Regional localization of a gene for nonspecific XLMR to Xp11.3-p11.23 (MRX51) and tentative localization of an MRX gene to Xq23-q26.1

Two families with nonspecific X-linked mental retardation (MRX) are present ed. In the first family, MRX51, three male patients showed mild to borderli ne mental retardation. Multipoint linkage analysis yielded a maximal LOD sc ore of 2.10 between markers DXS8012 and DXS1003, localizing the MRX51 gene at Xp11.3-p11.23. In the second family, XLMR7, three men showed moderate me ntal retardation (MR), and one possible female carrier had mild MR. Multipo int linkage analysis yielded an LOD score of 1.80 between markers DXS8063 a nd DXS1047, situating the disease gene at Xq23-q26.1. When the analysis was performed considering the affected female to be an expressing heterozygote carrier of the disease mutation, a maximal LOD score of 2.10 was found in the same region. Am. J. Med. Genet. 85:283-287, 1999. (C) 1999 Wiley-Liss, Inc.