Klinkert, KerstinLevernier, NicolasGross, PeterGentili, Christianvon Tobel, LukasPierron, MarieBusso, CoralieHerrman, SarahGrill, Stephan W.Kruse, KarstenGönczy, Pierre2019-06-182019-06-182019-06-182019-02-2610.7554/eLife.44552https://infoscience.epfl.ch/handle/20.500.14299/157768WOS:000461278600001How living systems break symmetry in an organized manner is a fundamental question in biology. In wild-type Caenorhabditis elegans zygotes, symmetry breaking during anterior-posterior axis specification is guided by centrosomes, resulting in anterior-directed cortical flows and a single posterior PAR-2 domain. We uncover that C. elegans zygotes depleted of the Aurora A kinase AIR-1 or lacking centrosomes entirely usually establish two posterior PAR-2 domains, one at each pole. We demonstrate that AIR-1 prevents symmetry breaking early in the cell cycle, whereas centrosomal AIR-1 instructs polarity initiation thereafter. Using triangular microfabricated chambers, we establish that bipolarity of air-1(RNAi) embryos occurs effectively in a cell-shape and curvature-dependent manner. Furthermore, we develop an integrated physical description of symmetry breaking, wherein local PAR-2-dependent weakening of the actin cortex, together with mutual inhibition of anterior and posterior PAR proteins, provides a mechanism for spontaneous symmetry breaking without centrosomes.BiologyLife Sciences & Biomedicine - Other Topicsanaphase-promoting complexanterior-posterior axisc-eleganscell polarityanteroposterior axissymmetry-breakingpattern-formationcortical flowspar proteinsa kinasetext::journal::journal article::research article