Explore the vast range of titles available.

EOMES and T-BET are related T-box transcription factors that control natural killer (NK) cell development. Here we demonstrate that EOMES and T-BET regulate largely distinct gene sets during this process. EOMES is dominantly expressed in immature NK cells and drives early lineage specification by inducing hallmark receptors and functions. By contrast, T-BET is dominant in mature NK cells, where it induces responsiveness to IL-12 and represses the cell cycle, likely through transcriptional repressors. Regardless, many genes with distinct functions are co-regulated by the two transcription factors. By generating two gene-modified mice facilitating chromatin immunoprecipitation of endogenous EOMES and T-BET, we show a strong overlap in their DNA binding targets, as well as extensive epigenetic changes during NK cell differentiation. Our data thus suggest that EOMES and T-BET may distinctly govern, via differential expression and co-factors recruitment, NK cell maturation by inserting partially overlapping epigenetic regulations.

ZBTB7A is frequently mutated in acute myeloid leukemia (AML) with t(8;21) translocation. However, the oncogenic collaboration between mutated ZBTB7A and the RUNX1–RUNX1T1 fusion gene in AML t(8;21) remains unclear. Here, we investigate the role of ZBTB7A and its mutations in the context of normal and malignant hematopoiesis. We demonstrate that clinically relevant ZBTB7A mutations in AML t(8;21) lead to loss of function and result in perturbed myeloid differentiation with block of the granulocytic lineage in favor of monocytic commitment. In addition, loss of ZBTB7A increases glycolysis and hence sensitizes leukemic blasts to metabolic inhibition with 2-deoxy-d-glucose. We observed that ectopic expression of wild-type ZBTB7A prevents RUNX1-RUNX1T1-mediated clonal expansion of human CD34+ cells, whereas the outgrowth of progenitors is enabled by ZBTB7A mutation. Finally, ZBTB7A expression in t(8;21) cells lead to a cell cycle arrest that could be mimicked by inhibition of glycolysis. Our findings suggest that loss of ZBTB7A may facilitate the onset of AML t(8;21), and that RUNX1-RUNX1T1-rearranged leukemia might be treated with glycolytic inhibitors.

Non-genetic mechanisms have recently emerged as important drivers of cancer therapy failure 1 , where some cancer cells can enter a reversible drug-tolerant persister state in response to treatment 2 . Although most cancer persisters remain arrested in the presence of the drug, a rare subset can re-enter the cell cycle under constitutive drug treatment. Little is known about the non-genetic mechanisms that enable cancer persisters to maintain proliferative capacity in the presence of drugs. To study this rare, transiently resistant, proliferative persister population, we developed Watermelon, a high-complexity expressed barcode lentiviral library for simultaneous tracing of each cell’s clonal origin and proliferative and transcriptional states. Here we show that cycling and non-cycling persisters arise from different cell lineages with distinct transcriptional and metabolic programs. Upregulation of antioxidant gene programs and a metabolic shift to fatty acid oxidation are associated with persister proliferative capacity across multiple cancer types. Impeding oxidative stress or metabolic reprogramming alters the fraction of cycling persisters. In human tumours, programs associated with cycling persisters are induced in minimal residual disease in response to multiple targeted therapies. The Watermelon system enabled the identification of rare persister lineages that are preferentially poised to proliferate under drug pressure, thus exposing new vulnerabilities that can be targeted to delay or even prevent disease recurrence. Lineage tracing by barcoding of individual cells using a lentivirus library shows that cycling and non-cycling drug-tolerant persister cells in cancer arise from different lineages with distinct transcriptional and metabolic programs.

Cancers are not composed merely of cancer cells alone; instead, they are complex ‘ecosystems’ comprising many different cell types and noncellular factors. The tumour stroma is a critical component of the tumour microenvironment, where it has crucial roles in tumour initiation, progression, and metastasis. Most anticancer therapies target cancer cells specifically, but the tumour stroma can promote the resistance of cancer cells to such therapies, eventually resulting in fatal disease. Therefore, novel treatment strategies should combine anticancer and antistromal agents. Herein, we provide an overview of the advances in understanding the complex cancer cell–tumour stroma interactions and discuss how this knowledge can result in more effective therapeutic strategies, which might ultimately improve patient outcomes.

Direct lineage reprogramming involves the conversion of cellular identity. Single-cell technologies are useful for deconstructing the considerable heterogeneity that emerges during lineage conversion. However, lineage relationships are typically lost during cell processing, complicating trajectory reconstruction. Here we present ‘CellTagging’, a combinatorial cell-indexing methodology that enables parallel capture of clonal history and cell identity, in which sequential rounds of cell labelling enable the construction of multi-level lineage trees. CellTagging and longitudinal tracking of fibroblast to induced endoderm progenitor reprogramming reveals two distinct trajectories: one leading to successfully reprogrammed cells, and one leading to a ‘dead-end’ state, paths determined in the earliest stages of lineage conversion. We find that expression of a putative methyltransferase, Mettl7a1 , is associated with the successful reprogramming trajectory; adding Mettl7a1 to the reprogramming cocktail increases the yield of induced endoderm progenitors. Together, these results demonstrate the utility of our lineage-tracing method for revealing the dynamics of direct reprogramming. Combinatorial tagging of single cells using expressed DNA barcodes, delivered by a lentiviral vector, is used to track individual cells and reconstruct their lineages and trajectories during cell fate reprogramming.

