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SUMMARY:Mechanics and patterning combine to orient cell divisions in a pla
 nar polarised epithelium - Guy Blanchard\, PDN\, University of Cambridge
DTSTART:20230306T143000Z
DTEND:20230306T153000Z
UID:TALK195997@talks.cam.ac.uk
CONTACT:Elena Scarpa
DESCRIPTION:The orientation of cell division (OCD) in the plane of epithel
 ia drives tissue morphogenesis and relaxes stresses\, with errors leading 
 to pathologies. Cell elongation and local stress anisotropy have separatel
 y been shown to influence OCD\, but it is unclear how interphase and mitot
 ic cues interact to determine OCD.\n\nWe tracked 730 dividing cells from i
 nterphase through cytokinesis in the planar polarised Drosophila embryonic
  ectoderm after gastrulation. The timing of known mitotic events relative 
 to cytokinesis is remarkably consistent across cells\, but planar OCD is h
 ighly variable.\n\nUsing laser ablation\, cell elongation as a proxy for l
 ocal stress\, and patterns of 3D cell shapes\, we show that planar tissue-
 scale stress anisotropy switches orientation at the onset of the first cel
 l divisions. OCD tracks this switch instantaneously\, showing that prior i
 nterphase stress and cell elongation do not determine OCD in this tissue. 
 Indeed\, we show that compression from neighbouring dividing cells re-orie
 nts OCD only if compression occurs during metaphase. Thus\, local stress a
 nisotropy\, resulting from a combination of tissue-scale stress anisotropy
  and local compression from neighbouring cells\, orients cell elongation i
 nstantaneously during metaphase\, which in turn directs OCD. \n\nHowever\,
  we also find that the mitotic spindle at the end of metaphase\, and hence
  the OCD\, are consistently oriented away from the metaphase cell long axi
 s and towards the anterior-posterior embryonic axis. This bias is very mil
 d in elongated cells\, stronger in more isotropic cells and its strength i
 s predicted by the local strength of planar polarised junctional Myosin II
 .\n\nWe conclude that in this Drosophila epithelium\, mechanics\, through 
 local stress anisotropy\, dominates OCD overall\, but where cells are not 
 strongly elongated Myosin II patterning takes over. \n
LOCATION:Online
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