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Acute liver failure (ALF) is a fulminant complication of multiple etiologies, characterized by rapid hepatic destruction, multi-organ failure and mortality. ALF treatment is mainly limited to supportive care and liver transplantation. Here we utilize the acetaminophen (APAP) and thioacetamide (TAA) ALF models in characterizing 56,527 single-cell transcriptomes to define the mouse ALF cellular atlas. We demonstrate that unique, previously uncharacterized stellate cell, endothelial cell, Kupffer cell, monocyte and neutrophil subsets, and their intricate intercellular crosstalk, drive ALF. We unravel a common MYC-dependent transcriptional program orchestrating stellate, endothelial and Kupffer cell activation during ALF, which is regulated by the gut microbiome through Toll-like receptor (TLR) signaling. Pharmacological inhibition of MYC, upstream TLR signaling checkpoints or microbiome depletion suppress this cell-specific, MYC-dependent program, thereby attenuating ALF. In humans, we demonstrate upregulated hepatic MYC expression in ALF transplant recipients compared to healthy donors. Collectively we demonstrate that detailed cellular/genetic decoding may enable pathway-specific ALF therapeutic intervention. A single-cell map of transcriptomic changes during acute liver failure unveils new insights into pathogenesis and potential therapeutic targets.

SummaryProtein degradation by proteasomes is important for the immune response against tumors. Antigens generated by the proteasome promote immune cell infiltration into tumors and improve tumors’ responses to immunotherapy. For example, immunoproteasomes – a subset of proteasomes induced by inflammatory signals – may improve the response of melanomas to immune checkpoint inhibitors (ICI) by eliciting tumor inflammation. Yet, it is unclear whether and how protein degradation by proteasomes impacts cancer progression and contributes to immune evasion and resistance. Here, we profile the proteasome-cleaved peptides in lung cancers and find that PSME4 serves as a novel inhibitory regulator of the immunoproteasome, playing an anti-inflammatory role in cancer. Biochemical assays combined with scRNA-seq, immunopeptidomics and in vivo analyses demonstrate that PSME4 promotes an immunosuppressive environment around the tumor and abrogates anti-tumor immunity by inhibiting antigen presentation and attenuating tumor inflammation. Furthermore, we find that PSME4 expression is correlated with responsiveness to ICI across several cancer types. Our findings suggest that PSME4-mediated regulation of proteasome activity is a novel mechanism of immune evasion in non-small-cell lung carcinoma and may be targeted therapeutically for restoring anti-tumor immunity.Graphical AbstractHighlightsMapping the degradation landscape in Non-Small Cell Lung Cancer (NSCLC) uncovers altered proteasome activity and compositionProteasome regulator PSME4 plays an anti-inflammatory role in NSCLC by attenuating immunoproteasome activityPSME4 restricts tumor antigen presentation and cytokine secretion, defining a ‘cold’ tumor environmentPSME4 drives tumor immune evasion and is associated with resistance to immunotherapy

The liver carries a remarkable ability to regenerate rapidly after acute zonal damage. Single-cell approaches are necessary to study this process, given the spatial heterogeneity of liver cell types. Here, we use spatially resolved single-cell RNA sequencing (scRNA-seq) to study the dynamics of mouse liver regeneration after acute acetaminophen (APAP) intoxication. We find that hepatocytes proliferate throughout the liver lobule, creating the mitotic pressure required to repopulate the necrotic pericentral zone rapidly. A subset of hepatocytes located at the regenerating front transiently upregulate fetal-specific genes, including Afp and Cdh17, as they reprogram to a pericentral state. Zonated endothelial, hepatic stellate cell (HSC), and macrophage populations are differentially involved in immune recruitment, proliferation, and matrix remodeling. We observe massive transient infiltration of myeloid cells, yet stability of lymphoid cell abundance, in accordance with a global decline in antigen presentation. Our study provides a resource for understanding the coordinated programs of zonal liver regeneration.

