Biology subjects

Tian, Y.

Publications and source records attributed to Tian, Y..

At least 109 records · Page 6Linked to original sources

bioRxiv2024

BMP4 is sufficient to induce a caudal organizer

The caudal part of a vertebrate embryo consists of somites, neural tube, lateral plate mesoderm derivatives and the tailbud. However, the minimal conditions and factors sufficient to induce the caudal region, particularly in humans, remain unresolved. Here, we show that BMP4 alone, when administered at appropriate dosage, is sufficient to induce the formation of an organizer for caudal induction. This organizer induces caudal cell fate specification and morphogenesis in zebrafish embryos. In 3D human pluripotent stem cells (hPSCs) aggregates, BMP4 can induce an elongated embryonic structure characterized by caudal fates. Importantly, hPSCs instructed by BMP4 are sufficient to induce a secondary caudal region when grafted into the animal pole of the zebrafish embryo. Our study thus uncovers BMP4 as the inducer in the formation of a caudal organizer in the vertebrate embryo. Significance statementWe demonstrate that BMP4 alone can induce the formation of a caudal organizer, a critical structure that guides the development of the caudal region in vertebrates. Using zebrafish embryos, embryonic explants, human pluripotent stem cell xenografts, and 3D human stem cell aggregates, we show that this organizer replicates morphogenesis and key differentiation pathways seen in natural development. Our findings uncover a novel role for BMP4 and define the minimal requirements for inducing this organizer, offering new insights into vertebrate development and potential applications in regenerative medicine.

developmental biology↗

bioRxiv2024

Non-gonadal PIWI protein, Aubergine, regulates regenerative stem cell proliferation and tumourigenesis in the Drosophila adult intestine.

The PIWI-interacting RNA (piRNA) biosynthesis pathway is best studied for its role suppressing Drosophila germline transposable elements. Piwi, the founding member of the pathway, is involved in adult intestinal stem cell (ISC) homeostasis. Whether a broader role of the PIWI pathway exists in the intestine, remains unknown. Here, we characterise a role of the PIWI family protein Aubergine (Aub) in ISCs. While dispensable for basal ISC self-renewal, upregulation of Aub by damage-induced reactive oxygen species drives regenerative ISC proliferation through increased protein synthesis, including translation of ISC factors Myc and Sox21a. Unexpectedly, such roles of Aub in ISCs appear uncoupled from its piRNA regulatory function. Additionally, Aub and mammalian PIWIL1, mediate tumorigenic intestinal growth in Drosophila and human organoids, respectively. Our results reveal regulated protein translation as a fundamental aspect of regenerative ISC function and discover a central role of Aub in such process.

developmental biology↗

bioRxiv2024

Structural basis of pseudoGTPase-mediated protein-protein interactions

GTPases regulate various cellular processes through conformational changes triggered by GTP or GDP binding. Recently, pseudoGTPases, the catalytically inactive counterparts of GTPases, have been identified across species from bacteria to human, although their functions and mechanisms remain unexplored. In this study, we demonstrate that the N-terminal region of the assembly chaperone AAGAB is a type i pseudoGTPase using biochemistry and X-ray crystallography. Furthermore, we discovered that the AAGAB pseudoGTPase domain (psGD) interacts with the {sigma} subunits of AP1 and AP2 adaptor complexes, heterotetrameric complexes involved in clathrin-mediated membrane trafficking. AAGAB psGD engages the {sigma} subunits via a unique interface distinct from the conventional GTPase interacting regions. Further biochemical and cell-based assays confirmed the crucial role of the newly identified interface in binding and membrane trafficking. Collectively, our results establish AAGAB pseudoGTPase domain as a critical protein-protein interaction module. These findings offer new insight into the structural basis and molecular mechanisms of pseudoGTPases. HighlightsO_LIAAGAB N-terminal region is a pseudoGTPase C_LIO_LIAAGAB pseudoGTPase domain interacts with and stabilizes AP1 and AP2 {sigma} subunits C_LIO_LIThe crystal structure of AAGAB psGD:AP1{sigma}3 is the first reported psGD complex structure, revealing a unique interface independent of guanine nucleotide regulation C_LIO_LIThe psGD:AP1{sigma}3 structure offers mechanistic insights into {sigma} subunits stabilization and protection through adaptor complex assembly C_LI

biochemistry↗

bioRxiv2024

Role of Arginine and its Metabolism in TGF-β-Induced Activation of Lung Fibroblasts

