Biology subjects

Liu, T.

Publications and source records attributed to Liu, T..

At least 415 records · Page 23Linked to original sources

bioRxiv2019

The Juvenile Idiopathic Arthritis (JIA) Susceptibility Locus, IL2RA, Includes An Intronic Enhancer That Is Attenuated By JIA-Associated Genetic Variants

Like most rheumatic diseases, genetic risk loci for juvenile idiopathic arthritis (JIA) are highly enriched for H3K4me1/H3K27ac histone marks, epigenetic signatures often associated with enhancer function. We sought to determine whether an H3K4me1/H3K27ac region of the JIA risk locus, IL2RA exhibits enhancer function and whether enhancer function is altered by JIA-associated genetic variants. We used a conventional luciferase reporter assay to query enhancer function across an H3K4me1/H3K27ac-marked region within the first intron of the IL2RA gene. We used the same approach to query the effects of 4 single nucleotide polymorphisms (SNPs) on enhancer function. We identified a 657 base pair region within the first intron of IL2RA that demonstrated brisk enhancer function. Enhancer activity was observable in both Jurkat T cells and myeloid HL60 cells. We identified 2 genetic variants, rs117119468 (C->T), and rs12722502 (C->T), that attenuated enhancer activity in this 657 bp region. Conclusions - The JIA-associated risk locus, IL2RA, contains at least one functional enhancer that is active in both lymphoid and myeloid cells. We identified 2 genetic variants that attenuate activity of this enhancer, making them strong candidates as causal variants.

genetics↗

bioRxiv2019

Altered brain function in anorexia nervosa and bulimia nervosa: A hierarchical series of task-based fMRI meta-analyses

BackgroundMany structural and functional magnetic resonance imaging (MRI) studies have reported differences in brain functional anatomy associated with eating disorders (EDs). We aimed to quantitatively synthesize the current literature of anorexia nervosa (AN) and bulimia nervosa (BN) with a goal of deriving a consensus across these studies. MethodsWe performed a hierarchical series of 49 activation likelihood estimation meta-analyses of 101 experiments from 63 studies at the disorder (AN+BN), diagnosis (AN or BN), and task (food-, body-, emotion- or cognitive function-related tasks) levels. We further performed sub-analyses at the diagnosis level to assess the influence of disease stage (current or recovered AN), subtype (restrictive AN, rAN), psychiatric comorbidity, medication, and data processing. ResultsWe did not observe consistent differences in brain activity across all hierarchies. Rather, we observed differences in brain activity in the right fusiform, left inferior parietal lobule and left precuneus that were primarily related to food (representing 19 experiments) and emotion (25 experiments) tasks performed by current AN patients (56 experiments). ConclusionsThe task-based functional MRI literature in AN and BN represents a heterogenous set of tasks and patients. Given this heterogeneity, we found very limited convergence across a rather large literature. Such limited convergence suggests individual task-based studies of EDs should be interpreted cautiously. We recommend that future studies of EDs carefully characterize patients based on nutritional status and that, beyond clinical diagnosis, studies utilize a trait- or cognitive-domain-based approach to define their populations of interest. Meta-ananlysis Registration"Meta-analysis of functional magnetic resonance imaging studies of eating disorders", https://www.crd.york.ac.uk/prospero (Registration Number: CRD42018086497).

