In LLC-Pk1 cells, and most cultured mammalian cells, cell division is highly regulated to achieve equal sized daughter cells. During this process, duplicated centrosomes separate and establish a bipolar array called the mitotic spindle. The mitotic spindle is responsible for aligning the chromosomes at the metaphase plate, and separating sister chromatids during anaphase. Spindle positioning and elongation are thought to be driven by the interaction between dynamic astral microtubules and cortical dynein. Extensive research has revealed that dynein is anchored to the cortex via the highly conserved NuMA/LGN/Gαi ternary complex in metaphase and the additional PIP/PIP2/NuMA, or 4.1G/R/NuMA, pathways during anaphase. Although substantial research has been conducted on the proteins involved with this process, it is unclear exactly how a cell is able to generate forces for spindle positioning and elongation. Here, I use photoactivation and FRAP techniques to investigate the role of the midzone during spindle elongation, and how cortical dynein is able to drive this process. I provide evidence that microtubule sliding in the midzone is not precisely coordinated with pole separation, however the two actions are interdependent. In addition, I demonstrate that cortical dynein dynamics are significantly enhanced during anaphase, most likely due to an increased length and stability of astral microtubules. I hypothesize that this increased turnover rate allows for rapid redistribution of dynein throughout the cortex to ensure proper spindle elongation.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:masters_theses_2-1395 |
| Date | 13 July 2016 |
| Creators | Jordan, Heather M |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses |
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