CD4+ T cell calibration of antigen-presenting cells optimizes antiviral CD8+ T cell immunity.

Antiviral CD8+ T cell immunity depends on the integration of various contextual cues, but how antigen-presenting cells (APCs) consolidate these signals for decoding by T cells remains unclear. Here, we describe gradual interferon-α/interferon-ß (IFNα/ß)-induced transcriptional adaptations that endow APCs with the capacity to rapidly activate the transcriptional regulators p65, IRF1 and FOS after CD4+ T cell-mediated CD40 stimulation. While these responses operate through broadly used signaling components, they induce a unique set of co-stimulatory molecules and soluble mediators that cannot be elicited by IFNα/ß or CD40 alone. These responses are critical for the acquisition of antiviral CD8+ T cell effector function, and their activity in APCs from individuals infected with severe acute respiratory syndrome coronavirus 2 correlates with milder disease. These observations uncover a sequential integration process whereby APCs rely on CD4+ T cells to select the innate circuits that guide antiviral CD8+ T cell responses.

Sex differences orchestrated by androgens at single-cell resolution.

Sex differences in mammalian complex traits are prevalent and are intimately associated with androgens1-7. However, a molecular and cellular profile of sex differences and their modulation by androgens is still lacking. Here we constructed a high-dimensional single-cell transcriptomic atlas comprising over 2.3 million cells from 17 tissues in Mus musculus and explored the effects of sex and androgens on the molecular programs and cellular populations. In particular, we found that sex-biased immune gene expression and immune cell populations, such as group 2 innate lymphoid cells, were modulated by androgens. Integration with the UK Biobank dataset revealed potential cellular targets and risk gene enrichment in antigen presentation for sex-biased diseases. This study lays the groundwork for understanding the sex differences orchestrated by androgens and provides important evidence for targeting the androgen pathway as a broad therapeutic strategy for sex-biased diseases.

Periportal macrophages protect against commensal-driven liver inflammation.

The liver is the main gateway from the gut, and the unidirectional sinusoidal flow from portal to central veins constitutes heterogenous zones, including the periportal vein (PV) and the pericentral vein zones1-5. However, functional differences in the immune system in each zone remain poorly understood. Here intravital imaging revealed that inflammatory responses are suppressed in PV zones. Zone-specific single-cell transcriptomics detected a subset of immunosuppressive macrophages enriched in PV zones that express high levels of interleukin-10 and Marco, a scavenger receptor that sequesters pro-inflammatory pathogen-associated molecular patterns and damage-associated molecular patterns, and consequently suppress immune responses. Induction of Marco+ immunosuppressive macrophages depended on gut microbiota. In particular, a specific bacterial family, Odoribacteraceae, was identified to induce this macrophage subset through its postbiotic isoallolithocholic acid. Intestinal barrier leakage resulted in inflammation in PV zones, which was markedly augmented in Marco-deficient conditions. Chronic liver inflammatory diseases such as primary sclerosing cholangitis (PSC) and non-alcoholic steatohepatitis (NASH) showed decreased numbers of Marco+ macrophages. Functional ablation of Marco+ macrophages led to PSC-like inflammatory phenotypes related to colitis and exacerbated steatosis in NASH in animal experimental models. Collectively, commensal bacteria induce Marco+ immunosuppressive macrophages, which consequently limit excessive inflammation at the gateway of the liver. Failure of this self-limiting system promotes hepatic inflammatory disorders such as PSC and NASH.

Microglial Function Is Distinct in Different Anatomical Locations during Retinal Homeostasis and Degeneration.

Microglia from different nervous system regions are molecularly and anatomically distinct, but whether they also have different functions is unknown. We combined lineage tracing, single-cell transcriptomics, and electrophysiology of the mouse retina and showed that adult retinal microglia shared a common developmental lineage and were long-lived but resided in two distinct niches. Microglia in these niches differed in their interleukin-34 dependency and functional contribution to visual-information processing. During certain retinal-degeneration models, microglia from both pools relocated to the subretinal space, an inducible disease-associated niche that was poorly accessible to monocyte-derived cells. This microglial transition involved transcriptional reprogramming of microglia, characterized by reduced expression of homeostatic checkpoint genes and upregulation of injury-responsive genes. This transition was associated with protection of the retinal pigmented epithelium from damage caused by disease. Together, our data demonstrate that microglial function varies by retinal niche, thereby shedding light on the significance of microglia heterogeneity.