SummaryThe liver carries a remarkable ability to regenerate rapidly after acute zonal damage. Single-cell approaches are necessary to study this process, given the spatial heterogeneity of multiple liver cell types. Here, we use spatially-resolved single cell RNA sequencing (scRNAseq) to study the dynamics of mouse liver regeneration after acute acetaminophen (APAP) intoxication. We find that hepatocytes proliferate throughout the liver lobule, creating the mitotic pressure required to repopulate the necrotic pericentral zone rapidly. A subset of hepatocytes located at the regenerating front transiently up-regulate fetal-specific genes, including Afp and Cdh17, as they reprogram to a pericentral state. Zonated endothelial, hepatic-stellate cell (HSC) and macrophage populations are differentially involved in immune recruitment, proliferation and matrix remodeling. We observe massive transient infiltration of myeloid cells, yet stability of lymphoid cell abundance, in accordance with global decline in antigen presentation. Our study provides a resource for understanding the coordinated programs of zonal liver regeneration.

Cigarette smoking constitutes a leading global cause of morbidity and preventable death

Neurons and oligodendrocytes are terminally differentiated cells that perform highly specialized functions, which depend on cascades of gene activation and repression to retain homeostatic control over a lifespan. Gene expression is regulated by three-dimensional (3D) genome organisation, from local levels of chromatin compaction to the organisation of topological domains and chromosome compartments. Whereas our understanding of 3D genome architecture has vastly increased in the past decade, it remains difficult to study specialized cells in their native environment without disturbing their activity. To develop the application of Genome Architecture Mapping (GAM) in small numbers of specialized cells in complex tissues, we combined GAM with immunoselection. We applied immunoGAM to map the genome architecture of specific cell populations in the juvenile/adult mouse brain: dopaminergic neurons (DNs) from the midbrain, pyramidal glutamatergic neurons (PGNs) from the hippocampus, and oligodendrocyte lineage cells (OLGs) from the cortex. We integrate 3D genome organisation with single-cell transcriptomics data, and find specific chromatin structures that relate with cell-type specific patterns of gene expression. We discover abundant changes in compartment organisation, especially a strengthening of heterochromatin compartments which establish strong contacts spanning tens of megabases, especially in brain cells. These compartments contain olfactory and taste receptor genes, which are de-repressed in a subpopulation of PGNs with molecular signatures of long-term potentiation (LTP). We also show extensive reorganisation of topological domains where activation of neuronal or oligodendrocyte genes coincides with formation of new TAD borders. Finally, we discover loss of TAD organisation, or ‘TAD melting’, at long (>1Mb) neuronal genes when they are most highly expressed. Our work shows that the 3D organisation of the genome is highly cell-type specific in terminally differentiated cells of the brain, and essential to better understand brain-specific mechanisms of gene regulation.

Bile acids were recently shown to regulate glucose homeostasis through diverse mechanisms involving the host and its microbiome. Herein, Shapiro et al. discuss the impact of bile acids on normal and impaired glycemic responses, including potential therapeutic implications in treating hyperglycemia and diabetes., Bile acids (BAs) are cholesterol-derived metabolites that facilitate the intestinal absorption and transport of dietary lipids. Recently, BAs also emerged as pivotal signaling molecules controlling glucose, lipid, and energy metabolism by binding to the nuclear hormone farnesoid X receptor (FXR) and Takeda G protein receptor 5 (TGR5) in multiple organs, leading to regulation of intestinal incretin secretion, hepatic gluconeogenesis, glycogen synthesis, energy expenditure, inflammation, and gut microbiome configuration. Alterations in BA metabolism and signaling are associated with obesity and type 2 diabetes mellitus (T2DM), whereas treatment of T2DM patients with BA sequestrants, or bariatric surgery in morbidly obese patients, results in a significant improvement in glycemic response that is associated with changes in the BA profile and signaling. Herein, we review the roles of BAs in glucose metabolism in health and disease; highlight the limitations, unknowns, and challenges in understanding the impact of BAs on the glycemic response; and discuss how this knowledge may be harnessed to develop innovative therapeutic approaches for the treatment of hyperglycemia and diabetes.

