Project Abstract

The applicant for this fellowship is Dr. Joel Chamberlain, a newly appointed non-tenure track faculty member in the Department of Medicine. The goal is to develop a treatment for the autosomal dominant disease myotonic dystrophy (DM1). Myotonic dystrophy is the most common form of muscular dystrophy in adults, and is characterized by a wide range of clinical features including myotonia (muscle hyperexcitability), progressive myopathy, cardiac conduction defects, hyperinsulinemia, and neuropsychiatric impairment. The multi-systemic manifestations of DM1 are attributable to dominant negative effects of a CTG repeat expansion expressed from the myotonic dystrophy protein kinase gene ( DMPK ) as part of the 3' untranslated region (3'-UTR) of the mRNA. The proposal is to develop RNA interference (RNAi) technologies to reduce the DM1 RNA. Initially, short-hairpin RNAs (shRNAs) will be tested to establish conditions for RNAi using shRNAs against lacZ to reduce ubiquitous ß-galactosidase expression in the ROSA26 mouse. The shRNA constructs will be delivered systemically to mice using type 6 adeno-associated viral vectors (AAV6), using technology developed in the Seattle Wellstone Center . Once conditions are established for shRNA systemic delivery, the feasibility of therapeutic RNAi for DM will be tested in the HSA LR mouse model of DM. Dr. Chamberlain will collaborate with the investigator who made this transgenic line, Dr. Charles Thornton, of the Rochester Wellstone Center . Dr. Thornton will provide the HSA LR mouse line and give advice and instruction concerning the characterization of the muscle defects to aid in analyses of the effects of the RNAi therapy. This collaborative effort will reveal whether RNAi can reduce muscle disease caused by expression of an expanded CTG repeat. Importantly, modulating mutant RNA expression should reveal the level of reduction necessary to eliminate muscle pathology. These approaches could result in a body-wide alleviation of dystrophic pathology in the HSA LR mouse and provide clues for the adaptation of these methods to target the human DM1 gene. The success of this approach may lead to a treatment DM1 and would offer a viable approach for treating other dominantly inherited disorders, regardless of whether RNA or protein is pathogenic. This project builds upon the aims of our Center, whose major goals are developing gene therapy for Duchenne muscular dystrophy using AAV vectors, constructing novel expression cassettes for muscle therapy and developing a greater understanding of the molecular basis of DM1. This project will expand our gene therapy efforts to include DM1 and will complement the DM1 research ongoing in Rochester.