Mechanisms of Skeletal Morphogenesis During Digit Tip Regeneration

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Project Summary My long-term career goal is to become a successful independent investigator in the field of musculoskeletal regenerative medicine, developing therapeutics to promote the regeneration of complex tissues after injury or disease. The objective of this proposal is to help me transition to independence by providing me with critical scientific skills to investigate the cellular and molecular mechanisms of murine digit tip regeneration versus fibrotic scarring. To reach this objective, a thorough training plan has been established, including research aims and tailored training activities. The proposed research project will seek to develop a novel mouse model and an induced pluripotent stem cell (iPSC) in vitro culture system in order to dissect the functional role of regulatory genes involved in embryonic limb development and morphogenesis, including Hox genes. The central hypothesis of the proposal is that HoxA cluster genes, and specifically Hoxa13, are required during digit regeneration to coordinate osteogenic differentiation, outgrowth, and patterning via Eph/ephrin and bone morphogenetic protein (BMP) signaling. We will investigate this hypothesis by conditionally deleting HoxA cluster genes from osteoblast lineage cells in transgenic mice in Aim 1 and by modulating Hoxa13 gene expression in iPSCs in vitro using a lentiviral-mediated approach in Aims 2 and 3a. Finally, we will evaluate the therapeutic potential of Hoxa13-expressing cells delivered to the wound site of non-regenerative digits in Aim 3b. The project outlined in this application combines basic science with a clinically relevant in vivo platform and cutting-edge transcriptomic and bioinformatic technologies to query the gene regulatory networks and signaling pathways that lead to regeneration versus scarring after musculoskeletal injury. This proposal also includes a comprehensive series of educational activities that will prepare me for my independent research faculty position. The world-class institutional environment at Washington University in St. Louis provides a multitude of resources to ensure the successful completion of the proposed work, as well as ample opportunities for career development. Finally, the assembled Scientific and Career Advisory Committee, along with new mentoring relationships that I am fostering in the developmental and regenerative biology communities, will monitor research progress, provide constructive feedback, and advocate for my professional development as I begin my independent research career.