Whole-mount and hematoxylin and eosin staining of outgrowths generated from the CDβ parental line and CDβ progenitor clones. (A and E) Transplantation of COMMA-D cell line engineered to express β-galactosidase (CDβ) parental cell line generates outgrowths containing ductal and alveolar structures. (B and F) Ductal progenitor cells give rise to outgrowths containing ducts only. (C and G) Alveolar progenitor clone generates mainly alveoli and a limited number of small ducts. (D and H) Multipotent progenitor clone generates outgrowths containing ductal and alveolar structures. Figures 1A to 1D are whole-mount-stained images taken at ×3.2 original magnification. Figures 1E to 1H are hematoxylin and eosin-stained images taken at ×10 original magnification.