Rho Flares Repair Local Tight Junction Leaks

• Published in: Developmental cell 2019-02, Vol.48 (4), p.445-459.e5
• Main Authors: Stephenson, Rachel E., Higashi, Tomohito, Erofeev, Ivan S., Arnold, Torey R., Leda, Marcin, Goryachev, Andrew B., Miller, Ann L.
• Format: Article
• Language: English
• Subjects: actin; Actins - metabolism; Adherens Junctions - metabolism; Animals; barrier assay; Caco-2 Cells - cytology; Epithelial Cells - metabolism; epithelium; Humans; junction contraction; leak pathway; Membrane Proteins - metabolism; myosin II; Phosphoproteins - metabolism; Rho GTPase; rho-Associated Kinases - metabolism; tight junction; Tight Junctions - metabolism; Tight Junctions - pathology; Xenopus; Xenopus laevis - metabolism; ZnUMBA (Zinc-based Ultrasensitive Microscopic Barrier Assay)
• ISSN: 1534-5807; 1878-1551
• DOI: 10.1016/j.devcel.2019.01.016

Tight junctions contribute to epithelial barrier function by selectively regulating the quantity and type of molecules that cross the paracellular barrier. Experimental approaches to evaluate the effectiveness of tight junctions are typically global, tissue-scale measures. Here, we introduce Zinc-based Ultrasensitive Microscopic Barrier Assay (ZnUMBA), which we used in Xenopus laevis embryos to visualize short-lived, local breaches in epithelial barrier function. These breaches, or leaks, occur as cell boundaries elongate, correspond to visible breaks in the tight junction, and are followed by transient localized Rho activation, or Rho flares. We discovered that Rho flares restore barrier function by driving concentration of tight junction proteins through actin polymerization and ROCK-mediated localized contraction of the cell boundary. We conclude that Rho flares constitute a damage control mechanism that reinstates barrier function when tight junctions become locally compromised because of normally occurring changes in cell shape and tissue tension. [Display omitted] •ZnUMBA is a novel zinc-based ultrasensitive microscopic barrier assay•ZnUMBA detects transient, localized tight junction breaches in developing epithelia•Rho flares rapidly repair tight junctions to minimize leakiness at breach points•Actomyosin-mediated junction contraction promotes tight junction reinforcement Epithelial barrier function is critical for normal organ function. Stephenson et al. present a barrier assay capable of detecting transient breaches of the epithelial barrier with high spatial and temporal resolution. Additionally, they find that Rho flares promote actomyosin-mediated junction contraction, which rapidly repairs transient leaks to maintain barrier integrity.