Aurora B kinase is expressed in polyploid MKs and localizes normally to the central spindle during endomitosis. (A) Study of Aurora B expression in CD41⁺ 2N to 4N and 8N or greater cells. The cells were sorted after incubation with Hoechst 33342 and CD41 staining. Western blot analysis showed that Aurora B protein was present in 2N to 4N and 8N or greater MK without marked differences between the 2 cell fractions. (Bi-iii) MKs were stained for tubulin (α and β, green), Aurora B (red), and DNA (blue). During telophase, the central spindle was highly concentrated, forming intercellular bridge (midbody). Aurora B was present in the midbody of the central spindle for dipolar mitosis (Bi) or endomitosis (8N, 4 poles) (Bii-iii). (Biii) For the high ploidy MK (16N, 8 poles), the merge image showed the staining for tubulin, Aurora B, DNA, and phase-contrast light. (C) During telophase Aurora B colocalized correctly with survivin to the central spindle of dipolar or multipolar endomitotic MKs as described in classic mitosis. Scale bars represent 10 μm.