The muscular dystrophies affect certain muscles more than others, even though affected genes are expressed uniformly in skeletal muscles. It is unclear why this occurs. Recent discoveries in the genetics and pathophysiology of the limb girdle muscular dystrophies present a new opportunity to examine this question. It is likely that dysferlin forms part of a large protein complex that modulates the process of membrane repair and resealing in muscle fibers. Certain mutations in the gene encoding dysferlin are known to cause multiple phenotypes affecting different muscles. The overall hypothesis of this project is that differences between skeletal muscle types at the molecular level are related to their varying responses to genetic insults; these differences will be examined in normal and diseased muscle tissue. Particular attention will be devoted to genes that are involved in membrane repair, but others will be explored as well. Aim 1 of the project is to analyze the histological features and gene expression profiles of 12 different human skeletal muscles obtained at post mortem examination from each of six control subjects, and to correlate these profiles with data previously obtained from six different mouse skeletal muscles. The hypothesis is that different skeletal muscles in normal human and murine subjects can be classified according to gene expression profiles, leading to interspecies correlations of specific muscle types. Aim 2 is to compare the gene expression profiles of muscles obtained from subjects with two forms of dysferlin deficiency (LGMD 2B and MM), as well as subjects with Duchenne Muscular Dystrophy and normal controls, and to correlate the results with existing data on the mouse models of dysferlinopathy and dystrophinopathy. We expect that levels of expression of modifying genes in various forms of dysferlin deficiency differ, resulting in distinct gene expression profiles of muscle specimens obtained from affected individuals. Aim 3 is to further characterize differentially expressed genes identified in Aims 1 and 2, including analyses of the subcellular localization of their protein products and interactions with proteins involved in muscular dystrophy. We expect that the protein products of some of the selected genes will localize to the sarcolemma or subsarcolemma, and a subset of these will associate with dysferlin or dystrophin. More knowledge about the genes and proteins involved in the muscular dystrophies will assist in the identification of targets for pharmacologic therapy of the muscular dystrophies.
