Project 461845

Duchenne muscular dystrophy (DMD) is a devastating inherited disease that causes severe muscle weakness and eventually death normally in the second decade of life. We have made the surprising discovery that the disease protein called dystrophin is expressed at high levels in muscle stem cells where it plays an important role in regulating their ability to regenerate muscle. In this application, we propose a comprehensive set of experiments to define the molecular mechanisms that are involved, characterize the changes in the muscle stem cell regenerative program, and evaluate the effect of a treatment to correct this problem. Together, these experiments will provide important new insights into the role played by muscle stem cells in DMD disease progression. We first will characterize the molecular composition of protein complexes affected by deficiencies in dystrophin. We will downregulate expression of these genes in muscle stem cells to assess their roles. We will examine what happens to these proteins following restoration of muscle stem cell function by potential treatments. Second, we will transplant dystrophin-deficient muscle stem cells and assess their ability to contribute to the stem cell and differentiated myofiber compartments. We will sequence the RNA in single cells to fully define the alterations in differentiation trajectory. We will also perform experiments to examine the effect of potential treatments. Third, we will deeply map alterations in chromosome accessibility and examine gene expression together to determine to what extent the gene expression program is compromised. In conclusion, our proposed experiments will provide important understanding of the defects in the mechanisms regulating the function muscle stem cells in DMD. These experiments will not only clarify molecular defects in DMD satellite cells but will point the way forward to strategies for potential therapeutic intervention.