Figure 1.

Whole mount analysis of ductal morphogenesis in transplanted glands. Mammary buds from ErbB3^+/+ or ErbB3^+/- and ErbB3^-/- day 12.5 embryos were transplanted into contralateral cleared mammary fat pads of 3-week-old Rag1^-/- females. The glands were harvested at (a, b) 4 weeks, (c, d) 7 weeks, (e, f) 20 weeks after transplantation, or (g, h) 1 day postpartum. Shown are paired contralateral transplanted glands from the same recipient mouse. The 20-week glands were from a mouse that was mated but did not deliver a litter and was not pregnant at time of sacrifice. The 1 day postpartum (1D PP) mouse was mated about 8 weeks after transplantation and a litter was delivered about 12 weeks after transplantation. The glands were harvested 1D PP. Inserts in panels g and h are hematoxylin and eosin stained sections of +/+ (panel g) and -/- (panel h) paired transplants at 1D PP.