Keratin, type I cytoskeletal 9 (KRT9)

Keratin, type I cytoskeletal 9 (KRT9), is a 623-residue cytoskeletal protein essential for the structural integrity and mechanical strength of the palmoplantar epidermis[1][2][5][6]. It polymerizes into intermediate filaments to maintain epithelial cell robustness, enabling the skin on palms and soles to tolerate substantial mechanical stress[1][2]. KRT9 expression is highly tissue-specific, restricted predominantly to the suprabasal layers of these specialized skin sites[1][5][6]. Mutations in the KRT9 gene cause epidermolytic palmoplantar keratoderma, a dominant-negative genodermatosis marked by thickened, hyperkeratotic skin on pressure points, due to loss of filament network integrity[1][5][6]. Beyond its structural role, aberrant expression patterns of KRT9 have been implicated in neurodegenerative and metabolic diseases as a circulating biomarker, notably Alzheimer’s disease and polycystic ovary syndrome[3]. There is currently no approved drug directly targeting KRT9, but mutation-specific RNA interference and molecular therapies are under preclinical investigation for correct gene function restoration in patients with EPPK[1][3].

Other names

Keratin 9Cytokeratin 9CK-9K9EPPKEPPK1Keratin-9, type I cytoskeletal 9epidermolytic palmoplantar keratoderma