neuroscience↗

bioRxiv2019

Genetic and environmental perturbations drive modular transcriptome responses

Understanding the plasticity, robustness, and modularity of transcriptome expression to genetic and environmental conditions is crucial to deciphering how organisms adapt in nature. To test how genome architecture influences transcriptome profiles, we quantified expression responses for distinct temperature-adapted genotypes of the nematode Caenorhabditis briggsae when exposed to chronic temperature stresses throughout development. We found that 56% of the 8795 differentially-expressed genes show genotype-specific changes in expression in response to temperature (genotype-by-environment interactions, GxE). Most genotype-specific responses occur under heat stress, indicating that cold versus heat stress responses involve distinct genomic architectures. The 22 co-expression modules that we identified differ in their enrichment of genes with genetic versus environmental versus interaction effects, as well as their genomic spatial distributions, functional attributes, and rates of molecular evolution at the sequence level. Genes in modules enriched for simple effects of either genotype or temperature alone tend to evolve especially rapidly, consistent with disproportionate influence of adaptation or weaker constraint on these subsets of loci. Chromosome scale heterogeneity in nucleotide polymorphism, however, rather than the scale of individual genes, predominate as the source of genetic differences among expression profiles, and natural selection regimes are largely decoupled between coding sequences and non-coding flanking sequences that contain cis-regulatory elements. These results illustrate how the form of transcriptome modularity and genome structure contribute to predictable profiles of evolutionary change.

genomics↗

bioRxiv2018

Cas4 nucleases can effect specific integration of CRISPR spacers

CRISPR-Cas systems incorporate short DNA fragments from invasive genetic elements into host CRISPR arrays in order to generate host immunity.Recently, we demonstrated that the Csa3a regulator protein triggers CCN PAM-dependent CRISPR spacer acquisition in the subtype I-A CRISPR-Cas system of Sulfolobus islandicus. However, the mechanisms underlying specific protospacer selection and spacer insertion remained unclear. Here, we demonstrate that two Cas4 family proteins (Cas4 and Csa1) have essential roles (a) in recognizing the 5 PAM and 3 nucleotide motif of protospacers and (b) in determining both the spacer length and its orientation. Furthermore, we identify uncovered amino acid residues of the Cas4 proteins that facilitate these functions. Overexpression of the Cas4 and Csa1 proteins, and also of an archaeal virus-encoded Cas4 protein, resulted in strongly reduced adaptation efficiency and the formers yielded a high incidence of PAM-dependent atypical spacer integration, or of PAM-independent spacer integration. We further demonstrated that, in the plasmid challenging experiments, overexpressed Cas4-mediated defective spacer acquisition, in turn, potentially enabled targeted DNA to escape subtype I-A CRISPR-Cas interference. In summary, these results define the specific involvement of diverse Cas4 proteins in in vivo CRISPR spacer acquisition. Furthermore, we provide support for an anti-CRISPR role for virus-encoded Cas4 proteins that involves compromising CRISPR-Cas interference activity by hindering spacer acquisition.\n\nImportanceThe Cas4 family endonuclease is an essential component of the adaptation module in many variants of CRISPR-Cas adaptive immunity systems. The Crenarchaeota Sulfolobus islandicus REY15A encodes two cas4 genes (cas4 and csa1) linked to the CRISPR arrays. Here, we demonstrate that Cas4 and Csa1 are essential to CRISPR spacer acquisition in this organism. Both proteins specify the upstream and downstream conserved nucleotide motifs of the protospacers and define the spacer length and orientation in the acquisition process. Conserved amino acid residues, in addition to the recently reported, were identified to be important for above functions. More importantly, overexpression of the Sulfolobus viral Cas4 abolished spacer acquisition, providing support for an anti-CRISPR role for virus-encoded Cas4 proteins that inhibit spacer acquisition.

molecular biology↗

bioRxiv2018

Cannabinoid 1-Receptor regulation of deep and distributed subcellular processes enables neurite outgrowth

Neurite outgrowth is an integrated whole cell process that represents the earliest steps in neuronal differentiation. We studied cannabinoid-1 receptor regulated neurite outgrowth to identify the different subcellular processes (SCPs) involved and how they come together to produce a whole cell response. We identified the genes that were differentially expressed after CB1 receptor stimulation. From the differentially expressed components we identified the SCPs involved and how the SCPs connect to one another both horizontally and vertically. We used these SCP networks to identify genes, which when knocked down would validate the involvement of the SCP in neurite outgrowth. We identified a varied list of SCPs including those involved in pyrimidine metabolism, lipid biosynthesis, mitochondrial transport function, mRNA splicing and stability in addition to those involved in membrane vesicle production, transport and fusion and microtubule dynamics. Overall these data and computational analyses show that the downstream SCPs required for neurite outgrowth are widely distributed and involve a range of normal cellular functions. Additionally, several of these processes can be considered distal in terms of their proximity to cell signaling pathways and the microtubule and membrane vesicle dynamics, the proximal SCPs required for neurite outgrowth. Hence we conclude that receptor regulation of neurite outgrowth is distributed and deep.

