ZFIN ID: ZDB-PUB-130211-14
The tight junction protein claudin-b regulates epithelial permeability and sodium handling in larval zebrafish, Danio rerio
Kwong, R.W., and Perry, S.F.
Date: 2013
Source: American journal of physiology. Regulatory, integrative and comparative physiology   304(7): R504--513 (Journal)
Registered Authors: Perry, Steve F.
Keywords: Claudin-b, epithelial permeability, sodium, tight junction proteins, zebrafish
MeSH Terms:
  • Animals
  • Chlorides/metabolism
  • Claudins/genetics
  • Claudins/metabolism*
  • Embryo, Nonmammalian/metabolism
  • Epithelium/physiology*
  • Gene Expression Regulation, Developmental/physiology
  • Gene Knockdown Techniques
  • Larva/growth & development
  • Larva/metabolism
  • Permeability
  • Protein Isoforms
  • Sodium/metabolism*
  • Sodium Chloride Symporters
  • Tight Junctions/metabolism*
  • Zebrafish/embryology
  • Zebrafish/growth & development*
  • Zebrafish/metabolism
PubMed: 23364531 Full text @ Am. J. Physiol. Regul. Integr. Comp. Physiol.

The functional role of the tight junction protein claudin-b in larval zebrafish (Danio rerio) was investigated. We showed that claudin-b protein is expressed at epithelial cell-cell contacts on the skin. Translational gene knockdown of claudin-b protein expression caused developmental defects, including edema in the pericardial cavity and yolk sac. Claudin-b morphants exhibited an increase in epithelial permeability to the paracellular marker polyethylene glycol (PEG-4000) and fluorescein isothiocyanate-dextran (FD-4). Accumulation of FD-4 was confined mainly to the yolk sac and pericardial cavity in the claudin-b morphants, suggesting these regions became particularly leaky in the absence of claudin-b expression. Additionally, Na+ efflux was substantially increased in the claudin-b morphants which contributed to a significant reduction in whole-body Na+ levels. These results indicate that claudin-b normally acts as a paracellular barrier to Na+. Nevertheless, the elevated loss of Na+ in the morphants was compensated by an increase in Na+ uptake. Notably, we observed that the increased Na+ uptake in the morphants was attenuated in the presence of the selective Na+/Cl--cotransporter (NCC) inhibitor metolazone, or during exposure to Cl--free water. These results suggested that the increased Na+ uptake in the morphants was at least in part mediated by NCC. Furthermore, treatment with an H+-ATPase inhibitor bafilomycin A1 was found to reduce Na+ uptake in the morphants, suggesting that H+-ATPase activity was essential to provide a driving force for Na+ uptake. Overall, the results suggest that claudin-b plays an important role in regulating epithelial permeability and Na+ handling in zebrafish.