Aurora A depletion reveals centrosome-independent polarization mechanism in C. elegans

Abstract

How living systems break symmetry in an organized manner is an important question in biology. In C. elegans zygotes, symmetry breaking normally occurs in the vicinity of centrosomes, resulting in anterior-directed cortical flows and establishment of a single posterior PAR-2 domain. Here, we report that zygotes depleted of the Aurora A kinase AIR-1 or of centrosomes establish two posterior domains, one at each pole. Using transgenic animals and microfabricated triangular chambers, we establish that such bipolarity occurs in a PAR-2- and curvature-dependent manner. Furthermore, we develop an integrated physical model of symmetry breaking, establishing that local PAR-dependent weakening of the actin cortex, together with mutual inhibition of anterior and posterior PAR proteins, provides a mechanism for self-organized PAR polarization without functional centrosomes in C. elegans.\n\nOne Sentence SummaryWe uncover a novel centrosome-independent mechanism of polarization in C. elegans zygotes