LOCALIZATION OF THE AUTOSOMAL RECESSIVE M USCULAR-DYSTROPHY GENE TO CHROMOSOME 2P13 IN AN ISOLATE FROM A HIGHLAND REGION OF DAGESTAN

A unique inbred Avar family from an isolate of the Dagestan highland w as studied. Unusual phenotypic expression of autosomal recessive progr essive muscular dystrophy was revealed in 12 members of this family fr om three generations. Limb-girdle (proximal) muscular dystrophy (LGMD) was detected in nine patients, while the other three patients display ed typical distal myopathy (DM). Genetic linkage analysis with several candidate loci determining various forms of muscular dystrophy allowe d a gene for this polymorphic syndrome to be assigned to chromosome 2p 13. In spite of the difference in clinical manifestation, all patient s appeared to be homozygous for a unique haplotype. This implies the f ounder effect and proves the same genetic basis of LGMD and DM in the family. Recombination analysis showed that the centromeric and telomer ic ends of the gene region are marked with D2S2111 and D2S327, respect ively (genetic distance < 1 cM). This region is overlapped by two larg er regions in which the genes for LGMD type 2B (LGMD2B) and Miyoshi my opathy were recently mapped. Complex analysis of clinical and genetic data indicated that LGMD2B, Miyoshi myopathy, and the revealed polymor phic syndrome may represent allelic variants of 2p13-linked autosomal recessive muscular dystrophy.