Distinct desmocollin isoforms occurinthesamedesmosomesand showreciprocally gradeddistributions inbovinenasalepidermis

Theadhesive coreofthedesmosome iscom- posedofcadherin-like glycoproteins oftwofamilies, desmo- collins anddesmogleins. Threeisoforms ofeachareexpressed inatissue-specific anddevelopmentally regulated pattern. In bovine nasal epidermis, thethree desmocollin (Dsc) isoforms areexpressed inoverlapping domains; Dsc3expression is strongest inthebasal layer, while Dsc2andDsclarestrongly expressed inthesuprabasal layers. Herein wehaveinvesti- gated whether different isoforms areassembled into thesame ordistinct desmosomes byperforming double immunogold labeling usingisoform-specific antibodies directed against DsclandDsc3. Theresults showthatindividual desmosomes harbor bothisoforms inregions wheretheir expression ter- ritories overlap. Quantification showedthattheratio ofthe proteins ineachdesmosome altered gradually frombasal to immediately suprabasal anduppersuprabasal layers, labeling forDsclincreasing andDsc3decreasing. Thusdesmosomes areconstantly modified ascells moveuptheepidermis, with continuing turnover ofthedesmosomal glycoproteins. Statis- tical analysis ofthequantitative datashoweda possible relationship between thedistributions ofthetwoisoforms. Thisgradual change indesmosomal composition mayconsti- tuteavertical adhesive gradient within theepidermis, having important consequences forcell positioning anddifferentiation. Themajordesmosomal glycoproteins, termed thedesmocol- lins anddesmogleins, aremembers ofthecadherin superfamily ofcalcium-dependent