Screening of subtle copy number changes in Aicardi syndrome patients with a high resolution X chromosome array-CGH.

Aicardi syndrome (AIC) is an uncommon neurodevelopmental disorder affecting almost exclusively females. Chief features include infantile spasms, corpus callosal agenesis, and chorioretinal abnormalities. AIC is a sporadic disorder and hypothesized to be caused by heterozygous mutations in an X-linked gene but up to now without any defined candidate region on the X chromosome. Array based comparative genomic hybridisation (array-CGH) has become the method of choice for the detection of microdeletions and microduplications at high resolution. In this study, for the first time, 18 AIC patients were analyzed with a full coverage X chromosomal BAC arrays at a theoretical resolution of 82 kb. Copy number changes were validated by real-time quantitation (qPCR). No disease associated aberrations were identified. For such conditions as AIC, in which there are no familial cases, additional patients should be studied in order to identify rare cases with submicroscopic abnormalities, and to pursue a positional candidate gene approach.

Genotype-phenotype correlations to aid in the prognosis of individuals with uncommon 20q13.33 subtelomere deletions: a collaborative study on behalf of the 'association des Cytogénéticiens de langue Française'.

The identification of subtelomeric rearrangements as a cause of mental retardation has made a considerable contribution to diagnosing patients with mental retardation. It is remarkable that for certain subtelomeric regions, deletions have hardly ever been reported so far. All the laboratories from the 'Association des Cytogénéticiens de Langue Française' were surveyed for cases where an abnormality of the subtelomere FISH analysis had been ascertained. Among 1511 cases referred owing to unexplained mental retardation, 115 (7.6%) patients showed a clinically significant subtelomeric abnormality. We report the clinical features and the molecular cytogenetic delineation of isolated de novo deletions on 20q13.33 in two cases. Detailed mapping was performed by micro-array CGH in one patient and confirmed by FISH in the two patients. We compare our data with the only three patients reported in the literature. Both patients shared a deleted region of approximately 1.33 Mb including 40 genes, with a 324 kb difference between the two patients. Haploinsufficiency for CHRNA4 and ARFGAP1 may have contributed towards a severe phenotype. In addition, the data in all patients suggest that haploinsufficiency for SOX18 may not cause the hypotrichosis-lymphedema-telangiectasia syndrome, or causes milder disease. Our study gives important information by defining the size of imbalance and better predicting the phenotype. Two clinically distinct phenotypes may be drawn, a mild mental retardation or a more complex and severe phenotype, according to the presence or absence of the CHRNA4 and ARFGAP1 genes respectively.

Characterization of mosaic supernumerary ring chromosomes by array-CGH: segmental aneusomy for proximal 4q in a child with tall stature and obesity.

We report on a 6-year-old girl with developmental delay, tall stature, and obesity. G-banded chromosome analysis revealed mosaicism for one to three small de novo rings in 82% of peripheral lymphocytes. Fluorescence in situ hybridization (FISH) studies and metaphase comparative genomic hybridization (CGH) demonstrated that the rings were derived from 4q10-4q13. A higher resolution investigation was initiated using array-CGH analysis and revealed a gain of 11 adjacent clones spanning a 16 Mb region at 4q11-q13.2 and including the insulin-like growth factor binding protein 7 (IGFBP7) gene. This finding suggests that postnatal overgrowth observed in our patient might be related to a dosage effect of the IGFBP7 gene.