![]() UNC-6/Netrin induces neuronal asymmetry and defines the site of axon formation. Shared receptors in axon guidance: SAX-3/Robo signals via UNC-34/Enabled and a Netrin-independent UNC-40/DCC function. Yu, T.W., Hao, J.C., Lim, W., Tessier-Lavigne, M. enabled, a dosage-sensitive suppressor of mutations in the Drosophila Abl tyrosine kinase, encodes an Abl substrate with SH3 domain-binding properties. Netrin-1 is required for commissural axon guidance in the developing vertebrate nervous system. The netrins define a family of axon outgrowth-promoting proteins homologous to C. The netrin 1 receptors Unc5h3 and Dcc are necessary at multiple choice points for the guidance of corticospinal tract axons. Slit and Robo control the development of dendrites in Drosophila CNS. Robo and Frazzled/DCC mediate dendritic guidance at the CNS midline. Netrin/DCC signaling controls contralateral dendrites of octavolateralis efferent neurons. Slit is the midline repellent for the robo receptor in Drosophila. The unc-5, unc-6, and unc-40 genes guide circumferential migrations of pioneer axons and mesodermal cells on the epidermis in C. Graded expression of semaphorin-1a cell-autonomously directs dendritic targeting of olfactory projection neurons. Komiyama, T., Sweeney, L.B., Schuldiner, O., Garcia, K.C. Semaphorin 3A is a chemoattractant for cortical apical dendrites. These data suggest that axon and dendrite of one neuron interpret common environmental cues with different receptors and downstream signaling pathways. ![]() Unexpectedly, the serine-threonine kinase PAR-4 (LKB1) was selectively required for the activity of the UNC-40 pathway in dendrite outgrowth. Although the endogenous ventrally secreted UNC-6 instructs axon guidance, dorsal or even membrane-tethered UNC-6 could support dendrite development. Its repulsive receptor UNC-5 repelled the axon from the ventral cell body, whereas the attractive receptor UNC-40 (DCC) was dendritically enriched and promotes antero-posterior dendritic growth. We found that the guidance cue UNC-6 (Netrin) is required for both axon and dendrite development. elegans motor neuron whose axon and dendrite adopt different trajectories and lengths. Emerging evidence suggests the same cues control dendrite development, but it is not understood how they differentially instruct axons and dendrites. Axons navigating through the developing nervous system are instructed by external attractive and repulsive cues.
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