PROJECT SUMMARY Cell development and differentiation require lineage specific mechanisms by which cells initiate programs of gene expression. In normal conditions, lineage determination involves activation of genes that are transcriptionally silent by specific transcription factors, chromatin remodelers, coactivators, and other lineage specific molecules. Skeletal muscle differentiation is an excellent model for studying fundamental principles of tissue-specific gene expression and differentiation as there is a significant understanding of mechanisms controlling myogenic-specific gene expression. However, emerging evidence shows a novel category of Copper (Cu)-binding factors that may have a previously unappreciated direct impact in the regulation of myoblast proliferation and differentiation. Cu is an essential trace metal that serves as a catalytic co-factor for a wide variety of enzymatic reactions that play critical roles in life. Cu deficiency and overload leads to pathophysiological conditions including Menkes and Wilson’s diseases, neutropenia, impaired iron absorption, peripheral neuropathy, mitochondrial deficiencies and hypertrophic cardiomyopathy. Therefore, the mechanisms for Cu distribution and usage in different tissues and organs, as well as the consequences due to dysregulated Cu acquisition, are important to human health. Limited information is available regarding Cu and Cu-binding factors and their mechanisms of action in myogenesis and most developmental processes. We propose to elucidate novel mechanisms of gene regulation that drive muscle differentiation and development and that are dependent on copper and Cu-binding transcription factors. We propose integrative studies that combine diverse molecular, biochemical and spectroscopic techniques to characterize novel molecular mechanisms by which Cu-binding factors regulate myogenic differentiation. We propose a novel model where Cu controls myogenesis by activating Cu-TFs that may act synchronously, either by acting on different promoters at the same time or by acting sequentially at different stages of differentiation, or both. Our experiments will identify new components and mechanisms for mammalian Cu-binding factors in the regulation of lineage-specific gene expression. Our studies also will establish a basis for understanding muscular diseases related to aberrant Cu biology using well-characterized mouse models for Menkes and Wilson’s diseases. Understanding the molecular mechanisms that drive lineage specific gene expression dependent on Cu will greatly advance our knowledge of several Cu-related diseases.