Posttranscriptional Gene Regulation by the DMD 3'UTR

Duch enne muscular dystrophy (DMD) and the milder Becker muscular dystrophy (BMD) are both caused by mutations in the DMD gene, which encodes the protein dystrophin. Its regulation is of therapeutic interest as even small changes in expression of functional dystrophin can significantly im pact disease severity in humans . While tissue specific distribution and transcriptional regulation of dystrophin has been characterized, the post transcriptional re gulation of dystrophin is not well understood. 3' UTRs have been shown t o regulate gene exp ression post transcriptionally by altering mRNA stability, localizing mRNA, or directly affecting translation, and the DMD 3' UTR is particularly interesting in that it contains very large, highly conserved regions that are more conserved than the coding region of the gene. In this dissertation, we take advantage of C2C12 mouse muscle cells and the pHRL Renilla reporter construct to dissect the regions of the DMD 3' UTR responsible for regulating expression during myogenesis. We identify highly conserved regions in the 3' UTR that alter mRNA stability and translation of a reporter co nstruct during differentiation. We characterize the DMD 3' UTR variants in a population of 1,222 humans that inclu de DMD and BMD patients. We conclude that if disease causing mutations exist in the DMD 3' UTR they are either extremely rare or cause a disease phenotype when a second mutation is present or affect the efficacy of developing treatments in human patients. Canine models of DMD are important tools for developing treatments for human DMD patients because they better recapitulate the disease phenotype and have an immune system more similar to human s' than other model organisms . In this dissertation, we characterize three canine models of DMD, each containing different classes of mutations that can be used to facilitate preclinical studies directed toward these specific mut ation classes in developing therapeutic approaches. This dissertation adds to the understanding of how dystrophin is regulated, the role the DMD 3' UTR has in dystrophin regulation and pathogenesis of disease, and characterizes additional canine models of DMD.