Hypothetical chloroplast reading frame 51 encodes a photosystem I assembly factor in cyanobacteria.

Hypothetical chloroplast open reading frames (ycfs) are putative genes in the plastid genomes of photosynthetic eukaryotes. Many ycfs are also conserved in the genomes of cyanobacteria, the presumptive ancestors of present-day chloroplasts. The functions of many ycfs are still unknown. Here, we generated knock-out mutants for ycf51 (sll1702) in the cyanobacterium Synechocystis sp. PCC 6803. The mutants showed reduced photoautotrophic growth due to impaired electron transport between photosystem II (PSII) and PSI. This phenotype results from greatly reduced PSI content in the ycf51 mutant. The ycf51 disruption had little effect on the transcription of genes encoding photosynthetic complex components and the stabilization of the PSI complex. In vitro and in vivo analyses demonstrated that Ycf51 cooperates with PSI assembly factor Ycf3 to mediate PSI assembly. Furthermore, Ycf51 interacts with the PSI subunit PsaC. Together with its specific localization in the thylakoid membrane and the stromal exposure of its hydrophilic region, our data suggest that Ycf51 is involved in PSI complex assembly. Ycf51 is conserved in all sequenced cyanobacteria, including the earliest branching cyanobacteria of the Gloeobacter genus, and is also present in the plastid genomes of glaucophytes. However, Ycf51 has been lost from other photosynthetic eukaryotic lineages. Thus, Ycf51 is a PSI assembly factor that has been functionally replaced during the evolution of oxygenic photosynthetic eukaryotes.

GRK2 kinases in the primary cilium initiate SMOOTHENED-PKA signaling in the Hedgehog cascade.

During Hedgehog (Hh) signal transduction in development and disease, the atypical G protein-coupled receptor (GPCR) SMOOTHENED (SMO) communicates with GLI transcription factors by binding the protein kinase A catalytic subunit (PKA-C) and physically blocking its enzymatic activity. Here, we show that GPCR kinase 2 (GRK2) orchestrates this process during endogenous mouse and zebrafish Hh pathway activation in the primary cilium. Upon SMO activation, GRK2 rapidly relocalizes from the ciliary base to the shaft, triggering SMO phosphorylation and PKA-C interaction. Reconstitution studies reveal that GRK2 phosphorylation enables active SMO to bind PKA-C directly. Lastly, the SMO-GRK2-PKA pathway underlies Hh signal transduction in a range of cellular and in vivo models. Thus, GRK2 phosphorylation of ciliary SMO and the ensuing PKA-C binding and inactivation are critical initiating events for the intracellular steps in Hh signaling. More broadly, our study suggests an expanded role for GRKs in enabling direct GPCR interactions with diverse intracellular effectors.

Reconstruction of single-cell lineage trajectories and identification of diversity in fates during the epithelial-to-mesenchymal transition.

Exploring the complexity of the epithelial-to-mesenchymal transition (EMT) unveils a diversity of potential cell fates; however, the exact timing and mechanisms by which early cell states diverge into distinct EMT trajectories remain unclear. Studying these EMT trajectories through single-cell RNA sequencing is challenging due to the necessity of sacrificing cells for each measurement. In this study, we employed optimal-transport analysis to reconstruct the past trajectories of different cell fates during TGF-beta-induced EMT in the MCF10A cell line. Our analysis revealed three distinct trajectories leading to low EMT, partial EMT, and high EMT states. Cells along the partial EMT trajectory showed substantial variations in the EMT signature and exhibited pronounced stemness. Throughout this EMT trajectory, we observed a consistent downregulation of the EED and EZH2 genes. This finding was validated by recent inhibitor screens of EMT regulators and CRISPR screen studies. Moreover, we applied our analysis of early-phase differential gene expression to gene sets associated with stemness and proliferation, pinpointing ITGB4, LAMA3, and LAMB3 as genes differentially expressed in the initial stages of the partial versus high EMT trajectories. We also found that CENPF, CKS1B, and MKI67 showed significant upregulation in the high EMT trajectory. While the first group of genes aligns with findings from previous studies, our work uniquely pinpoints the precise timing of these upregulations. Finally, the identification of the latter group of genes sheds light on potential cell cycle targets for modulating EMT trajectories.

