Comparison of the Opn-CreER and Ck19-CreER Drivers in Bile Ducts of Normal and Injured Mouse Livers

Inducible cyclization recombinase (Cre) transgenic mouse strains are powerful tools for cell lineage tracing and tissue-specific knockout experiments. However, low efficiency or leaky expression can be important pitfalls. Here, we compared the efficiency and specificity of two commonly used cholangiocyte-specific Cre drivers, the Opn-iCreER(T2) and Ck19-CreER(T) drivers, using a tdTomato reporter strain. We found that Opn-iCreER(T2) triggered recombination of the tdTomato reporter in 99.9% of all cholangiocytes while Ck19-CreER(T) only had 32% recombination efficiency after tamoxifen injection. In the absence of tamoxifen, recombination was also induced in 2% of cholangiocytes for the Opn-iCreER(T2) driver and in 13% for the Ck19-CreER(T) driver. For both drivers, Cre recombination was highly specific for cholangiocytes since recombination was rare in other liver cell types. Toxic liver injury ectopically activated Opn-iCreER(T2) but not Ck19-CreER(T) expression in hepatocytes. However, ectopic recombination in hepatocytes could be avoided by applying a three-day long wash-out period between tamoxifen treatment and toxin injection. Therefore, the Opn-iCreER(T2) driver is best suited for the generation of mutant bile ducts, while the Ck19-CreER(T) driver has near absolute specificity for bile duct cells and is therefore favorable for lineage tracing experiments.