KRT77 (keratin 77) encodes a type II epithelial keratin that plays important roles in epidermal development and environmental adaptation. KRT77 is expressed in human and mouse sweat gland ducts and shows coordinated expression with other epidermal differentiation markers during skin morphogenesis 12. The gene is located within the type II keratin gene cluster on chromosome 12.13 and represents one of seven novel type II keratins identified in hair follicle/epidermal appendages 34. Functionally, KRT77 contributes to keratinocyte structural integrity, with compensation mechanisms evident when absent - KRT77-deficient mice show upregulated KRT1 expression, suggesting functional redundancy among type II keratins 1. The gene exhibits environmental adaptation significance, with insertion variants correlating with climate parameters in cattle populations 5. KRT77 appears in disease contexts, being upregulated in viral myocarditis plasma exosomes 6 and decreasing during COVID-19 recovery 7. In psoriasis, KRT77 upregulation is associated with normalized keratinocyte function through inhibition of Notch signaling 8. These findings indicate KRT77's dual roles in normal epidermal homeostasis and pathological responses.