Arginine is a conditionally essential amino acid with known roles in protein production, nitric oxide synthesis, biosynthesis of proline and polyamines, and regulation of intracellular signaling pathways. Arginine biosynthesis and catabolism have been linked to TGF-{beta}-induced activation of fibroblasts in the context of pulmonary fibrosis; however, a thorough study on the metabolic and signaling roles of arginine in the process of fibroblast activation has not been conducted. Here, we used metabolic dropouts and labeling strategies to determine how activated fibroblasts utilize arginine. We found that arginine limitation leads to activation of GCN2 while inhibiting TGF-{beta}-induced mTORC1 activation and collagen protein production. Extracellular citrulline could rescue the effect of arginine deprivation in an ASS1-dependent manner. Using metabolic tracers of arginine and its precursors, we found little evidence of arginine synthesis or catabolism in lung fibroblasts treated with TGF-{beta}. Extracellular ornithine or glutamine were the primary sources of ornithine and polyamines, not arginine. Our findings suggest that the major role for arginine in lung fibroblasts is for charging of arginyl-tRNAs and for promotion of mTOR signaling. Highlights- Arginine depletion inhibits TGF-{beta}-induced transcription in human lung fibroblasts (HLFs). - Arginine is not significantly catabolized in HLFs either through NOS or ARG dependent pathways. - Extracellular glutamine and ornithine are the primary sources of polyamines in lung fibroblasts. - The primary role of arginine in lung fibroblasts is for signaling through mTOR and GNC2.

cell biology↗

bioRxiv2024

Using a Deep Learning Approach for Model-based Control of Deep Brain Stimulation

Deep brain stimulation (DBS) has been developed as a treatment method for various neurological disorders, including Parkinsons disease, essential tremor and depression. Although DBS is effective, it often loses efficacy over sustained periods because a constant stimulation is applied without adapting to the patients current clinical state. In contrast, an adaptive closed-loop DBS system can offer more tailored stimulation in real-time based on a feedback biomarker. In early 2024, we developed a model-based DBS control framework that consists of three main functions: (1) a biophysically reasonable encoding model, (2) a simple decoding model, and (3) a controller. We used a polynomial fit function in the decoding model to approximate the neural-motor relationship, from DBS-induced Vim neural activity to muscle fiber electromyography (EMG). Despite promising results, the polynomial method is inaccurate in capturing the full representation of the neural-motor (EMG) function across different DBS frequencies. In this work, to capture the nonlinear intricate relationship between the neural and EMG patterns, we developed a one-dimensional convolutional neural network (1-D CNN) as a decoding model to predict the EMG signal directly from the DBS-induced Vim neural activity. The 1-D CNN network outputted a high R2 value of 0.997 which significantly outperformed the polynomial method (R2 = 0.277) and a deep learning approach based on long short-term memory (R2 = 0.296). We anticipate that our work highlights the need for a data-driven approach that can reliably map neural activities to symptomatic signals like EMG for better adjusting DBS parameters.

neuroscience↗

bioRxiv2024

Morphine-induced hyperalgesia impacts small extracellular vesicle miRNA composition and function

Morphine and other synthetic opioids are widely prescribed to treat pain. Prolonged morphine exposure can paradoxically enhance pain sensitivity in humans and nociceptive behavior in rodents. To better understand the molecular mechanisms underlying opioid-induced hyperalgesia, we investigated changes in miRNA composition of small extracellular vesicles (sEVs) from the serum of mice after a morphine treatment paradigm that induces hyperalgesia. We observed significant differential expression of 18 miRNAs in sEVs from morphine-treated mice of both sexes compared to controls. Several of these miRNAs were bioinformatically predicted to regulate cyclic AMP response element binding protein (CREB), a well-characterized transcription factor implicated in pain and drug addiction. We confirmed the binding and repression of Creb mRNA by miR-155 and miR-10a. We tested if serum-derived sEVs from morphine-treated mice could elicit nociceptive behavior in naive recipient mice. Intrathecal injection of 1 g sEVs did not significantly impact basal mechanical and thermal threshold in naive recipient mice. However, prophylactic 1 g sEV administration in recipient mice resulted in faster resolution of complete Freunds adjuvant-induced mechanical and thermal inflammatory hypersensitivity. Other behaviors assayed following administration of these sEVs were not impacted including sEV conditioned place preference and locomotor sensitization. These results indicate that morphine regulation of serum sEV composition can contribute to analgesia and suggest a potential for sEVs to be a non-opioid therapeutic intervention strategy to treat pain.