SWATH-MS-based proteogenomic analysis reveals the involvement of alternative splicing in poplar upon lead stress.

Alternative splicing (AS) regulates gene expression and increases proteomic diversity for the fine tuning of stress responses in plants, but the exact mechanism through which AS functions in plant stress responses is not thoroughly understood. Here, we investigated how AS functions in poplar (Populus trichocarpa), a popular plant for bioremediation, in response to lead (Pb) stress. Using a proteogenomic analysis, we determine that Pb stress induced alterations in AS patterns that are characterized by an increased use of nonconventional splice sites and a higher abundance of Pb-responsive splicing factors (SFs) associated with Pb-responsive transcription factors. A strong Pb(II)-inducible chaperone protein, PtHSP70, that undergoes AS was further characterized. Overexpression of its two spliced isoforms, PtHSP70-AS1 and PtHSP70-AS2, in poplar and Arabidopsis significantly enhances the tolerance to Pb. Further characterization shows that both isoforms can directly bind to Pb(II), and PtHSP70-AS2 exhibits 10-fold higher binding capacities and a greater increase in expression under Pb stress, thereby reducing cellular toxicity through Pb(II) extrusion and conferring Pb tolerance. AS of PtHSP70 is found to be regulated by PtU1-70K, a Pb(II)-inducible core SF involved in 5'-splice site recognition. Because the same splicing pattern is also found in HSP70 orthologs in other plant species, AS of HSP70 may be a common regulatory mechanism to cope with Pb(II) toxicity. Overall, we have revealed a novel post-transcriptional machinery that mediates heavy metal tolerance in diverse plant species. Our findings offer new molecular targets and bioengineering strategies for phytoremediation and provide new insight for future directions in AS research.

Cofactorless oxygenases guide anthraquinone-fused enediyne biosynthesis.

The anthraquinone-fused enediynes (AFEs) combine an anthraquinone moiety and a ten-membered enediyne core capable of generating a cytotoxic diradical species. AFE cyclization is triggered by opening the F-ring epoxide, which is also the site of the most structural diversity. Previous studies of tiancimycin A, a heavily modified AFE, have revealed a cryptic aldehyde blocking installation of the epoxide, and no unassigned oxidases could be predicted within the tnm biosynthetic gene cluster. Here we identify two consecutively acting cofactorless oxygenases derived from methyltransferase and α/ß-hydrolase protein folds, TnmJ and TnmK2, respectively, that are responsible for F-ring tailoring in tiancimycin biosynthesis by comparative genomics. Further biochemical and structural characterizations reveal that the electron-rich AFE anthraquinone moiety assists in catalyzing deformylation, epoxidation and oxidative ring cleavage without exogenous cofactors. These enzymes therefore fill important knowledge gaps for the biosynthesis of this class of molecules and the underappreciated family of cofactorless oxygenases.

Indole-3-Propionic Acid Protects Against Heart Failure With Preserved Ejection Fraction.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is a common but poorly understood form of heart failure, characterized by impaired diastolic function. It is highly heterogeneous with multiple comorbidities, including obesity and diabetes, making human studies difficult. METHODS: Metabolomic analyses in a mouse model of HFpEF showed that levels of indole-3-propionic acid (IPA), a metabolite produced by gut bacteria from tryptophan, were reduced in the plasma and heart tissue of HFpEF mice as compared with controls. We then examined the role of IPA in mouse models of HFpEF as well as 2 human HFpEF cohorts. RESULTS: The protective role and therapeutic effects of IPA were confirmed in mouse models of HFpEF using IPA dietary supplementation. IPA attenuated diastolic dysfunction, metabolic remodeling, oxidative stress, inflammation, gut microbiota dysbiosis, and intestinal epithelial barrier damage. In the heart, IPA suppressed the expression of NNMT (nicotinamide N-methyl transferase), restored nicotinamide, NAD+/NADH, and SIRT3 (sirtuin 3) levels. IPA mediates the protective effects on diastolic dysfunction, at least in part, by promoting the expression of SIRT3. SIRT3 regulation was mediated by IPA binding to the aryl hydrocarbon receptor, as Sirt3 knockdown diminished the effects of IPA on diastolic dysfunction in vivo. The role of the nicotinamide adenine dinucleotide circuit in HFpEF was further confirmed by nicotinamide supplementation, Nnmt knockdown, and Nnmt overexpression in vivo. IPA levels were significantly reduced in patients with HFpEF in 2 independent human cohorts, consistent with a protective function in humans, as well as mice. CONCLUSIONS: Our findings reveal that IPA protects against diastolic dysfunction in HFpEF by enhancing the nicotinamide adenine dinucleotide salvage pathway, suggesting the possibility of therapeutic management by either altering the gut microbiome composition or supplementing the diet with IPA.

