Characterization of WT1-expressing interneurons and investigation of their role in locomotion

Abstract

Mammalian locomotion is controlled by a specialized neural network, known as the locomotor central pattern generator (CPG), which is situated entirely within the ventral spinal cord. A number of studies completed over the past two decades have indicated that this neural network is comprised of interneurons that can be categorized into populations based on the combinatorial expression of transcription factors throughout development. This thesis focuses on one such genetically defined population, the WT1-expressing cells, which are located in the ventral spinal cord postnatally. Here I characterize these neurons and investigate their role during fictive locomotion in the neonatal mouse spinal cord. In the first part of the thesis, I describe an upright in vitro spinal cord preparation that we developed which enables recordings to be made from WT1-expressing interneurons while keeping the core components of the locomotor CPG intact. In the second part of the thesis, I use this preparation to record from WT1+ cells and demonstrate that they are an inhibitory interneuronal population, which primarily project commissural axons, and are involved in regulating left-right alternation during fictive locomotion. In the final part of the thesis, I use a viral tracing approach to identify upstream synaptic partners of these neurons in order to provide insight into the network structure of the locomotor CPG. Taken together the data presented in this thesis provides key information regarding the development and function of this neural network.