neuroscience↗

bioRxiv2024

HIF-1α regulates mitochondrial function in bone marrow-derived macrophages, but not in tissue-resident alveolar macrophages

HIF-1 plays a critical role in shaping macrophage phenotype and effector function. We have previously shown that tissue-resident alveolar macrophages (TR-AMs) have extremely low glycolytic capacity at steady-state, but can shift toward glycolysis under hypoxic conditions. Here, using inducible HIF-1 knockout (Hif1a-/-) TR-AMs and bone marrow-derived macrophages (BMDMs) and show that TR-AM HIF-1 is required for the glycolytic shift under prolyl hydroxylase inhibition, but is dispensable at steady-state for inflammatory effector function. In contrast, HIF-1 deletion in BMDMs led to diminished glycolytic capacity at steady-state and reduced inflammatory capacity, but higher mitochondrial function. Gene set enrichment analysis revealed enhanced c-Myc transcriptional activity in Hif1a-/- BMDMs, and upregulation of gene pathways related to ribosomal biogenesis and cellular proliferation. The findings highlight the heterogeneity of HIF-1 function in distinct macrophage populations and provide new insight into how HIF-1 regulates gene expression, inflammation, and metabolism in macrophages.

cell biology↗

bioRxiv2024

APC coordinates GSK3 phosphorylation of SETD8 to suppress colorectal cancer

Colorectal cancer (CRC) is the second-leading cause of cancer-related deaths with increasing incidence globally. Mutations in the tumor suppressor APC initiate CRC at least in part by preventing the GSK3 kinase from phosphorylating {beta}-CATENIN, leading to its constitutive stabilization and transactivation of mitogenic target genes. While the importance of {beta}-CATENIN phosphorylation by GSK3 is well-established, APC regulation of GSK3 activity upon other targets with potential oncogenic relevance are not understood. Here, we identify the H4K20 methyltransferase SETD8 as target of APC-coordinated GSK3 phosphorylation in the intestinal epithelium. We found that phosphorylation by GSK3 restrains the oncogenic activity of SETD8, with loss of phosphorylation sensitizing mice to oncogenic insults. Mechanistically, phosphorylation alters the role of SETD8 in transcriptional regulation, most notably by preventing it from activating oncogenic YAP signaling and a fetal-like transcriptional program. These results underscore the importance of SETD8 in CRC and represent a novel {beta}-CATENIN -independent oncogenic consequence of APC loss. SignificanceGSK3 is thought to restrain colorectal cancer primarily by phosphorylation of {beta}-CATENIN. We show that GSK3 also phosphorylates SETD8, preventing SETD8 activation of oncogenic programs including YAP-driven fetal-like gene expression.

cancer biology↗

bioRxiv2024

Identification and characterization of ugpE required for the full virulence of Streptococcus suis

Streptococcus suis (S. suis) is an emerging zoonotic pathogen that threatens both animal and human health worldwide. UgpE is a protein subunit of the Ugp (uptake of glycerol phosphate) transporter system that is involved in glycerophospholipid synthesis in bacterial membranes. In this study, an ugpE deletion mutant was constructed and the effects of ugpE deletion on cell morphology, biofilm formation, and virulence were investigated. Deletion of ugpE did not affect bacterial growth but impaired cell chain formation and capsular synthesis by downregulating the mRNA levels of the capsular regulon genes cps-2B, cps-2C, and cps-2S. Deletion of ugpE also led to decreased tolerance to heat, oxidative, and acid-base stress. Crystal violet staining and scanning electron microscopy demonstrated ugpE negatively regulated biofilm formation in liquid culture and the rdar biofilm morphotype on agar plates. Moreover, ugpE deletion not only reduced hemolysin activity, survival in whole human blood, and anti-phagocytosis ability against porcine alveolar macrophages (PAM) but also enhanced bacterial adhesion and invasion of human cerebral microvascular endothelial cells (hCMEC/D3) by upregulating the expression of multiple genes associated with cell adhesion. In a mouse infection model, ugpE deletion significantly attenuated virulence and lowered the number of viable bacteria in the blood and major organs, as well as distribution of macrophages. In conclusion, this study identified UgpE as a novel virulence factor that plays a pivotal role in the regulation of virulence and biofilm formation of S. suis.

