Biology subjects

Wen, X.

Publications and source records attributed to Wen, X..

At least 73 records · Page 4Linked to original sources

bioRxiv2022

Biomimetic S-adenosylmethionine regeneration for nucleophilic and radical alkylation reactions and aminopropyltransfer

S-Adenosylmethionine (SAM) is an enzyme cofactor involved in methylation, aminopropyl transfer, and radical reactions. This versatility renders SAM-dependent enzymes of great interest in biocatalysis. The usage of SAM analogues adds to this diversity. However, high cost and instability of the cofactor impedes the investigation and usage of these enzymes. While SAM regeneration protocols from the methyltransferase (MT) byproduct S-adenosylhomocysteine are available, aminopropyl transferases and radical SAM enzymes are not covered. Here, we report an efficient one-pot system to supply or regenerate SAM and SAM analogues for all three enzyme classes. The systems flexibility is showcased by the transfer of an ethyl group with a cobalamin-dependent radical SAM MT using S-adenosylethionine as a cofactor. This shows the potential of SAM (analogue) supply and regeneration for the application of diverse chemistry, as well as for mechanistic studies using cofactor analogues.

biochemistry↗

bioRxiv2022

Probabilistic integration of transcriptome-wide association studies and colocalization analysis prioritizes molecular pathways of complex traits

Transcriptome-wide association studies (TWAS) and colocalization analysis are complementary integrative genetic association approaches routinely used to identify functional units underlying complex traits in post-genome-wide association study (post-GWAS) analyses. Recent studies suggest that both approaches are individually imperfect, but joint usage can yield robust and powerful inference results. This paper introduces a new statistical framework, INTACT, to perform probabilistic integration of TWAS and colocalization evidence for implicating putative causal genes. This procedure is flexible and can work with a wide range of existing TWAS and colocalization approaches. It has the unique ability to quantify the uncertainty of implicated genes, enabling rigorous control of false-positive discoveries. Taking advantage of this highly-desirable feature, we describe an efficient algorithm, INTACT-GSE, for gene set enrichment analysis based on the integrated TWAS and colocalization analysis results. We examine the proposed computational methods and illustrate their improved performance over the existing approaches through simulation studies. Finally, we apply the proposed methods to the GTEx data and a variety of GWAS summary statistics derived from complex and molecular traits previously analyzed by Hukku et al. and Sinnott-Armstrong et al. We find empirical evidence that the proposed methods improve and complement existing putative gene implication methods and are advantageous in evaluating and identifying key gene sets and biological pathways.

genetics↗

bioRxiv2022

Human blastoid from primed human embryonic stem cells

Artificial human blastoids are used to investigate early embryo development, pregnancy failures, and birth deficiencies, previously impossible without human embryos. Recent methods generating blastoids used human naive pluripotent stem cells, which are prone to genomic instability during in vitro culturing. Here, we introduce a simple, robust, and scalable method for generating human blastoids from more stable, primed human pluripotent stem cells (hPSC). Using a non-cell-adhesive hydrogel, hPSC aggregates formed an asymmetric blastoid structure with a cellular distribution similar to that of a human blastocyst, with in vitro implantation capability. Single-cell RNA-seq followed by cellular trajectory analysis revealed that hydrogel promoted differentiation to tri-lineage cells associated with a blastocyst. This model will allow studies on the underlying mechanisms of human pre- and postimplantation processes, consider elaborating on the potential implications of the model on assistive reproductive technology. One Sentence SummaryNo more than 125 characters and spaces.

bioengineering↗

bioRxiv2022

Mapping genomic regulation of kidney disease and traits through high-resolution and interpretable eQTLs

Expression quantitative trait locus (eQTL) studies illuminate genomic variants that regulate specific genes and contribute to fine-mapped loci discovered via genome-wide association studies (GWAS). Efforts to maximize their accuracy are ongoing. Using 240 glomerular (GLOM) and 311 tubulointerstitial (TUBE) micro-dissected samples from human kidney biopsies, we discovered 5,371 GLOM and 9,787 TUBE eQTLs by incorporating kidney single-nucleus open chromatin data and transcription start site distance as an "integrative prior" for Bayesian statistical fine mapping. The use of an integrative prior resulted in higher resolution eQTLs illustrated by (1) smaller numbers of variants in credible sets with greater confidence, (2) increased enrichment of partitioned heritability for GWAS of two kidney traits, (3) an increased number of variants colocalized with the GWAS loci, and (4) enrichment of computationally predicted functional regulatory variants. A subset of variants and genes were validated experimentally in vitro and using a Drosophila nephrocyte model. More broadly, this study demonstrates that tissue-specific eQTL maps informed by single-nucleus open chromatin data have enhanced utility for diverse downstream analyses.

