Fig. 5. Effect of MMTV-SmoM2 on mammosphere formation and regeneration of the mammary gland. (A) Pairwise comparison of log-transformed mammosphere-formation efficiency values for five paired sets of primary epithelial cell preparations. MMTV-SmoM2 cells showed a 2-fold increase in mammosphere-forming efficiency relative to wild-type cells in four of the five sample pairs. Key to symbols: open circles, MMTV-SmoM2; red filled circles, MMTV-SmoM2 average; open trianges, wild type; blue filled triangles, wild-type average. (B) Statistical evaluation of mammosphere-forming efficiency as a function of genotype, including all five paired samples shown in A. (C) Photomicrographs of representative mammospheres from wild-type and MMTV-SmoM2 mice. (D) Photomicrographs of representative outgrowths of transplanted mammospheres derived from wild-type and MMTV-SmoM2 mice. (E) Limiting-dilution transplantation analysis as a function of genotype. (F) Photomicrographs of representative outgrowths from limiting-dilution transplantations (100 cells) derived from wild-type and MMTV-SmoM2 mice, respectively. Inset shows a strongly affected outgrowth with increased side budding and branching.