The protein encoded by this gene is a member of the keratin gene family. The keratins are intermediate filament proteins responsible for the structural integrity of epithelial cells and are subdivided into cytokeratins and hair keratins. Keratin 15 is a type I keratin without a defined type II partner. Keratin 15 is expressed primarily in the basal keratinocytes of stratified tissues, including the fetal epidermis and fetal nail. Expression of keratin 15 is downregulated in some hyperproliferating situations, such as psoriasis and hypertrophic scars. Because keratinocytes in psoriasis and hypertrophic scars are activated, it is suggested that keratin 15 expression is not compatible with keratinocyte activation and the keratin 15 gene is downregulated to maintain the activated phenotype.