genomics↗

bioRxiv2022

Mammary Tissue-Derived Extracellular Matrix Hydrogels Reveal the Role of the Irradiated Microenvironment in Breast Cancer Recurrence

Radiation therapy (RT) is essential for triple negative breast cancer (TNBC) treatment. However, patients with TNBC continue to experience recurrence after RT. The role of the extracellular matrix (ECM) of irradiated breast tissue in tumor recurrence is still unknown. In this study, we evaluated the structure, molecular composition, and mechanical properties of irradiated murine mammary fat pads (MFPs) and developed ECM hydrogels from decellularized tissues (dECM) to assess the effects of RT-induced ECM changes on breast cancer cell behavior. Irradiated MFPs were characterized by increased ECM deposition and fiber density compared to unirradiated controls, which may provide a platform for cell invasion and proliferation. ECM component changes in collagens I, IV, and VI, and fibronectin were observed following irradiation in both MFPs and dECM hydrogels. Encapsulated TNBC cell proliferation and invasive capacity was enhanced in irradiated dECM hydrogels. In addition, TNBC cells co-cultured with macrophages in irradiated dECM hydrogels induced M2 macrophage polarization and exhibited further increases in proliferation. Our study establishes that the ECM in radiation-damaged sites promotes TNBC invasion and proliferation as well as an immunosuppressive microenvironment. This work represents an important step toward elucidating how changes in the ECM after RT contribute to breast cancer recurrence.

cancer biology↗

bioRxiv2022

Mircubactin B rescues the lethal effect of cell wall biosynthesis mutations in Bacillus subtilis.

Growth of most rod-shaped bacteria is accompanied by the insertion of new peptidoglycan into the cylindrical cell wall. This insertion, which helps maintain and determine the shape of the cell, is guided by a complex protein machinery called the rod complex or elongasome. Although most of the proteins in this complex are essential under normal growth conditions, cell viability can be rescued, for reasons that are not understood, by the presence of a high (mM) Mg2+ concentration. We screened for natural product compounds that could rescue the growth of mutants affected in rod-complex function. By screening >2,000 extracts from a diverse collection of actinobacteria, we identified a new compound, mirubactin B, related to the known iron siderophore mirubactin A, which rescued growth in the low micromolar range, and this activity was confirmed by synthesising mirubactin B. The compound also displayed toxicity at higher concentrations, and this effect appears related to iron homeostasis. However, several lines of evidence suggest that the mirubactin B rescuing activity is not due simply to iron sequestration. The results demonstrate a novel antibacterial compound and add to growing evidence that bacterial siderophores have a range of activities beyond simple iron sequestration.

microbiology↗

bioRxiv2022

Zfp281 inhibits the pluripotent-to-totipotent state transition in mouse embryonic stem cells

The cell-fate transition between pluripotent and totipotent states determines embryonic development and the first cell-lineage segregation. However, limited by the scarcity of totipotent embryos, regulators on this transition remain largely elusive. A novel model to study the transition has been recently established, named the 2-cell-like (2C-like) model. The 2C-like cells are rare totipotent-like cells in the mouse embryonic stem cell (mESC) culture. Pluripotent mESCs can spontaneously transit into and out of the 2C-like state. We previously dissected the transcriptional roadmap of the transition. In this study, we revealed that Zfp281 is a novel regulator for the pluripotent-to-totipotent transition in mESCs. Zfp281 is a transcriptional factor involved in the cell-fate transition. Our study shows that Zfp281 represses transcripts upregulated during the 2C-like transition via Tet1 and consequentially inhibits mESCs from transiting into the 2C-like state. Interestingly, we found that the inhibitory effect of Zfp281 on the 2C-like transition leads to an impaired 2C-like-transition ability in primed-state mESCs. Altogether, our study reveals a novel mediator for the pluripotent-to-totipotent state transition in mESCs and provides insights into the dynamic transcriptional control of the transition.

