Mice

All mice used in this study were backcrossed onto and maintained on the FVB/n background, in a specific pathogen-free facility. Animal procedures were conducted in accordance with protocols approved by the Johns Hopkins Animal Care and Use Committee. The CMV::rtTA;TetO-Twist1 (Twist1-inducible) mouse strain was obtained as previously described (5,6). The MMTV-PyMT (21) (FVB/N-Tg(MMTV-PyVT)634Mul/J), C3(1)-TAg (22) (FVB-Tg(C3–1-TAg)cJeg/JegJ), and mTmG (23) mouse lines were obtained from the Jackson lab. The C3(1)TAg;mTmG was obtained by crossing the C3(1)-TAg and mTmG lines.