cell biology↗

bioRxiv2018

Multiplexed Profiling of Single-cell Extracellular Vesicles Secretion

Extracellular vesicles (EVs) are important intercellular mediators regulating health and disease. Conventional EVs surface marker profiling, which was based on population measurements, masked the cell-to-cell heterogeneity in the quantity and phenotypes of EVs secretion. Herein, by using spatially patterned antibodies barcode, we realized multiplexed profiling of single-cell EVs secretion from more than 1000 single cells simultaneously. Applying this platform to profile human oral squamous cell carcinoma (OSCC) cell lines led to deep understanding of previously undifferentiated single cell heterogeneity underlying EVs secretion. Notably, we observed the decrement of certain EV phenotypes (e.g. CD63+EVs) were associated with the invasive feature of both OSCC cell lines and primary OSCC cells. We also realized multiplexed detection of EVs secretion and cytokines secretion simultaneously from the same single cells to investigate multidimensional spectrum of intercellular communications, from which we resolved three functional subgroups with distinct secretion profiles by visualized clustering. In particular, we found EVs secretion and cytokines secretion were generally dominated by different cell subgroups. The technology introduced here enables comprehensive evaluation of EVs secretion heterogeneity at single cell level, which may become an indispensable tool to complement current single cell analysis and EV research.\n\nSignificanceExtracellular vesicles (EVs) are cell derived nano-sized particles medicating cell-cell communication and transferring biology information molecules like nucleic acids to regulate human health and disease. Conventional methods for EV surface markers profiling cant tell the differences in the quantity and phenotypes of EVs secretion between cells. To address this need, we developed a platform for profiling an array of surface markers on EVs from large numbers of single cells, enabling more comprehensive monitoring of cellular communications. Single cell EVs secretion assay led to previously unobserved cell heterogeneity underlying EVs secretion, which might open up new avenues for studying cell communication and cell microenvironment in both basic and clinical research.

bioengineering↗

bioRxiv2018

The Effects of Global Signal Regression on Estimates of Resting-state BOLD fMRI and EEG Vigilance Correlations

Global signal regression (GSR) is a commonly used albeit controversial preprocessing approach in the analysis of resting-state BOLD fMRI data. While the effects of GSR on resting-state functional connectivity measures have received much attention, there has been relatively little attention devoted to its effects on studies looking at the relation between resting-state BOLD measures and independent measures of brain activity. In this study we used simultaneously acquired EEG-fMRI data in humans to examine the effects of GSR on the correlation between resting-state BOLD fluctuations and EEG vigilance measures. We show that GSR leads to a positive shift in the correlation between the BOLD and vigilance measures. This shift leads to a reduction in the spatial extent of negative correlations in widespread brain areas, including the visual cortex, but leads to the appearance of positive correlations in other areas, such as the cingulate gyrus. The results obtained using GSR are consistent with those of a temporal censoring process in which the correlation is computed using a temporal subset of the data. Since the data from these retained time points are unaffected by the censoring process, this finding suggests that the positive correlations in cingulate gyrus are not simply an artifact of GSR.

neuroscience↗

bioRxiv2018

A heterochromatic histone methyltransferase lowers nucleosome occupancy at euchromatic promoters

