Dissecting the interplay between forces and dynamics of the mitotic apparatus and kinetochore attachments

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Cell division, the process of generating two cells from one, is essential to life. A single cell undergoes consecutive cell divisions to generate a fully developed organism. Moreover, within any organism, dying cells are continuously replaced by new cells via cell division. A key process in cell division is the equal partitioning of the replicated DNA into two daughter cells, a process known as mitosis. During mitosis, the DNA condenses into chromosomes, each constituted by two sister chromatids and the cell cytoskeleton reorganizes into a structure known as the mitotic spindle. The microtubules (MTs) of the mitotic spindle interact with the chromosomes by connecting to specialized protein structures, the kinetochores (KTs) that assemble on each sister chromatid. The MTs of the mitotic spindle can produce forces that can move the chromosomes within the cell and eventually separate the sister chromatids and deliver them to opposite poles, ensuring formation of two daughter cells with correct DNA content. Understanding the mechanisms that regulate mitotic chromosome segregation is a key aspect of our understanding of how life is maintained and propagated. This research project explores the mechanisms responsible for generation of forces within the mitotic apparatus that lead to movement of chromatids such that they are accurately separated during mitosis. The findings of this research will be communicated and disseminated broadly. Moreover, the project will offer opportunities for interdisciplinary research training and education. Finally, an outreach activity, designed for teaching children (grades 5-8) about cell division, will be developed and offered as a permanent activity at the SEEDS - Blacksburg Nature Center and to local schools (through the Biological Sciences Outreach Program). The specific objective of this project is to dissect the interplay between forces and dynamics of the mitotic apparatus and kinetochore (KT) attachment state during specific mitotic stages. The central hypothesis is that not only the forces produced by the mitotic spindle and the dynamics of the mitotic apparatus are important to ensure correct KT attachment and accurate chromosome segregation, but that, in turn, the KT attachment state (e.g., correct vs. incorrect) can influence the dynamics of the mitotic apparatus and the distribution of forces within the mitotic spindle. The overall objective of this project will be achieved by addressing the following aims: 1. Quantitatively dissect the interplay between KT attachment types and kinetochore-fiber length/angle required for promoting and maintaining spindle pole separation. 2. Define the independent roles of MT poleward flux and KT mechanical properties in correction of KT mis-attachments. 3. Identify the mitotic apparatus mechanical properties that control anaphase chromosome dynamics. Quantitative experimental approaches will be combined with mathematical modeling to reach a level of knowledge that goes beyond the pure understanding of cellular and molecular mechanisms and allows to make predictions on how such mechanisms respond to perturbations. This project will also have broader impacts, which will be ensured through initiatives in various areas including research dissemination, interdisciplinary training of graduate and undergraduate students, and outreach to K-12 students.