Characterization of Corn1 mice: Alteration of epithelial and stromal cell gene expression

PURPOSE: Corn1 is an autosomal recessive mutation characterized by corneal epithelial hyperplasia and stromal neovascularization. The aim of the prese nt study is to examine the expression patterns of specific epithelial and s tromal proteins in corn/corn1 mutant mice. METHODS: Immunohistochemistry with antibodies directed against keratins 1, 4, 5, 12, and 14 as well as loricrin, filaggrin, and involucrin were perfor med in corn1/corn1 and wild type, A.By/SnJ strain, mice at 4 weeks of age. Western blot hybridization was performed to confirm the presence of involuc rin in corneas. In situ and northern blot hybridization were used to evalua te the expression of keratin 12, lumican, and keratocan in these mice. RESULTS: In corn1/corn1 mice, focal areas of corneal epithelial hyperplasia alternate with epithelium with normal appearance. Both regions of normal a nd hyperplastic corneal epithelium were labeled by anti-keratin 12 antibodi es through all corneal epithelial layers. The anti-keratin 14 antibody only labeled the basal cell layer in normal epithelial areas, whereas it labele d both basal and suprabasal cell layers in hyperplastic areas. In wild type mice, anti-keratin 12 antibodies labeled all corneal epithelial layers, wh ereas anti-keratin 14 labeled the basal corneal epithelial cells only. Posi tive staining by anti-involucrin antibody was demonstrated in the basal cor neal epithelial layer of wild type mice and normal areas of corn1/corn1 mic e. Similarly, as observed with anti-keratin 14 antibody, the anti-involucri n antibody labeled both basal and suprabasal cell layers of hyperplastic co rneal epithelium of corn1/corn1 mice. Antibodies against keratin 1, keratin 4, loricrin, and fillagrin did not label the corneas of wild type mice or corn1/corn1 mice. Northern hybridization indicated that the expressions of keratocan and lumican mRNA levels were up regulated in corn1/corn1 mice, bu t keratin 12 mRNA remained similar to that of the wild type mice. In situ h ybridization revealed that the lumican mRNA was detected in epithelial and stromal cells of corn1/corn1 mice, whereas keratocan mRNA was only detected in stromal cells. CONCLUSIONS: Hyperproliferative epithelial cells of corn1/corn1 mice have i ncreased levels of expression of keratin 14 and involucrin, but do not exhi bit the phenotypical characteristics of cornification. These observations i ndicate that factors associated with the phenotypes of corn1/corn1 mice do not alter the cornea-type epithelial differentiation of keratin 12 expressi on, but cause aberrant expression of lumican by corneal epithelial cells.