The Transmembrane Serine Protease HAT-Like 4 Is Important for Epidermal Barrier Function to Prevent Body Fluid Loss

The study investigated the role of the transmembrane serine protease HAT-like 4 (HAT-L4) in epidermal barrier function. HAT-L4 was found to be expressed in various epithelial cells and exocrine glands, with significant presence in skin keratinocytes and sebaceous glands. Researchers generated HAT-L4 knockout mice to assess its physiological function. While these mice showed no defects in hair growth, wound healing, water repulsion, or body temperature regulation, they experienced greater body fluid loss and higher mortality compared to wild-type controls, particularly in a trans-epidermal body fluid loss test. Additionally, HAT-L4-deficient adult mice drank water more frequently. These findings suggested that HAT-L4 played a crucial role in maintaining epidermal barrier integrity to prevent body fluid loss.