A New Look Into an Old Problem: Keratins as Tools to Investigate Determination, Morphogenesis, and Differentiation in Skin

The study investigated keratin and keratin mRNA expression during the differentiation of stem cells into epidermis and hair follicles, as well as follicle morphogenesis. It found that type I keratin K14 was expressed early in embryonal basal cells and elevated in the basal layer of developing epidermis, but suppressed in developing matrix cells, indicating a biochemical distinction between diverging cell types. This expression pattern suggested a narrow developmental window for irreversible divergence in basal and matrix cells. In contrast, a hair-specific type I keratin was expressed late in hair matrix development, indicating that keratin expression might be a consequence of cell organization and differentiation rather than a cause.