Modeling the cell cycle: why do certain circuits oscillate?

Computational modeling and the theory of nonlinear dynamical systems allow one to not simply describe the events of the cell cycle, but also to understand why these events occur, just as the theory of gravitation allows one to understand why cannonballs fly in parabolic arcs. The simplest examples of the eukaryotic cell cycle operate like autonomous oscillators. Here, we present the basic theory of oscillatory biochemical circuits in the context of the Xenopus embryonic cell cycle. We examine Boolean models, delay differential equation models, and especially ordinary differential equation (ODE) models. For ODE models, we explore what it takes to get oscillations out of two simple types of circuits (negative feedback loops and coupled positive and negative feedback loops). Finally, we review the procedures of linear stability analysis, which allow one to determine whether a given ODE model and a particular set of kinetic parameters will produce oscillations.

The STARD9/Kif16a kinesin associates with mitotic microtubules and regulates spindle pole assembly.

During cell division, cells form the microtubule-based mitotic spindle, a highly specialized and dynamic structure that mediates proper chromosome transmission to daughter cells. Cancer cells can show perturbed mitotic spindles and an approach in cancer treatment has been to trigger cell killing by targeting microtubule dynamics or spindle assembly. To identify and characterize proteins necessary for spindle assembly, and potential antimitotic targets, we performed a proteomic and genetic analysis of 592 mitotic microtubule copurifying proteins (MMCPs). Screening for regulators that affect both mitosis and apoptosis, we report the identification and characterization of STARD9, a kinesin-3 family member, which localizes to centrosomes and stabilizes the pericentriolar material (PCM). STARD9-depleted cells have fragmented PCM, form multipolar spindles, activate the spindle assembly checkpoint (SAC), arrest in mitosis, and undergo apoptosis. Interestingly, STARD9-depletion synergizes with the chemotherapeutic agent taxol to increase mitotic death, demonstrating that STARD9 is a mitotic kinesin and a potential antimitotic target.

Genome-wide Identification of Structure-Forming Repeats as Principal Sites of Fork Collapse upon ATR Inhibition.

DNA polymerase stalling activates the ATR checkpoint kinase, which in turn suppresses fork collapse and breakage. Herein, we describe use of ATR inhibition (ATRi) as a means to identify genomic sites of problematic DNA replication in murine and human cells. Over 500 high-resolution ATR-dependent sites were ascertained using two distinct methods: replication protein A (RPA)-chromatin immunoprecipitation (ChIP) and breaks identified by TdT labeling (BrITL). The genomic feature most strongly associated with ATR dependence was repetitive DNA that exhibited high structure-forming potential. Repeats most reliant on ATR for stability included structure-forming microsatellites, inverted retroelement repeats, and quasi-palindromic AT-rich repeats. Notably, these distinct categories of repeats differed in the structures they formed and their ability to stimulate RPA accumulation and breakage, implying that the causes and character of replication fork collapse under ATR inhibition can vary in a DNA-structure-specific manner. Collectively, these studies identify key sources of endogenous replication stress that rely on ATR for stability.

FL-circAS: an integrative resource and analysis for full-length sequences and alternative splicing of circular RNAs with nanopore sequencing.

