X-LINKED MENTAL-RETARDATION WITH NEONATAL HYPOTONIA IN A FRENCH FAMILY (MRX15) - GENE ASSIGNMENT TO XP11.22-XP21.1

Linkage analysis was performed in a family with non-specific X-linked mental retardation (MRX 15). Hypotonia in infancy was the most remarka ble physical manifestation, The severity of mental deficiency was vari able among the patients, but all of them had poor or absent speech, Si gnificant lod scores at a recombination fraction of zero were detected with the marker loci DXS1126, DXS255, and DXS573 (Zmax = 2.01) and re combination was observed with the two flanking loci DXS164 (Xp21.1) an d DXS988 (Xp11.22), identifying a 17 cM interval. This result suggests a new gene localization in the proximal Xp region, In numerous famili es with non-specific X-linked mental retardation (MRX), the correspond ing gene has been localized to the paracentromeric region in which a l ow recombination rate impairs the precision of mapping. (C) 1996 Wiley -Liss, Inc.