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| Probing the Role of Spindle Midzone in Cytokinesis |
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| L.-g. Cao and Y.-l. Wang (1996) |
| Mole. Biol. Cell 7:225-232. |
| To probe the role of spindle midzone in signaling cytokinesis in cultured cells, a perforation was generated with a microneedle between the midzone and the cortex. We ask if the perforation can block crucial cytokinesis signals that may emanate from the spindle midzone toward the cortex. |
| Effects of Membrane Perforation Created during Metaphase and Early Anaphase |
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Size = 240 x 220 pixels.| When the perforation is created during metaphase and the first 1-2 min of anaphse, cleavage occurs only on the side facing the mitotic spindle. The perforation extends into a slit which moves rapidly across the equatorial zone. The cell fails to divide into two due to the lack of cleavage on the other side of the perforation. These observations suggest that signals emanating from the metaphase chromosomal region are required for the initiation of cytokinesis. |
| Effects of Membrane Perforation Created during Mid-Anaphase |
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Size = 180 x 172 pixels.| When the perforation is created after the first 1-2 min of anaphase, cleavage occurs on both sides of the perforation. Thus the signal from the chromosomal region must be transient in nature and is not continuously required for sustained cleavage activity. |
| Behavior of Membrane Perforation Created out of the Equatorial Zone |
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Size = 312 x 236 pixels.| When the perforation is created outside the equatorial plane, the cell divides normally. The perforation migrates toward the center of the spindle and disappears. These observations suggest that the cleavage signal is highly localized along the equatorial plane and that there is a general cortical/membrane movement toward the central equatorial region. |