Figure 2

TBX3 over-expression causes accelerated mammary gland development and hyperplasia. A) Whole mount analysis of the 4th mammary gland from 7-weeks, 10-weeks, 12-weeks old virgin mice and day 10.5 dpc pregnant mice. Acceleration of mammary gland development is observed in doxycycline induced double transgenic mice from 7 to 12 weeks of age. TEBs are present in un-induced control mice at 7- and 10- weeks of age (arrows), whereas TEBs in doxycycline induced double transgenic mice pass the fat pad and start to disappear. At all time points, branching morphogenesis was promoted in the doxycycline induced double transgenic mice. Representative whole mount of the 4th mammary gland from 10.5 dpc pregnant un-induced double transgenic mouse has less alveoli tissue than the 4th mammary gland from day 10.5 dpc pregnant doxycycline induced double transgenic mouse (n = 3). All images were captured at 5× magnification. Image insets were captured at 20× magnification. B) Whole mount analysis of the 1st mammary gland from un-induced double transgenic mice and doxycycline induced double transgenic mice at 12 weeks of age and pregnant 10.5 dpc. Mammary glands from doxycycline induced double transgenic mice displayed enhanced side branching and advanced development of alveolar structure. Images were captured at 10× magnification. Hematoxylin and eosin stain performed on the 3rd mammary gland of doxycycline induced and un-induced double transgenic mice at 15 weeks of age showed mild hyperplasia (arrows) and disturbed organization in the mammary epithelium (arrowheads) (n = 3). Images were captured at 40× magnification.