Muscle stem cells are important in regenerating muscle tissue. Upon injury, muscle stem cells leave quiescence and differentiate to help regenerate damaged tissue. Pax7 is a marker of muscle stem cells that is conserved across many species. As muscle stem cells differentiate to regenerate tissue, Pax7 expression is downregulated, making this marker useful for studying muscle stem cells in vivo. To visualize this marker, the Mourkioti lab generated a Pax7EGFP mouse model by inserting an enhanced green fluorescent protein (EGFP) cassette in the Pax7 gene, allowing for EGFP expression driven by endogenous promoter and regulatory elements. After visualizing tissue from this mouse model under two-photon microscopy, the Mourkioti lab became the first to successfully visualize muscle stem cells in vivo in live animals. Using these imaging techniques, the lab has also discovered characteristics of muscle stem cells that have never before been reported.
The aims of my project were to develop methods to characterize these newfound properties of muscle stem cells and utilize these methods to characterize the cells under wild type and diseased conditions. The results of this study revealed significant differences among the wild type and diseased phenotypes of the muscle stem cell characteristics, suggesting the novel structures are implicated in the muscle regeneration process. Through this process, I learned so much about muscle physiology, as well as imaging, tissue isolation, genotyping, and other analysis techniques. I also gained valuable insight into how the research process works within the context of this fascinating topic. This project not only provided valuable lessons for me as a student, but will also be rewarding for the muscle research field at large, as studying these structures will provide further insight into the muscle regeneration process and potential therapeutic treatments for muscular dystrophy, a disease, which to date, has no known cure. I am extremely grateful for my experience this summer and wish to thank the Mourkioti lab and College Alumni Society for making it possible!