UC San Diego

The spinal cord represents the final stage of generating motor behaviors, where descending commands or sensory inputs must be transformed into behaviorally-relevant pattern of motor neuron activity. Networks along the rostrocaudal axis of the spinal cord regulate diverse motor behaviors such as respiration, forelimb, trunk, and hindlimb movements, mediated by stringent innervations of motor neurons to muscle fibers. However, how the network properties of the central nervous system enable these diverse motor outputs remains elusive. To address this question, we set out to investigate whether a cardinal class of spinal cord neurons are diversified in diffeernt spinal segment.

This dissertation describes a series of original work that aims to elucidate the diversification of spinal neurons in different segments of the spinal cord. The first chapter is an introduction into the developmental processes of spinal cord development.

The second chapter proceeds from this review to explore whether spinal neurons are further diversified in different spinal segments to underlie distinct network operation and motor outputs. In particular, we studied V2a interneurons as a model to address this question. Using viral tracing and RNA-sequencing, we uncovered how V2a interneurons exhibit distinct anatomical connectivity schemes and distinct genetic signatures in forelimb regulating- and hidnlimb regulating-segments of the spinal cord. It is my hope that our studies establish a framework of how diversification of spinal neurons along the rostrocaudal axis underlies distinct intrinsic network properties in different spinal segments that ultimately contribute to diverse motor outputs that the spinal cord regulates.