Circular RNAs (circRNAs) are RNA molecules with a continuous loop structure characterized by back-splice junctions (BSJs). While analyses of short-read RNA sequencing have identified millions of BSJ events, it is inherently challenging to determine exact full-length sequences and alternatively spliced (AS) isoforms of circRNAs. Recent advances in nanopore long-read sequencing with circRNA enrichment bring an unprecedented opportunity for investigating the issues. Here, we developed FL-circAS (https://cosbi.ee.ncku.edu.tw/FL-circAS/), which collected such long-read sequencing data of 20 cell lines/tissues and thereby identified 884 636 BSJs with 1 853 692 full-length circRNA isoforms in human and 115 173 BSJs with 135 617 full-length circRNA isoforms in mouse. FL-circAS also provides multiple circRNA features. For circRNA expression, FL-circAS calculates expression levels for each circRNA isoform, cell line/tissue specificity at both the BSJ and isoform levels, and AS entropy for each BSJ across samples. For circRNA biogenesis, FL-circAS identifies reverse complementary sequences and RNA binding protein (RBP) binding sites residing in flanking sequences of BSJs. For functional patterns, FL-circAS identifies potential microRNA/RBP binding sites and several types of evidence for circRNA translation on each full-length circRNA isoform. FL-circAS provides user-friendly interfaces for browsing, searching, analyzing, and downloading data, serving as the first resource for discovering full-length circRNAs at the isoform level.

An intranasal influenza virus vector vaccine protects against Helicobacter pylori in mice.

Helicobacter pylori is a human pathogen that infects almost half of the population. Antibiotic resistance in H. pylori threatens health and increases the demand for prophylactic and therapeutic vaccines. Traditional oral vaccine research faces considerable challenges because of the epithelial barrier, potential enterotoxicity of adjuvants, and the challenging conditions of the gastric environment. We developed an intranasal influenza A virus (IAV) vector vaccine based on two live attenuated influenza viruses with modified acidic polymerase protein (PA) genes encoding the A subunit of H. pylori neutrophil-activating protein (NapA), named IAV-NapA, including influenza virus A/WSN/33 (WSN)-NapA and A/Puerto Rico/8/34 (PR8)-NapA. These recombinant influenza viruses were highly attenuated and exhibited strong immunogenicity in mice. Vaccination with IAV-NapA induced antigen-specific humoral and mucosal immune responses while stimulating robust Th1 and Th17 cell immune responses in mice. Our findings suggest that prophylactic and therapeutic vaccination with influenza virus vector vaccines significantly reduces colonization of H. pylori and inflammation in the stomach of mice.IMPORTANCEHelicobacter pylori is the most common cause of chronic gastritis and leads to severe gastroduodenal pathology in some patients. Many studies have shown that Th1 and Th17 cellular and gastric mucosal immune responses are critical in reducing H. pylori load. IAV vector vaccines can stimulate these immune responses while overcoming potential adjuvant toxicity and antigen dosing issues. To date, no studies have demonstrated the role of live attenuated IAV vector vaccines in preventing and treating H. pylori infection. Our work indicates that vaccination with IAV-NapA induces antigen-specific humoral, cellular, and mucosal immunity, producing a protective and therapeutic effect against H. pylori infection in BALB/c mice. This undescribed H. pylori vaccination approach may provide valuable information for developing vaccines against H. pylori infection.

xQTLbiolinks: a comprehensive and scalable tool for integrative analysis of molecular QTLs.

Genome-wide association studies (GWAS) have identified thousands of disease-associated non-coding variants, posing urgent needs for functional interpretation. Molecular Quantitative Trait Loci (xQTLs) such as eQTLs serve as an essential intermediate link between these non-coding variants and disease phenotypes and have been widely used to discover disease-risk genes from many population-scale studies. However, mining and analyzing the xQTLs data presents several significant bioinformatics challenges, particularly when it comes to integration with GWAS data. Here, we developed xQTLbiolinks as the first comprehensive and scalable tool for bulk and single-cell xQTLs data retrieval, quality control and pre-processing from public repositories and our integrated resource. In addition, xQTLbiolinks provided a robust colocalization module through integration with GWAS summary statistics. The result generated by xQTLbiolinks can be flexibly visualized or stored in standard R objects that can easily be integrated with other R packages and custom pipelines. We applied xQTLbiolinks to cancer GWAS summary statistics as case studies and demonstrated its robust utility and reproducibility. xQTLbiolinks will profoundly accelerate the interpretation of disease-associated variants, thus promoting a better understanding of disease etiologies. xQTLbiolinks is available at https://github.com/lilab-bioinfo/xQTLbiolinks.

The transcription factor RppA regulates chlorophyll and carotenoid biosynthesis to improve photoprotection in cyanobacteria.

