PhD Transfer Exam – Serge Parent (Bruce/Winklbauer labs)

PhD Transfer Exam

Friday December 11th, 11:10 am – Room 432, Ramsay Wright Building, University of Toronto

Serge Parent (Winklbauer/Bruce labs)

“Characterization of the initiation and progression of intercellular adhesion between homotypic and heterotypic cells derived from Brachet’s Cleft in Xenopus and zebrafish gastrulae “

Abstract

The ability of cells within an organism to move and rearrange into separate tissues is a defining feature of animals, but it is unclear how cells initiate and maintain their separation status. My objective is to determine how tissue separation is achieved at the cellular level between adhering embryonic cells. Brachet’s cleft is a naturally occurring example of tissue separation in Xenopus laevis and zebrafish gastrulae. Brachet’s cleft has cells of one type, the ectoderm, on one side, and cells of another type, the mesoderm, on the other. In a recent publication we report the existence of “slippery” adhesions between cells taken from either side of Brachet’s cleft, named cleft adhesions. We found that the cytoskeleton at the cell-cell contact between heterotypic cell pairs was not downregulated, as it was in homotypic cell pairs. We also found extracellular matrix (ECM) at cell-cell contact sites. My hypothesis is that adhesion between embryonic cells consists of 2 phases – an initial, weaker ECM-based adhesion, and a later, stronger cadherin-based adhesion – and that adhesion between homotypic cell pairs progresses normally to the second phase, but is halted between heterotypic cell pairs at the first phase. Using cells taken from Brachet’s cleft in Xenopus laevis and zebrafish I will study the kinetics and cellular basis of these cleft adhesions and compare them to cell-cell adhesion between homotypic cells.
Ramsay Wright is a wheelchair accessible building.