Prof Stephanie Woo
University of California Merced
The early zebrafish endoderm as a model of mesenchymal-to-epithelial transitions
Our lab investigates the cell biological mechanisms underlying tissue morphogenesis. Although much progress has been made in understanding the molecular genetics of tissue specification and organ patterning, the dynamic cell behaviors that contribute to organ shape and function are less well understood. The gastrointestinal epithelium is derived from an embryonic tissue called the endoderm. During development, endodermal cells are highly migratory but display different migration behaviors depending on developmental stage. At early stages, they exhibit directionally random, single-cell migration, but at later stages, they undergo a mesenchymal-to-epithelial transition (MET) to converge and adhere together into a coherent endodermal sheet. Our lab uses high-resolution imaging of live zebrafish embryos to investigate the transition from single-cell migration to endodermal sheet formation. We have identified three cellular processes that appear to contribute to sheet formation: the initiation of Cadherin-dependent adhesion complexes, changes in a form of cell-cell interaction called contact-mediated repulsion, and changes in the attachment of the plasma membrane to the cortical actin cytoskeleton. These studies establish the developing zebrafish endoderm as a much-needed in vivo model of de novo epithelium formation.