Changes in nuclear DNA and RNA during epidermal keratinization.

The distribution of nucleic acids within nuclei of epidermal cells in skin from guinea-pig ear was investigated using an indirect enzyme digestion technique to observe both DNA and RNA, and a direct Schiff-Thallium reaction technique, to observe DNA alone. Similar results were obtained by both methods. The distribution of DNA and RNA change gradually in nuclei as epidermal cells differentiate. DNA in cells of the lower strata is localized in essentially the same areas in which electron-opaque components are seen by conventional electron microscopy. With the cytochemical treatments, however, we found that DNA is not present in all electron-opaque areas of nuclei in superficial granular cells. RNA is present in the nucleoli of cells in all layers, but its density is also lower in the upper granular cells. We postulate that nucleic acids in nuclei of granular cells gradually decrease and that the space is filled with newly synthesized electron-dense protein, as part of the differentiation process.