Wnt signaling and the establishment of cell polarity

Wnt signaling involves multiple mediators and molecular targets functions to regulate cell division, polarity, shape, motility, and fate. In addition to the best-studied regulation of gene expression by the Wnt/β-catenin or canonical pathway, Wnt proteins signal via Frizzled and Disheveled to regulate epithelial cell polarity, asymmetric cell divisions, and cell movements by noncanonical pathways. These include the planar cell polarity pathway in the fly wing and a similar pathway that controls convergent extension movements in vertebrates and mammalian cochlear cell polarization. Although historically cell polarity decisions have been associated exclusively with the noncanonical pathways, there is an emerging role for β-catenin-dependent Wnt signaling in cell polarization. This chapter discusses multiple targets of Wnt pathways implicated in cell polarity regulation during embryonic development and the relationship between canonical and noncanonical Wnt pathways.