MOLECULAR STUDIES IN AUTOSOMAL DOMINANT LIMB GIRDLE MUSCULAR DYSTROPHY(LGMD)

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Limb Girdle Muscular Dystrophy is major form of muscular dystrophy affecting both adults and children. The autosomal recessive LGMD have made major progress in understanding these disorders through positional cloning and candidate protein analysis. We propose to take a similar approach to the autosomal dominant form of this disease. Through the previous funding period we have collected 23 autosomal dominant families (LGMD1) comprising 795 individuals. From this group we have previously linked a large family to chromosome 5 (LGMD1a). Recently, we have identified another LGMD1 locus on chromosome 7q36 (LGMD1D). In collaboration with Dr. Carol Westbrook, we have previously established a 2 megabase YAC/BAC contig across the chromosome 5 LGMD1A region and have screened 33 ESTs lying within this region for muscle expression. Currently, we are characterizing and evaluating positive clones for potential mutations. We propose to continue to narrow the LGMD1A minimal candidate region and perform candidate gene analysis using direct selection if needed, to identify the gene defect. Once the LGMD1A gene defect is identified, we will begin mapping the LGMD1D region on chromosome 7q36 to identify this gene defect. Physical mapping for the chromosome 7q36 region will be done in conjunction with Dr. Eric Green, who is responsible for forming contigs on chromosome 7 for the sequencing initiative of the chromosome for Washington University. Three large YAC contigs already span the current LGMD1D region, with two gaps. We will also utilize direct selection for this analysis but we anticipate sequence data to be available to assist in identifying the LGMD1D gene. Once the LGMD1A or LGMD1D gene is identified, we will work with our consultant Dr. Lou Kunkel to evaluate the function of the protein, assess the extent of mutations in small and isolated LGMD cases, and evaluate any genotype/phenotype correlations.