Recent advances in understanding tight junctions.

Tight junctions (TJs) are one type of cell-cell junction in epithelial cell types in vertebrates. They form a paracellular diffusion barrier and create the boundary between the apical and basolateral plasma membrane domains. The molecular constituents of TJs have mostly been identified, and now their cell biology has shifted to understanding of their formation, dynamics, and functional regulation as well as their relationship to the organization of epithelial cells. Accumulating novel findings are supported by new methods, including super-resolution microscopy, quantitative microscopy, biophysical measurements, and genome editing-mediated gene manipulation. As a conceptual breakthrough, liquid-liquid phase separation seems to be involved in the formation of TJs as super-molecular complexes. This short article summarizes seminal studies in the cell biology of TJs from the last three years.