Counting actin in contractile rings reveals novel contributions of cofilin and type II myosins to fission yeast cytokinesis

Cytokinesis depends on actomyosin contractile rings, but little is known about the amount of polymerized actin in them. We counted such actin molecules in wild-type and mutant fission yeast. The cofilin mutant had twice as much actin and a proportional increase in type II myosins and formin. Myosin mutants reduced actin by half and slowed the rate of actin loss.