PhD Proposal Seminar – Sirma User (Bruce Lab)

Structural and Molecular Characterization of the EVL-Deep Cell Boundary during Zebrafish Development

Abstract

Epiboly is the first morphogenetic event during zebrafish development, when the epithelial enveloping layer (EVL) cells spread from the animal to the vegetal pole to surround and enclose the embryo, while mesenchymal deep cells underneath the EVL, intercalate to thin and spread without intermixing with the EVL cells. This is similar to the ectoderm-mesoderm boundary in frog embryos, where Eph receptors and their Ephrin ligands mainly facilitate the adhesive and repulsive movements of tissue-specific cells without mixing. Our lab showed that EVL and deep cells interact through filopodia, however it is not yet known whether these interactions, as well as Eph/Ephrin signaling, function at the EVL-deep cell boundary formation during zebrafish development and how this might contribute to embryonic tissue formation.

I hypothesize that the physiological gap in between EVL and deep cell compartments in zebrafish embryos is both a result and a requirement for successful adhesion and repulsion events that drive tissue boundary formation during early epiboly, and that Eph/Ephrin signaling regulates this through filopodial interactions. My first aim is to develop a method to measure the cell free volume in between EVL and deep cells to capture volume differences at different stages of the development, as well as in different experimental conditions. Together with molecular manipulation of interfacial processes, this approach will enable me to identify the physiological function of the gap. In addition, pharmacological disruption of Eph/Ephrin signaling suggested a potential role in epiboly and EVL-deep cell boundary. Therefore, my second aim is to identify specific Eph receptor and Ephrin ligand pair(s) involved in these events. I am currently developing various constructs to examine Eph-Ephrin pairs as candidates for future experiments. Finally, I plan to identify spatio-temporal regulations of identified receptor-ligand partners at the EVL-deep cell boundary. The goal of my project is to understand the molecular mechanisms underlying these cellular movements and interactions during early embryogenesis and identify developmental defects that may contribute to the adult organism later in the development.