Clonal analysis of mouse mammary luminal epithelial cell transplants.

Cellular barcoding is a powerful tool for analyzing the clonal outputs of large numbers of co-transplanted cells. The extensive growth and bi-lineage differentiation potential of transplanted basal cells isolated from the normal adult female mouse mammary gland is well established, but analyses of similarly performed luminal cell transplants have been limited due to their more restricted outputs. Here we report detecting macroscopic, branched gland structures 8 weeks after transplanting approximately 10⁵ purified, barcoded EpCAM⁺⁺CD49f^low luminal cells into a cleared fat pad in two syngeneic mice. DNA sequencing revealed 23 clones of variable size and composition. Notably, these included 10 bi-lineage clones, that were ~10 times larger than either the 5 basal and 8 luminal clones also present. These results support the ability of rare luminal cells to produce both single and bi-lineage clones when stimulated to do so in an <i>in vivo</i> transplantation setting.