Connexin Expression Patterns in the Rat Cornea: Molecular Evidence for Communication Compartments

PURPOSE.To identify and localize candidate connexin family members in adult rat cornea that may be important in coordinating corneal cell biology. METHODS.To identify candidate connexin family members in adult rat cornea, a RT-PCR–based screening approach was initially adopted. Fourteen pairs of connexin isoform-specific primers were used to amplify connexin transcripts from two populations of RNA isolated from either the central cornea or the whole cornea. Immunohistochemistry and confocal microscopy were then used to confirm the presence and localization of connexins. RESULTS.Eight connexin transcripts (Cxs 26, 30.3, 31, 31.1, 33, 37, 43, 50) are present in central cornea, and the peripheral cornea additionally expresses Cxs 30, 40, 45, and 46. No Cx32 or Cx36 transcripts were amplified. Immunohistochemistry revealed that Cxs 26, 30, 31.1, 37, and 43 are expressed in spatially distinct patterns within the cornea. Cx26 and Cx43 occur in basal cells of the whole corneal epithelium and between endothelial cells. Cx26 also immunolocalizes to the first layer of intermediate epithelial cells, and Cx43 antibody labels stromal keratocytes. Cx30 is expressed in the peripheral corneal epithelium and disappears toward the central cornea. Cx31.1 expression is restricted to superficial corneal epithelial cells, and Cx37 spans the intermediate corneal epithelium. CONCLUSION.The spatially distinct cellular expression patterns of Cxs 26, 30, 31.1, 37, and 43 in the corneal epithelium imply that gap junctions play important roles in controlling corneal epithelial proliferation and differentiation and overall corneal maintenance.