Pax-6 is expressed early in the differentiation of a corneal epithelial model system

J Cell Physiol. 2009 Aug;220(2):348-56. doi: 10.1002/jcp.21771.


Pax-6 is a regulatory gene with a major role during visual system development, but its association with corneal epithelial differentiation is not clearly established. Using the RCE1-(5T5) cell line, which mimics corneal epithelial differentiation, we analyzed Pax-6 biological role. Immunostaining of proliferating colonies and confluent sheets showed that Pax-6-positive cells were also K3 keratin-positive, suggesting that Pax-6 is expressed in differentiating cells. Pax-6 mRNA was barely expressed in early cell cultures; but after confluence, its levels raised up to fivefold as demonstrated by Northern blot and RT-qPCR. The raise in Pax-6 expression preceded for 9 h the increase in LDH-H and LDH-M mRNAs, previously shown as early markers of corneal epithelial cell differentiation. The full-length mRNAs encoding for the two major Pax-6 isoforms were found at very low levels in proliferating cells, and abundantly expressed in the confluent stratified epithelia; Pax-6 mRNA was 2- to 2.5-fold more abundant than Pax-6(5a) mRNA. The ectopic expression of Pax-6 or Pax-6(5a) decreased proliferative ability leading to the formation of abortive, non-proliferative colonies. In contrast, culture conditions that delay or block corneal epithelial cell differentiation reduced or inhibited the expression of Pax-6. Collectively, results show that Pax-6 is the earlier differentiation marker expressed by corneal epithelial cells, and open the possibility for a major role of Pax-6 as the main driver of the differentiation of corneal epithelial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biomarkers / metabolism
  • Cadaverine / metabolism
  • Cell Differentiation / physiology*
  • Cell Line
  • Cornea* / cytology
  • Cornea* / physiology
  • Epithelial Cells / cytology
  • Epithelial Cells / physiology*
  • Eye Proteins / genetics
  • Eye Proteins / metabolism*
  • Gene Expression Regulation, Developmental
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Keratin-3 / genetics
  • Keratin-3 / metabolism
  • Lactate Dehydrogenases / genetics
  • Lactate Dehydrogenases / metabolism
  • PAX6 Transcription Factor
  • Paired Box Transcription Factors / genetics
  • Paired Box Transcription Factors / metabolism*
  • Phenotype
  • Rabbits
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*


  • Biomarkers
  • Eye Proteins
  • Homeodomain Proteins
  • Keratin-3
  • PAX6 Transcription Factor
  • Paired Box Transcription Factors
  • Repressor Proteins
  • Lactate Dehydrogenases
  • Cadaverine