Characterisation of a desmocollin isoform (bovine DSC3) exclusively expressed in lower layers of stratified epithelia.

Desmocollins are cadherin-like glycoproteins involved in cell adhesion and plaque formation in desmosome junctions. Three distinct isoforms, the products of different genes, have been found in bovine tissues. We have reported previously that one of these, DSC3, is expressed only in basal and lower suprabasal layers of stratified epithelia. Using RT-PCR we have now obtained the complete cDNA coding sequence of mature bovine DSC3. It has alternatively spliced 'a' and 'b' forms found in other desmocollins but is unique in having a 43 instead of a 46 base pair exon. We have characterised a monoclonal antibody, 07-4G, which is specific for the Dsc3 protein, recognising an epitope in the extracellular domain. Immunofluorescent staining with 07-4G confirms that this isoform is found only in stratified epithelia, being strongly expressed in the basal cell layers of these tissues. The intensity of expression fades gradually in the suprabasal layers and disappears completely below the upper limit of desmosome expression. These results suggest that Dsc3 plays an important role in cell epithelial differentiation.