microbiology↗

bioRxiv2024

Fine Mapping Regulatory Variants by Characterizing Native CpG Methylation with Nanopore Long Read Sequencing

5-methylcytosine (5mC) is the most common chemical modification occurring on the CpG sites across the human genome. Bisulfite conversion combined with short-read whole genome sequencing can capture and quantify the modification at single nucleotide resolution. However, the PCR amplification process could lead to duplicative methylation patterns and introduce 5mC detection bias. Additionally, the limited read length also restricts co-methylation analysis between distant CpG sites. The bisulfite conversion process presents a significant challenge for detecting variant-specific methylation due to the destruction of allele information in the sequencing reads. To address these issues, we sought to characterize the human methylation profiling with the nanopore long-read sequencing, aiming to demonstrate its potential for long-range co-methylation analysis with native modification call and intact allele information retained. In this regard, we first analyzed the nanopore demo data in the adaptive sampling sequencing run targeting all human CpG islands. We applied the linkage disequilibrium (LD) R2 to calculate the co-methylation in nanopore data, and further identified 27,875, 50,481, 26,542 and 51,189 methylation haplotype blocks (MHB) in COLO829, COLO829BL, HCC1395 and HCC1395BL cell lines, respectively. Interestingly, while we found that majority of the co-methylation were in a short range ([≤]200bp), a small portion (1[~]3%) showed long distance ([≥]1,000bp), suggesting potential remote regulatory mechanisms across the genome. To further characterize the epigenetic changes related to transcription factor binding, we profiled the 5mC percentage changes surrounding various motif sites in JASPAR collection and found that CTCF and KLF5 binding sites showed reduced methylation, while FOXE1 and ZNF354A sites showed increased methylation. To further investigate the allele-specific 5mCG in the prostate genome, we designed a target region covering methylation quantitative trait loci (mQTL) and genome-wide association study (GWAS) risk germline variants and generated long reads with adaptive sampling run in the 22Rv1 cell line. To identify the allele-specific methylation in the 22Rv1 cell line, we performed long-read based phasing and compared the 5mCG signals between the two haplotypes. As a result, we identified 6,390 haplotype-specific methylated regions in the 22Rv1 cell line (p-MWU [≤] 1e-5 and delta [≥] 50%). By examining haplotype-specific methylated regions near the phasing variants, we identified examples of allele-specific methylated regions that showed allele-specific accessibility in the ATAC-seq data. By further integrating the ATAC-seq data of 22Rv1, we found that methylation levels were negatively correlated with chromatin accessibility at the genome-wide scale. Our study has revealed native methylome profiling while preserving haplotype information, offering a novel approach to uncovering the regulatory mechanisms of the human prostate genome.

