DESCRIPTION (provided by applicant): In nature, mechanical signaling plays fundamental roles in processes as diverse as cell volume regulation and the senses of touch and hearing. Recent work in nematodes, flies and mammals has implicated DEG/ENaC and TRP ion channels in osmo- and touch- sensation. Still, little is understood of how these channels function in vivo and how their activities are coordinated to maximize perception. In this proposal I combine experimental approaches uniquely applicable in C. elegans to characterize specific DEG/ENaC and TRP channels that act in well-characterized neurons to mediate mechanosensory perception. Aim I. I have identified a novel TRP-like stretch-sensitive ion channel in body touch neurons that is independent of the MEC-4 DEG/ENaC ion channel that senses gentle touch. Using in vivo calcium imaging, we have also found that touch receptors respond to harsher touch via a mechanism independent of MEC-4. My hypothesis is that the novel stretch-sensitive ion channel mediates calcium transients elicited by harsh touch and is required for normal responses to harsh touch, I will further characterize the stretch-sensitive channel, identify its gene and generate a knockout to test for its role in harsh touch behavioral responses. Aim II. In independent experiments I found that two novel DEG/ENaCs are expressed in the polymodal sensory neurons ASH (known to also require TRP channels OSM-9 and OCR-2 for function). DEG/ENaC deg-1 is co-expressed in these neurons. I have null mutants for all three DEG/ENaCs and I found that at least one of them (others are untested) shows defects in ASH-mediated nose touch response and osmolarity avoidance behavior. I will combine genetic, electrophysiological, behavioral, and imaging approaches to fully characterize the roles of DEG/ENaCs in ASH neuronal function. At completion of this work, I will be well positioned to address whether TRPs and DEG/ENaCs are functionally redundant or whether they "sense" distinct stimuli