It seemed possible that partial loss of function in Clic could, in principle, lead to a global improvement in negative geotaxis behavior that manifested as blunted sensitivity to ethanol in eRING assays. We addressed this issue by carefully examining two key components of negative geotaxis, latency to initiate the behavior and climbing speed, in control and Clic mutants in the absence of ethanol. Climbing speed in negative geotaxis assays was indistinguishable in ClicG04072/+, ClicEY04209/+ and control w1118 flies (Supplemental Figure S5A and C; two-sample t tests; ClicG04072/+, t(28)=1.66, p=0.107; ClicEY04209/+, t(28)=0.891, p=0.381; n=14–15). Although climbing latency was decreased in ClicG0472/+ (Supplemental Figure S5B; two-sample t test; t(26)=3.40, p=0.002, n=13–14), this effect was not seen in ClicEY04209/+ (Supplemental Figure S5D; two-sample t test; t(27)=1.26, p=0.218; n=14). We conclude that partial loss of function in Clic does not consistently alter negative geotaxis in flies and, therefore, that the blunted ethanol sensitivity in Clic mutants must be independent of global improvements in negative geotaxis or climbing behavior.
