Wnt signalling in Caenorhabditis elegans: regulating repressors and polarizing the cytoskeleton.

Wnt proteins are secreted, cysteine-rich glycoprotein ligands with numerous roles during animal development. Recent studies of endoderm induction during embryogenesis in the nematode Caenorhabditis elegans challenge the prevailing view that Wnt signalling specifies cell fate by converting transcriptional repressors into activators. Instead, a mitogen-activated protein kinase (MAPK)-related pathway converges with Wnt signalling in C. elegans to relieve transcriptional repression. Furthermore, Wnt signalling induces endoderm in part by aligning the mitotic spindle in a responding cell along the anterior-posterior body axis. To orient mitotic spindles, Wnt signalling might directly target the cytoskeleton, prior to any regulation of gene transcription in responding cells.