ABSTRACT This application is for a Mentored Clinical Scientist Research Career Development Award (K08) for Dr. Lauren Katz. She is currently conducting research on craniofacial skeletal muscle and has observed that this muscle type has a unique regenerative program compared to muscles of the limb and trunk. This K08 will enhance Dr. Katz's ability to 1) become an expert in craniofacial muscle stem cells and regeneration, 2) conduct basic science research at the highest level in a tissue rarely studied, 3) acquire cutting-edge skills in stem cell techniques including single-cell RNA sequencing (scRNA-seq) and ex vivo cell transplantation, 4) gain skills in proposal development, manuscript preparation, and data presentation, and 5) develop a high-quality independent research program that will allow for collaborative opportunities with scientists and clinicians from across disciplines. To achieve these goals, Dr. Katz has devised a clear and focused training plan and has identified individuals who are experts in the aforementioned disciplines. Her multidisciplinary mentoring team consists of: Drs. James White (basic scientist, skeletal muscle regeneration and stem cells), William Maixner (clinician-scientist, oral and craniofacial research), Shannon Wallet (basic scientist, oral and craniofacial research), Elisabeth Barton (basic scientist, skeletal muscle regeneration), Kevin Byrd (clinician-scientist, oral stem cells), Lyndon Cooper (clinician-scientist, oral stem cells), Eric Everett (basic scientist, oral biology), Jimena Giudice (basic scientist, skeletal muscle research), and Simon Gregory (basic scientist, scRNA-seq). There exists a clinical need to rebuild functional craniofacial muscle in patients suffering from certain diseases (muscular dystrophy, hemifacial microsomia), facial trauma, and tumor resections. The lack of a comprehensive investigation of the craniofacial musculature and its stem population has resulted in a poor understanding of the regenerative capacity of this tissue when faced with disease or trauma. Our current knowledge of skeletal muscles and their stem cell populations comes from the limb muscles; however, it is known that distinct differences in embryological origin exist between muscles of the limb and those of the craniofacial region. Therefore, the objectives of this study are to use injury models to elucidate the in vivo regenerative capacity of craniofacial skeletal muscle and to perform deep phenotyping on isolated craniofacial satellite cells to identify molecular targets specific to craniofacial muscle regeneration. Regenerative capacity will be assessed using in vivo models of muscle regeneration and in vitro cellular function assays (Aim 1). scRNA-seq and ex vivo stem cell transplantation will be utilized to identify craniofacial muscle-specific regulators of myogenesis (Aim 2) and identified targets will be investigated using lentiviral vectors and knockout models (Aim 3). Together, the K08 training and me...