Retinoic acid induction of featherlike structures from reticulate scales.

Retinoic acid-induced transformation of reticulate scales to feather-like structures (Dhouailly and Hardy, '78) provides a useful model to study biochemical differentiation in avian skin. In this study, immunofluorescent analysis of reticulate scale-feathers (RSFs) indicates that they contain beta keratin in feather barbs and, thus, are true feathers, biochemically. Epidermal cells that would otherwise produce only alpha keratin in reticulate scales are induced to reorganize and differentiate into barb ridge cells that accumulate feather beta keratins. The mechanism for these dramatic morphological and biosynthetic responses to retinoic acid is unknown.