Targeting CreERT2 expression to keratin 8-expressing murine simple epithelia using bacterial artificial chromosome transgenesis

Keratin 8 (K8) is a type II keratin that is associated with the type I keratins K18 or K19 in single layered epithelia. We generated a bacterial artificial chromosome (BAC) transgenic mouse line that expresses the tamoxifen inducible CreER(T2) inserted into the endogenous murine K8 gene. The transgenic mouse line contains two copies of the BAC transgene. To determine the expression specificity and inducibility of CreER(T2), the K8-CreER(T2) mice were bred with a Gt(ROSA 26)( ACTB-tdTomato-EGFP ) fluorescent protein-based reporter transgenic mouse line. We demonstrated that CreER(T2) and the endogenous K8 gene share the same patterns of expression and that the enzymatic activity of CreER(T2) can be efficiently induced by tamoxifen in all K8-expressing tissues. This mouse line will be useful for studying gene function in development and homeostasis of simple epithelia, and investigating both tissue lineage hierarchy and the identity of the cells of origin for epithelial cancers.