rpm-1 and syd-2 regulate posterior dorsal cord termination. (A) Schematic of the posterior GABAergic motor neurons (VD12, DD6, and VD13) (inspired by Worm Atlas). The posterior tip of the dorsal cord was visualized using P
GFP (juIs76) and epifluorescent microscopy. Highlighted are the posterior termination sites of DD6 (asterisk) and VD13 (arrow). The VD13 process terminates extension above the VD13 cell body (arrowhead). In rpm-1 mutants, posterior termination is impaired and the dorsal cord is overextended. In rpm-1; syd-2 double mutants, failed extension (undergrowth) and termination defects (overextension) were observed. Scale bar, 10 μm. (B) Quantitation of posterior termination defects for the indicated genotypes. For each genotype, the mean is shown from five or more counts (at least 20 worms/count). Analysis was performed on young adults grown at 23°C. Error bars represent the standard error of the mean. Significance was determined using an unpaired Student’s t test: ***P < 0.001.