Figure 1.
Neurons that lack β-spectrin develop normally. (A–D) Representative images of migrating DD growth cones in wild-type (A and C) and unc-70(s1502) (B and D) embryos. Embryos are curled up in the egg, and the soma of the DD neurons are along the ventral nerve cord (vnc); commissural axons extend to the dorsal nerve cord (dnc). GABA motor neurons are visualized by expressing GFP under the promoter of the vesicular GABA transporter gene unc-47 (oxIs12(Punc-47∷GFP); McIntire et al., 1997). Bar, 10 μm. (A and B) Growth cones extend across the epidermis. Closed arrowheads indicate growth cones migrating near the midline, displaying a rounded shape with radial protrusions. Open arrowheads indicate growth cones that have reached the dorsal muscle quadrant. These growth cones flatten and send protrusions to the dorsal cord. (C and D) Slightly older embryos extend processes along the dorsal nerve cord. Asterisks indicate commissures that have reached the dorsal nerve cord and are beginning to extend anterior and posterior processes along the nerve cord. (E) Percentage of growth cones with specific morphologies in wild-type and unc-70(s1502) embryos. Wild type, n = 155 neurons; unc-70(s1502), n = 192 neurons.