Embryogenesis of stratified squamous epithelium. I. Tissue-specific expression of keratin proteins

Although several types of modified stratified squamous epithelia are present in the adult mammal, most are presumably derived from similar embryonic progenitors. Mechanisms responsible for region-specific specialization are poorly understood. To correlate epithelial diversification with the expression of tissue-specific markers, we analyzed keratin protein composition in four representative types of rat squamous epithelia from early embryonic through adult phases of development. Keratin subsets synthesized in palatal mucosa were qualitatively similar, but differed dramatically in relative abundance. Tongue mucosa synthesized a different, but consistent subset of keratins which also changed quantitatively throughout morphogenesis. In contrast, different keratin genes were sequentially expressed during histogenesis of backskin and footpad epidermis. These data indicate that tissue-specific keratin biosynthesis is genetically predetermined early in embryogenesis.