Gene redundancies in the dystrophin-associated protein complex

Disruption of the dystrophin-associated protein (DAP) complex is a common finding in several forms of muscular dystrophies. Sequence analysis of the genes encoding DAP have revealed that they often share sequence similarities with other genes encoding additional components of the same complex. In the last few years we and other groups, using these gene sequences as probes, identified novel transcripts grouped into the following gene families: 1) dystrobrevins from dystrophin; 2) delta-sarcoglycan from gamma-sarcoglycan; 3) gamma-syntrophins from alpha/beta-syntrophins; 4) epsilon sarcoglycan from alpha-sarcoglycan. In addition, we identified novel genes encoding homologues of the calpain gene, which is mutated in limb- girdle muscular dystrophy 2A. Among these novel transcripts, we demonstrated the delta-sarcoglycan involvement in human as weli as in animal model diseases (BIO 14.6 hamster). For all the others, further search for families linked to these loci or gene knockout experiments are required to interpret correctly their actual specific function.