3p deletion syndrome is a rare disorder involving developmental delay, dysmorphic physical features, and growth retardation. Molecular mapping of several cases in the literature have identified a critical region on chromosome 3p26. We present a child patient with characteristic features of 3p deletion syndrome and a de novo unbalanced translocation involving chromosomes 3 and 13. Fine mapping of this rearrangement using fluorescence in situ hybridization (FISH) and array-based comparative genomic hybridization (aCGH) revealed an unbalanced abnormality including a 4.5 Mb terminal deletion of chromosome 3p, telomeric to ITPR1 on 3p26.2, which was not previously identified with routine cytogenetic analysis. In addition, these investigations confirmed and refined the boundaries of a 26.5 Mb deletion of chromosome 13. This study confirms the minimal candidate region for 3p deletion syndrome, provides further evidence implicating haploinsufficiency of CNTN4 in the disorder, and demonstrates the utility of high-resolution investigations of rare chromosomal rearrangements.

A nonsense mutation was identified in the first family with HSS of Latin American ethnical background. Our data provide molecular genetic evidence for a 3rd stop mutation in exon 2 of the CDSN gene being responsible for HSS. All to date known nonsense mutations responsible 3 for HSS are clustered in a region of 40 amino acids which is in accordance with a dominant negative effect conferred by aggregates of truncated CDSN proteins.

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