Changes in expression of the endogenous beta-galactoside-binding 14-kDa lectin of chick embryonic skin during...

Changes in the expression pattern of the gene for the endogenous beta-galactoside-binding 14-kDa lectin of chick embryo were examined immunohistochemically during epidermal differentiation in vivo and in vitro with special reference to detailed localization of the 14-kDa lectin. The gene expression was visualized by the HRP-staining method following in situ hybridization, in which sulfonated cDNA was employed as a probe. The 14-kDa lectin gene expression (mRNA) was detected mainly in the intermediate layer of the epidermis: it was faint in 13-day-old embryos, gradually increased in intensity during epidermal differentiation, and became intensely positive in 17-day-old embryo. The expression of the gene in skin explants was suppressed by vitamin A, which induces mucous metaplasia of the epidermis in vitro. The anti-14-kDa lectin reaction was positive mainly in the intermediate layer of the differentiating epidermis, coinciding chronologically with expression of the gene at the light microscopic level. Immunoelectron microscopy revealed that the positive reaction was primarily localized in desmosomes, in tonofilament bundles anchored to the desmosomes, along the outer surface of the plasma membrane, and in the intercellular space. Essentially the same staining pattern was observed in differentiating epidermis in vitro. The positive reaction was markedly reduced in the epidermis in which differentiation had been suppressed in vitro by the addition of vitamin A.