PCP and Septins govern the polarized organization of the actin cytoskeleton during convergent extension

Abstract

Convergent extension (CE) is a collective cell movement required for embryonic axis elongation, neural tube closure, and kidney tubule elongation. During CE, iterative cell intercalations drive the elongation of a tissue. In order to move, cells reorganize their actin cytoskeleton; the implication of actin regulators during CE, then, is expected. Interestingly, two other groups of proteins have been shown to be required for this cell behavior: Planar Cell Polarity proteins (PCP) and Septins, both of which interact with the actin cytoskeleton. Disruption of any of these systems have substantial overlap in terms of embryonic phenotypes, but how they interact to govern CE is largely unknown. Here, we find that PCP proteins and Septins sequester actomyosin activity, create flows of actin across the anterior side of cells, and bundle actin into a node and cable system that displays a planar polarized gradient of stiffness.