Asymmetric Cell Division in Early Embryogenesis

Pattern formation in early development is faciliated in part by asymmetric cell divisions, where a cell divides into two daughter cells that may be different in size, contain different molecular species, and ultimately give rise to different tissues in the adult organism. We use the worm C. elegans as a model system to study the biophysical aspects of this process. One particularly interesting manifestation of asymmetric division is in the establishment of a germ cells that will go on to form the reproductive gonad in the adult organism. As with many organisms, C. elegans germ cells contain RNA and protein rich germ granules ("P-granules") that are though to play a role in keeping the germ cells in an undifferentiated stem-cell like state. However, the mechanism by which P-granules localize within the cell cytoplasm prior to an asymmetric division, as well as their nature and function, remain poorly understood. 

The Cytoskeleton - Mechanics, Assembly, and Transport

The cytoskeleton is a dynamic network of biopolymer filaments that plays a central role in many fundamental biological processes, including cell migration, cell division, and intracellular transport. Like all materials, both living and non-living, the cytoskeleton exhibits fluctuations due to underlying microscopic motion. In non-living materials this motion is due to thermal fluctuations. Although thermal fluctuations are thought to be important in biological systems as well, for example in giving rise to diffusive transport, non-thermal fluctuations from motor activity and other non-equilibrium processes also play an important role. Much of the microscopic biophysical details of these processes has been illuminated by single molecule approaches. However, the way in which these processes act collectively within the cytoplasm remains very poorly understood. We use the bending dynamics of microtubules, as well as exogenous microscopic probe particles, to  investigate the nature of this collective activity and the way in which it gives rise to fluctuating intracellular forces.