A) The upper panel indicates the FACS strategy followed to purify the different mammary epithelial subpopulations found in the mouse mammary gland (basal, luminal HR-, luminal HR+, and MaSCs). The lower panel shows the normalized expression of miR-424(503) and miR-503 revealing that MaSCs express the highest levels. The error bars show the standard deviation. FACS was performed at two different stages of the ovarian cycle (estrus and diestrus). Carmine-red staining of the structure of the mammary tree at the time of purification is also provided. The scale bar indicates 5 millimeters (mm). 