Description
Adult stem cells have the ability to self-renew and to generate specialized cells. Self-renewal is dependent on extrinsic niche factors but few of those signals have been identified. We show that adult mammary glands contain a Wnt-responsive cell population that is enriched for stem cells. In cell culture experiments, exposure to purified Wnt protein clonally expands mammary stem cells for many generations and maintains their ability to generate functional glands in transplantation assays. We propose here that Wnt3A treated mammary stem cells retain their stemness through the regulation of its downstream target genes.