10779/crick.12464681.v1 Mario Aguilar-Aragon Mario Aguilar-Aragon Teresa T Bonello Teresa T Bonello Graham P Bell Graham P Bell Georgina C Fletcher Georgina C Fletcher Barry J Thompson Barry J Thompson Adherens junction remodelling during mitotic rounding of pseudostratified epithelial cells. The Francis Crick Institute 2020 E-cadherin cortex mitosis myosin Thompson FC001180 0601 Biochemistry and Cell Biology Developmental Biology 2020-06-25 13:42:02 Journal contribution https://crick.figshare.com/articles/journal_contribution/Adherens_junction_remodelling_during_mitotic_rounding_of_pseudostratified_epithelial_cells_/12464681 Epithelial cells undergo cortical rounding at the onset of mitosis to enable spindle orientation in the plane of the epithelium. In cuboidal epithelia in culture, the adherens junction protein E-cadherin recruits Pins/LGN/GPSM2 and Mud/NuMA to orient the mitotic spindle. In the pseudostratified columnar epithelial cells of Drosophila, septate junctions recruit Mud/NuMA to orient the spindle, while Pins/LGN/GPSM2 is surprisingly dispensable. We show that these pseudostratified epithelial cells downregulate E-cadherin as they round up for mitosis. Preventing cortical rounding by inhibiting Rho-kinase-mediated actomyosin contractility blocks downregulation of E-cadherin during mitosis. Mitotic activation of Rho-kinase depends on the RhoGEF ECT2/Pebble and its binding partners RacGAP1/MgcRacGAP/CYK4/Tum and MKLP1/KIF23/ZEN4/Pav. Cell cycle control of these Rho activators is mediated by the Aurora A and B kinases, which act redundantly during mitotic rounding. Thus, in Drosophila pseudostratified epithelia, disruption of adherens junctions during mitosis necessitates planar spindle orientation by septate junctions to maintain epithelial integrity.