Transgenic mouse model expressing tdTomato under involucrin promoter as a tool for analysis of epidermal differentiation and wound healing

The epidermis is a stratified tissue composed of different keratinocyte layers that create a barrier protecting the body from external influences, pathogens, and dehydration. The barrier function is mainly achieved by its outermost layer, the stratum corneum. To create a mouse model to study pathophysiological processes in the outermost layers of the epidermis in vivo and in vitro we prepared a construct containing red fluorescent td-Tomato reporter sequence under the control of involucrin promoter and its first intron. Transgenic mice were generated by pronuclear injection and the expression and regulation of the transgene was determined by in vivo imaging and fluorescent microscopy. The promoter targeted the transgene efficiently and specifically into the outermost epidermal layers although weak expression was also found in epithelia of tongue and bladder. The regulation of expression in the epidermis, i.e. fluorescence intensity of the reporter, could be easily followed during wound healing and dermatitis. Thus, these transgenic mice carrying the tdTomato reporter could be used as a valuable tool to study impact of various genes dysregulating the epidermal barrier and to follow effects of therapeutic agents for treatment of skin diseases in vivo.