The formation of red blood cells begins with the differentiation of multipotent haematopoietic progenitors. Reconstructing the steps of this differentiation represents a general challenge in stem-cell biology. Here we used single-cell transcriptomics, fate assays and a theory that allows the prediction of cell fates from population snapshots to demonstrate that mouse haematopoietic progenitors differentiate through a continuous, hierarchical structure into seven blood lineages. We uncovered coupling between the erythroid and the basophil or mast cell fates, a global haematopoietic response to erythroid stress and novel growth factor receptors that regulate erythropoiesis. We defined a flow cytometry sorting strategy to purify early stages of erythroid differentiation, completely isolating classically defined burst-forming and colony-forming progenitors. We also found that the cell cycle is progressively remodelled during erythroid development and during a sharp transcriptional switch that ends the colony-forming progenitor stage and activates terminal differentiation. Our work showcases the utility of linking transcriptomic data to predictive fate models, and provides insights into lineage development in vivo . Single-cell transcriptomics, fate assays and a computational theory enable prediction of cell fates during haematopoiesis, discovery of regulators of erythropoiesis and reveal coupling between the erythroid, basophil and mast cell fates. The hierarchy of blood cell lineages Allon Klein, Merav Socolovsky and colleagues examine the emergence of distinct blood cell lineages from mouse haematopoietic progenitors. Their approach combines single-cell transcriptomics, cell fate potential assays and population balance analysis—a computational method for predicting cell fate probabilities from population snapshots. They use a new flow-cytometry strategy to sort cells with newly defined markers of erythroid differentiation and validate the findings at the single-cell level. The results show that differentiation is a continuous, albeit hierarchical, process. They also reveal that erythroid and mast cell fates are coupled, and that remodelling the expression of cell cycle regulators is very important as erythroid cells proceed to terminal differentiation.

T H 17 and T reg cell development are reciprocally regulated by de novo fatty acid synthesis, and inhibition of acetyl-CoA carboxylase 1 (ACC1) attenuates T H 17 cell–mediated autoimmune disease. Interleukin-17 (IL-17)-secreting T cells of the T helper 17 (T H 17) lineage play a pathogenic role in multiple inflammatory and autoimmune conditions and thus represent a highly attractive target for therapeutic intervention. We report that inhibition of acetyl-CoA carboxylase 1 (ACC1) restrains the formation of human and mouse T H 17 cells and promotes the development of anti-inflammatory Foxp3 + regulatory T (T reg ) cells. We show that T H 17 cells, but not T reg cells, depend on ACC1-mediated de novo fatty acid synthesis and the underlying glycolytic-lipogenic metabolic pathway for their development. Although T H 17 cells use this pathway to produce phospholipids for cellular membranes, T reg cells readily take up exogenous fatty acids for this purpose. Notably, pharmacologic inhibition or T cell–specific deletion of ACC1 not only blocks de novo fatty acid synthesis but also interferes with the metabolic flux of glucose-derived carbon via glycolysis and the tricarboxylic acid cycle. In vivo , treatment with the ACC-specific inhibitor soraphen A or T cell–specific deletion of ACC1 in mice attenuates T H 17 cell–mediated autoimmune disease. Our results indicate fundamental differences between T H 17 cells and T reg cells regarding their dependency on ACC1-mediated de novo fatty acid synthesis, which might be exploited as a new strategy for metabolic immune modulation of T H 17 cell–mediated inflammatory diseases.

In mice, only the zygotes and blastomeres from 2-cell embryos are authentic totipotent stem cells (TotiSCs) capable of producing all the differentiated cells in both embryonic and extraembryonic tissues and forming an entire organism 1 . However, it remains unknown whether and how totipotent stem cells can be established in vitro in the absence of germline cells. Here we demonstrate the induction and long-term maintenance of TotiSCs from mouse pluripotent stem cells using a combination of three small molecules: the retinoic acid analogue TTNPB, 1-azakenpaullone and the kinase blocker WS6. The resulting chemically induced totipotent stem cells (ciTotiSCs), resembled mouse totipotent 2-cell embryo cells at the transcriptome, epigenome and metabolome levels. In addition, ciTotiSCs exhibited bidirectional developmental potentials and were able to produce both embryonic and extraembryonic cells in vitro and in teratoma. Furthermore, following injection into 8-cell embryos, ciTotiSCs contributed to both embryonic and extraembryonic lineages with high efficiency. Our chemical approach to totipotent stem cell induction and maintenance provides a defined in vitro system for manipulating and developing understanding of the totipotent state and the development of multicellular organisms from non-germline cells. Under chemically defined conditions, mouse pluripotent stem cells can be induced to closely resemble authentic totipotent stem cells that can differentiate to both embryonic and extraembryonic lineages.

