Regional localization of a nonspecific X-linked mental retardation gene (MRX59) to Xp21.2-p22.2

Linkage analysis was performed on a four-generation family with nonspecific mental retardation (MRX59). The five affected males, ranging in age from 2 years to 52 years, have a normal facial appearance and mild to severe ment al impairment. Four obligate carriers are physically normal and not retarde d. A maximum LOD score of 2.41 at theta = 0.00 was observed with the micros atellite markers, DMD45 in Xp21.2, DXS989 in Xp22.1, and DXS207 in Xp22.2. Recombinations were detected within the dystrophin gene (DMD) in one of the affected males and between DXS207 and DXS987 in Xp22.2 in one of the carri ers, These recombinants define the proximal and distal boundaries of a cand idate gene region. Genetic localization of this familial condition made pre natal diagnosis informative for one of the obligate carriers, Am. J. Med. G enet. 85:266-270, 1999 (C) 1999 Wiley-Liss, Inc.