A Novel Epithelial Keratin, hK6irs1, Is Expressed Differentially in All Layers of the Inner Root Sheath, Including Specialized Huxley Cells of the Human Hair Follicle

The study identified and characterized a novel human epithelial keratin, hK6irs1, which was specifically expressed in all layers of the inner root sheath (IRS) of the hair follicle, including specialized Huxley cells. The hK6irs1 gene, spanning 9.2 kb of DNA and including nine exons, was found to be the human ortholog of the mouse K6irs gene. The expression of hK6irs1 mRNA and protein began in the lowermost bulb and coincided with the onset of terminal differentiation in the IRS layers. This discovery provided detailed insights into the molecular composition of hair follicles and could have implications for understanding hair biology and related disorders.