PROJECT SUMMARY/ABSTRACT Emerging technologies, such as cell-based repair strategies, offer new promise for some of the most devastating medical conditions that currently lack treatments. However, to harness the full therapeutic potential of stem cells, it will be necessary to understand how to direct their differentiation to appropriate cell phenotypes and ensure that their phenotype and function persist after transplantation into a pathologic environment. These gaps in knowledge are the cornerstones of my long-term training plan. My research vision is focused on creating human induced pluripotent stem cell (iPSC)-based tissues that enable the study of human central nervous circuits to accelerate the identification of therapeutic targets for neural circuit restoration in the setting of disease and injury. To do so, I will build upon my doctoral studies and publications using pre-clinical spinal cord injury as a testbed for my hypotheses regarding the therapeutic potential of transplanted human iPSC-derived neural tissue. Spinal cord injury (SCI) is a devastating condition, resulting in irreversible, life-changing disabilities. However, pre- clinical studies and clinical reports have demonstrated a remarkable innate neuroplastic potential of the injured central nervous system. Key to this neuroplasticity are spinal interneurons. Spinal interneurons are recognized as having potential for serving as synaptic relays across sites of spinal trauma and altering their activity to facilitate functional plasticity. The primary goal of this proposal is to determine if specific interneuronal sub-types generated from human stem cells can be used to restore functional connectivity in the injured nervous system. Building upon my previous work, I will use cutting edge technology to generate and phenotype human excitatory spinal interneurons to investigate formation of functional neural networks in vitro (Aim 1) and assess their phenotypic persistence and functional changes after transplantation into the intact and injured spinal cord (Aim 2). I will transplant human iPSC-derived neurons into a transgenic mouse model (excitatory and inhibitory V2a- DREADD) with SCI, which will enable functional interrogation of host-donor-host connections with the use of designer drugs. Successful completion of this project will reveal the first insight into the therapeutic potential of engineered human interneurons for neural repair and will provide the preliminary data I will use in future career development grant applications. Completing this work at Gladstone Institutes will enable me to develop an impeccable professional network to learn cellular engineering, master single cell RNA techniques for characterization, and build novel analytical workflows to visualize multi-dimensional data. More importantly, it will give me the opportunity to take advantage of resources at Gladstone and UCSF to strengthen my scientific communication skills and pursue professional development op...