John White Department Chair, James Crow Professor, Fellowship of the Royal Society Co-PI  LOCI Departments: Anatomy, Biomedical Engineering, Molecular Biology Colleges: Medical School & the Graduate School Research Areas: Cell Cycle Control, Cancer Biology, Cell Structure, Cell Motility, Cell Communication Phone: 608-265-4813/5-5428 Email: jwhite1@wisc.edu Lab website: www.molbio.wisc.edu/white Address: 401A R.M. Bock Labs                    1525 Linden Drive                    Madison, WI 53706

The research in my laboratory is focussed on two basic problems: how a cell in a developing metazoan cleaves and how the two daughter cells can acquire different fates. We are studying these processes in developing embryos of the nematode Caenorhabditis elegans. In addition, we are studying cell fusion, a striking feature of the development of the epithelium of C. elegans (Podbilewicz and White, 1994).

An animal cell cleaves by the progressive constriction of an equatorial contractile ring. We are interested in how the cleavage plane is specified, how the contractile ring forms and how the daughter cells finally become pinched off.

The first few divisions of the C. elegans embryo are asymmetric and determinative (White and Strome, 1996). My laboratory has been studying the dynamic changes in the cytoskeleton that occur during these divisions. In the course of this work we revealed a mechanism that orients the mitotic spindle and hence the cleavage plane during determinative divisions (Hyman and White, 1987) and how polarity gets established in early blastomeres (Hird and White, 1993). Recent work has revealed that a molecular complex associated with the motor protein dynene is localized to a discrete focus within the cell and acts to align the mitotic spindle.

In addition to our studies of cell division in wild-type animals, we are studying mutant animals in which these processes are perturbed. Recently, a genetic screen was initiated which has yielded an interesting collection of temperature-sensitive cell division mutants (O'Connell et al., 1998). The cellular phenotypes of these mutants are currently being determined. These data should reveal the molecular nature of some of the mechanisms of cell division.

Cell fusion is a fundamental although little studied aspect of developmental biology. Cells such as gametes or skeletal muscle cells fuse at precise developmental stages. We are studying the fusions that occur in the epithelium of C. elegans through the use of advanced microscopy and genetic techniques.