Dissecting regulation and function of unc-6/Netrin via the generation of cis-regulatory alleles

Project Summary The “Netrin system” has well-studied roles in axon pathfinding and less studied roles in synapse formation in animals from worms to humans. I propose to study the relative contribution of UNC- 6/Netrin derived from multiple neuronal and non-neuronal sources by characterizing the expression and phenotypic effects of cis-regulatory alleles of unc-6 in the nematode Caenorhabditis elegans. We hypothesize that deleting different sections of the cis-regulatory region of unc-6 will result in alleles that lose expression in subsets of neurons and non-neuronal cells, depending on the locations of transcription factor (TF) binding sites that regulate expression in these cells. This work will enable me to identify circuit organizer TFs and their binding sites that regulate unc-6 expression in different cell types and neuronal circuits, and may enable me to distinguish between unc-6-expressing cells required for axon guidance and synapse formation. To achieve these goals, I will pursue two specific aims.1) Generate cis-regulatory alleles of unc-6. 3) Assess the functional consequence of neuron-type specific expression of unc-6. I have identified the neurons expressing unc-6 in WT worms expressing an unc- 6::sl2::gfp::h2b reporter allele generated by CRISPR/Cas9-mediated genome engineering, using the NeuroPAL system to identify individual neurons. I will generate cis-regulatory alleles of unc-6 by using CRISPR/Cas9-mediated genome engineering to delete portions of the unc-6 cis-regulatory region, and assess the which neurons lose expression in each cis-regulatory mutant. To assess the functional consequences of neuron-type specific expression of unc-6, I will use reagents that enable the visualization of neurites and synapses of neurons to assess the circuit-specific effects of unc-6 cis- regulatory alleles on axon pathfinding and synapse formation. Through this work, I will elucidate the regulation of unc-6, as well as its function in axon guidance and synapse formation in various neuronal circuits. Through the pursuit of this project, I will develop skills in rigorous hypothesis-driven research, literature review, written and oral communication of research results, and mentorship that I will need to become an independent neurogenetics researcher. Dr. Hobert's lab and Columbia University are an ideal environment in which to pursue the proposed project and my postdoctoral training. The lab has made many impactful contributions to the neurogenetics field, Dr. Hobert has an excellent training record, and Columbia University is a world-leading research institution at which neuroscience is a major focus.