THE BOVINE DESMOCOLLIN FAMILY - A NEW GENE AND EXPRESSION PATTERNS REFLECTING EPITHELIAL-CELL PROLIFERATION AND DIFFERENTIATION

We have discovered a third bovine desmocollin gene, DSC3, and studied expression of all three desmocollin genes, DSC1, 2, and 3, by Northern blotting, RT-PCR and in situ hybridization. DSC1 is strongly expresse d in epidermis and tongue papillae, showing a ''skin''-type pattern re sembling that previously described for keratins 1 and 10. Expression i s absent from the epidermal basal layer but appears in the immediate s uprabasal layers and continues uniformly to the lower granular layer. In tongue epithelium, expression is suprabasal and strictly localized to papillae, being absent from interpapillary regions. In other epithe lia low level DSC1 expression is detectable only by RT-PCR. The distri bution of Dscl glycoproteins, detected by an isoform-specific monoclon al antibody, closely reflects mRNA distribution in epidermis and tongu e. DSC2 is ubiquitously expressed in epithelia and cardiac muscle. In stratified epithelia, expression appears immediately suprabasal, conti nuing weakly to the lower granular layer in epidermis and to just abov e half epithelial thickness in interpapillary tongue, oesophageal, and rumenal epithelia. DSC3 expression is restricted to the basal and imm ediately suprabasal layers in stratified epithelia. In deep rete ridge s DSC expression strikingly resembles the distribution of stem, transi t-amplifying, and terminally differentiating cells described by others . DSC3 expression is strongly basal, DSC2 is strong in 5-10 suprabasal layers, and then weakens to be superseded by strong DSC1. These resul ts suggest that desmocollin isoform expression has important functiona l consequences in epithelial proliferation, stratification, and differ entiation. The data also provide a standard for nomenclature of the de smocollins.