Letter to the Editor: Mapping of the loci for mental retardation syndromes in the distal Xq

Abstract

We constructed a deletion map of the distal Xq, using previously reported male interstitial deletions within Xq27-Xqter. The map consists of 12 large interstitial deletions, ranging from 100-9,000 kb. All but one fall within Xq27{r_arrow}proximal Xq28, forming a {open_quotes}deletion contig{close_quotes} between DXS51 (Xq26.3) and DXS455 (proximal 1/3 of Xq28). The region contains only a few genes, most of which are implicated in mental retardation (MR). Some of the deletions span more than one MR locus. The phenotype of affected males is typically limited to mental impairment unless the F9, IDS, or F8 gene is included in the deletion. In the distal 2/3 of Xq28 only one large deletion of about 300 kb has been reported, and those remaining are small, intragenic deletions of <1 kb. This indicates that most deletions in this region are male-lethal. 39 refs., 1 fig.