Precise cell division is essential for life. Mistakes during this process lead to many diseases, including cancer. The mitotic spindle is the engine that moves chromosomes, and it therefore plays an essential role in ensuring that newly-born cells inherit a complete genetic blueprint. A key feature of the spindle is its bipolarity, a geometry that ensures bi-directional chromosome movements. Non-bipolar geometries, such as monopolarity or multipolarity, cause errors in chromosome segregation that are incompatible with life. Therefore, non-bipolar structures must be reorganized to be bipolar prior to the onset of the anaphase stage of mitosis. Spindle formation is a complex process that is mediated by many microtubule-associated proteins (MAPs) and molecular motors (i.e., kinesins and dynein). The mechanisms of spindle assembly can vary among organisms, and can show remarkable plasticity even within a single organism. The malleability of spindle assembly is derived from how MAPs and motor proteins engage each other, either directly or indirectly through a network of dynamic MTs. The sophisticated nature of these systems-level relationships has made it difficult to fully understand the mechanisms that drive spindle formation, despite decades of research. Our unique approach has been to isolate and characterize human cell lines that survive in the absence of the major spindle assembly pathway driven by the kinesin Eg5 in eukaryotes. Our work has taught us that human cells can assemble a proper mitotic spindle using an auxiliary pathway. Furthermore, we identified a kinesin (Kif15) that is essential for this alternate mechanism. Ongoing work in our lab has unveiled systems-level changes in cells that require Kif15 for cell division, motivating efforts to obtain a better understanding of how spindle motors function at a systems level within the spindle. In this renewal application, we will address three key questions: 1) How does Kif15 drive spindle assembly?; 2) How is Kif15 activity regulated during cell division?; and 3) What roles do motors and chromosomes play in centrosome clustering? This work will advance our understanding of spindle mechanics and have immediate relevance to the development of anti-mitotic chemotherapeutic strategies.
Regulation of microtubule dynamics and organization during cell division Ryoma Ohi, Ph.D. PROJECT NARRATIVE Bipolarity is an essential feature of the mitotic spindle, a microtubule-based machine that segregates a replicated set of chromosomes equally among two daughter cells during mitosis. Using chemical genetics, we discovered a new spindle assembly pathway, the protein factor (Kif15) that drives it, tools to study how the new spindle assembly pathway works, and relevance of Kif15 to other aspects of mitosis. In this renewal application, we will address three key questions: 1) How does Kif15 drive spindle assembly?; 2) How is Kif15 activity regulated during cell division?; and 3) What roles do motors and chromosomes play in centrosome clustering?
Showing the most recent 10 out of 18 publications
