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The cover image is from studies performed for the publication by S. L. Kline-Smith, A. Khodjakov, P. Hergert, and C. E. Walczak (2004). Depletion of centromeric MCAK leads to chromosome congression and segregation defects due to improper kinetochore attachments. Mol. Biol. Cell 15 1146-1159. We wanted to explore the role of the centromeric-bound MCAK, a kinesin-related protein that depolymerizes microtubules. Xenopus S3 cells were injected with a centromere dominant-negative version of MCAK during prophase, then allowed to progress through mitosis. Disruption of centromeric MCAK results in defective chromosome congression and segregation despite the presence of a morphologically normal bipolar spindle. For example, the cell in this image has several chromosomes remaining at the spindle poles for an extended period of time and is delayed in mitosis as a result. Correlative studies in mammalian PtK2 cells have demonstrated that the chromosomes "stuck" at spindle poles have highly defective kinetochoremicrotubule attachments, such as syntelic (both kinetochores attached to one spindle pole) and combined syntelic-merotelic (one kinetochore attached to both poles) attachments, which would inhibit proper congression to the metaphase plate furing mitosis. These findings suggest that the microtubule depolymerase activity of centromeric MCAK is required for resolution of improper microtubule attachments during mitosis. —S. L. Kine-Smith, A. Khodjakov, P. Hergert, and C. E. Walczak