The sequential expression of tenascin mRNA in epithelium and mesenchyme during feather morphogenesis.

I have studied the distribution of tenascin and its transcript during feather germ morphogenesis using immunohistochemistry and in situ hybridization. Anti-tenascin staining is intense in the periphery of dermal core condensations in both the feather rudiment and bud. There is faint anti-tenascin immunoreactivity in the overlying epithelium, but the apex of the bud is unstained. The appearance of tenascin in the developing feather is transient, as no significant anti-tenascin staining can be detected in the feather shaft or follicle at later stages of development. In situ hybridization with a tenascin cDNA probe reveals tenascin mRNA in the epithelial placode of the feather rudiment and early bud. In contrast, tenascin mRNA is concentrated in the dermis in the late feather bud. Therefore, at the time when inductive events are taking place, the expression of tenascin flips from the epithelium overlying tenascin-rich mesenchyme to the mesenchyme itself.