RhoA- and Cdc42-induced antagonistic forces underlie symmetry breaking and spindle rotation in mouse oocytes

• DOI: 10.1371/journal.pbio.3001376
• Publication Date: 2021-09-07T18:06:13Z
• Authors: Benoit Dehapiot; Raphaël Clément; Anne Bourdais; Virginie Carrière; Sébastien Huet; Guillaume Halet
• Keywords: Polar body; Spindle pole body; Astral microtubules; Cell Cortex; Aurora B kinase

Mammalian oocyte meiotic divisions are highly asymmetric and produce a large haploid gamete 2 small polar bodies. This relies on the ability of cell to break symmetry position its spindle close cortex before anaphase occurs. In metaphase II–arrested mouse oocytes, is actively maintained parallel cortex, until fertilization triggers sister chromatid segregation rotation spindle. The latter must indeed reorient perpendicular enable cytokinesis ring closure at base body. However, mechanisms underlying breaking have remained elusive. this study, we show that results from antagonistic forces. First, an inward contraction furrow dependent RhoA signaling, second, outward attraction exerted both sets chromatids by Ran/Cdc42-dependent polarization actomyosin cortex. By combining live segmentation tracking with numerical modeling, demonstrate configuration becomes unstable as ingression progresses. leads spontaneous breaking, which implies neither direction nor set eventually gets discarded biologically predetermined.