H3K9me3 (histone H3 modified with tri-methylation at lysine 9) is a hallmark of transcriptional silencing and heterochromatin. However, its global effects on the genome, including euchromatin, are less well understood. Here we develop Formaldehyde-Assisted Identification of Regulatory Elements (FAIRE) for C. elegans to examine the chromatin configuration of mutants that lack virtually all H3K9me3, while leaving H3K9me1 and H3K9me2 intact. We find that nucleosomes are mildly disrupted, and levels of H3K9me2 and H3K27me3 rise in mutant embryos. In addition to these expected changes, the most dramatic change occurs in euchromatin: many regions encompassing transcription start sites (TSSs) gain an average of two nucleosomes in mutants. The affected regions normally lack H3K9me3, revealing a locus non-autonomous role for H3K9me3. Affected TSSs are associated with genes that are active in epithelia and muscles, and implicated in development, locomotion, morphogenesis and transcription. Mutant embryos develop normally under ideal laboratory conditions but die when challenged, with defects in morphogenesis and development. Our findings reveal that H3K9me3 protects transcription start sites within euchromatin from nucleosome deposition. These results may be relevant to mammals, where diseases that disrupt the nuclear lamina and heterochromatin can alter epithelial and muscle gene expression.

developmental biology↗

bioRxiv2018

A wrappable microwire electrode for awake, chronic interfacing with small diameter autonomic peripheral nerves

Bioelectronic medicine requires the ability to monitor and modulate nerve activity in awake patients over time. The vagus nerve is a promising stimulation target, and preclinical models often use mice. However, an awake, chronic mouse vagus nerve interface has yet to be demonstrated. Here, we developed a functional wrappable microwire electrode to chronically interface with the small diameter mouse cervical vagus nerve ([~]100 m). In an acute setting, the wrappable microwire had similar recording performance to commercially available electrodes. A chronic, awake mouse model was then developed to record spontaneous compound action potentials (CAPs). Viable signal-to-noise ratios (SNRs) were obtained from the wrappable microwires between 30 and 60 days (n = 8). Weekly impedance measurements showed no correlation between SNR or time. The wrappable microwires successfully interfaced with small diameter nerves and has been validated in a chronic, awake preclinical model, which can better facilitate clinical translation for bioelectronic medicine.

bioengineering↗

bioRxiv2018

Rapidly Assessing the Quality of Targeted Proteomics Experiments Through Monitoring Stable-isotope Labeled Standards

Targeted proteomics experiments based on selected reaction monitoring (SRM) have gained wide adoption in clinical biomarker, cellular modeling and numerous other biological experiments due to their highly accurate and reproducible quantification. The quantitative accuracy in targeted proteomics experiments is reliant on the stable-isotope, heavy-labeled peptide standards which are spiked into a sample and used as a reference when calculating the abundance of endogenous peptides. Therefore, the quality of measurement for these standards is a critical factor in determining whether data acquisition was successful. With improved MS instrumentation that enables the monitoring of hundreds of peptides in hundreds to thousands of samples, quality assessment is increasingly important and cannot be performed manually. We present Q4SRM, a software tool that rapidly checks the signal from all heavy labeled peptides and flags those that fail quality control metrics. Using four metrics, the tool detects problems both with individual SRM transitions and the collective group of transitions that monitor a single peptide. The programs speed enables its use at the point of data acquisition and can be ideally run immediately upon the completion of an LC-SRM-MS analysis.

bioinformatics↗

bioRxiv2018

Characterization and mechanism of lead and zinc biosorption by growing Verticillium insectorum J3

Verticillium insectorum J3 was isolated from a local lead-zinc deposit tailing, and its biosorption characteristics and reaction to the toxicities of different Pb(II) and Zn(II) concentrations were investigated. SEM, FTIR, a pH test and a desorption experiment were carried out to identify a possible mechanism. The biosorption of J3 presented an inhibition trend at low concentrations (25-75 mg L-1) and promotion at high concentrations (100-300 mg L-1). J3 absorbed Pb(II) prior to Zn(II) and produced alkaline substances, while mycelial and pellet morphology modifications were important for the removal of Pb(II) and Zn(II) under different stressful conditions (SEM results). Both intracellular accumulation and extracellular absorption may contribute to the removal of Pb(II) at lower concentrations (25-50 mg L-1), although mainly extracellular biosorption occurred at higher concentrations (75-300 mg L-1). However, Zn(II) bioaccumulation occurred at all concentrations assayed. Verticillium insectorum J3 may have evolved active defenses to alleviate the toxicity of heavy metals and proved to be a highly efficient biosorbent, especially for Pb(II) at high concentrations. This study is a useful reference for the development of biotreatment technologies to mitigate heavy metal waste.

