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MECP2 duplications in six patients with complex sex chromosome rearrangements.

ABSTRACT: Duplications of the Xq28 chromosome region resulting in functional disomy are associated with a distinct clinical phenotype characterized by infantile hypotonia, severe developmental delay, progressive neurological impairment, absent speech, and proneness to infections. Increased expression of the dosage-sensitive MECP2 gene is considered responsible for the severe neurological impairments observed in affected individuals. Although cytogenetically visible duplications of Xq28 are well documented in the published literature, recent advances using array comparative genomic hybridization (CGH) led to the detection of an increasing number of microduplications spanning MECP2. In rare cases, duplication results from intrachromosomal rearrangement between the X and Y chromosomes. We report six cases with sex chromosome rearrangements involving duplication of MECP2. Cases 1-4 are unbalanced rearrangements between X and Y, resulting in MECP2 duplication. The additional Xq material was translocated to Yp in three cases (cases 1-3), and to the heterochromatic region of Yq12 in one case (case 4). Cases 5 and 6 were identified by array CGH to have a loss in copy number at Xp and a gain in copy number at Xq28 involving the MECP2 gene. In both cases, fluorescent in situ hybridization (FISH) analysis revealed a recombinant X chromosome containing the duplicated material from Xq28 on Xp, resulting from a maternal pericentric inversion. These cases add to a growing number of MECP2 duplications that have been detected by array CGH, while demonstrating the value of confirmatory chromosome and FISH studies for the localization of the duplicated material and the identification of complex rearrangements.

SUBMITTER: Breman AM

PROVIDER: S-EPMC3060318 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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MECP2 duplications in six patients with complex sex chromosome rearrangements.

Breman Amy M AM Ramocki Melissa B MB Kang Sung-Hae L SH Williams Misti M Freedenberg Debra D Patel Ankita A Bader Patricia I PI Cheung Sau Wai SW

European journal of human genetics : EJHG 20101201 4

Duplications of the Xq28 chromosome region resulting in functional disomy are associated with a distinct clinical phenotype characterized by infantile hypotonia, severe developmental delay, progressive neurological impairment, absent speech, and proneness to infections. Increased expression of the dosage-sensitive MECP2 gene is considered responsible for the severe neurological impairments observed in affected individuals. Although cytogenetically visible duplications of Xq28 are well documented ...[more]

PMID: 21119712

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Project description:The genus Pseudis comprises six frogs of the family Hylidae and only P. tocantins had heteromorphic sex chromosomes detected by classical cytogenetics. In this species, the W chromosome is larger than the Z chromosome and has a large heterochromatic block located between the centromere and the nucleolus organizer region (NOR) in the long arm. This large heterochromatic band is enriched for the PcP190 satellite DNA (satDNA), whereas the Z chromosome bears a smaller C-band adjacent to the centromere in the long arm that is not detected by PcP190 probes. To assess sex chromosome differentiation in the genus Pseudis, we investigated the PcP190 satDNA in P. bolbodactyla, P. cardosoi, P. minuta, and P. paradoxa and in one species of Lysapsus, which is the sister genus of Pseudis. PcP190 sequences were isolated, sequenced, and the diversity of this class of satDNA was analyzed. To evaluate whether sex-related variations in PcP190 satDNA were present, we used in situ hybridization (for P. bolbodactyla, P. paradoxa, P. cardosoi, and P. minuta) and Southern blotting analysis (for all species). We found a low level of sex chromosome heteromorphism in P. bolbodactyla, as a PcP190 cluster was detected in the short arm of one of the homologs of pair 7 exclusively in females. In P. paradoxa, P. minuta, and P. cardosoi, PcP190 satDNA is not sex-related, although a cluster of PcP190 sequences could be recognized in the NOR-bearing chromosomes 7 of P. paradoxa and P. minuta and their homologous chromosome 5 of P. cardosoi. By tracking cytogenetic data in a species tree, we may hypothesize that the positioning of the PcP190 site adjacently to the NOR (as observed in the long arm of the W chromosome of P. tocantins) is a derived condition with respect to the location of the PcP190 site apart from the NOR, in the short arm of the NOR-bearing chromosomes 7 (as present in P. bolbodactyla, P. paradoxa, and P. minuta) or 5 (as present in P. cardosoi) and we discuss about the emergence of PcP190 satDNA as a sex-related trait.

Dataset Information

MECP2 duplications in six patients with complex sex chromosome rearrangements.

Publications

MECP2 duplications in six patients with complex sex chromosome rearrangements.

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