Heterotypic cell-cell communication regulates glandular stem cell multipotency.

Glandular epithelia, including the mammary and prostate glands, are composed of basal cells (BCs) and luminal cells (LCs)1,2. Many glandular epithelia develop from multipotent basal stem cells (BSCs) that are replaced in adult life by distinct pools of unipotent stem cells1,3-8. However, adult unipotent BSCs can reactivate multipotency under regenerative conditions and upon oncogene expression3,9-13. This suggests that an active mechanism restricts BSC multipotency under normal physiological conditions, although the nature of this mechanism is unknown. Here we show that the ablation of LCs reactivates the multipotency of BSCs from multiple epithelia both in vivo in mice and in vitro in organoids. Bulk and single-cell RNA sequencing revealed that, after LC ablation, BSCs activate a hybrid basal and luminal cell differentiation program before giving rise to LCs-reminiscent of the genetic program that regulates multipotency during embryonic development7. By predicting ligand-receptor pairs from single-cell data14, we find that TNF-which is secreted by LCs-restricts BC multipotency under normal physiological conditions. By contrast, the Notch, Wnt and EGFR pathways were activated in BSCs and their progeny after LC ablation; blocking these pathways, or stimulating the TNF pathway, inhibited regeneration-induced BC multipotency. Our study demonstrates that heterotypic communication between LCs and BCs is essential to maintain lineage fidelity in glandular epithelial stem cells.

Spatiotemporal regulation of multipotency during prostate development.

The prostate is formed by a branched glandular epithelium composed of basal cells (BCs) and luminal cells (LCs). Multipotent and unipotent stem cells (SCs) mediate the initial steps of prostate development whereas BCs and LCs are self-sustained in adult mice by unipotent lineage-restricted SCs. The spatiotemporal regulation of SC fate and the switch from multipotency to unipotency remain poorly characterised. Here, by combining lineage tracing, whole-tissue imaging, clonal analysis and proliferation kinetics, we uncover the cellular dynamics that orchestrate prostate postnatal development in mouse. We found that at an early stage of development multipotent basal SCs are located throughout the epithelium and are progressively restricted at the distal tip of the ducts, where, together with their progeny, they establish the different branches and the final structure of prostate. In contrast, pubertal development is mediated by unipotent lineage-restricted SCs. Our results uncover the spatiotemporal regulation of the switch from multipotency to unipotency during prostate development.

Publisher Correction: Early lineage segregation of multipotent embryonic mammary gland progenitors.

In the version of this Article originally published, ref. 52 was incorrectly only attributed to its corresponding author, Fre, S., and an older title was used. The correct citation should have been: Lilja, A. M. et al. Clonal analysis of Notch1-expressing cells reveals the existence of unipotent stem cells that retain long-term plasticity in the embryonic mammary gland. Nat. Cell Biol. https://doi.org/10.1038/s41556-018-0108-1 (2018)'. This has now been amended in all online versions of the Article.

Early lineage segregation of multipotent embryonic mammary gland progenitors.

The mammary gland is composed of basal cells and luminal cells. It is generally believed that the mammary gland arises from embryonic multipotent progenitors, but it remains unclear when lineage restriction occurs and what mechanisms are responsible for the switch from multipotency to unipotency during its morphogenesis. Here, we perform multicolour lineage tracing and assess the fate of single progenitors, and demonstrate the existence of a developmental switch from multipotency to unipotency during embryonic mammary gland development. Molecular profiling and single cell RNA-seq revealed that embryonic multipotent progenitors express a unique hybrid basal and luminal signature and the factors associated with the different lineages. Sustained p63 expression in embryonic multipotent progenitors promotes unipotent basal cell fate and was sufficient to reprogram adult luminal cells into basal cells by promoting an intermediate hybrid multipotent-like state. Altogether, this study identifies the timing and the mechanisms mediating early lineage segregation of multipotent progenitors during mammary gland development.