Recurrent 70.8 Mb 4q22.2q32.3 duplication due to ovarian germinal mosaicism.

A mosaicism is defined by the presence of two or more populations of cells with different genotypes in one individual. Chromosomal germinal mosaicism occurs in germ cells before the onset of meiosis. Previously, few studies have described germinal mosaicism. In this study, we report on two siblings who carried identical pure and direct interstitial 4q22.2q32.3 duplication. Procedure investigations included complete clinical description, conventional cytogenetic analysis, fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH) array experiments and microsatellite study searching for parental origin of the duplication. Microarray CGH and further FISH experiments with BAC clones showed the same 70.8 Mb direct duplication, dup(4)(q22.2q32.3). Molecular studies of the 4q duplication were consistent with maternal origin associated with mitotic or meiotic rearrangements. This structural chromosomal aberration was associated in both cases with increased nuchal translucency, growth retardation and dysmorphy. Cardiopathy and lung malformations were only evident in the first case. These clinical manifestations are similar to those previously reported in previous studies involving pure 4q trisomy of the same region, except for thumb and renal abnormalities that were not obvious in the presented cases. The amplified region included genes involved in neurological development (NEUROG2, MAB21L2, PCDH10/18 and GRIA2). The recurrent 4q duplication in these siblings is consistent with a maternal ovarian germinal mosaicism. This is the first description of germinal mosaicism for a large chromosomal duplication and highlights that genetic counselling for apparently de novo chromosome aberration should be undertaken with care.

Cryptic Xp duplication including the SHOX gene in a woman with 46,X, del(X)(q21.31) and premature ovarian failure.

BACKGROUND: Premature ovarian failure (POF) is defined as amenorrhoea for >6 months, occurring before the age of 40, with an FSH serum level in the menopausal range. Although Xq deletions have been known for a long time to be associated with POF, the mechanisms involved in X deletions in order to explain ovarian failure remain unknown. In order to look for potentially cryptic chromosomal imbalance, we used high-resolution genomic analysis to characterize X chromosome deletions associated with POF. METHODS: Three patients with POF presenting terminal Xq deletions detected by conventional cytogenetics were included in the study. Genome wide microarray comparative genomic hybridization (CGH) at a resolution of 1 Mb and fluorescence in situ hybridization (FISH) was performed. RESULTS: Microarray CGH and FISH studies characterized the three deletions as del(X)(q21.2), del(X)(q21.31) and del(X)(q22.33). Microarray CGH showed that the del(X)(q21.31) was also associated with a Xpter duplication including the SHOX gene. In these patients with POF, deletions or duplications of autosomes have been excluded. CONCLUSION: This study is the first one using microarray in patients with POF. It demonstrates that putative X chromosome deletions can be associated with other chromosomal imbalances such as duplications, and therefore illustrates the use of microarray CGH to screen chromosomal abnormalities in patients with POF.