A Transgenic MMTV-Flippase Mouse Line for Molecular Engineering in Mammary Gland and Breast Cancer Mouse Models

Genetically engineered mouse models have become an indispensable tool for breast cancer research. Combination of multiple site-specific recombination systems such as Cre/loxP and Flippase (Flp)/Frt allows for engineering of sophisticated, multi-layered conditional mouse models. Here, we report the generation and characterization of a novel transgenic mouse line expressing a mouse codon-optimized Flp under the control of the mouse mammary tumor virus (MMTV) promoter. These mice show robust Flp-mediated recombination in luminal mammary gland and breast cancer cells but no Flp activity in non-mammary tissues, with the exception of limited activity in salivary glands. These mice provide a unique tool for studying mammary gland biology and carcinogenesis in mice.