Claudins and JAM-A coordinately regulate tight junction formation and epithelial polarity

Area of Science:

• Cell Biology
• Epithelial Biology
• Membrane Protein Function

Background:

• Tight junctions (TJs) are critical for epithelial barrier function and polarity.
• The precise roles of TJ components, such as claudins and scaffolding proteins (ZO-1/ZO-2), in TJ organization and polarity remain incompletely understood.

Purpose of the Study:

• To elucidate the distinct and cooperative roles of TJ components, including claudins, ZO-1/ZO-2, and JAM-A, in the formation of TJ structures, epithelial barriers, and epithelial polarity.

Main Methods:

• Systematic knockout of TJ components using genome editing in epithelial cells.
• Assessment of TJ structure, epithelial barrier integrity (paracellular permeability to electrolytes and macromolecules), and epithelial polarity.

Main Results:

• ZO-1/ZO-2 deficiency abolished TJ structures and epithelial barriers.
• Claudin deficiency disrupted TJ strands and the electrolyte barrier but preserved membrane appositions and the macromolecule barrier, without affecting epithelial polarity.
• Simultaneous knockout of claudins and JAM-A led to loss of membrane appositions, macromolecule barrier defects, and sporadic polarity issues.

Conclusions:

• Claudins and ZO-1/ZO-2 play distinct roles in TJ formation and barrier function.
• Claudins and JAM-A cooperate to establish TJ-mediated membrane appositions and regulate epithelial polarity.