Aurora A depletion reveals centrosome-independent polarization mechanism in Caenorhabditis elegans

• Main Authors: Kerstin Klinkert, Nicolas Levernier, Peter Gross, Christian Gentili, Lukas von Tobel, Marie Pierron, Coralie Busso, Sarah Herrman, Stephan W Grill, Karsten Kruse, Pierre Gönczy
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2019-02-01
• Series: eLife
• Subjects: symmetry breaking; Aurora A; anterior-posterior polarity; physical analysis
• Online Access: https://elifesciences.org/articles/44552

How 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.