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Six scientists in the field of stem cell research comment on our basic understanding of stem cells and other pluripotent cells, on their potential therapeutic use and on key challenges that remain.

Loss of autophagy increases the accumulation of mitochondria and the respiration status of haematopoietic stem cells, which perturbs their self-renewal and regeneration activities, and promotes cellular aging.

Haematopoietic stem cell (HSC) function is known to degrade with age; here, replication stress is shown to be a potent driver of the functional decline of HSCs during physiological ageing in mice due to decreased expression of mini-chromosome maintenance helicase components and reduced activity of the DNA replication machinery.

Passegué and colleagues reveal that pro-inflammatory IL-1 accelerates cell division and induces PU.1-mediated differentiation of HSCs into myeloid cells, whereas chronic IL-1 exposure compromises HSC function.

Passegué and colleagues discuss recent advances in our understanding of the metabolic control of stem cell function, and how stem cell metabolism relates to homeostasis and ageing.

The cytokine interferon-α stimulates the turnover and proliferation of hematopoietic cells in vivo (pages 696–700). The findings hint at a new strategy to treat hematopoietic cancers.

Mitchell et al. identify reduced osteoprogenitors and increased mesenchymal stromal cells in old bone marrow niche, which creates an IL1-mediated inflammatory milieu that skews myeloid differentiation and impairs haematopoietic regeneration.

Fetal haematopoietic stem cells (HSCs) self-renew extensively to build the blood system from scratch. The protein Lin28b negatively regulates the microRNA let-7 to keep levels of its target Hmga2 high, hence conferring high self-renewal potential to fetal HSCs. This regulatory circuit can be experimentally modulated to boost the lower self-renewal activity of quiescent adult HSCs.

Autophagy is shown to be an essential mechanism that protects haematopoietic stem cells from metabolic stress; the transcription factor FOXO3A maintains a pro-autophagy gene expression program that poises haematopoietic stem cells to rapidly mount a protective autophagic response upon metabolic stress.

During emergency myelopoiesis in mice, clusters of self-renewing granulocyte/macrophage progenitors (GMP) are transiently formed in the bone marrow cavity to produce a burst of myeloid cells; in leukaemia, GMP clusters persist and constantly generate myeloid leukaemia cells.

FOXM1, a transcription factor with roles in cell cycle progression, is highly expressed in the majority of solid tumours. Here the authors show that FOXM1 is an ideal therapeutic target in B-cell acute lymphoblastic leukaemia (ALL) due to its dispensability for normal B-cell development.

Single-cell transcriptomics studies on human and mouse non-small cell lung cancer and conditional knockout mouse models show that IL-4 from bone marrow basophils drives the development of granulocyte-monocyte progenitors to myeloid cells that suppress antitumour immunity.

Natural killer T cells in the thymus are CD1d-restricted cells that are selected at the CD4⁺CD8⁺ double-positive stage and require a variety of transcription factors for their development. Orkin, Winau and colleagues show that the histone demethylase UTX serves an essential role in the transcriptional control of the thymic maturation of these cells through multiple epigenetic mechanisms.

What causes hematopoietic stem cell loss of functionality? Here, Alvarez et al. show that loss of origin licensing factor MCM3 induces replicative stress (RS), causing aberrant erythrocyte maturation, but mice strains with higher tolerance to RS can overcome this defect.

Just as stem cells are crucial for tissue development and regeneration, cancer stem cells underlie tumour formation and maintenance. But do cancer stem cells invariably arise from normal stem cells?

Direct imaging of the lung microcirculation in mice indicates that it is a major site of mature platelet production from megakaryocytes.

Acute infection and other insults cause extensive remodelling in the bone marrow to drive the production of new blood cells, often prioritizing the production of mature myeloid cells at the expense of other blood cell types. Here, the authors describe how haematopoiesis is affected by acute demand and how this can contribute to inflammatory disease and cancer when dysregulated.

This Review outlines the ways in which leukaemic stem cells (LSCs) take advantage of normal haematopoietic stem cell properties to promote survival and expansion in myeloid leukaemogenesis. Opportunities for treatment of this disease by targeting LSC-specific mechanisms are also discussed.