Estrogen receptor stem cells found in mammary glands
The mammary gland is composed two main cellular subtypes: the basal cells and luminal cells. While luminal cells secrete water and nutriments to produce the milk during lactation, the basal cells, through their contraction, guide the circulation of the milk throughout the ductal tree. Luminal cells can be subdivided into estrogen (ER)/progesterone (PR) positive and negative cells. In this study published in Cell Reports , Alexandra Van Keymeulen and colleagues generated a new transgenic line-allowing lineage tracing of ER+ luminal cells to investigate luminal cell heterogeneity and identify the origin of ER+ luminal cells and the mechanisms regulating their pubertal expansion and adult maintenance. Surprisingly and in sharp contrast with the common thought, which hypothesized the existence of a population of common progenitors that give rise to ER+ and ER- cells, Alexandra Van Keymeulen and colleagues found that the ER+ lineage is maintained by a lineage restricted ER+ luminal