LOCALIZATION OF A GENE FOR X-LINKED NONSPECIFIC MENTAL-RETARDATION (MRX24) IN XP22.2P22.3

Nonspecific X-linked mental retardation (MRX) includes several distinc t 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 o ver the X chromosome. Two-point linkage analysis demonstrated close li nkage 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 su ggested a localization of the MRX locus (MRX24) between DXS278 and DXS 207. 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. (C) 1 995 Wiley-Liss, Inc.