange of blood cells through vascular connections cannot fully explain the degree of hypomethylation found in the blood cell of the non-affected twin. We propose an additional mechanism through which sharing of aberrant methylation patterns in discordant twins, limited to blood cells, might occur. In a BWS-discordant MZ triplet, an intermediate level of demethylation was found in one of the non-affected sibs; this child showed mild signs of BWS. This finding supports the theory that a methylation error proceeds and possibly triggers the twinning process.
Asunto(s)
Síndrome de Beckwith-Wiedemann/genética , Metilación de ADN/genética , Padre , Células Madre Hematopoyéticas/metabolismo , Madres , Cromosomas Humanos Par 11/genética , Femenino , Impresión Genómica , Genotipo , Humanos , Masculino , Fenotipo , Placentación/genética , Embarazo , Gemelos/genética , Gemelos Dicigóticos/genética , Gemelos Monocigóticos/genéticaRESUMEN
BACKGROUND AND PURPOSE: Approximately 2% of the general population harbor intracranial aneurysms. The prognosis after rupture of an intracranial aneurysm is poor; 50% of the patients die as a result of the rupture. Familial occurrence of intracranial aneurysms suggests there are genetic factors involved in the development of such aneurysms. METHODS: A large, consanguineous pedigree with 7 of 20 siblings affected by intracranial aneurysms was compiled and a genomewide linkage analysis on this family was performed using Illumina's single nucleotide polymorphism-based linkage panel IV, which includes 5861 single nucleotide polymorphisms. A nonparametric linkage affecteds-only approach with GENEHUNTER was used. RESULTS: Two loci with suggestive linkage (nonparametric linkage=3.18) on chromosome regions 1p36 and Xp22 were identified. Additional microsatellite markers were genotyped in the 2 candidate loci and showed suggestive linkage to the locus on chromosome 1 with a nonparametric linkage of 3.18 at 1p36.11-p36.13 and significant linkage to the locus on chromosome X with a nonparametric linkage of 4.54 at Xp22.2-p22.32. CONCLUSIONS: The 2 potential loci for intracranial aneurysms, which we identified in this large Dutch family, overlap with loci that have already been identified in previous linkage studies from different populations. Identification of genes from these loci will be important for a better understanding of the disease pathogenesis.
Asunto(s)
Cromosomas Humanos Par 1 , Cromosomas Humanos X , Ligamiento Genético , Genómica , Aneurisma Intracraneal/genética , Adulto , Anciano de 80 o más Años , Salud de la Familia , Femenino , Predisposición Genética a la Enfermedad/epidemiología , Humanos , Recién Nacido , Aneurisma Intracraneal/epidemiología , Masculino , Repeticiones de Microsatélite , Persona de Mediana Edad , Países Bajos , Linaje , Polimorfismo de Nucleótido SimpleRESUMEN
Amplification of region 17p11.2 approximately p12 has been found in 13%-29% of high-grade osteosarcomas, suggesting the presence of an oncogene or oncogenes that may contribute to their development. To determine the location of these putative oncogenes, we established 17p11.2 approximately p12 amplification profiles by semiquantitative PCR, using 15 microsatellite markers and seven candidate genes in 19 high-grade osteosarcomas. Most of the tumors displayed complex amplification profiles, with frequent involvement of marker D17S2041 in 17p12 and TOP3A in 17p11.2 and, in some cases, very high-level amplification of PMP22 and MAPK7 in 17p11.2. Our findings suggest that multiple amplification targets, including PMP22, TOP3A, and MAPK7 or genes close to these candidate oncogenes, may be present in 17p11.2 approximately p12 and thus contribute to osteosarcoma tumorigenesis.