genetics↗

bioRxiv2024

Cryo-EM Structure of an Active Bacterial SIR2-STAND Filament

Bacterial antiviral STANDs (Avs) are evolutionarily related to the nucleotide-binding leucine-rich repeat containing receptors (NLRs) widely distributed in immune systems across animals and plants. EfAvs5, an Avs type 5 protein from Escherichia fergusonii, contains an N-terminal SIR2 effector domain, a nucleotide-binding oligomerization domain (NOD) and a C-terminal sensor domain, conferring protection against diverse phage invasions. Despite the established roles of SIR2 and STAND in prokaryotic and eukaryotic immunity, the mechanism underlying their collaboration remains unclear. Here we present cryo-EM structures of EfAvs5 filaments, elucidating the mechanisms of dimerization, filamentation, filament clustering, ATP binding and NAD+ hydrolysis, all of which are crucial for anti-phage defense. The SIR2 domains and NODs engage in the intra- and inter-dimer interaction to form an individual filament, while the outward C-terminal domains contribute to bundle formation. Filamentation potentially stabilizes the dimeric SIR2 configuration, thereby activating the NADase activity of EfAvs5. EfAvs5 is deficient in the ATPase activity, but elevated ATP concentrations can impede its NADase activity. Together, we uncover the filament assembly of Avs5 as a unique mechanism to switch enzyme activities and perform anti-phage defenses, emphasizing the conserved role of filamentation in immune signaling across diverse life forms. KeypointsO_LIEfAvs5 depletes NAD+ for anti-phage defense. C_LIO_LIEfAvs5 assembles as bundled filaments that can hydrolyze NAD+. C_LIO_LIThe SIR2 domain and NOD collaborate to form an individual filament. C_LIO_LIThe building block of the filament is EfAvs5 dimer. C_LIO_LIThe activity of the EfAvs5 complex is regulated by ATP. C_LI

microbiology↗

bioRxiv2024

Haplotype-resolved genomes provide insights into the origin and function of genome diversity in bivalves

Bivalves are famed for exhibiting vast genetic diversity of poorly understood origins and functional significance. Within bivalves, oysters are an ancient group showing remarkable genetic and phenotypic variability alongside extensive adaptability, serving as an ideal system to understand the origins and functional significance of genomic diversity. Here, we reveal the divergent genomic landscape of Crassostrea oysters, characterized by a history of genome size reduction associated with transposable elements (TEs). By constructing a haplotype-resolved genome for Kumamoto oyster C. sikamea, we demonstrate the widespread presence of haplotype divergent sequences (HDS); genomic regions present in just one haplotype. Combined with population resequencing, we define the role of genomic divergence driven by TEs in shaping oyster genetic diversity. Comparisons of haplotype-resolved genomes across four bivalve orders reveal that while extensive HDS is common, its origins may differ markedly. We show that HDS are a hotspot of genetic innovation, harboring rapidly evolving genes of various evolutionary ages, while also strongly influencing gene expression phenotypes. A widespread lack of allele-specific expression shared among oyster individuals indicates that haplotype polymorphism provides a key source of expression variation, promoting phenotypic plasticity and adaptation. These findings advance understanding on the origins of genomic diversity and its role in adaptive evolution.

genomics↗

bioRxiv2024

Fluralaner treatment of chickens kills the southern house mosquito, Culex quinquefasciatus

The control of zoonotic and vector-borne pathogens is challenging due to the limited availability of intervention tools. West Nile virus (WNV) is an example of globally distributed zoonotic arbovirus that circulates between Culex species mosquitoes and avian hosts, with spillover transmission to humans, resulting in disease cases. Interventions delivering systemic insecticides to vertebrate hosts used by vector species, known as xenointoxication, are potential tools for managing vector populations by creating toxic bloodmeals. In this study, we evaluated the impact of three systemic insecticides on the mortality of Cx. quinquefasciatus: fenbendazole (Safe-Guard(R) Aquasol), ivermectin (Ivomec(R) Pour-On), and fluralaner (Bravecto(R)). We found no significant difference in the feeding rates of mosquitoes that fed on treated chickens compared to those fed on untreated chickens, suggesting that the treatment did not repel mosquitoes. The mortality of Cx. quinquefasciatus mosquitoes feeding on fluralaner-treated chickens was significantly higher (p < 0.01) than those fed on control chickens at 3 and 7 days post-treatment, but this effect was not observed in mosquitoes fed on chickens treated with fenbendazole or ivermectin. No differences in mortality were observed among the groups at 14, 26, or 56 days post-treatment. These data support fluralaner as a xenointoxication tool to control Cx. quinquefasciatus populations and decrease the risk of human exposure to their associated pathogens.

biochemistry↗

bioRxiv2024

Decoding protein glycosylation by an integrative mass spectrometry-based de novo sequencing strategy

