Claudin 4 knockout mice: normal physiological phenotype with increased susceptibility to lung injury

Am J Physiol Lung Cell Mol Physiol. 2014 Oct 1;307(7):L524-36. doi: 10.1152/ajplung.00077.2014. Epub 2014 Aug 8.


Claudins are tight junction proteins that regulate paracellular ion permeability of epithelium and endothelium. Claudin 4 has been reported to function as a paracellular sodium barrier and is one of three major claudins expressed in lung alveolar epithelial cells (AEC). To directly assess the role of claudin 4 in regulation of alveolar epithelial barrier function and fluid homeostasis in vivo, we generated claudin 4 knockout (Cldn4 KO) mice. Unexpectedly, Cldn4 KO mice exhibited normal physiological phenotype although increased permeability to 5-carboxyfluorescein and decreased alveolar fluid clearance were noted. Cldn4 KO AEC monolayers exhibited unchanged ion permeability, higher solute permeability, and lower short-circuit current compared with monolayers from wild-type mice. Claudin 3 and 18 expression was similar between wild-type and Cldn4 KO alveolar epithelial type II cells. In response to either ventilator-induced lung injury or hyperoxia, claudin 4 expression was markedly upregulated in wild-type mice, whereas Cldn4 KO mice showed greater degrees of lung injury. RNA sequencing, in conjunction with differential expression and upstream analysis after ventilator-induced lung injury, suggested Egr1, Tnf, and Il1b as potential mediators of increased lung injury in Cldn4 KO mice. These results demonstrate that claudin 4 has little effect on normal lung physiology but may function to protect against acute lung injury.

Keywords: RNA sequencing; alveolar epithelial barrier; alveolar fluid clearance; permeability; ventilator-induced lung injury.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Lung Injury / genetics
  • Acute Lung Injury / physiopathology
  • Alveolar Epithelial Cells / physiology
  • Animals
  • Capillary Permeability
  • Cells, Cultured
  • Claudin-4 / genetics*
  • Claudin-4 / metabolism
  • Female
  • Gene Knockout Techniques
  • Genetic Predisposition to Disease
  • Hyperoxia / genetics
  • Hyperoxia / metabolism
  • Lung / pathology
  • Mice
  • Mice, 129 Strain
  • Mice, Knockout
  • Phenotype
  • Transcriptome
  • Ventilator-Induced Lung Injury / genetics*
  • Ventilator-Induced Lung Injury / physiopathology


  • Claudin-4
  • Cldn4 protein, mouse