Plays a central role in hair and nail formation. Essential component of keratin intermediate filaments in the companion layer of the hair follicle.
Highly expressed in hair follicles from scalp. Specifically expressed in the of the hair companion layer follicle, a single layered band of flat and vertically oriented cells between the cuboidal outer root sheath (ORS) cells and the inner root sheath (IRS) that stretches from the lowermost bulb region to the isthmus of the follicle. Also expressed in medullated hairs. In nails, it is almost exclusively present in the nail bed (at protein level).