The transgenic construct consisted of cDNA encoding cre recombinase adjoined to the mouse Krt2-6a promoter. Cre-mediated recombination was observed in the companion cell layer of hair follicles, a discrete cell population located between the inner and outer root sheaths. With retinoic acid treatment, the expression domain is expanded to the interfollicular basal and outer root sheath cells. (J:88795)