Fig. 3.
Mammary ductal outgrowth is accelerated in mice heterozygous for REA but severely impaired in mice homozygous null for REA. Mice heterozygous for REA show hyperstimulation of amphiregulin upon E2 treatment. A, Whole-mount staining of the number four inguinal mammary glands from REAf/f, REAf/+ PRCre/+, and REAf/f PRCre/+ virgin mice at 6, 8, and 15 wk of age. Scale bars, 2 mm. B, Ductal length of the mammary glands at 6 wk of age. Distance from the lymph node to the end of the longest extended duct was measured. The horizontal line in box plots represents the median length from eight mammary glands per group. C, The number of TEB per mammary gland was counted in whole mounts of number four inguinal glands (n = 8 mammary glands per group) at 6 wk of age. D, REAf/f and REAf/+ PRCre/+ mice at 6 wk of age were ovariectomized, allowed to rest for 2 wk, and were then injected with oil vehicle (Veh) or E2 (0.05 μg/g of body weight/d) for 5 d. Amphiregulin mRNA was measured by qRT-PCR. n = 7 mice per group, mean ± sd; #, P < 0.05 vs. wild type. N.A., Not available.