The cellular constituents forming the haematopoietic stem cell (HSC) niche in the bone marrow are unclear, with studies implicating osteoblasts, endothelial and perivascular cells. Here we demonstrate that mesenchymal stem cells (MSCs), identified using nestin expression, constitute an essential HSC niche component. Nestin + MSCs contain all the bone-marrow colony-forming-unit fibroblastic activity and can be propagated as non-adherent ‘mesenspheres’ that can self-renew and expand in serial transplantations. Nestin + MSCs are spatially associated with HSCs and adrenergic nerve fibres, and highly express HSC maintenance genes. These genes, and others triggering osteoblastic differentiation, are selectively downregulated during enforced HSC mobilization or β3 adrenoreceptor activation. Whereas parathormone administration doubles the number of bone marrow nestin + cells and favours their osteoblastic differentiation, in vivo nestin + cell depletion rapidly reduces HSC content in the bone marrow. Purified HSCs home near nestin + MSCs in the bone marrow of lethally irradiated mice, whereas in vivo nestin + cell depletion significantly reduces bone marrow homing of haematopoietic progenitors. These results uncover an unprecedented partnership between two distinct somatic stem-cell types and are indicative of a unique niche in the bone marrow made of heterotypic stem-cell pairs. A stem-cell niche made for two The identity of the cells that form the haematopoietic stem-cell niche in the bone marrow has been unclear. Paul Frenette and colleagues have now identified nestin-expressing mesenchymal stem cells as niche-forming cells. These cells show a close physical association with haematopoietic stem cells, express high levels of genes involved in stem-cell maintenance, and their depletion reduces bone-marrow homing of haematopoietic progenitors. This work reveals the stem-cell niche in the bone marrow as a partnership between two distinct somatic stem-cell types. The identity of the cells that form the haematopoietic stem cell (HSC) niche in bone marrow has been unclear. These authors identify nestin-expressing mesenchymal stem cells as niche-forming cells. These nestin-expressing cells show a close physical association with HSCs and express high levels of genes involved in HSC maintenance, and their depletion reduces bone marrow homing of haematopoietic progenitors.

Somatic TP53 mutations are highly prevalent in therapy-related acute myeloid leukaemia and myelodysplastic syndrome, which arise as complications of cytotoxic chemotherapy or radiotherapy; although it was believed that these TP53 mutations are directly induced by cytotoxic therapy, new data indicate that they predate cytotoxic therapy and that haematopoietic progenitors harbouring these pre-existing mutations may selectively expand after exposure to chemotherapy or radiotherapy. TP53 mutations predate cytotoxic therapy The clonal haematopoietic disorders known as therapy-related acute myeloid leukaemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) typically develop 1 to 5 years after exposure to chemotherapy or radiotherapy. TP53 mutations are selectively enriched in t-AML/t-MDS, and were thought to be directly induced by cytotoxic therapy. Now Daniel Link and colleagues present genome sequencing data that suggest the TP53 mutations predate cytotoxic therapy. It appears that rare haematopoietic stem/progenitor cells in blood or bone marrow carry age-related TP53 mutations, and that these cells undergo clonal expansion only after selective pressure applied by chemotherapy. Therapy-related acute myeloid leukaemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) are well-recognized complications of cytotoxic chemotherapy and/or radiotherapy 1 . There are several features that distinguish t-AML from de novo AML, including a higher incidence of TP53 mutations 2 , 3 , abnormalities of chromosomes 5 or 7, complex cytogenetics and a reduced response to chemotherapy 4 . However, it is not clear how prior exposure to cytotoxic therapy influences leukaemogenesis. In particular, the mechanism by which TP53 mutations are selectively enriched in t-AML/t-MDS is unknown. Here, by sequencing the genomes of 22 patients with t-AML, we show that the total number of somatic single-nucleotide variants and the percentage of chemotherapy-related transversions are similar in t-AML and de novo AML, indicating that previous chemotherapy does not induce genome-wide DNA damage. We identified four cases of t-AML/t-MDS in which the exact TP53 mutation found at diagnosis was also present at low frequencies (0.003–0.7%) in mobilized blood leukocytes or bone marrow 3–6 years before the development of t-AML/t-MDS, including two cases in which the relevant TP53 mutation was detected before any chemotherapy. Moreover, functional TP53 mutations were identified in small populations of peripheral blood cells of healthy chemotherapy-naive elderly individuals. Finally, in mouse bone marrow chimaeras containing both wild-type and Tp53 +/− haematopoietic stem/progenitor cells (HSPCs), the Tp53 +/− HSPCs preferentially expanded after exposure to chemotherapy. These data suggest that cytotoxic therapy does not directly induce TP53 mutations. Rather, they support a model in which rare HSPCs carrying age-related TP53 mutations are resistant to chemotherapy and expand preferentially after treatment. The early acquisition of TP53 mutations in the founding HSPC clone probably contributes to the frequent cytogenetic abnormalities and poor responses to chemotherapy that are typical of patients with t-AML/t-MDS.