Fig. 1. Whole-mount and histological analysis of mammary glands from wild-type and MMTV-SmoM2 mice. (A) Whole-mount showing a normal TEB array from a wild-type mouse at 5 weeks of age. Terminal structures are indicated with an asterisk; side-buds are arrowed. (B) Whole-mount showing a TEB array from an MMTV-SmoM2 transgenic mouse at 5 weeks of age. Symbols are as described in A. (C) Quantification of TEB number in wild-type versus MMTV-SmoM2 mice at 5 weeks of age. (D) Histological preparation of a TEB in a wild-type gland showing organized cap and body cell layers, as well as normal periductal stroma condensing around the neck of the TEB (arrow). (E) Histological preparation of TEB in an MMTV-SmoM2 transgenic gland showing abnormal histology associated with the side-budding phenotype (arrow). TEBs can also show disorganized cap and body cell layers (inset). (F) Whole-mount from a 10-week-old wild-type mouse showing normal duct patterning and blunt-ended ducts (arrowhead). (G) Whole-mount from a 10-week-old MMTV-SmoM2 mouse showing an increase in side budding and branching (arrowhead). Inset shows retained TEB-like structures. (H) Branch-point analysis and quantification of retained TEB-like structures at 10 weeks of age as a function of genotype. (I) Histological preparation of a normal mature duct in a wild-type gland. (J) Histological preparation of a mature duct in an MMTV-SmoM2 gland. Inset shows retained TEB-like structures (arrows). (K,L) Dual immunofluorescence for SMO and SMA in (K) wild-type and (L) MMTV-SmoM2 ducts. Arrowheads indicate SMO-expressing cells. Scale bars: 50 µm.