Unraveling the mechano-responsive mechanisms at Focal Adherens Junctions

Abstract

Formation and maintenance of cell-cell junctions is paramount for proper epithelial and endothelial barrier formation. Cell-cell adhesions are regulated by chemical and mechanical cues from the environment. Mechanical regulation of both epithelial and endothelial barrier occurs predominantly through the cadherin junctions and the actin cytoskeleton. In this thesis we investigate a subset of cadherin junctions that are mechanically regulated, the Focal Adherens Junctions (FAJs). We discovered that these junctions are different in morphology and in a state of remodeling induced through actomyosin contractility. More importantly they seem to have a different molecular composition compared to stable, mature cadherin junctions. Indeed, we discovered the tension dependent recruitment of vinculin, VASP, zyxin and TES at the FAJs. To further elucidate the molecular composition of FAJs, we performed a pull down on these junctions and analyzed the protein sample using Mass Spectrometry. This resulted in a list of novel proteins possibly involved in FAJs formation. Lastly, in this thesis we establish the use of Salivary Gland Organoids (SGOs) as a tool to study branching morphogenesis. The ability to image this process, which is regulated by changes in tissue mechanics and involves massive remodeling of cell-cell junctions, live on the microscope, will allow us to investigate the importance of FAJs and the proteins involved in these mechanosensitive cell-cell junctions in branching morphogenesis.