Localization of a gene for X-linked nonspecific mental retardation (MRX24) in Xp22.2-p22.3.

ABSTRACT

Nonspecific X-linked mental retardation (MRX) includes several distinct genetic entities in which mental retardation is not associated with additional distinguishing physical changes. We report linkage data in a Spanish family with MRX, using polymorphic DNA markers distributed over the X chromosome. Two-point linkage analysis demonstrated close linkage between the MRX locus and DXS85 in Xp22.3 with a peak lod score of 2.28 at a theta = 0.00. Analysis of multiple informative meioses suggested a localization of the MRX locus (MRX24) between DXS278 and DXS207. Multipoint linkage analysis resulted in a maximum LOD score of 2.45 at 3 cM proximal to DXS85, and allowed us to reject a localization of the MRX24 gene in all other regions from Xp21-Xqter. These findings localize the MRX24 gene in the chromosomal region Xp22.2-p22.3.