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Abstract
BackgroundA number of proteins accumulate in the spindle midzone and midbody of dividing animal cells. Besides proteins essential for cytokinesis, there are also components essential for interphase functions, suggesting that the spindle midzone and/or midbody may play a role in regulating the following cell cycle.ResultsWe microsurgically severed NRK epithelial cells during anaphase or telophase, such that the spindle midzone/midbody was associated with only one of the daughter cells. Time-lapse recording of cells severed during early anaphase indicated that the cell with midzone underwent cytokinesis-like cortical contractions and progressed normally through the interphase, whereas the cell without midzone showed no cortical contraction and an arrest or substantial delay in the progression of interphase. Similar microsurgery during telophase showed a normal progression of interphase for both daughter cells with or without the midbody. Microsurgery of anaphase cells treated with cytochalasin D or nocodazole indicated that interphase progression was independent of cortical ingression but dependent on microtubules.ConclusionsWe conclude that the mitotic spindle is involved in not only the separation of chromosomes but also the regulation of cell cycle. The process may involve activation of components in the spindle midzone that are required for the cell cycle, and/or degradation of components that are required for cytokinesis but may interfere with the cell cycle.
Highlights
A number of proteins accumulate in the spindle midzone and midbody of dividing animal cells
Staining of severed daughter cells with antibodies against aurora B (Figure 1A), which is known to relocate from centromeres to the spindle midzone during early anaphase [12,13], confirmed that the spindle midzone was removed from one of the daughter cells
All the daughter cell with spindle midzone showed cytokinesis-like cortical contraction activities, while the daughter cell without spindle midzone showed no cortical contraction (Figure 2, see Additional file 1)
Summary
A number of proteins accumulate in the spindle midzone and midbody of dividing animal cells. Besides proteins essential for cytokinesis, there are components essential for interphase functions, suggesting that the spindle midzone and/or midbody may play a role in regulating the following cell cycle. Antiparallel, interdigitating microtubules and many associated proteins become organized into discrete bundles in the spindle midzone [1], the region between separated chromosomes. It is generally recognized that, at least for cultured animal cells, midzone microtubules play a major role in cytokinesis. Cleavage furrows, both normal and ectopic, are associated with similar microtubule bundles [2,3,4], while regions physically blocked from midzone microtubules by micromanipulation are unable to undergo cytokinesis [5]. Continuous interactions of midzone microtubules with the cell cortex are required for sustaining the cytokinesis of cultured animal cells [6]
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