Fig. 2. vab-7 specifies DB posterior axonal polarity. (A) Morphologies of DA and DB motoneurones. DA (nine) and DB (seven) cell bodies are located in the ventral nerve cord (VNC). Representative DA (blue) and DB (red) neurones are composed of dendritic processes in the VNC, circumferential commissures, and axons extending along the dorsal nerve cord (DNC). Note dendritic and axonal projections from DA (anterior) and DB (posterior) adopt opposite trajectories. (B,C) The cell bodies of DA and DB motoneurones visualized with unc-129::GFP. (B) Wild type. (C) A vab-7(e1562) mutant; both DA and DB are present. (High background in A,B is due to unc-129::GFP expression in intestinal cells.) (D-G) Dorsal views of adult animals. Anterior is towards left. Arrows point to the DNC and arrowheads identify DB commissures. (D) DB motor axons project posteriorly in the DNC of a wild-type animal. (E) vab-7 is required for posterior DB axonal outgrowth. In vab-7(e1562), DB motor axons adopt a DA-like anterior trajectory. Mutations in unc-4 (F) and unc-37 (G) restore posterior DB axonal polarity. Scale bars: in B, 50 µm in B,C; in D, 10 µm in D-F; in G, 4 µm.
