Establishing cell polarity in development.

Polarity is a common feature of many different cell types, including the Caenorhabditis elegans zygote, the Drosophila oocyte and mammalian epithelial cells. The initial establishment of cell polarity depends on asymmetric cues that lead to reorganization of the cytoskeleton and polarized localization of several cortical proteins that act downstream of the polarization cues. The past year revealed that homologs of the C. elegans par (partitioning defective) genes are also essential for establishing polarity in Drosophila and vertebrate cells. There is growing evidence that the proteins encoded by these genes interact with key regulators of both the actin and the microtubule cytoskeletons.