Fig. 2: The Hox gene lin-39 (Scr/Dfd/Hox4-5) controls the cholinergic identity of motor neurons necessary for locomotion.

a Schematic of a C. elegans hermaphrodite showing the cell bodies of MNs that control locomotion (red) and egg-laying (green). Expression profile of cho-1, unc-17, and lin-39 is summarized in the color-filled table. b Representative images of a cho-1 fosmid-based reporter in WT and lin-39(n1760) mutant animals (L4 stage). Motor neurons that control locomotion (e.g., DA, DB, VA, VB) express cho-1 at L4. VC motor neurons mature later (day 1 adult) and do not express cho-1 at L4. The identity of individual motor neurons is annotated. White arrowheads indicate MN nuclei because the cho-1 reporter is localized to the nucleus (H2B). mChOpti signal is shown in white for better contrast. Left image: anterior to the vulva, Right image: posterior to the vulva. c Quantification of the number of motor neurons expressing cho-1 in panel (b). The motor neurons that consistently lose cho-1 expression in lin-39(n1760) mutants are VA5, VB6, AS6, VA7, and VB8. n = 22 animals. d and e Quantification of the number of sex-shared motor neurons expressing unc-17 (endogenous reporter ot907 [UNC-17::mKate]) and ace-2 (fosmid-based reporter otEx4432 [ace-2::GFP]) in WT and lin-39(n1760) mutant hermaphrodites at L4. n = 19-25 animals. f and g Auxin treatment was initiated at L4 and images were scored at young adult stage (Day 1). Quantification of the number of sex-shared motor neurons expressing UNC-17::GFP upon auxin or EtOH treatment. n = 24 animals. For quantifications in c–f, box and whisker plots were used with the presentation of all data points. Unpaired t-test (two-sided) with Welch’s correction was performed and p-values were annotated. Box boundaries indicate the 25th and 75th percentile. The limits indicate minima and maxima values, whereas center values (mean) are highlighted in red. h Schematic summarizing our findings in MNs that control locomotion. Source data are provided as a Source data file. Scale bars: 5 μm.