Nonsyndromic X-linked mental retardation: Mapping of MRX58 to the pericentromeric region

Austrian family with nonsyndromic X-linked mental retardation (MRX) is repo rted in which the obligatory carrier females are normal, and 5 affected mal es have mild to moderate mental retardation. Linkage analysis indicated an X pericentromeric localization, with flanking markers DXS989 and DXS1111 an d a maximum multipoint LOD score of 2.09 (theta = 0) for the 7 cosegregatin g markers DXS1243, CybB, MAOB, DXS988, ALAS2, DXS991, and AR. MRX58 thus ma pped within a 50-cM interval between Xp11.3 and Xq13.1 and overlapped with 23 other MRX families already described. This pericentromeric clustering of MRX families suggests allelism, with a minimum of 2 X-linked mental retard ation (XLMR) genes in this region. (C) 1999 Wiley-Liss, Inc.