TGFbeta-like signaling and spicule development in Caenorhabditis elegans

A TGFbeta-like signal is required for spicule development in Caenorhabditis elegans males. This signal appears to originate in the male-specific musculature and is required for the migrations of cells within the proctodeum. The migrations of these cells form cellular molds, the spicule traces, in which the cuticle of the spicules is secreted. Mutations in daf-4, sma-2, sma-3, and sma-4, which disrupt TGFbeta-like signaling, result in aberrant migrations and morphologically abnormal spicules. daf-4, and hence the TGFbeta-like signal, is required prior to or during cell migrations. Therefore, the TGFbeta-like signal may act to prime the migrating cells or as a guidance cue. Mutations in lin-31 result in identical cell migration and spicule morphology defects. Thus, lin-31, which encodes a "winged helix" protein (Miller et al., Genes Dev. 7, 933-947, 1993), may be a component of this TGFbeta-like signaling pathway.