Research Summary

Cytokinesis is mediated by an actin-based contractile ring that is attached to the overlying cell membrane. Cytokinesis is highly regulated in time and space. The contractile ring assembles in the cell cortex after anaphase onset at a site midway between the two poles of the mitotic spindle thereby ensuring that the two sets of chromosomes are equally partitioned into the two daughter cells. We are using the nematode C. elegans and cultured human cells as model systems to dissect this complex process. We are using a combination of forward and reverse genetics, biochemistry, and live cell imaging to address the following unsolved problems: How is the cleavage furrow positioned? How does the contractile ring assemble and function? How does the central spindle assemble and function? How is completion of cytokinesis achieved?

We are particularly interested in the assembly and function of the central spindle. Central spindle assembly begins at the metaphase to anaphase transition, when chromosomes move polewards on shrinking kinetochore microtubules. At this time, non-kinetochore spindle microtubules become bundled to form the central spindle. We discovered an evolutionarily conserved protein complex, centralspindlin, consisting of a Rho family GAP, CYK-4, and a kinesin like protein, ZEN-4, that is directly involved in central spindle assembly. The central spindle is essential for completion of cytokinesis and it also regulates cleavage furrow formation. We want to understand in mechanistic terms how this motor/RhoGAP complex functions to coordinate central spindle assembly and how it regulates early and late events in cytokinesis.

In C. elegans embryos, cleavage furrow formation requires either the central spindle or astral microtubules. These two supramolecular structures appear to regulate furrow formation by distinct molecular mechanisms that converge at the GTPase RhoA. We will identify the mechanisms that lead to local activation of RhoA.

Selected Publications

Pavicic-Kaltenbrunner, V., Mishima, M., and M. Glotzer. (2007). Cooperative Assembly of CYK-4/MgcRacGAP and ZEN-4/MKLP1 to Form the Centralspindlin Complex Mol. Biol. Cell, 10.1091/mbc.E07-05-0468. (PubMed)

Werner, M., E. Munro, and M. Glotzer. (2007). Astral signals spatially bias cortical Myosin recruitment to break symmetry and promote cytokinesis. Curr Biol. 17:1286-1297. (PubMed)

Petronczki, M., M. Glotzer, N. Kraut, and J. M. Peters. (2007). Polo- kinase 1 triggers the initiation of cytokinesis in human cells by promoting recruitment of the RhoGEF Ect2 to the central spindle. Dev Cell. 12:713-725. (PubMed)

Hizlan, D., M. Mishima, P. Tittmann, H. Gross, M. Glotzer, and A. Hoenger. (2006). Structural analysis of the ZEN-4/CeMKLP1 motor domain and its interaction with microtubules. J Struct Biol. 153:73-84. (PubMed)

Piekny A, Werner M, Glotzer M. (2006). Cytokinesis: welcome to the Rho zone. Trends Cell Biol. 15:651-8. Review. (PubMed)

Yuce O, Piekny A, Glotzer M. (2005). An ECT2-centralspindlin complex regulates the localization and function of RhoA. J Cell Biol. 170:571-82. (PubMed)

Glotzer, M. (2005). "The molecular requirements for cytokinesis." Science 307: 1735-9. (PubMed)

Mishima, M., Pavicic, V., Gruneberg, U., Nigg, E. A. and Glotzer, M. (2004). "Cell cycle regulation of central spindle assembly." Nature 430: 908-13. (PubMed)

Glotzer, M. (2004). "Cleavage furrow positioning." J Cell Biol 164: 347-51. (PubMed)

Dechant, R. and Glotzer, M. (2003). "Centrosome Separation and Central Spindle Assembly Act in Redundant Pathways that Regulate Microtubule Density and Trigger Cleavage Furrow Formation." Dev Cell 4: 333-44. (PubMed)