A transgene construct containing 3.5 kb of sequence upstream of the ATG start site of the mouse Krt8 gene (purified from BAC clone RP23-254K21), the beta globin intron, SV40 polyadenylation site and a cre/ERT2 segment was injected into C57Bl/6 fertilized eggs. Four of seven founder mice displayed the expected pattern of expression and Founder line 17 was subsequently established. The transgenic animals were then bred to CD1 mice.