A complex submicroscopic chromosomal imbalance in 19p13.11 with one microduplication and two microtriplications

Isolated bladder exstrophy associated with a de novo 0.9 Mb microduplication on chromosome 19p13.12

BACKGROUND

The exstrophy-epispadias complex (BEEC) is a urogenital birth defect of varying severity. The causes of the BEEC are likely to be heterogeneous, with individual environmental or genetic risk factors still being largely unknown. In this study, we aimed to identify de novo causative copy number variations (CNVs) that contribute to the BEEC.

METHODS

Array-based molecular karyotyping was performed to screen 110 individuals with BEEC. Promising CNVs were tested for de novo occurrence by investigating parental DNAs. Genes located in regions of rearrangements were prioritized through expression analysis in mice to be sequenced in the complete cohort, to identify high-penetrance mutations involving small sequence changes.

RESULTS

A de novo 0.9 Mb microduplication involving chromosomal region 19p13.12 was identified in a single patient. This region harbors 20 validated RefSeq genes, and in situ hybridization data showed specific expression of the Wiz gene in regions surrounding the cloaca and the rectum between GD 9.5 and 13.5. Sanger sequencing of the complete cohort did not reveal any pathogenic alterations affecting the coding region of WIZ.

CONCLUSIONS

The present study suggests chromosomal region 19p13.12 as possibly involved in the development of CBE, but further studies are needed to prove a causal relation. The spatiotemporal expression patterns determined for the genes encompassed suggest a role for Wiz in the development of the phenotype. Our mutation screening, however, could not confirm that WIZ mutations are a frequent cause of CBE, although rare mutations might be detectable in larger patient samples. 19p13.12, microduplication, bladder exstrophy-epispadias complex, array-based molecular karyotyping, in situ hybridization analysis, copy number variations, WIZ gene.

Split hand-foot malformation, tetralogy of Fallot, mental retardation and a 1 Mb 19p deletion-evidence for further heterogeneity?

Congenital limb malformations are the second most common birth defects observed in infants. Split hand foot malformation (SHFM), also known as central ray deficiency, ectrodactyly and cleft hand/foot, occurs isolated or in combination with other malformations. We report on a male patient with SHFM, tetralogy of Fallot and a clinical phenotype suggestive of Angelman syndrome. Using array based genome analysis (3K BACs and 500K SNPs), we identified a de novo deletion of chromosome 19p13.11, confirmed by Fluorescent In Situ Hybridization analysis. The deletion is 0.99 Mb in size and contains 28 genes. The proximal breakpoint of the deletion is in EPS15L1, which may be involved in vertebrate limb development. Subsequent screening of 21 syndromic and nonsyndromic SHFM patients (TP73L mutation negative) for rearrangements using Multiplex Ligation-dependent Probe Amplification did not detect other deletions or duplications in chromosome 19. These findings suggest that our patient may have a new contiguous gene syndrome and indicates that SHFM is genetically more heterogeneous than currently known.