Absence of nonmuscle myosin IIA accumulation in the contractile ring during MK mitosis or endomitosis. Cells were stained for tubulin (α and β, green) and nonmuscle myosin IIA (red). DNA was stained with TOTO (blue). (A) Only 13% of dipolar mitotic/endomitotic MKs showed a clear accumulation of myosin II at the midzone or in the midbody, 13% showed either a signal at the threshold of detection or an incomplete accumulation at one part of the furrow, and 74% were negative. (B) Myosin II accumulation was not observed in the midzone or in the midbody of multipolar endomitosis. arrow indicates the location of midbody. (C) Myosin II accumulation was clearly detected in the midzone and the midbody of control U937 cells in mitosis.