Investigating novel functions of septate junction proteins during morphogenesis in Drosophila

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The final shape of an animal is determined by developmental events that rely on morphogenetic (change in form) processes including cell shape changes and cell rearrangements. Many of the mechanisms that provide spatial and temporal control over morphogenesis are conserved in all animals, yet knowledge is still lacking on how these processes work. For example, the current understanding of mechanisms that allow mechanical forces to propagate through a tissue is inadequate to fully explain morphogenesis in many developmental events. Thus investigating these control mechanisms in a simple model organism such as the fruit fly (Drosophila melanogaster) provide understanding of basic developmental processes that are shared by all animals. The Ward lab has identified a number of proteins that appear to function together in several morphogenetic events during embryogenesis in the fly. This research focuses on the molecular functions of these proteins in generating and propagating mechanical forces through a tissue during embryogenesis. In addition to the scientific advancements that will result from this study, this project will increase the participation of first generation and underrepresented minority high school and college students in authentic scientific research. Specifically, the PI will develop a new program to engage high school students from Kansas City, KS in a summer-long research experience centered on using model system genetics to study development. The PI is also a mentor for several programs aimed at increasing the participation of underrepresented groups in the sciences at the University of Kansas, including teaching a course on developing skills to apply to graduate school in STEM disciplines.Morphogenetic events are triggered and controlled by developmentally-regulated signaling pathways that lead to actomyosin dynamics in individual cells. These forces must then be propagated through the epithelium and maintained in order to elicit appropriate tissue-level morphological changes. Although much is known about actomyosin dynamics, less is known about the cellular mechanisms involved in force propagation through a tissue. In preliminary studies, the PI determined that a large collection of genes that encode core septate junction (SJ) components are required for embryonic morphogenetic events in the fly. The SJ is a large protein complex that functions as an occluding junction. Importantly, the requirement for these genes occurs prior to the formation of the occluding junction, indicating a novel function for these proteins in morphogenesis. The overall goal of this project is to provide mechanistic understanding of how SJ proteins facilitate morphogenetic processes during dorsal closure (DC), a well-studied developmental event that occurs midway through Drosophila embryogenesis. The following aims will be addressed: (1) to determine if SJ proteins regulate the assembly and dynamics of actomyosin complexes during DC, (2) to determine if SJ proteins are required for biomechanical or adhesive functions during DC, and (3) to determine if SJ proteins are required to maintain apical/basal polarity. Actomyosin dynamics will be examined by live imaging and on fixed tissues with antibodies that reveal activated myosin complexes, while biomechanical properties will be probed by laser microsurgery experiments.