Genetic analysis of nematode cell differentiation

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We will continue our study of genes needed for neuronal differentiation and function using the six touch receptor neurons (TRNs) of the nematode Caenorhabditis elegans. Our previous research identified genes needed for the generation, specification, maintenance, and function of the TRNs. In the last grant period, we 1) identified a “double negative” type of neuronal specification, where an inhibitory transcription factor prevents the expression of a repressor transcription factor; 2) analyzed the effects of tubulin mutations on neuronal outgrowth; 3) used the suppression of mutations affecting a TRN-specific β-tubulin and a TRN-specific α-tubulin acetyltransferase as sensitized backgrounds to identify other genes needed for neuronal outgrowth, finding genes needed for protein degradation and gap-junction function; 4) discovered a novel balancing system needed for proper neurite outgrowth in which the protein degradation machinery is opposed by the HSP90 chaperone system; 5) demonstrated the usefulness of the Million Mutation Project (MMP) strains, a collection of completely sequence strains from the Waterston and Moerman labs, as a tool for gene discovery and identified many new touch mutants; 6) investigated neuronal ensheathment and discovered 14 new genes affecting it, including genes that are important for mechanosensory ECM, adhesion complexes, axon guidance, and axonal transport; and 7) discovered a synthetic ensheathment phenotype that we will exploit in the future. The general goal of the research going forward is to exploit these findings to understand how the differentiation of individual neurons is controlled and how mechanical inputs are sensed and modified. The most important experiments for the future are the elucidation of the molecular structure of the transduction complex using cryo-EM and the discovery and analysis of genes whose loss causes an increase in touch sensitivity, since these will be negative regulators of touch. We also intend to continue analyzing the new touch genes uncovered by our work with the MMMP strains, to revisit the analysis of an important cholesterol-binding component of the touch system (MEC-2), to exploit the discovery of a synthetic genetic relationship affecting TRN ensheathment to discover and characterize additional genes needed for this process. The health relatedness of our work comes from the discovery of new genes and new interactions among genes that are similar in humans and other mammals.