Miyoshi Myopathy (Limb Girdle Muscular Dystrophy type 2B (LGMD2B)) is an inherited autosomal recessive form of muscular dystrophy that is caused by mutations in the dysferlin gene. The mechanisms by which loss of dysferlin causes progressive muscle degeneration are not well understood. As a result, there are currently no treatments for this disease. In mammals, dysferlin mutant muscles exhibit a defect in damage-induced muscle membrane fusion, while in C. elegans, mutations in the dysferlin homolog
fer-1 cause sterility due to defects in membrane fusion during spermatogenesis. Previous in situ hybridization studies have suggested that
fer-1 expression in C. elegans is restricted to the germline and it is unclear if
fer-1 is expressed more widely or if similar muscle membrane fusion defects occur in worms. To address these questions, we have analyzed
fer-1 expression patterns.
fer-1 exhibits clear somatic expression, since we were able to amplify
fer-1 transcripts using RT-PCR from RNA derived from L1 stage animals, which contain no germ line. To examine if
fer-1 is expressed in muscle, we cultured cells from animals expressing the muscle specific P<sub>
myo-3</sub>::dsRed2 transgene and isolated red fluorescent cells using FACS sorting.
fer-1 transcript was present in the RNA from dsRed-positive cells, showing that
fer-1 is expressed in muscle. Currently we are performing microarray profiling of
fer-1 mutants to identify transcriptional changes which define the dysferlin mutant state. In the future, we will construct GFP transgenes expressing
fer-1 transcriptional targets (dysferlin ‘beacons) in the
fer-1 mutant background. Using these dysferlin molecular ‘beacons and the high-throughput screening capability of the COPAS Biosort (‘Wormsorter), we will screen for RNAi induced genes knockdowns or drugs that can suppress the expression of dysferlin ‘beacons in
fer-1 mutants. These genes or drugs will then be tested for functional improvement of the dystrophic state using an established mouse model of LGMD2B. Our studies show that the homology between mammalian dysferlin and C. elegans
fer-1 are greater than previously appreciated and establish C. elegans as an in vivo screening tool for the identification of treatments for LGMD2B.