PROJECT SUMMARY This proposal describes a 5-year training program for the development of a clinician-scientist investigator in stem cell biology and large-scale genomics. The primary goal of this application is to serve as a basis for training Rick Nelson, MD, PhD in the critical skills necessary to become an independent scientific investigator studying inner ear hair cell degeneration. Dr. Nelson is currently an Assistant Professor at Indiana University School of Medicine where he will expand his scientific skills through course work, university resources and mentoring. Hearing loss and vestibular dysfunction affect millions of people worldwide and the common pathophysiologic finding is loss of the mechanosensitive hair cells. Eri Hashino, PhD will serve as Dr. Nelson's primary mentor and train him in stem cell biology. Dr. Hashino is an international leader is stem cell biology and has trained numerous postdoctoral fellows and clinician-scientists. Richard JH Smith, MD at University of Iowa will serve as Dr. Nelson's co-mentor and train him in large-scale genomic approaches and bioinformatics. Dr. Smith is an internationally renowned clinician-scientist and leader in human genetics. Dr. Nelson will also enroll in the Independent Investigator Incubator (I3) program at Indiana University, which provides guidance in scientific and career development. D. Wade Clapp, MD is an internationally recognized clinician-scientist who will serve as a career advisor for Dr. Nelson. His advisory committee will provide broad expertise that spans research planning and career development. In this proposal, the PI will establish a novel model of hair cell degeneration using mouse stem cell-derived 3D cultures containing mechanosensitive hair cells. CRISPR gene editing technology will be used to disrupt the Tmprss3 gene, which is known to cause hair cell degeneration in mice and humans. Next, the PI will use proteomic approaches to establish the protein interactome of the Tmprss3 serine protease in hair cells. Finally, single-cell RNA sequencing (RNA-seq) technology will be used to study global alterations in gene expression that lead to hair cell degeneration. The scientific environment, support from the Department of Otolaryngology at Indiana University and the internationally renowned mentors together make this project feasible. These factors maximize the potential to attain Dr. Nelson's long-term career goal of becoming an independent clinician-investigator and discovering new targets to prevent or delay hair cell degeneration.