Positioning the Plane of Cell Division During Cytokinesis

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Abstract Successful cell division requires positioning of the division plane so that the segregated sets of chromosomes are cleanly partitioned into two separate cells. Furthermore, in some cell types, including stem cells, the division plane must be coordinated with localized cell fate determinants. Errors in division plane positioning can cause chromosome gain or loss, mis-segregation of cell fate determinants, or a failure of cytokinesis, all of which can accelerate tumor formation. In metazoans, the division plane is determined by the position of the mitotic spindle during anaphase. We have found that two pathways act redundantly and cooperatively to position the division plane. One pathway involves the central spindle and the second involves astral microtubules. The two pathways have been demonstrated to be mechanistically and genetically distinct. To understand the mechanism by which these microtubule-based structures regulate formation of a properly positioned actomyosin-based contractile ring, we will use a multidisciplinary strategy, combining genetic and cell biological analysis in C. elegans embryos and human cells, with optogenetics, biochemistry and live cell imaging. We will define the mechanisms that result in local activation of RhoA, determine how local zones of active RhoA mediate contractile ring assembly, and determine how a global signal to activate RhoA activation can be shaped by asters/centrosomes. These studies will provide insights into the mechanism of cell division and other biological processes that involve local regulation of cytoskeletal elements by Rho family of GTPases, such as cell polarization and cell migration.