DISTINCT DESMOCOLLIN ISOFORMS OCCUR IN THE SAME DESMOSOMES AND SHOW RECIPROCALLY GRADED DISTRIBUTIONS IN BOVINE NASAL EPIDERMIS

The adhesive core of the desmosome is composed of cadherin like glycop roteins of two families, desmocollins and desmogleins. Three isoforms of each are expressed in a tissue-specific and developmentally regulat ed pattern. In bovine nasal epidermis, the three desmocollin (Dsc) iso forms are expressed in overlapping domains; Dsc3 expression is stronge st in the basal layer, while Dsc2 and Dsc1 are strongly expressed in t he suprabasal layers. Herein we have investigated whether different is oforms are assembled into the same or distinct desmosomes by performin g double immunogold labeling using isoform-specific antibodies directe d against Dsc1 and Dsc3. The results show that individual desmosomes h arbor both isoforms in regions where their expression territories over lap, Quantification showed that the ratio of the proteins in each desm osome altered gradually from basal to immediately suprabasal and upper suprabasal layers, labeling for Dsc1 increasing acid Dsc3 decreasing. Thus desmosomes are constantly modified as cells move up the epidermi s, with continuing turnover of the desmosomal glycoproteins. Statistic al analysis of the quantitative data showed a possible relationship be tween the distributions of the two isoforms. This gradual change in de smosomal composition may constitute a vertical adhesive gradient withi n the epidermis, having important consequences for cell positioning an d differentiation.