Single-cell transcriptomics serves as a powerful tool to identify cell states within populations of cells, and to dissect underlying heterogeneity at high resolution. Single-cell transcriptomics on pluripotent stem cells has provided new insights into cellular variation, subpopulation structures and the interplay of cell cycle with pluripotency. The single-cell perspective has helped to better understand gene regulation and regulatory networks during exit from pluripotency, cell-fate determination as well as molecular mechanisms driving cellular reprogramming of somatic cells to induced pluripotent stage. Here we review the recent progress and significant findings from application of single-cell technologies on pluripotent stem cells along with a brief outlook on new combinatorial single-cell approaches that further unravel pluripotent stem cell states.

Acute liver failure (ALF) is a fulminant complication of multiple etiologies, characterized by rapid hepatic destruction, multi-organ failure and mortality. ALF treatment is mainly limited to supportive care and liver transplantation. Here we utilize the acetaminophen (APAP) and thioacetamide (TAA) ALF models in characterizing 56,527 single-cell transcriptomes to define the mouse ALF cellular atlas. We demonstrate that unique, previously uncharacterized stellate cell, endothelial cell, Kupffer cell, monocyte and neutrophil subsets, and their intricate intercellular crosstalk, drive ALF. We unravel a common MYC-dependent transcriptional program orchestrating stellate, endothelial and Kupffer cell activation during ALF, which is regulated by the gut microbiome through Toll-like receptor (TLR) signaling. Pharmacological inhibition of MYC, upstream TLR signaling checkpoints or microbiome depletion suppress this cell-specific, MYC-dependent program, thereby attenuating ALF. In humans, we demonstrate upregulated hepatic MYC expression in ALF transplant recipients compared to healthy donors. Collectively we demonstrate that detailed cellular/genetic decoding may enable pathway-specific ALF therapeutic intervention.

Single-cell RNA sequencing (scRNA-seq) has broad applications across biomedical research. One of the key challenges is to ensure that only single, live cells are included in downstream analysis, as the inclusion of compromised cells inevitably affects data interpretation. Here, we present a generic approach for processing scRNA-seq data and detecting low quality cells, using a curated set of over 20 biological and technical features. Our approach improves classification accuracy by over 30 % compared to traditional methods when tested on over 5,000 cells, including CD4+ T cells, bone marrow dendritic cells, and mouse embryonic stem cells. Electronic supplementary material The online version of this article (doi:10.1186/s13059-016-0888-1) contains supplementary material, which is available to authorized users.

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of cardiometabolic syndrome, which often also includes obesity, diabetes, and dyslipidemia. It is rapidly becoming the most prevalent liver disease worldwide. A sizable minority of NAFLD patients develop nonalcoholic steatohepatitis (NASH), which is characterized by inflammatory changes that can lead to progressive liver damage, cirrhosis, and hepatocellular carcinoma. Recent studies have shown that in addition to genetic predisposition and diet, the gut microbiota affects hepatic carbohydrate and lipid metabolism as well as influences the balance between pro‐inflammatory and anti‐inflammatory effectors in the liver, thereby impacting NAFLD and its progression to NASH. In this review, we will explore the impact of gut microbiota and microbiota‐derived compounds on the development and progression of NAFLD and NASH, and the unexplored factors related to potential microbiome contributions to this common liver disease.

Analysing transcriptomes of cell populations is a standard molecular biology approach to understand how cells function. Recent methodological development has allowed performing similar experiments on single cells. This has opened up the possibility to examine samples with limited cell number, such as cells of the early embryo, and to obtain an understanding of heterogeneity within populations such as blood cell types or neurons. There are two major approaches for single-cell transcriptome analysis: quantitative reverse transcription PCR (RT-qPCR) on a limited number of genes of interest, or more global approaches targeting entire transcriptomes using RNA sequencing. RT-qPCR is sensitive, fast and arguably more straightforward, while whole-transcriptome approaches offer an unbiased perspective on a cell’s expression status.

