Pioneer Axon Guidance by UNC-129, a <i>C. elegans</i> TGF-β

Abstract

The unc-129 gene, like the unc-6 netrin gene, is required to guide pioneer motoraxons along the dorsoventral axis of Caenorhabditis elegans . unc-129 encodes a member of the transforming growth factor–β (TGF-β) superfamily of secreted signaling molecules and is expressed in dorsal, but not ventral, rows of body wall muscles. Ectopic expression of UNC-129 from ventral body wall muscle disrupts growth cone and cell migrations that normally occur along the dorsoventral axis. Thus, UNC-129 mediates expression of dorsoventral polarity information required for axon guidance and guided cell migrations in C. elegans .