PT - JOURNAL ARTICLE AU - Yoo-Shick Lim AU - Smita Mallapur AU - Gautam Kao AU - Xing-Cong Ren AU - William G. Wadsworth TI - Netrin UNC-6 and the Regulation of Branching and Extension of Motoneuron Axons from the Ventral Nerve Cord of <em>Caenorhabditis elegans</em> AID - 10.1523/JNEUROSCI.19-16-07048.1999 DP - 1999 Aug 15 TA - The Journal of Neuroscience PG - 7048--7056 VI - 19 IP - 16 4099 - http://www.jneurosci.org/content/19/16/7048.short 4100 - http://www.jneurosci.org/content/19/16/7048.full SO - J. Neurosci.1999 Aug 15; 19 AB - In the Caenorhabditis elegans embryo, some ventral midline motoneurons extend a process circumferentially to the dorsal midline and a process longitudinally along ventral nerve cord interneurons. Circumferential migrations are guided by netrin UNC-6, which repels motoneuron axons dorsally. Although the motoneuron cell bodies and the longitudinal axons are positioned along UNC-6-expressing interneurons in the ventral nerve cord, the circumferential processes extend only from the motoneuron cell bodies and from defined locations along some longitudinal axons. This implies a mechanism regulates motoneuron branching of UNC-6-responsive processes. We show that expression of unc-6ΔC, which encodes UNC-6 without domain C, partially rescues circumferential migration defects inunc-6 null animals. This activity depends on the netrin receptors UNC-5 and UNC-40. These results indicate that UNC-6ΔC can provide the circumferential guidance functions of UNC-6. Furthermore, we show that expression of unc-6ΔC causes motoneuron branching and the extension of processes from abnormal positions along the ventral nerve cord. This activity is also UNC-5- and UNC-40-dependent. We propose that local interactions mediated by domain C regulate motoneuron branching and responsiveness to the UNC-6 cue.