Fig. 9. Neural guidance defects in dgn-1 mutants. Homozygous and heterozygous dgn-1 mutants have axon guidance, branching and fasciculation defects in the DA/DB motoneurons (marker: evIs82[unc-129::GFP]). (A) Approximately 31% of dgn-1(cg121) homozygotes have side-switching defects in commissural DA/DB axons, which migrate from the ventral nerve cord (vnc) to the dorsal nerve cord (dnc). Heterozygotes show side-switching at a lower frequency. In this cg121/+ heterozygote, the DA6 commissure is abnormally extending on the right side, while the neighboring DB6 commissure is correctly extending on the right. (B-D) A variety of other, low penetrance defects are also seen in dgn-1 mutants. (B) Extra process arising from the neural cell body (arrowheads). (C) Abnormal axon branching (arrow) and aberrant anterior/posterior migration of processes (arrowheads). (D) Defasciculation (arrowhead) of axons in the dorsal nerve cord. Anterior is down in each image. Scale bar: 10 µm.