[
International Worm Meeting,
2019]
The C. elegans egg-laying circuit is intensively studied as a model for understanding neural circuit function, yet some features of this circuit remain unexplained. For example, eggs in the uterus promote circuit activity and egg laying is coordinated with locomotion behavior, but the mechanisms underlying these phenomena are not understood. These gaps suggest that there may be additional components of the egg-laying circuit that have yet to be identified. By examining animals carrying various GFP reporter constructs, we discovered that the two PVP neurons produce previously undescribed structures that lie right on top of the egg-laying circuit. While PVP is born and extends its process along the ventral cord during embryogenesis, we discovered that at the late L4 stage, the PVP process develops a branch at the vulva that extends dorsally from the ventral cord and ends in a winged cilium lying over the surface of the uterus. The branch and cilium develop at the same time that the cells making up the rest of the egg-laying circuit differentiate. In the male, PVPs do not appear to form branches or cilia, suggesting that the PVP cilia sense a hermaphrodite-specific stimulus. We used a histamine-gated chloride channel to specifically inactivate the PVPs and this resulted in changes to locomotion behavior, including reduced forward speed and increase reversals. My results confirm that PVPs help to regulate roaming and dwelling behaviors, as had been suggested by earlier studies (Flavell et al. 2013, Cell 154 1023-1035). We have not seen an effect of inhibiting PVP on egg-laying behavior. We hypothesize the PVP cilia sense a hermaphrodite-specific behavior, likely egg laying, and then signal to the locomotion circuit to alter locomotion. Future experiments include expressing a fluorescent calcium reporter in PVP to observe when the cell is active and further analysis of the behavioral effects of activating or inactivating PVP.