The dystrophin associated protein complex is a multimeric protein complex found in many different tissues, including muscle. Genetic defects in the dystrophin associated protein complex lead to muscular dystrophy in humans. The dystrophin associated protein complex plays several different roles in the plasma membrane. However, given that large percentages of patients with muscular dystrophy remain to be molecularly diagnosed, there is a possibility that some of the components may not have been identified yet. Furthermore, we do not know how the dystrophin complex is exactly assembled, processed and transported to the plasma membrane. The nematode C. elegans is an established genetic model organism, and possesses most of components of the dystrophin associated protein complex. In C. elegans, mutations in components of the dystrophin associated protein complex cause a unique locomotory phenotype that is not observed in any other class of uncoordinated or hyperactive mutants, and lead to muscle degeneration under certain conditions. We previously designed a genetic screen that identifies specifically mutants exhibiting the same locomotory phenotype as the dystrophin mutant, and identified several genes encoding known components of the dystrophin complex. Additionally, we identified a novel gene that encodes an acetylcholine/choline transporter. In a modified genetic screen we now have identified at least two additional novel genes. We have cloned one of the genes and are continuing to characterize the gene. We propose to expand the genetic screen to completion and identify mutants that exhibit the same locomotory phenotype as the dystrophin mutant. We will determine whether these mutants represent known genes or novel genes of the dystrophin associated complex. We will clone the novel genes by a combination of genetic mapping and transformation rescue. These novel genes may be unidentified components of the dystrophin complex, regulate assembly or trafficking of the complex, and mediate cellular functions. We will characterize the molecular functions of these novel genes using genetic, molecular and cell biology techniques. We will also identify and study the functional mammalian homologues. These findings will improve our understanding of the pathogenesis mechanism of muscular dystrophy in humans and may help to devise new therapeutic strategies.
