The development of therapeutics for muscle wasting disease demands a better understanding of the cellular pathways that regulate muscle stem cell proliferation and differentiation. Therefore, the identification of novel epigenetic pathways that drive muscle stem cell function has great clinical implications for treatment of diseases such as Duchenne Muscular Dystrophy. Our preliminary data suggest that RE1-Silencing Transcription Factor (REST) plays a key role in regulating muscle stem cell function. REST is known to be a major transcriptional repressor, and represses neuronal genes in non-neuronal tissue by recruiting chromatin modifiers. However, our data show that REST also regulates muscle-specific genes by recruiting muscle-specific transcription factors, which determine muscle cell lineage commitment. In light of this, my project aims to delineate the role of REST protein complexes in muscle cells by first identifying which proteins REST associates with. This will be accomplished by fusing REST to a biotin ligase that will promiscuously biotinylate any protein that associates with REST. A biotin pull down will be performed, and the tagged proteins will be identified via LC/MS/MS mass spectrometry. Following this, high-priority candidate REST interactors will be selected. Gain and loss of function experiments will then be performed, including CRISPR/Cas9-mediated gene knockout and siRNA knockdown. We will assess the role of these REST-interactors on muscle stem cell proliferation and homing by cell transplantation into irradiated NOD-SCID mice, followed by bioluminescent imaging. These experiments will yield results that can be used to piece together the role of REST in the epigenetics of myogenic differentiation.