De Novo Filament Formation by Human Hair Keratins K85 and K35 Follows a Filament Development Pattern Distinct from Cytokeratin Filament Networks

The study investigated the filament formation of human hair keratins K85 and K35, revealing a unique development pattern distinct from cytokeratin filament networks. In SW-13 cells, K85 and K35 formed short filaments around the nucleus without creating extensive networks. Mutations in K85 affected filament formation differently, with the delCT mutation disrupting formation and the R78H mutation not affecting it. The head domain of K85 was essential for filament formation. These findings suggested that K85–K35's unique assembly function might be crucial for early-stage hair formation and could have implications for understanding hair structure and addressing hair-related disorders.