Conditional Gene Expression in the Epidermis of Transgenic Mice Using the Tetracycline-Regulated Transactivators tTA and rTA Linked to the Keratin 5 Promoter

The study demonstrated the use of tetracycline-regulated transactivators (tTA and rTA) linked to the keratin 5 promoter to achieve conditional gene expression in the epidermis of transgenic mice. By modulating doxycycline levels, researchers could control β-galactosidase activity, with significant increases observed in the epidermis, particularly in hair follicles and the basal layer. The K5/tTA line showed a 500-fold increase in enzyme activity without doxycycline, while K5/rTA lines exhibited a 3- to 50-fold increase with doxycycline induction. This system allowed for precise temporal and quantitative control of gene expression, proving useful for studying epidermal biology, including growth control, differentiation, carcinogenesis, and wound healing. The findings suggested that the K5 promoter might be more effective than the CMV promoter for maintaining expression in keratinocytes.