How Signaling Molecules Affect the Invagination and Posterior Migration of the Drosophila Salivary Gland

Johns Hopkins University, Baltimore MD

Investigators

Abstract

How Signaling Molecules Affect the Invagination and Posterior Migration of the Drosophila Salivary Gland The model organism Drosophila melanogaster serves as a valuable system for the understanding of human congenital diseases. As the animal model with some of the most sophisticated tools available for the purposes of genetic manipulation, it provides unlimited potential for discovery of essential signaling pathways in organ formation and positioning. Our laboratory utilizes the embryonic Drosophila salivary gland (SG), visible during the processes of cellular invagination and directed cell migration through the use of fluorescent staining, as a model of simple, unbranched epithelial tube formation analogous to formation of the human digestive system and associated glandular tissues. Whereas the cellular mechanisms contributing to the two key processes mentioned above have been described by our group and others, the signaling pathways involved in their coordination remain largely undiscovered. We hypothesize that the transcription factor Hückebein (Hkb) mediates localized secretion of the signaling molecule gene encoded by folded gastrulation (fog) in the SG, activating a candidate SG-expressed G-protein-coupled-receptor to coordinate apical constriction during tissue invagination. We propose that Hkb-mediated trafficking of Fog and, potentially, its cognate GPCR to the apical membrane is through Hkb-dependent transcription of the gene encoding the kinesin-binding protein Klarsicht, which has been implicated in vesicle trafficking. We also seek to uncover the signaling interactions between the SG and the surrounding tissues that mediate its posterior migration, which our laboratory has previously determined to be the circular visceral mesoderm (cVM), gastric caecae, somatic mesoderm, and fat body. We hypothesize that a to be discovered ligand and receptor pair work together to initiate posterior migration of the internalized SG along the visceral mesoderm, facilitating the reorientation of tube movement from a dorsal to a posterior trajectory. Utilizing various tools of genetic manipulation, including targeted gene silencing by RNA interference, gene disruption by CRISPR/Cas9 genetic editing, in combination with tissue-specific misexpression by the Gal4/UAS system, I propose to test the molecular mediators of the GPCR pathway involved in SG cell invagination and identify the signaling molecules contributing to posterior migration of the internalized SG. This research will help to uncover the roles of both autocrine and paracrine signaling in SG morphogenesis, and perhaps even reveal developmental pathways contributing to the etiology of congenital diseases in a variety of organisms.