PATTERNS OF DESMOCOLLIN SYNTHESIS IN HUMAN EPITHELIA - IMMUNOLOCALIZATION OF DESMOCOLLIN-1 AND DESMOCOLLIN-3 IN SPECIAL EPITHELIA AND IN CULTURED-CELLS

Murine monoclonal antibodies (mAbs) which specifically react, in immun oblot and immunolocalization experiments, with the human desmosomal ca dherins, desmocollins Dsc1 (mAb Dsc1-U100) and Dsc3 (mAb Dsc3-U114),, have allowed to study systematically the synthesis of these proteins i n tissues and cultured cells. Application of these mAbs in immunofluor escence microscopy on human skin has shown the presence of Dsc1 in the suprabasal layers of interfollicular epidermis and a specific cell la yer of the hair follicle root sheath, whereas Dsc3 has been identified in all living epidermal layers as a ell as in glandular ducts and in basal matrix cells acid the outer root sheath of hair follicles, Dsc3, but not Dsc1, it also present in desmosomes of the basal as well as s uprabasal cell layers of other stratified epithelia such as vagina, to ngue and esophagus as well as in cells of the basal laver of bladder u rothelium and the complex epithelium of trachea. All the diverse one-l ayered (''simple'') epithelia examined were as negative for both, Dsc1 and Dsc3, as were the non-epithelial desmosomes of the intercalated d isks of the myocardium. A special situation has been discovered in the thymus, Here the usually single-layered cells of the thymic reticular epithelium are connected by Dsc3 possessing desmosomes, as they also contain typical (type 1) hemidesmosomes, whereas Dsc1 is only detected in the ''Hassall bodies'', spheroidal formations of densely parked re ticulum-derived cells which also produce cytokeratins 1 and 10, indica tive of suprabasal epidermal differentiation, In cell cultures most, p robably all, desmosomes of diverse cell lines derived from stratified squamous epithelia or squamous cell carcinomas, including primary kera tinocytes, HaCaT keratinocytes and A-431 carcinoma cells, contain Dsc3 , BS contrast, Dsc1 has only been detected in local piles of keratinoc ytes that appear to be in the process of suprabasal differentiation, T he antibodies have also allowed to demonstrate that desmosomes of cell lines can contain more than one desmocollin isoform. The observations made by immunofluorescence microscopy are compared with results obtai ned by in situ hybridization of mRNAs, and the potential value of thes e mAbs in histology and pathology is discussed.