Mechanics and patterning combine to orient cell divisions in a planar polarised epithelium

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• Guy Blanchard, PDN, University of Cambridge
• Monday 06 March 2023, 14:30-15:30
• Online.

If you have a question about this talk, please contact Elena Scarpa.

https://us06web.zoom.us/j/82089026611?pwd=L2FyclJFL2lYR0J3SFBDbHQyUFp6UT09 

The orientation of cell division (OCD) in the plane of epithelia drives tissue morphogenesis and relaxes stresses, with errors leading to pathologies. Cell elongation and local stress anisotropy have separately been shown to influence OCD , but it is unclear how interphase and mitotic cues interact to determine OCD .

We tracked 730 dividing cells from interphase 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 highly variable.

Using laser ablation, cell elongation as a proxy for local stress, and patterns of 3D cell shapes, we show that planar tissue-scale stress anisotropy switches orientation at the onset of the first cell divisions. OCD tracks this switch instantaneously, showing that prior interphase stress and cell elongation do not determine OCD in this tissue. Indeed, we show that compression from neighbouring dividing cells re-orients OCD only if compression occurs during metaphase. Thus, local stress anisotropy, resulting from a combination of tissue-scale stress anisotropy and local compression from neighbouring cells, orients cell elongation instantaneously during metaphase, which in turn directs OCD .

However, 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 axis and towards the anterior-posterior embryonic axis. This bias is very mild in elongated cells, stronger in more isotropic cells and its strength is predicted by the local strength of planar polarised junctional Myosin II.

We 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.

This talk is part of the Morphogenesis Seminar Series series.

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• Graduate-Seminars
• Morphogenesis Seminar Series
• Online

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