Calcium spikes accompany the cleavage furrow ingression and cell separation during fission yeast cytokinesis

The role of calcium signaling during cytokinesis has long remained ambiguous. The studies of embryonic cell division discovered that calcium concentration increases transiently at the division plane just before the cleavage furrow ingression, leading to the hypothesis that these calcium transients trigger the contractile ring constriction. However, such calcium transients have only been found in animal embryos and their function remains controversial. Here we explored cytokinetic calcium transients in the model organism fission yeast. We adopted GCaMP, a genetically encoded calcium indicator, to determine the intracellular calcium level. We validated GCaMP as a highly sensitive calcium indicator which allowed us to capture the calcium transients stimulated by osmotic shocks. To identify calcium transients during cytokinesis, we first identified a correlation between the intracellular calcium level and cell division. Next, we discovered calcium spikes at the start of the cleavage furrow ingression and the end of the cell separation using time-lapse microscopy to. Inhibition of these calcium spikes slowed down the furrow ingression and led to frequent lysis of the daughter cells. We conclude that like the larger animal embryos fission yeast triggers cytokinetic calcium transients which promote the ring constriction and daughter cell integrity (194). Highlight summary for TOCCalcium rises transiently at the division plane during embryonic cell cytokinesis, but the conservation and function of such calcium transients remain unclear. We identified similar calcium spikes during fission yeast cytokinesis and demonstrated that these spikes promote the contractile ring constriction and the daughter cell integrity (257).