Expression of a single pair of desmosomal glycoproteins renders the corneal epithelium unique amongst stratified epithelia.

PURPOSE To determine desmosomal glycoprotein isoform expression in bovine corneal, limbal, and conjunctival epithelium and desmosomal profile and distribution during corneal re-epithelialization. METHODS Immunofluorescence (IF) for desmosomal components on cryostat sections of fresh epithelia was supported by immunoblot analysis of tissue lysates. Wounded corneas maintained in organ culture were examined by IF at times up to full re-epithelialization (96 hours). RESULT Immunofluorescence for desmoplakin confirmed desmosome presence throughout all three epithelia. Plakoglobin was also ubiquitous. Of the desmosomal glycoproteins, desmocollin 2 (Dsc2) and desmoglein 2 (Dsg2) were expressed throughout, but Dsc3 and Dsg3 were confined to the limbus and conjunctiva, and Dscl and Dsgl were absent. Dsc2 and Dsg2 IFs were stronger in superficial layers, but Dsc3 and Dsg3 were stronger basally, fading suprabasally. Glycoprotein expression in cornea and conjunctiva was confirmed by immunoblot analysis. No change in glycoprotein expression occurred during re-epithelialization. CONCLUSIONS Uniquely among stratified epithelia, cornea expresses only a single pair of desmosomal glycoproteins, Dsc2 and Dsg2. Expression of Dsc3 and Dsg3 in limbus and conjunctiva coincides with their association with cell proliferation in other epithelia, but corneal epithelial cells did not express Dsc3 or Dsg3 during re-epithelialization. Absence of Dscl and Dsgl correlates with lack of keratinization in ocular epithelia. These expression patterns may have significance for the specific properties and differentiation patterns of the epithelia. Presence of desmosomes throughout re-epithelialization raises the question of how migrating cells mutually re-position.