Apr 9
Rho flares locally reinforce the tight junction barrier
Epithelial tissues are sheets of cells that create barriers in multicellular organisms, and disruption in epithelial barrier function is associated with disease. In vertebrates, tight junctions form between epithelial cells to selectively regulate which molecules can cross the barrier. In addition to serving as barriers, epithelial tissues can bend, fold, and stretch to help shape organisms and facilitate organ function, and cells within epithelia die and are replaced by cell division. While these events have the potential to disrupt barrier function, very little is known about how or whether barrier function is maintained during these processes. To answer these questions, we developed a barrier assay compatible with live imaging and discovered short-lived, localized breaches of tight junctions. These short-lived breaches correspond to visible “breaks” in tight junction proteins and are followed by “Rho flares”, or transient localized activation of the small GTPase RhoA, which promotes actomyosin contractility. We found that contraction of the junction reinforces tight junction proteins and re-establishes the barrier. Taken together, we propose that Rho flares are part of a damage control mechanism to locally repair barrier breaches in the face of events that challenge tight junctions so that overall barrier function is not compromised.