microbiology↗

bioRxiv2018

Surge of Corticocardiac Coupling in SHRSP Rats Exposed to Forebrain Cerebral Ischemia

Sudden death is an important but under-recognized consequence of stroke. Acute stroke can disturb central control of autonomic function, and result in cardiac dysfunction and sudden death. Previous study showed that bilateral common carotid artery ligation (BCCAL) in spontaneously hypertensive stroke-prone rats (SHRSP) is a well-established model for forebrain ischemic sudden death. This study aims to investigate the temporal dynamic changes in electrical activities of the brain and heart and functional interactions between the two vital organs following forebrain ischemia. EEG and ECG signals were simultaneously collected from 9 SHRSP and 8 Wistar-Kyoto (WKY) rats. RR interval and cardiac arrhythmias were analyzed to investigate the cardiac response to brain ischemia. EEG power and coherence (CCoh) analysis were conducted to study the cortical response. Corticocardiac coherence (CCCoh) and directional connectivity (CCCon) were analyzed to determine brain-heart connection. Heart rate variability (HRV) was analyzed to evaluate autonomic functionality. BCCAL resulted in 100% mortality in SHRSP within 14 hours, whereas no mortality was observed in WKY. The functionality of both the brain and the heart were significantly altered in SHRSP compared to WKY after BCCAL. SHRSP rats, but not WKY rats, exhibited intermittent surge of CCCoh, which paralleled the elevated CCCon and reduced HRV, following the onset of ischemia until sudden death. Elevated brain-heart coupling invariably associated with the disruption of the autonomic nervous system and the risk of sudden death. This study may improve our understanding of the mechanism of ischemic stroke-induced sudden death.

physiology↗

bioRxiv2018

Feasibility of constructing multi-dimensional genomic maps of juvenile idiopathic arthritis

BackgroundJuvenile idiopathic arthritis (JIA) is one of the most common chronic conditions of childhood. Like many common chronic human illnesses, JIA likely involves complex interactions between genes and the environment, mediated by the epigenome. Such interactions are best understood through multi-dimensional genomic maps that identify critical genetic and epigenetic components of the disease. However, constructing such maps in a cost-effective way is challenging, and this challenge is further complicated by the challenge of obtaining biospecimens from pediatric patients at time of disease diagnosis, prior to therapy, as well as the limited quantity of biospecimen that can be obtained from children,particularly those who are unwell. In this paper, we demonstrate the feasibility and utility of creating multi-dimensional genomic maps for JIA from limited sample numbers.\n\nMethodsTo accomplish our aims, we used an approach similar to that used in the ENCODE and Roadmap Epigenomics projects, which used only 2 replicates for each component of the genomic maps. We used genome-wide DNA methylation sequencing, whole genome sequencing on the Illumina 10x platform, RNA sequencing, and chromatin immunoprecipitation-sequencing for informative histone marks (H3K4me1 and H3K27ac) to construct a multi-dimensional map of JIA neutrophils, a cell we have shown to be important in the pathobiology of JIA.\n\nResultsThe epigenomes of JIA neutrophils display numerous differences from those from healthy children. DNA methylation changes, however, had only a weak effect on differential gene expression. In contrast, H3K4me1 and H3K27ac, commonly associated with enhancer functions, strongly correlated with gene expression. Furthermore, although unique/novel enhancer marks were associated with insertion-deletion events (indels) identified on whole genome sequencing, we saw no strong association between epigenetic changes and underlying genetic variation. The initiation of treatment in JIA is associated with a re-ordering of both DNA methylation and histone modifications, demonstrating the plasticity of the epigenome in this setting.\n\nConclusionsThese findings, generated from a small number of patient samples, demonstrate how multidimensional genomic studies may yield new understandings of biology of JIA and provide insight into how therapy alters gene expression patterns.