Glycoproteins, representing over 50% of human proteins and most biopharmaceuticals, are crucial for regulating various biological processes. The complexity of multiple glycosylation sites, often leading to incomplete sequence coverage and ambiguous glycan modification profiles. Here, we developed an integrative mass spectrometry-based approach for decoding unknown glycoproteins, which is featured with the combination of deglycosylation-mediated de novo sequencing with glycosylation site characterization. We utilized enzymatic deglycosylation of N-/ O-glycan to achieve comprehensive sequence coverage. Additionally, EThcD fragmentation enables the identification of high-quality long peptides, facilitating precise protein assembly. We subsequently applied this method to de novo sequencing of the highly glycosylated therapeutic fusion protein Etanercept (Enbrel(R)). We also sequenced three new tumor necrosis factor receptor (TNFR): Fc-fusion biologics with largely unknown sequences, unveiling subtle distinctions in the primary sequences. Furthermore, we characterized N- and O-glycosylation modifications of these proteins at subunit, glycopeptide, and glycan levels. This strategy bridges the gap between the de novo sequencing and glycosylation modification, providing complete information of the primary structure and glycosylation modifications for glycoproteins. Notably, our method could be a robust solution for accurate sequencing of the glycoproteins and has practical value not only in basic research but also in the biopharmaceutical industry.

biochemistry↗

bioRxiv2024

AutoMorFi: Automated Whole-image Morphometry in Fiji/ImageJ for Diverse Image Analysis Needs

Running on the highly popular and accessible ImageJ/Fiji platform for biological image analysis, we have established AutoMorFi as a streamlined interface for automated whole-image morphometric analysis that generates at least 47 measurements per cell or object in under 1 minute. We performed multiple validated cluster and principal component analyses on nonredundant morphometric parameters derived from AutoMorFi for various cell types, objects, and organisms. We used images of rodent macrophages, human postmortem brain tissues from multiple sclerosis (MS) and Alzheimers disease (AD) patients, iPSC/animal models for Downs syndrome and autism spectrum disorder (ASD), and organisms such as sea anemone and corals. AutoMorFis adaptability extends across diverse imaging modalities including brightfield, confocal, or widefield fluorescence microscopy as well as underwater photography. Due to its unlimited and unbiased sampling across any image and high potential for modification and customization, using AutoMorFi has led to the discovery of new distinguishing features in previously studied cell types and organisms as well as the development of rapid diagnostic approaches. AutoMorFi represents a transformative tool that will accelerate morphometric analysis and offer broad relevance in biological studies.

cell biology↗

bioRxiv2024

Dissecting cell-free DNA fragmentation variation in tumors using cell line-derived xenograft mouse

Cell-free DNA (cfDNA) is increasingly studied for its diverse applications in non-invasive detection. Non-randomly cleaved by nucleases and released into the bloodstream, cfDNA exhibits a variety of intrinsic fragmentation patterns indicative of cell status. Particularly, these fragmentation patterns have recently been demonstrated to be effective in predicting cancer and its tissue-of-origin, owing to increased variation of fragmentation features observed in tumor patients. However, there remains a lack of detailed exploration of altered cfDNA fragmentation profiles in tumors, which consist of a mixture of both non-tumor cfDNA and circulating tumor DNA (ctDNA). Hence, we leveraged the human tumor cell line-derived xenograft (CDX) mouse model, where different tumor cell lines were implanted into different anatomical sites, to isolate pure ctDNA and separately investigate the fragment properties of CDX-induced cfDNA and ctDNA. We found an enrichment of short cfDNA fragments in both CDX-induced cfDNA and ctDNA compared to normal plasma cfDNA, with more elevated short fragments in ctDNA. Moreover, the CDX-induced cfDNA fragmentation features distinguished between CDX models of different tumor cell lines, while the ctDNA fragmentation features conversely discriminate between CDX models of different anatomical sites. The results suggested that both non-tumor cfDNA and ctDNA contribute to the increased variation observed in tumors, and that cfDNA fragmentation may be highly variable and susceptible to regulations by both original cells and cells within the local niche.

