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【Abstract】

Tight junctions act as continuous intercellular barriers between epithelial cells. These barriers are required to separate tissue spaces and regulate in and out movement of solutes across the epithelium. The actomyosin contractility regulates the permeability and morphology of tight junctions. The circumferential actomyosin belt, through its connections to the tight junctions, functions as force-transmitter between neighboring cells thereby integrating overall shape changes of cell sheets during animal development. The tight junction is close to the apical actin network that exerts inward contractions orthogonal to the tight junction. To determine the contribution of apical actin network to the overall integrity of a cell, we laser-ablated the apical surface of polarized MDCK epithelial cells. We found that laser ablation disrupted the apical cytoskeleton network, decreased in-plane tension, and increased the apical surface area. The tight junction also became less tortuous in shape after laser ablation. Upon addition of ROCK inhibitor Y27632, the density of the apical actin network increased and tight junction tortuosity decreased. Our findings show the importance of the apical actin network in exerting in-plane apical tension to regulate tight junction mechanobiology and epithelial cell shape. Currently, we are also looking into the connection of the actin-myosin network in the terminal web in regulating tight junctions through expansion microscopy.