Forces and molecules that shape tissue across the evolution of Drosophilid species

University Of Washington, Seattle WA

Investigators

Abstract

Animals exhibit an amazing variety of shapes and forms, yet the variations have evolved by modifying fundamental developmental processes shared by all animals. For example, a human hand, a bat's wing, and a whale's flipper all arise from a common set of instructions that direct the activities of highly conserved molecules that regulate cellular structure, signaling, and adhesion. Although these processes that give tissues and organs their shape are essential to multicellular life, surprisingly little is known about the underlying mechanisms that regulate the shapes of tissues. This project investigates the physical forces, cellular behaviors, and molecular regulators that determine tissue shape by exploring the formation of eggshell appendages in Drosophila melanogaster (fruit flies) and related Dipteran (fly) species. This work develops a novel technique to measure cellular forces and generates new genomic and gene expression data from across a variety of unexplored species. Additionally, this project brings teachers and students into the laboratory to carry out independent research projects, learn firsthand about the logic and methods of science, and develop STEM lesson plans related to the mechanisms underlying, and evolution of tissue shape. Epithelial tubes are important features of multi-cellular life and form the framework controlling the shape of many internal organs. While the molecular and cellular mechanisms underlying tube formation are heavily studied, the mechanisms controlling tube morphology are less well understood. This project uses the dorsal appendages (DAs) of the Drosophila eggshell as a system in which to study the control of tube shape. The DA system is an ideal system in which to address questions of tube formation both because the fundamental mechanisms underlying patterning and the initiation of tube formation have already been heavily studied, and because eggshell appendages vary considerably in shape from one Drosophilid species to another allowing comparative approaches. Within the context of DA formation, the investigators measure the pattern of physical forces exerted by follicle cells on the extracellular matrix, and test whether these forces at the basal surface predict the extent of tube elongation and overall tube geometry. The role of apical cell-shape changes on tube morphology, are also being examined with a special focus on the roles of the motor protein, myosin and the polarity protein, Par3 (Bazooka in flies). Finally, the group is profiling transcriptional differences between species with unique appendage morphologies, with the aim of identifying the molecular changes that facilitated the evolution of shape. This work reveals and describes the forces that drive changes in organ shape and tissue morphogenesis. Furthermore the project provides hands-on opportunities for teachers and students to be involved in basic research in genetics, biomechanics and development. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.