KRT85 Gene: Keratin 85 - Function, Mutations, and Related Diseases

KRT85 (keratin 85) is a protein-coding gene that encodes a type II hair keratin, specifically keratin 85 (also known as hair keratin, type II, Hb5). This intermediate filament protein is a key structural component of hair shafts, forming heterodimers with type I hair keratins. KRT85 is expressed primarily in the hair follicle cortex and contributes to the mechanical strength and integrity of hair. Mutations in KRT85 are associated with autosomal dominant monilethrix, a hair shaft disorder characterized by beaded hair and fragility. The gene is located on chromosome 12q13.13 within a cluster of type II keratin genes.

Tissue Expression

Cell Line Expression

Hotspot Mutations

Mutation functional classification

• Intermediate filament organization (Reactome: R-HSA-6809371)

• Keratinization (Reactome: R-HSA-6805567)

• Formation of the cornified envelope (Reactome: R-HSA-6809374)

Keratin 85 (KRT85) is a 507-amino acid type II hair keratin with a molecular weight of approximately 56 kDa. It contains a central alpha-helical rod domain flanked by non-helical head and tail regions. The rod domain features heptad repeats that facilitate coiled-coil dimerization with type I keratins (e.g., KRT35, KRT36). These dimers assemble into intermediate filaments that provide mechanical resilience to hair shafts. KRT85 is expressed specifically in the hair follicle cortex and is essential for proper hair shaft formation. Mutations in the helix initiation motif of the rod domain cause autosomal dominant monilethrix by exerting a dominant-negative effect on filament assembly.