Mouse embryonic stem cells derived from the epiblast1 contribute to the somatic lineages and the germline but are excluded from the extra-embryonic tissues that are derived from the trophectoderm and the primitive endoderm2 upon reintroduction to the blastocyst. Here we report that cultures of expanded potential stem cells can be established from individual eight-cell blastomeres, and by direct conversion of mouse embryonic stem cells and induced pluripotent stem cells. Remarkably, a single expanded potential stem cell can contribute both to the embryo proper and to the trophectoderm lineages in a chimaera assay. Bona fide trophoblast stem cell lines and extra-embryonic endoderm stem cells can be directly derived from expanded potential stem cells in vitro. Molecular analyses of the epigenome and single-cell transcriptome reveal enrichment for blastomere-specific signature and a dynamic DNA methylome in expanded potential stem cells. The generation of mouse expanded potential stem cells highlights the feasibility of establishing expanded potential stem cells for other mammalian species.

Polycomb repressive complexes (PRCs) are important histone modifiers, which silence gene expression; yet, there exists a subset of PRC-bound genes actively transcribed by RNA polymerase II (RNAPII). It is likely that the role of Polycomb repressive complex is to dampen expression of these PRC-active genes. However, it is unclear how this flipping between chromatin states alters the kinetics of transcription. Here, we integrate histone modifications and RNAPII states derived from bulk ChIP-seq data with single-cell RNA-sequencing data. We find that Polycomb repressive complex-active genes have greater cell-to-cell variation in expression than active genes, and these results are validated by knockout experiments. We also show that PRC-active genes are clustered on chromosomes in both two and three dimensions, and interactions with active enhancers promote a stabilization of gene expression noise. These findings provide new insights into how chromatin regulation modulates stochastic gene expression and transcriptional bursting, with implications for regulation of pluripotency and development., Polycomb repressive complexes modify histones but it is unclear how changes in chromatin states alter kinetics of transcription. Here, the authors use single-cell RNAseq and ChIPseq to find that actively transcribed genes with Polycomb marks have greater cell-to-cell variation in expression.

Summary T helper 2 (Th2) cells regulate helminth infections, allergic disorders, tumor immunity, and pregnancy by secreting various cytokines. It is likely that there are undiscovered Th2 signaling molecules. Although steroids are known to be immunoregulators, de novo steroid production from immune cells has not been previously characterized. Here, we demonstrate production of the steroid pregnenolone by Th2 cells in vitro and in vivo in a helminth infection model. Single-cell RNA sequencing and quantitative PCR analysis suggest that pregnenolone synthesis in Th2 cells is related to immunosuppression. In support of this, we show that pregnenolone inhibits Th cell proliferation and B cell immunoglobulin class switching. We also show that steroidogenic Th2 cells inhibit Th cell proliferation in a Cyp11a1 enzyme-dependent manner. We propose pregnenolone as a “lymphosteroid,” a steroid produced by lymphocytes. We speculate that this de novo steroid production may be an intrinsic phenomenon of Th2-mediated immune responses to actively restore immune homeostasis., Graphical Abstract, Highlights • Differential upregulation of the steroid biosynthetic pathway during Th2 differentiation • T helper cells produce the steroid pregnenolone in vitro and in vivo • Steroidogenic Th2 cells suppress Th cell proliferation in a Cyp11a1-dependent manner • Pregnenolone inhibits B cell immunoglobulin class switching in vitro, Immune cells signal by secreting cytokines and by direct cell-to-cell contact. Although steroids are known to be immunoregulators, immune cells are not generally thought to be steroidogenic. Here, Mahata et al. demonstrate that T helper (Th) cells synthesize and secrete the steroid pregnenolone in vitro and in vivo. Pregnenolone inhibits Th cell proliferation and B cell immunoglobulin class switching, and steroidogenic Th cells inhibit Th cell proliferation. This evidence suggests that steroidogenic Th cells contribute to immune homeostasis.

