Deletion of VCX-A due to NAHR plays a major role in the occurrence of mental retardation in patients with X-linked ichthyosis

Hum Mol Genet. 2005 Jul 1;14(13):1795-803. doi: 10.1093/hmg/ddi186. Epub 2005 May 11.


X-linked ichthyosis (XLI) is often associated with a recurrent microdeletion at Xp22.31 due to non-allelic homologous recombination between the CRI-S232 low-copy repeat regions flanking the STS gene. The clinical features of these patients may include mental retardation (MR) and the VCX-A gene has been proposed as the candidate MR gene. Analysis of DNA from four XLI patients with MR by array-comparative genomic hybridization (array-CGH) on a 150 kb resolution X chromosome-specific array revealed a 1.5 Mb interstitial microdeletion with breakpoints in the CRI-S232 repeat sequences, each of which harbors a VCX gene. We demonstrate that the recombination sites in all four cases are situated in the 1 kb repeat unit 2 region present at the 3' ends of the VCX-A and VCX-B genes thereby deleting VCX-A and VCX-B1 but not VCX-B and VCX-C. Array-CGH with DNA of an XLI patient with MR and an inherited t(X;Y)(p22.31;q11.2) showed an Xpter deletion of 8.0 Mb resulting in the deletion of all four VCX genes and duplication of both VCY homologs. These data confirm the role of VCX-A in the occurrence of MR in XLI patients. Moreover, we propose a VCX/Y teamwork-dependent mechanism for the incidence of mental impairment in XLI patients.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromosomes, Human, X / genetics*
  • Chromosomes, Human, Y / genetics
  • Gene Deletion*
  • Humans
  • Ichthyosis, X-Linked / genetics*
  • Intellectual Disability / genetics*
  • Male
  • Nuclear Proteins / genetics
  • Recombination, Genetic / genetics*
  • Translocation, Genetic / genetics


  • Nuclear Proteins
  • VCX protein, human
  • VCY protein, human