Figure 1

TBX3 transgene expression is tightly controlled by doxycycline administration within mammary glands of double-transgenic mice. A) Diagram of tetracycline inducible TBX3 transgene cassette. In the presence of doxycycline, the tetracycline reverse transcriptional activator (rtTA), expressed in mammary epithelium, binds to the tetracycline-operator (Tet-On), which in turn activates the transcription of TBX3 and firefly luciferase. B) Left panel: In vivo detection of luciferase reporter activity. Fifteen-week old doxycycline induced and un-induced double transgenic female mice were injected with an aqueous solution of luciferin into the peritoneal cavity. Images were taken with an ICCD camera five minutes later. Right panel: Luciferase reporter activity in tet-TBX3; MMTV-rtTA transgenic mammary glands. Mammary glands from doxycycline induced and un-induced double transgenic mice were dissected and lysates were prepared. The luciferase activity of 10μl of total protein lysate was measured. Numbers on X-axis indicate the pair of mammary gland used in the assay (n = 1). C) Immunohistochemical analysis of TBX3 expression in doxycycline induced and un-induced double transgenic littermates at 10 weeks of age. Images were captured at 40× magnification.