Aging is characterized by progressive loss of physiological and cellular functions, but the molecular basis of this decline remains unclear. We explored how aging affects transcriptional dynamics using single-cell RNA sequencing of unstimulated and stimulated naive and effector memory CD4+ T cells from young and old mice from two divergent species. In young animals, immunological activation drives a conserved transcriptomic switch, resulting in tightly controlled gene expression characterized by a strong up-regulation of a core activation program, coupled with a decrease in cell-to-cell variability. Aging perturbed the activation of this core program and increased expression heterogeneity across populations of cells in both species. These discoveries suggest that increased cell-to-cell transcriptional variability will be a hallmark feature of aging across most, if not all, mammalian tissues.

Nature Communications 6: Article number: 8687 (2015); Published: 22 October 2015; Updated: 11 January 2016. The original version of this Article contained an error in the spelling of the author Tomislav Ilicic, which was incorrectly given as Tomislav Illicic. This has now been corrected in both the PDF and HTML versions of the Article.

Single-cell RNA-sequencing (scRNA-seq) facilitates identification of new cell types and gene regulatory networks as well as dissection of the kinetics of gene expression and patterns of allele-specific expression. However, to facilitate such analyses, separating biological variability from the high level of technical noise that affects scRNA-seq protocols is vital. Here we describe and validate a generative statistical model that accurately quantifies technical noise with the help of external RNA spike-ins. Applying our approach to investigate stochastic allele-specific expression in individual cells, we demonstrate that a large fraction of stochastic allele-specific expression can be explained by technical noise, especially for lowly and moderately expressed genes: we predict that only 17.8% of stochastic allele-specific expression patterns are attributable to biological noise with the remainder due to technical noise., Single-cell RNA-sequencing (scRNA-seq) can be applied to dissect the kinetics of gene expression and patterns of allele-specific expression. Here, Kim et al. report a generative statistical model that can separate biological variability from technical noise by quantifying technical noise using external RNA spike-ins.

The differences between individual cells can have profound functional consequences, in both unicellular and multicellular organisms. Recently developed single-cell mRNA-sequencing methods enable unbiased, high-throughput, and high-resolution transcriptomic analysis of individual cells. This provides an additional dimension to transcriptomic information relative to traditional methods that profile bulk populations of cells. Already, single-cell RNA-sequencing methods have revealed new biology in terms of the composition of tissues, the dynamics of transcription, and the regulatory relationships between genes. Rapid technological developments at the level of cell capture, phenotyping, molecular biology, and bioinformatics promise an exciting future with numerous biological and medical applications.

Background Hematopoietic stem cells (HSCs) are a rare cell type with the ability of long-term self-renewal and multipotency to reconstitute all blood lineages. HSCs are typically purified from the bone marrow using cell surface markers. Recent studies have identified significant cellular heterogeneities in the HSC compartment with subsets of HSCs displaying lineage bias. We previously discovered that the transcription factor Bcl11a has critical functions in the lymphoid development of the HSC compartment. Results In this report, we employ single-cell transcriptomic analysis to dissect the molecular heterogeneities in HSCs. We profile the transcriptomes of 180 highly purified HSCs (Bcl11a+/+ and Bcl11a−/−). Detailed analysis of the RNA-seq data identifies cell cycle activity as the major source of transcriptomic variation in the HSC compartment, which allows reconstruction of HSC cell cycle progression in silico. Single-cell RNA-seq profiling of Bcl11a−/− HSCs reveals abnormal proliferative phenotypes. Analysis of lineage gene expression suggests that the Bcl11a−/− HSCs are constituted of two distinct myeloerythroid-restricted subpopulations. Remarkably, similar myeloid-restricted cells could also be detected in the wild-type HSC compartment, suggesting selective elimination of lymphoid-competent HSCs after Bcl11a deletion. These defects are experimentally validated in serial transplantation experiments where Bcl11a−/− HSCs are myeloerythroid-restricted and defective in self-renewal. Conclusions Our study demonstrates the power of single-cell transcriptomics in dissecting cellular process and lineage heterogeneities in stem cell compartments, and further reveals the molecular and cellular defects in the Bcl11a-deficient HSC compartment. Electronic supplementary material The online version of this article (doi:10.1186/s13059-015-0739-5) contains supplementary material, which is available to authorized users.

