Project Summary Duchenne muscular dystrophy (DMD) is a lethal, progressive, muscle-wasting disease that involves defects in the regenerative capacity of the pathological muscle. In recent years, expanding knowledge of epigenetic mechanisms that influence muscle growth and regeneration has shown that manipulating those mechanisms can be therapeutically useful. The focus of our study is to determine factors that affect the expression of important epigenetic regulators that can influence gene expression in skeletal muscle stem cells, called satellite cells. We will test the novel hypothesis that the protein Klotho (KL) influences myogenesis through the epigenetic regulation of satellite cell activation and differentiation, thereby affecting muscle regeneration. We will investigate this through the following aims: Aim 1. Determine whether KL influences satellite cell activation and differentiation through changes in histone methylation. We will assay whether down-regulation of specific histone demethylases in muscle is a significant component of the mechanism through which KL affects satellite cell proliferation and expression of myogenic regulatory genes. We will also assay for genes that experience changes in histone methylation at H3K27 in muscle cells stimulated with KL. Aim 2. Determine whether manipulating KL expression affects histone methylation in satellite cells from mdx mice, a model for DMD. We will assay for changes in nuclear targeting or expression of specific histone demethylases that result from genetically restoring KL expression to dystrophic, mdx mice. We will also assay for genes experiencing changes in H3K27 methylation, caused by KL transgene expression in mdx mice We anticipate that our findings will establish novel regulatory roles for KL, in which the protein plays an epigenetic regulatory role that affects myogenesis. Furthermore, the results from this study can provide the identity of new therapeutic targets to treat DMD by improving muscle regeneration.