cancer biology↗

bioRxiv2024

Identify Regulatory eQTLs by Multiome Sequencing in Prostate Single Cells

While genome-wide association studies and expression quantitative trait loci (eQTL) analysis have made significant progress in identifying noncoding variants associated with prostate cancer risk and bulk tissue transcriptome changes, the regulatory effect of these genetic elements on gene expression remains largely unknown. Recent developments in single-cell sequencing have made it possible to perform ATAC-seq and RNA-seq profiling simultaneously to capture functional associations between chromatin accessibility and gene expression. In this study, we tested our hypothesis that this multiome single-cell approach allows for mapping regulatory elements and their target genes at prostate cancer risk loci. We applied a 10X Multiome ATAC + Gene Expression platform to encapsulate Tn5 transposase-tagged nuclei from multiple prostate cell lines for a total of 65,501 high quality single cells from RWPE1, RWPE2, PrEC, BPH1, DU145, PC3, 22Rv1 and LNCaP cell lines. To address data sparsity commonly seen in the single-cell sequencing, we performed targeted sequencing to enrich sequencing data at prostate cancer risk loci involving 2,730 candidate germline variants and 273 associated genes. Although not increasing the number of captured cells, the targeted multiome data did improve eQTL gene expression abundance by about 20% and chromatin accessibility abundance by about 5%. Based on this multiomic profiling, we further associated RNA expression alterations with chromatin accessibility of germline variants at single cell levels. Cross validation analysis showed high overlaps between the multiome associations and the bulk eQTL findings from GTEx prostate cohort. We found that about 20% of GTEx eQTLs were covered within the significant multiome associations (p-value [≤] 0.05, gene abundance percentage [≥] 5%), and roughly 10% of the multiome associations could be identified by significant GTEx eQTLs. We also analyzed accessible regions with available heterozygous SNP reads and observed more frequent association in genomic regions with allelically accessible variants (p = 0.0055). Among these findings were previously reported regulatory variants including rs60464856-RUVBL1 (multiome p-value = 0.0099 in BPH1) and rs7247241-SPINT2 (multiome p-value = 0.0002- 0.0004 in 22Rv1). We also functionally validated a new regulatory SNP and its target gene rs2474694-VPS53 (multiome p-value = 0.00956 in BPH1 and 0.00625 in DU145) by reporter assay and SILAC proteomics sequencing. Taken together, our data demonstrated the feasibility of the multiome single-cell approach for identifying regulatory SNPs and their regulated genes.

genetics↗

bioRxiv2024

ATF4 and mTOR regulate metabolic reprogramming in TGF-β-treated lung fibroblasts

Idiopathic pulmonary fibrosis is a fatal disease characterized by the TGF-{beta}-dependent activation of lung fibroblasts, leading to excessive deposition of collagen proteins and progressive replacement of healthy lung with scar tissue. We and others have shown that fibroblast activation is supported by metabolic reprogramming, including the upregulation of the de novo synthesis of glycine, the most abundant amino acid found in collagen protein. How fibroblast metabolic reprogramming is regulated downstream of TGF-{beta} is incompletely understood. We and others have shown that TGF-{beta}-mediated activation of the Mechanistic Target of Rapamycin Complex 1 (mTORC1) and downstream upregulation of Activating Transcription Factor 4 (ATF4) promote increased expression of the enzymes required for de novo glycine synthesis; however, whether mTOR and ATF4 regulate other metabolic pathways in lung fibroblasts has not been explored. Here, we used RNA sequencing to determine how both ATF4 and mTOR regulate gene expression in human lung fibroblasts following TGF-{beta}. We found that ATF4 primarily regulates enzymes and transporters involved in amino acid homeostasis as well as aminoacyl-tRNA synthetases. mTOR inhibition resulted not only in the loss of ATF4 target gene expression, but also in the reduced expression of glycolytic enzymes and mitochondrial electron transport chain subunits. Analysis of TGF-{beta}-induced changes in cellular metabolite levels confirmed that ATF4 regulates amino acid homeostasis in lung fibroblasts while mTOR also regulates glycolytic and TCA cycle metabolites. We further analyzed publicly available single cell RNAseq data sets and found increased expression of ATF4 and mTOR metabolic targets in pathologic fibroblast populations from the lungs of IPF patients. Our results provide insight into the mechanisms of metabolic reprogramming in lung fibroblasts and highlight novel ATF4 and mTOR-dependent pathways that may be targeted to inhibit fibrotic processes.

cell biology↗