Chlorophyll is an essential photosynthetic pigment but also a strong photosensitizer. Excessive free chlorophyll and its precursors can cause oxidative damage to photosynthetic organisms. Cyanobacteria are the oldest oxygenic photosynthetic organisms and the ancestors of the chloroplast. Owing to their complex habitats, cyanobacteria require precise regulation of chlorophyll synthesis to respond to environmental factors, especially changes in light. Chlorophyll synthase, encoded by chlG, is the enzyme catalyzing the final step of chlorophyll biosynthesis, which is closely related to photosynthesis biogenesis. However, the transcriptional regulation on chlG remains unclear. Here, the transcription factor, regulator of photosynthesis and photopigment-related gene expression A (RppA) was identified to bind to the chlG promoter by screening a yeast one-hybrid library in the cyanobacterium Synechocystis sp. PCC 6803. The rppA knock-out mutant showed a phenotype of slow growth and severe oxidative damage under dark-light transition conditions. The up-regulated transcriptional expression of chlG was significantly higher and more chlorophyll and its precursors accumulated in the rppA knock-out mutant than those in the wild-type strain during the transition from darkness to light, indicating RppA represses the expression of chlG in Synechocystis. Meanwhile, RppA could synchronously promote the transcription of carotenoids biosynthesis-related genes to enhance carotenoids synthesis during the dark-light transition. These results reveal synergistic regulation of chlorophyll and carotenoids biosynthesis in cyanobacteria in response to frequent dark-light transitions, which slows down chlorophyll biosynthesis while promoting carotenoids biosynthesis to avoid oxidative damage caused by excessive reactive oxygen species accumulation.

Mitochondrial copper overload promotes renal fibrosis via inhibiting pyruvate dehydrogenase activity.

Copper is a trace element essential for numerous biological activities, whereas the mitochondria serve as both major sites of intracellular copper utilization and copper reservoir. Here, we investigated the impact of mitochondrial copper overload on the tricarboxylic acid cycle, renal senescence and fibrosis. We found that copper ion levels are significantly elevated in the mitochondria in fibrotic kidney tissues, which are accompanied by reduced pyruvate dehydrogenase (PDH) activity, mitochondrial dysfunction, cellular senescence and renal fibrosis. Conversely, lowering mitochondrial copper levels effectively restore PDH enzyme activity, improve mitochondrial function, mitigate cellular senescence and renal fibrosis. Mechanically, we found that mitochondrial copper could bind directly to lipoylated dihydrolipoamide acetyltransferase (DLAT), the E2 component of the PDH complex, thereby changing the interaction between the subunits of lipoylated DLAT, inducing lipoylated DLAT protein dimerization, and ultimately inhibiting PDH enzyme activity. Collectively, our study indicates that mitochondrial copper overload could inhibit PDH activity, subsequently leading to mitochondrial dysfunction, cellular senescence and renal fibrosis. Reducing mitochondrial copper overload might therefore serve as a strategy to rescue renal fibrosis.

ipaQTL-atlas: an atlas of intronic polyadenylation quantitative trait loci across human tissues.

Functional interpretation of disease-associated non-coding variants remains a significant challenge in the post-GWAS era. Our recent study has identified 3'UTR alternative polyadenylation (APA) quantitative trait loci (3'aQTLs) and connects APA events with QTLs as a major driver of human traits and diseases. Besides 3'UTR, APA events can also occur in intron regions, and increasing evidence has connected intronic polyadenylation with disease risk. However, systematic investigation of the roles of intronic polyadenylation in human diseases remained challenging due to the lack of a comprehensive database across a variety of human tissues. Here, we developed ipaQTL-atlas (http://bioinfo.szbl.ac.cn/ipaQTL) as the first comprehensive portal for intronic polyadenylation. The ipaQTL-atlas is based on the analysis of 15 170 RNA-seq data from 838 individuals across 49 Genotype-Tissue Expression (GTEx v8) tissues and contains ∼0.98 million SNPs associated with intronic APA events. It provides an interface for ipaQTLs search, genome browser, boxplots, and data download, as well as the visualization of GWAS and ipaQTL colocalization results. ipaQTL-atlas provides a one-stop portal to access intronic polyadenylation information and could significantly advance the discovery of APA-associated disease susceptibility genes.