Agathe Chaigne did her thesis at CIRB under the supervision of Marie-Emilie Terret, INSERM Researcher, in the team of Marie-Hélène Verlhac, Director of Research.
She received this award for her work on asymmetric egg cell division.
Cortical tension and spindle positioning in the mouse oocyte
Abstract: Meiotic divisions are highly asymmetrical in size, generating one very large cell, the oocyte, and two small cells, the polar globules. This asymmetry is made possible by the migration of the spindle during the first division to the nearest cortex. This migration does not depend on microbutules, but on Myosin-II and a network of actin filaments nucleated by the cooperation of the straight filament nucleators Formin-2 and Spire1/2. Preliminary observations in the laboratory described a thickening of the actin cortex during spindle migration, yet it had been shown that cortical tension, a parameter describing oocyte stiffness, decreases during spindle migration. I have shown that this thickening is essential for spindle migration and is nucleated by the branched filament nucleator Arp2/3, under the control of the Mos/MAPK pathway. In addition, it decreases cortical tension by delocalizing Myosin-II, which is essential for spindle migration. Finally, I have shown that the voltage drop is a mechanism for amplifying the force imbalance initially present (thanks to the slight decentering of the nucleus), which triggers spindle migration.
