DIFFERENTIAL EXPRESSION OF HUMAN CORNIFIN-ALPHA AND CORNIFIN-BETA IN SQUAMOUS DIFFERENTIATING EPITHELIAL TISSUES AND SEVERAL SKIN-LESIONS

Cornifins/small proline-rich proteins (SPRRs) belong to a family of pr oline-rich proteins that function as cornified envelope precursors, We report here an immunohistochemical analysis of human cornifin-alpha a nd -beta expression in several stratified squamous epithelia. In norma l human skin, cornifin-alpha was expressed in the granular layer of th e epidermis of palmoplantar skin, in the inner lining cells of the fol licular infundibulum, and in the inner root sheath of the hair follicl e. It was also expressed in the upper squamous layers of the oral, eso phageal, and vaginal epithelia, Cornifin-beta was detected in oral, es ophageal, and vaginal epithelia, but not in normal skin, Immunoblot an alysis revealed quantitative differ; ences in cornifin-alpha expressio n in skin from different regions, Studies of specimens from various sk in diseases showed that (i) cornifin-alpha was upregulated in inflamma tory skin diseases, hyperplastic lesions, and in well-differentiated s quamous cell carcinomas (SCCs), (ii) the expression of cornifin-beta w as absent in inflammatory skin but was detected in highly differentiat ed keratinocytes in well-differentiated SCCs of the skin and some othe r hyperproliferative skin lesions, and in SCCs of the oral mucosa and esophagus. Northern blot analysis revealed that cornifin-alpha mRNA wa s present in all the squamous epithelial tissues studied, whereas corn ifin-beta mRNA was expressed in oral mucosal epithelia and verrucous c arcinoma of the skin but neither in normal nor in psoriatic skin, Thes e results indicate that (i) the amount of cornifin alpha/SPRR1 express ion in normal human skin depends on the body region, (ii) cornifin-alp ha/SPRR1, but not cornifin-beta, contributes to the integrity of the h air follicle, and (iii) the expression of cornifin-beta is induced in some hyperplastic skin diseases only when the keratinocytes undergo ex tensive squamous differentiation.