Claudin 2 mRNA and protein are present in human keratinocytes and may be regulated by all-trans-retinoic acid

Skin Pharmacol Physiol. 2008;21(4):211-7. doi: 10.1159/000135637. Epub 2008 May 29.


Tight junctions are composed of claudins, occludins, junctional adhesion molecules and plaque proteins. Claudin 2 protein forms a cation-selective channel which confers increased permeability in renal epithelial cells and in the intestine where its expression is restricted to the leaky epithelium. Immunohistochemical staining revealed claudin 2 staining in the granular layer of adult epidermis. Analysis of Western blots revealed bands corresponding to the molecular weight of claudin 2 in Madin-Darby canine kidney II cells, human kidney, adult skin and neonatal keratinocytes. Reverse transcriptase polymerase chain reaction on mRNA and cDNA sequence analysis found a 99% sequence homology between our cDNA and human claudin 2 (NIH BLAST sequence). Further, we show that all-trans-retinoic acid increases the expression of claudin 2 in keratinocytes in a dose-dependent manner. The discovery of claudin 2 transcript and protein in the skin could be of importance in epidermal differentiation, barrier function and pathological conditions.

MeSH terms

  • Adult
  • Animals
  • Blotting, Western
  • Cells, Cultured
  • Claudins
  • Dogs
  • Epidermis / drug effects
  • Epidermis / metabolism
  • Humans
  • Immunohistochemistry
  • Infant, Newborn
  • Keratinocytes / drug effects
  • Keratinocytes / metabolism*
  • Membrane Proteins / biosynthesis*
  • Membrane Proteins / genetics
  • Permeability
  • Polymerase Chain Reaction
  • RNA, Messenger / biosynthesis*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tight Junctions / metabolism
  • Tretinoin / pharmacology*


  • CLDN2 protein, human
  • Claudins
  • Membrane Proteins
  • RNA, Messenger
  • Tretinoin