Marina Ezcurra, Sunkyung Lee, Peter Swoboda and William R. Schafer. Discrimination of favorable and noxious substances is fundamental for survival. The C.elegans polymodal amphid neuron ASH is the primary neuron for detection of aversive stimuli, and mediates avoidance of water-soluble repellents, high osmolarity and mechanical stimuli such as touch on the nose.
npr-1 encodes a seven transmembrane receptor related to mammalian neuropeptide Y receptors. As shown by de Bono et al, natural variation at a single amino acid residue of NPR-1 determines whether the nematodes exhibit solitary or social feeding. Solitary strains such as N2 bear the NPR-1 215 V receptor, while social strains bear NPR-1 215F. Previous studies have shown that ASH neurons express the NPR-1 receptor, and since social feeding is mediated by the nociceptive neuron ASH, we investigated whether how the
npr-1 genotype might affect ASH sensory responses. Preliminary behavioral experiments performed in the lab show that
npr-1 mutants have higher sensitivity to the repellents glycerol and copper, indicating that the lower NPR-1 activity in 215F might result in higher sensitivity to noxious stimuli. We are carrying out additional behavioral experiments to explore the role of
npr-1 in response to noxious stimuli, and using calcium imaging to investigate the role of
npr-1 in aversive detection in ASH.. In addition to ASH, ASK and ADL also play roles in detection of chemical repellents. ASK is particularly interesting as it mediates both attractive and repulsive behaviors in C. elegans, but it is not yet know how this polymodality is mediated. Several genes expressed in ASK, such as the TRPV channel
osm-9, the soluble cyclic nucleotide gated channel subunit
tax-4, and the GPCR alpha subunits
gpa-3 and
odr-3, are known to be involved in sensory transduction. To test the role of these and other genes in ASK, we have generated a transgenic cameleon line expressed under an ASK specific promoter. This line will be used for calcium imaging to monitor the responses of ASK in mutants of the candidate genes.