Figure 1. The motivated displacement assay (MDA): (A) Frame subtraction data following heat-shock of the indicated genotypes (3 replicates, with ~12 worms per replicate per genotype). ns = not significant, *P<0.05, **P<0.01, ***P<0.001, ****P< 0.0001 based on Tukey's multiple comparison test. Horizontal bars denote means and standard deviations. (B) Design of the MDA. A 10 cm-diameter agar plate is seeded on its periphery with an E. coli 1 cm-wide ring. Worms suspended in M9 buffer are pipetted onto the center. Once the M9 dries, the worms crawl towards the food. Worms reaching the food are counted and removed from the plate every 10 minutes. Data from MDA for the indicated genotypes are shown for non-heat shocked (C-D) and heat shocked (E-F) animals, including estimates of differences in the time to reach food based on restricted mean survival time analysis. A total of 1,098 N2 (598 non-HS, 500 HS), 1,099
ceh-17 (604 non-HS, 495 HS), 1,549
aptf-1 (n=1,020 non-HS, 529 HS), and 1,266
ceh-17;
aptf-1 (n=585 non-HS, 681 HS) worms were studied across four trials. (G) Data shown in C and E is displayed as a ratio of heat-shocked to non-heat-shock worms reaching the food as a function of time. Dotted lines denote the standard error of the mean. (H) Hazard ratios comparing heat shocked to non-heat shock conditions within genotype are presented based on Cox Proportional Hazards model. The hazard ratio represents the relative likelihood of reaching the food in HS versus non-HS; thus, values >1 imply worms are more likely to reach food with HS than without HS, whereas values <1 imply worms are less likely to reach food with HS than without HS.