genomics↗

bioRxiv2018

HMMRATAC, the Hidden Markov ModeleR for ATAC-seq

ATAC-seq has been widely adopted to identify accessible chromatin regions across the genome. However, current data analysis still utilizes approaches initially designed for ChIP-seq or DNase-seq, without taking into account the transposase digested DNA fragments that contain additional nucleosome positioning information. We present the first dedicated ATAC-seq analysis tool, a semi-supervised machine learning approach named HMMRATAC. HMMRATAC splits a single ATAC-seq dataset into nucleosome-free and nucleosome-enriched signals, learns the unique chromatin structure around accessible regions, and then predicts accessible regions across the entire genome. We show that HMMRATAC outperforms the popular peak-calling algorithms on published human and mouse ATAC-seq datasets.

bioinformatics↗

bioRxiv2018

TOXOPLASMA ACTIVATES HOST HYPOXIA INDUCIBLE FACTOR-1 BY CYTOPLASMIC TRAPPING AND LAMP1-DEPENDENT LYSOSOMAL DEGRADATION OF PROLYL-HYDROXYLASE 2

Hypoxia Inducible Factor-1 is a metazoan heterodimeric transcription factor that senses changes in O2 levels. HIF-1 subunit abundance is post-translationally regulated by prolyl-hydroxylase domain enzymes (PHDs), which use molecular O2 and -ketoglutarate to hydroxylate two prolyl-residues in HIF-1. Three PHDs have been identified and PHD2 is the most critical regulator of HIF-1. HIF-1 can also be activated independently of hypoxia and in some cases this is due to changes in PHD2 abundance through poorly understood mechanisms. Previously, we reported that under O2-replete conditions that the intracellular parasite Toxoplasma gondii activates HIF-1 by reducing PHD2 protein abundance. Here, we demonstrate that Toxoplasma regulates PHD2 through a multistep process. First, PHD2 is a nucleocytoplasmic protein and Toxoplasma induces PHD2 cytoplasmic accumulation to separate it from nuclear HIF-1. PHD2 is then degraded by lysosomes independently of the major autophagic processes, macroautophagy or chaperone-mediated autophagy. Rather, PHD2 interacts with the major lysosomal membrane protein, LAMP1, which is required for HIF-1 activation. These data therefore highlight for the first time that cytoplasmic trapping and subsequent lysosomal degradation of a host nucleocytoplasmic protein is a mechanism used by a microbial pathogen to regulate host gene expression.

cell biology↗

bioRxiv2018

Open-pFind enables precise, comprehensive and rapid peptide identification in shotgun proteomics

Shotgun proteomics has grown rapidly in recent decades, but a large fraction of tandem mass spectrometry (MS/MS) data in shotgun proteomics are not successfully identified. We have developed a novel database search algorithm, Open-pFind, to efficiently identify peptides even in an ultra-large search space which takes into account unexpected modifications, amino acid mutations, semi- or non-specific digestion and co-eluting peptides. Tested on two metabolically labeled MS/MS datasets, Open-pFind reported 50.5-117.0% more peptide-spectrum matches (PSMs) than the seven other advanced algorithms. More importantly, the Open-pFind results were more credible judged by the verification experiments using stable isotopic labeling. Tested on four additional large-scale datasets, 70-85% of the spectra were confidently identified, and high-quality spectra were nearly completely interpreted by Open-pFind. Further, Open-pFind was over 40 times faster than the other three open search algorithms and 2-3 times faster than three restricted search algorithms. Re-analysis of an entire human proteome dataset consisting of [~]25 million spectra using Open-pFind identified a total of 14,064 proteins encoded by 12,723 genes by requiring at least two uniquely identified peptides. In this search results, Open-pFind also excelled in an independent test for false positives based on the presence or absence of olfactory receptors. Thus, a practical use of the open search strategy has been realized by Open-pFind for the truly global-scale proteomics experiments of today and in the future.

