Synthesis of RNA and protein taking place during cornification was studied in human epidermis by autoradiography. Cytidine-3H incorporation was observed in almost all nuclei except 17.7% of nuclei scattered randomly and located in the outermost layer. Histidine-3H and arginine-3H concentrated in granular cells, while methionine-3H tended to concentrate in basal cells and phenylalanine-3H had a more general distribution. In the granular layer 10.4% and 10.7% of cells failed to incorporate histidine-3H and arginine-3H, respectively. The results suggest: (1) proteins of different composition are synthesized in different layers of the epidermis; and (2) granular cells stop synthesis of RNA and protein at a finite time before they are completely keratinized. This process occurs independently in granular cells suggesting that cell differentiation is regulated within individual cells.
Fukuyama K, Epstein WL. Synthesis of RNA and Protein During Epidermal Cell Differentiation in Man. Arch Dermatol. 1968;98(1):75-79. doi:10.1001/archderm.1968.01610130081016