Poster abstracts

Poster number 52 submitted by Kristin Heller

rAAV mediated gene therapy for Duchenne Muscular Dystrophy

Kristin N. Heller (Dept of Pediatrics, The Ohio State University & Center for Gene Therapy, Nationwide Childrens Hospital), Louise R. Rodino-Klapac, Chrystal L. Montgomery, Vinod Malik (Dept of Pediatrics, The Ohio State University & Center for Gene Therapy, Nationwide Childrens Hospital), Vinod Malik, Kimberly M. Shontz, K.Reed Clark (Dept of Pediatrics, The Ohio State University & Center for Gene Therapy, Nationwide Childrens Hospital)

Abstract:
Duchenne Muscular Dystrophy (DMD) is a severe muscle disease caused by mutations in the dystrophin gene. Dystrophin helps link integral membrane proteins to the actin cytoskeleton and stabilizes the sarcolemma during muscle activity. We have focused on two unique approaches utilizing adeno-associated virus (AAV) to develop treatments for DMD using the mdx mouse model. Our first strategy involves the retinal isoform of dystrophin (Dp260) which is found in the outer plexiform layer of the retina. Pre-clinical studies in transgenic mice demonstrated the capacity of DP260 to compensate for the missing 427kDa muscle dystrophin. Transgenic expression of Dp260 in mdx/utr (-/-) mice converts their disease course from a severe, lethal muscular dystrophy to a viable, mild myopathic phenotype (Gaedigk R, et al 2006). Our initial studies (focused on optimizing dose/gene expression by intramuscular injection) delivering AAV5.mck.humanDp260 to the mdx mouse have produced sub-therapeutic levels of expression. As an alternative strategy, we are generating two vectors containing an overlapping homologous region of Dp260. These vectors will be delivered to muscle to generate the full-length cassette by homologous recombination. Our second strategy involves the upregulation of α7 integrin, a laminin receptor in skeletal and cardiac muscle that links the extracellular matrix to the actin skeleton, similar to that of the dystrophin-glycoprotein complex. Burkin et al. 2005 showed that transgenic expression of the rat isoform in the mdx/utr -/- DKO mouse promoted satellite cell proliferation and activation, maintenance of muscle integrity, promoted hypertrophy and reduced cardiomyopathy. We have generated rAAV8.human α7 integrin and delivered it to the TA of mdx mice. As mdx mice have endogenous α7 expression, we will be analyzing human α7 expression and other biomarkers of efficacy. Subsequent studies will focus on improvement in muscle physiology and pathology.

References:
Burkin, D. J., G. Q. Wallace, et al. (2005).\

Keywords: rAAV, Duchenne Muscular Dystrophy, gene therapy