Synthesis of RNA and Protein During Epidermal Cell Differentiation in Man

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.