A myosin filament cage drives multiple aspects of mitosis unique to cells dividing within a polarized epithelium

Here we used mouse intestinal organoids expressing endogenously tagged myosin to clarify its roles in those aspects of mitosis unique to division within a polarized epithelium. Super-resolution imaging of rounded metaphase cells revealed a never-before-seen myosin filament cage that only forms in this context, exhibits apical/basal polarity, maintains roundness by resisting surrounding tissue pressure, and repositions laterally to form a contractile ring predetermined to drive planar division and asymmetric cleavage furrow progression. Attenuating cage function inhibited interkinetic nuclear migration and metaphase cell rounding, causing the division plane to shift from planar to orthogonal and resulting in organoids possessing multiple lumens. Following the apical domain marker ZO-1 showed that the new lumens originate at the interface between stacked daughter cells created by orthogonal divisions. We conclude that cells dividing within polarized epithelia create a myosin filament cage designed specifically to drive those aspects of cell division unique to their context.