Genetic localisation of MRX27 to Xq24-26 defines another discrete gene for non-specific X-linked mental retardation.

A large family with non-specific X-linked mental retardation (MRX) was first described in 1991 [Glass et al., 1991], with a suggestion of linkage to Xq26-27. The maximum lod score was 1.60 (theta = 0.10) with the F9 locus. The localisation of this MRX gene has now been established by linkage to microsatellite markers. Peak pairwise lod scores of 4.02 and 4.01 (theta = 0.00) were attained at the DXS1114 and DXS994 loci respectively. This MRX gene is now designated MRX27 and is localised to Xq24-26 by recombination events detected by DXS424 and DXS102. This regional localisation spans 26.2 cM on the genetic background map and defines another distinct MRX interval by linkage to a specific region of the X chromosome.