https://phys.org/news/2018-05-embryonic-mammary-gland-stem-cells.html > The mammary gland is the tissue that produces milk during lactation, allowing the survival of young mammalian offspring. The mammary gland is composed of basal cells, which surround the inner luminal cells. The luminal cells can be subdivided into ductal cells and alveolar cells that produce the milk. The basal cells allow the circulation of the milk from the alveoli to the nipple region through their contractile properties. During mammary gland expansion during puberty and into adult life, distinct pools of unipotent stem cells replenish the basal and luminal lineages independently of each other. However, it remains unclear how mammary gland tissue initially develops. Are embryonic mammary gland progenitors multipotent, meaning that their progenitors are capable of giving rise to both basal and luminal cells? If so, when does the switch from multipotency to unipotency occur? And what are the molecular mechanisms that regulate multipotency and basal and luminal lineage segregation? > The research team led by Prof. Cédric Blanpain, MD/Ph.D., professor at the Université libre de Bruxelles, Belgium, report that by using a combination of lineage tracing, molecular profiling, single cell sequencing and functional experiments, Aline Wuidart and colleagues demonstrated that the mammary gland initially develops from multipotent progenitors during the early steps of embryonic mammary gland morphogenesis, whereas postnatal mammary gland development is mediated by lineage-restricted stem cells.