Figure 12.

Differential expression of axon guidance cues and receptors in A-class motor neurons. Embryonic DA motor neurons extend commissures to innervate muscles on the dorsal side whereas larval VA motor axons are retained in the ventral nerve cord. DA axons are steered dorsally by interaction of the repulsive cue UNC-6 (netrin) with receptors, UNC-40 (DCC) and UNC-5, and the CLR-1 receptor tyrosine phosphatase [90,91]. VAs do not express these receptors and project ventrally directed axons. Enrichment of the Wnt receptors lin-17 in the embryonic A-class motor neuron dataset and mig-1 in the larval A-class motor neuron profile could be indicative of a Wnt-dependent mechanism for directing anterior outgrowth of DA and VA motor axons.