GSK3 at the edge: regulation of developmental specification and cell polarization.

GSK3 is a multifunctional protein kinase that is pivotal for the regulation of metabolism, the cytoskeleton, and gene expression. Multicellular eukaryotes utilize GSK3 as a molecular switch to specify distinct cell fates, but also to organize these cells spatially within the developing organism. We discuss the central role of GSK3 in control of the Wnt, Hedgehog, cAMP (in Dictyostelium), and other signaling pathways, but also focus on significant new evidence that GSK3 is required to establish cell polarity.