Asymmetric mechanics of cell-size control during asymmetric cell divisions in sensory organs precursors

In Drosophila Sensory Organ Precursors (SOP), asymmetric cell division gives rise to two daughter cells with different cell size, the PIIB being smaller than its sibling the PIIA daughter cell. Most of the studies of cytokinetic mechanics focus on the equatorial constriction ring and the positioning of the spindle, however an actomyosin cortex is also present at the poles of dividing cells. In this study, we show that in wild-type SOP, an asymmetry of cortical actin is built during division, with more cortical actin in the bigger PIIA daughter. By using nanobody targeting experiments as well as FRAP, laser ablation and mutant conditions, we investigate how this polar actin cortex regulates cell shape to generate a proper asymmetric cytokinesis in SOPs. We demonstrate that this polar cortex has a big contribution to the final cytokinesis shape and that perturbing this asymmetry of cortical actin leads to daughter cell size inversion