How do molecules work together to orchestrate cellular processes? Cell division involves dramatic reorganization of intracellular structures and cellular morphology. The assembly of the mitotic spindle, segregation of the chromosome and partitioning of the cytoplasm are supported by the concerted effort of molecules. Over the years, our lab has been studying such phenomena through the characterization of key molecular players and basic biophysical processes. Recently, we are increasingly drawn to the question of how cells overcome physical extremes, for example, cell size.

The large cytoplasms in fish and amphibian embryonic cells are organized by radial arrays of microtubules called asters. Asters grow, interact and position themselves in the millimeter-sized cytoplasms. Asters allow large cells to explore its own shape and size and properly determine its future cleavage plane. In addition to studying whole embryos, we are using the Xenopus egg extract system to reconstitute the assembly, interaction and movement of microtubule asters. The key advantage of this biochemical system is its accessibility by a variety of powerful imaging methods and molecular perturbations. Our efforts will help us understand how molecular processes give rise to the cellular physiology at micrometer and minute scales.