Strikingly, MCAK localization was strongly reduced at MT plus-ends that were in the vicinity of chromosomes as compared to astral MT plus-end or plus-ends near spindle poles (Supplemental Fig. S 1b; Fig. 1a b).
To control for this, we performed control cytoplasmic targeting on cellular structures other than chromosomes, including near the plasma membrane, and near the spindle midzone.
We were able to elicit the defects in cytokinesis from chromosome tip ablation near the spindle midzone or on tips of short arms distal from the spindle midzone near the separating chromosome masses, making it more likely to be a result of DNA damage rather than perturbation of midzone cytoskeletal organization long known to cause cytokinetic defect [18].
Fragments of endoplasmic reticulum occur near the spindle pole bodies, but do not form a cap.
In contrast, equivalent irradiation of non-telomeric chromosome regions or control irradiations in either the adjacent cytoplasm or adjacent to chromosome tips near the spindle midzone during anaphase caused no change in the eventual completion of cytokinesis.
In a separate control cohort consisting of 33 cells in which the laser was focused adjacent to the tips of the longer chromosomes and near the spindle midzone similar to our tip ablation, all cells completed cytokinesis without exhibiting the "no furrow" or "furrow regression" responses.
Although most mRNAs are silent in oocytes, there is evidence that specific mRNAs [60] localize on mitotic and meiotic microtubules, and some of them, coding for key meiotic/mitotic proteins, such as cyclin B1, may be translated in oocytes locally, on or near the spindle [73].
During mitosis, Kinesin-5 motors function near the spindle midzone to maintain pole to pole distance.
Chromosome bridges, however, often contained CenpA signals at both their ends near the spindle poles.
Prior to anaphase, a small population of Myo8A-GFP accumulates at the cortex near the spindle midzone.