A vasopressin receptor antagonist, [1-( β -mercapto- β , β -pentamethylenepropionic acid), 2- o -ethyl- d -tyrosine, 4-valine, 9-tyrosylamide] arginine vasopressin (d(CH 2 ) 5 [ o -ethyl- d -Tyr 2 ,Val 4 ,Tyr–NH 2 9 ]AVP), has been prepared. This antagonist is a potent antiantidiuretic, antivasopressor and antioxytocic peptide with p A 2 values of 7.69–7.94 and affinities of 1.12–11.0 nM. When radioiodinated at the phenyl moiety of the tyrosylamide residue at position 9, this peptide was demonstrated to bind to vasopressin V 2 and V 1a receptors with a dissociation constant of 0.22–0.75 nM. This ligand is a good tool for further studies on human vasopressin V 2 receptor localization and characterization, when used in combination with a selective vasopressin V 1a ligand.

A statistical method that uses spike-ins to model the dependence of technical noise on transcript abundance in single-cell RNA-seq experiments allows identification of genes wherein observed variability in read counts can be reliably interpreted as a signal of biological variability as opposed to the effect of technical noise. Single-cell RNA-seq can yield valuable insights about the variability within a population of seemingly homogeneous cells. We developed a quantitative statistical method to distinguish true biological variability from the high levels of technical noise in single-cell experiments. Our approach quantifies the statistical significance of observed cell-to-cell variability in expression strength on a gene-by-gene basis. We validate our approach using two independent data sets from Arabidopsis thaliana and Mus musculus.

Nat. Methods; doi:10.1038/nmeth.2645; corrected after print 11 October 2013 In the version of this article initially published online, the dilution for the ERCC Spike-In Control Mix added to the lysis mix was given as 1:40,000 in the Online Methods. The actual dilution used was 1:400. The error has been corrected for the PDF and HTML versions of this article.

Objective Immunophilin FKBP51 assists polypeptide folding, participates in glucocorticoid actions and may play a role in glucocorticoid resistance. FKBP51 is altered in patients with asthma, but its role in chronic obstructive pulmonary disease (COPD) characterized by dysregulation of several pro/antiinflammatory genes is less clear. Methods We assessed changes in nuclear/cytosolic FKBP51 protein using SDS-PAGE/WB and FKBP51 mRNA by qRT-PCR in cells isolated from induced sputum of stable COPD patients treated with formoterol/budesonide or formoterol/budesonide/theophylline for 4 wk. Results Expression of FKBP51 was higher in formoterol/budesonide/theophylline-treated patients, compared with formoterol/budesonide group in both cytosolic and nuclear fractions by about 57% and 31%, respectively (P < 0.001, P < 0.01). FKBP51 mRNA was only slightly, but not significantly, higher in patients on formoterol/budesonide/theophylline. Conclusions Increased FKBP51 in COPD patients treated with formoterol/budesonide/theophylline may be important in altering signaling from corticosteroid receptors.

SummaryEmbryonic stem cell (ESC) culture conditions are important for maintaining long-term self-renewal, and they influence cellular pluripotency state. Here, we report single cell RNA-sequencing of mESCs cultured in three different conditions: serum, 2i, and the alternative ground state a2i. We find that the cellular transcriptomes of cells grown in these conditions are distinct, with 2i being the most similar to blastocyst cells and including a subpopulation resembling the two-cell embryo state. Overall levels of intercellular gene expression heterogeneity are comparable across the three conditions. However, this masks variable expression of pluripotency genes in serum cells and homogeneous expression in 2i and a2i cells. Additionally, genes related to the cell cycle are more variably expressed in the 2i and a2i conditions. Mining of our dataset for correlations in gene expression allowed us to identify additional components of the pluripotency network, including Ptma and Zfp640, illustrating its value as a resource for future discovery.