NSF 0417129 Berg, Celeste A. B. Project Summary How do cell-cell interactions regulate cell shapes and movements during development? Oogenesis in the fruit fly Drosophila melanogaster is an excellent model system for answering this question. In the fruit fly ovary, follicle cells surround the oocyte in a single-layer sheet; signaling from the oocyte induces a subset of follicle cells to change their shape and position and form two tubes. These cells secrete eggshell proteins into the tube lumens to produce the dorso-lateral respiratory appendages of the eggshell. Interactions between cells coordinate this morphogenetic process. Two cell types make each tube: cells expressing the transcription factor Broad form the roof and sides of each tube, while cells expressing the rhomboid-lacZ reporter gene make the floor (Dorman et al. 2004). Evidence suggests that a "boundary" exists between the roof- and floor-forming cells since they 1) express different cell-fate and adhesion markers, 2) exhibit distinct behaviors, 3) never intermingle, and 4) coordinate their movements, even in patterning and morphogenesis mutants (James et al. 2002; James and Berg 2003; Dorman et al. 2004; Ward and Berg, unpub.). The boundary hypothesis predicts that an organizing center facilitates communication between the sub-domains of the dorsal-appendage primordia. Unlike previously described boundaries (reviewed by Irvine and Rauskolb 2001), this proposal argues that the boundary between the roof- and floor-forming cells is important for morphogenesis and that signaling across this border coordinates the movement of these two cell types. Aim one proposes experiments to test this hypothesis by examining the behavior of cell clones that are misplaced in the epithelium. Aim two investigates the signaling center by disrupting candidate molecules that are induced by the initial patterning processes and that likely coordinate the activity of the roof and floor cells. Intellectual Merit: The proposed studies will provide insight into events that produce cell shapechanges and movements within an epithelial tube (e.g., neurulation or kidney development). Boundaries regulate the growth and patterning of many insect and vertebrate tissues (reviewed by Blair 1995; Dahmann and Basler 1999; Irvine and Rauskolb 2001). This proposal extends the boundary hypothesis to encompass the regulation of cell shape-changes and movements, thus providing a new paradigm for examining disparate morphogenetic processes. Broader Impact: This proposal addresses fundamental, unsolved aspects of biology: How is cell fate translated into specific behaviors? How do cells coordinate their activities? How is the fidelity of a morphogenetic process maintained to ensure production of functional structures? The proposed studies evaluate the link between patterning and morphogenesis, provide insight into aberrations that contribute to birth defects and illuminate related processes, such as tumor growth and metastasis. The investigator trains undergraduates and graduate students at a large, diverse state university and has developed an outreach program to bring minority high-school students into the lab. She has used the materials and tools associated with this project to develop a genetics laboratory-course required of all UW biology majors (670-800 students each year). This project will introduce students to the critical thinking and scientific methods that are used to understand developmental mechanisms and will expose these students to cell biological and genetic approaches in a highly tractable model organism.
