Cytoplasmic flow is a cell size sensor that scales anaphase

Olga Afonso

During early embryogenesis, fast mitotic cycles without interphase lead to cell size decrease, while scaling mechanisms must keep cellular structures proportional to cell size. For instance, as cells become smaller, if the position of nuclear envelope reformation (NER) did not adapt, NER would have to happen beyond the cell boundary. We found that NER position in anaphase does scale with cell size. What scales is chromosome motility, mediated by cytoplasmic flows which themselves scale. Flows are a consequence of friction between viscous cytoplasm and bulky cargo transported by dynein on astral microtubules. As an emerging property, confinement in cells of different sizes yields scaling of cytoplasmic flows. Thus, flows are a cell geometry sensor that feeds back size information to the anaphase machinery, scaling NER.