Revisiting the Significance of Keratin Expression in Complex Epithelia

The document discusses the role of keratin genes in epithelial cells and tissues, highlighting that the 54 keratin genes in the human genome are differentially regulated and can provide insights into the type of epithelial tissue, cell differentiation status, and biological context. It emphasizes that the principles for interpreting keratin expression were established in the 1980s but have been revisited with the advent of single cell transcriptomics. Re-analysis of single cell RNAseq data from human and mouse skin has supported previous views on the importance and regulation of keratin genes in keratinocytes and has refined the understanding of how keratin gene expression changes during keratinocyte differentiation. The findings suggest that keratin gene expression does not simply distinguish between mitotic and post-mitotic states and call for a more nuanced use of keratin genes as biomarkers in epithelial biology.