bioinformatics↗

bioRxiv2018

Dynamic virulence-related regions of the fungal plant pathogen Verticillium dahliae display remarkably enhanced sequence conservation

Selection pressure impacts genomes unevenly, as different genes adapt with differential speed to establish an organisms optimal fitness. Plant pathogens co-evolve with their hosts, which implies continuously adaption to evade host immunity. Effectors are secreted proteins that mediate immunity evasion, but may also typically become recognized by host immune receptors. To facilitate effector repertoire alterations, in many pathogens, effector genes reside in dynamic genomic regions that are thought to display accelerated evolution, a phenomenon that is captured by the two-speed genome hypothesis. The genome of the vascular wilt pathogen Verticillium dahliae has been proposed to obey to a similar two-speed regime with dynamic, lineage-specific regions that are characterized by genomic rearrangements, increased transposable element activity and enrichment in in planta-induced effector genes. However, little is known of the origin of, and sequence diversification within, these lineage-specific regions. Based on comparative genomics among Verticillium spp. we now show differential sequence divergence between core and lineage-specific genomic regions of V. dahliae. Surprisingly, we observed that lineage-specific regions display markedly increased sequence conservation. Since single nucleotide diversity is reduced in these regions, host adaptation seems to be merely achieved through presence/absence polymorphisms. Increased sequence conservation of genomic regions important for pathogenicity is an unprecedented finding for filamentous plant pathogens and signifies the diversity of genomic dynamics in host-pathogen co-evolution.

microbiology↗

bioRxiv2018

Thermoneutrality induces skeletal muscle myopathy via brown adipose tissue in an IRF4- and myostatin-dependent manner

Skeletal muscle and brown adipose tissue (BAT) share a common lineage and have been functionally linked, as exercise increases browning through the actions of various myokines. It is unknown, however, whether BAT can affect skeletal muscle function. Our prior work has shown that loss of the transcription factor IRF4 in BAT (BATI4KO) reduces adaptive thermogenesis. Here, we note that these mice also have reduced exercise capacity relative to wild-type littermates, associated with diminished mitochondrial function, ribosomal protein synthesis, and mTOR signaling in muscle, in addition to the signature ultrastructural abnormalities of tubular aggregate myopathy. Within brown adipose tissue, loss of IRF4 caused the induction of a myogenic gene expression signature, which includes an increase in the secreted factor myostatin, a known inhibitor of muscle function. Reduction of myostatin activity by the injection of neutralizing antibodies or soluble ActRIIB receptor rescued the exercise capacity of BATI4KO mice. Additionally, overexpression of IRF4 in brown adipocytes reduced serum myostatin and increased mitochondrial function and exercise capacity in muscle. A physiological role for this system is suggested by the observation that mice housed at thermoneutrality show lower exercise capacity with increased serum myostatin; both of these abnormalities are corrected by surgical removal of BAT. Collectively, our data point to an unsuspected level of BAT-muscle cross-talk driven by IRF4 and myostatin.\n\nHighlightsO_LIMice lacking IRF4 in BAT have a decrease in exercise capacity, accompanied by histological, ultrastructural, signaling, gene expression, and bioenergetic evidence of myopathy in white vastus.\nC_LIO_LILoss of IRF4 promotes the expression of a myogenic signature in BAT, including the myokine myostatin.\nC_LIO_LINeutralization of serum myostatin rescues the ability of BATI4KO mice to exercise normally, while overexpression of IRF4 in BAT allows mice to run better than wild-type counterparts.\nC_LIO_LIThermoneutrality reduces the level of IRF4 in BAT of WT mice, resulting in a myopathic phenotype that can be reversed by surgical excision of BAT.\nC_LI

physiology↗