CWN-1 functions with DSH-2 to regulate C. elegans asymmetric neuroblast division in a beta-catenin independent Wnt pathway.

In Caenorhabditis elegans, Wnt signaling regulates many asymmetric cell divisions. During embryogenesis, the C. elegans Dishevelled (Dsh) homolog, DSH-2, regulates asymmetric neuroblast division of the ABpl/rpppa blast cell. Dsh is a key intracellular component of both beta-catenin dependent and beta-catenin independent Wnt pathways. In C. elegans, most of the well-characterized asymmetric cell divisions regulated by Wnts are dependent on beta-catenin. In the ABpl/rpppa neuroblast division, however, we determined that DSH-2 regulates cell polarity through a beta-catenin independent Wnt pathway. We also established that the C. elegans Wnt homolog, cwn-1, functions to regulate asymmetric division of the ABpl/rpppa blast cell. Our results indicated that cwn-1 does not act alone in this process, and it functions with another redundant ligand that appears not to be a Wnt. Finally, we show widespread requirements for DSH-2 during embryogenesis in the generation of many other neurons. In particular, DSH-2 function is necessary for the correct production of the embryonic ventral cord motor neurons. This study demonstrates a role for DSH-2 and Wnt signaling in neuronal specification during C. elegans embryogenesis.