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 duri ng embryogenesis ill the nematode Caenorhabditis elegans challenge the prev ailing view that Wnt signalling specifies cell fate by converting transcrip tional repressors into activators. Instead, a mitogen-activated protein kin ase (MAPK)-related pathway converges with Wnt signalling in C. elegans to r elieve transcriptional repression. Futhermore, Wnt signalling induces endod erm in part by aligning the mitotic spindle in a responding cell along the anterior-posterior bony axis. To orient mitotic spindles, Wnt signalling mi ght directly target the cytoskeleton, prior to any regulation of gene trans cription in responding cells.