Investigating the role of calcium dynamics and the gap junction subunit Innexin3 in Drosophila epithelial morphogenesis

Abstract

Cell-cell adhesions and intercellular ion channels, such as gap junctions regulate the synchronization of cells in an epithelium and promote proper embryonic epithelial organization and morphogenesis. Gap junctions regulate the exchange of small molecules and ions, such as calcium (Ca2+) between apposed cells. The strict maintenance of Ca2+ ion concentration across a cell membrane allows Ca2+ to function as an effective intracellular signal in epithelial sheet morphogenesis, including development and wound repair, where it coordinates cell behavior throughout the tissue. Here I used live imaging to observe Drosophila dorsal closure (DC), a model of epithelial sheet morphogenesis. I quantified endogenous calcium flashes in the lateral epidermis, the spread of Ca2+ following single cell wounds, and perturbed extracellular Ca2+ concentrations to demonstrate the necessity of calcium in maintaining the coordinated movements of epithelial sheets in DC. I also genetically and pharmacologically reduced gap junction subunit functionality. I have observed that the knockdown of single ion channel subunits results in the partial penetrance of morphological abnormalities during DC. The intercellular calcium dynamics in the lateral epidermis are modified in gap junction mutants. Lastly, pan-innexin inhibition using gap junction antagonists completely halts DC, resulting in a large coordinated release of intracellular Ca2+ and disruption of cell junction adhesion in the amnioserosa.