cell biology↗

bioRxiv2022

Modulation of RNA polymerase processivity affects double-strand break repair in the presence of a DNA-end binding protein

Homologous recombination is the predominant double-strand DNA break repair pathway in Escherichia coli. A recent report of non-homologous end joining involving the Ku-like Gam protein of bacteriophage Mu (MuGam) has sparked interest in understanding the functions of DNA end-binding proteins in bacteria. MuGam binds to DNA ends, but how it interferes with DNA repair or transcription in live bacteria remains elusive. In E. coli, RNA polymerase secondary channel interactors, such as the Gre factors, play a role in coordinating transcription with DNA replication and break repair. Here we show that MuGam inhibits break repair by slowing down DNA resection and impeding recombination in living cells. Loss of GreA restores break repair in the presence of MuGam by allowing for increased DNA resection due to a potential release of MuGam from the DNA. Using MuGam as a DNA break sensor, we found that breaks are generated when translation is inhibited, more so in the presence of GreA, supporting the model where transcription-translation uncoupling increases transcription/replication collisions. Significantly, this work reveals that modulation of RNA polymerase can impact DNA break repair in presence of a Ku-like protein.

molecular biology↗

bioRxiv2021

MiR-144 regulates adipogenesis by mediating formation of C/EBPα-FoxO1 protein complex

Excessive adipogenesis caused obesity, which was a serious risk of health and led to a series of diseases, including type II diabetes (T2D) for example. Adipocyte as the basic unit of adipose tissue has emerged as one of significant target of the treatment of obesity-related metabolic syndromes by revealed its adipogenic molecular mechanism. MicroRNAs (miRNAs) have been demonstrated involving adipogenesis, and played a crucial role in the competitive endogenous RNA (ceRNA) effect. Besides that, C/EBP as a crucial adipogenic regulator still lacked epigenetic explanation during pre-adipocyte adipogenesis. In this study, we first verified FoxO1 was one of the ceRNA of C/EBP. They co-regulated adipogenesis through formed a protein complex that directly bound to its promoter to activate AdipoQ, and AdipoQ (Adiponectin) was a negative adipocytokines that suppressed adipogenesis, which played an important role in retaining adipogensis balance. Moreover, an adipose tissue specific enriched miRNA, miR-144 was the key regulator of the ceRNA effect between C/EBP and FoxO1, which mediated the C/EBP-FoxO1 complex formation, thus altered AdipoQ, furthermore regulated pre-adipocyte adipogenesis. This research will provide a new supplementary idea of the C/EBP epigenetic role in pre-adipocyte adipogenesis.

cell biology↗

bioRxiv2021

Analyzing and Reconciling Colocalization and Transcriptome-wide Association Studies from the Perspective of Inferential Reproducibility

Transcriptome-wide association studies and colocalization analysis are popular computational approaches for integrating genetic association data from molecular and complex traits. They show the unique ability to go beyond variant-level genetic association evidence and implicate critical functional units, e.g., genes, in disease etiology. However, in practice, when the two approaches are applied to the same molecular and complex trait data, the inference results can be markedly different. This paper systematically investigates the inferential reproducibility between the two approaches through theoretical derivation, numerical experiments, and analyses of 4 complex trait GWAS and GTEx eQTL data. We identify two classes of inconsistent inference results. We find that the first class of inconsistent results may suggest an interesting biological phenomenon, i.e., horizontal pleiotropy; thus, the two approaches are truly complementary. The inconsistency in the second class can be understood and effectively reconciled. To this end, we propose a novel approach for locus-level colocalization analysis. We demonstrate that the joint TWAS and locus-level colocalization analysis improves specificity and sensitivity for implicating biological-relevant genes.

genetics↗

bioRxiv2021

Genomic insights into the population history and biological adaptation of Southwestern Chinese Hmong-Mien people

Hmong-Mien-speaking (HM) populations, widely distributed in South China, North of Thailand, Laos and Vietnam, have experienced different settlement environments, dietary habits and pathogen exposure. However, their specific biological adaptation also remained largely uncharacterized, which is important in the population evolutionary genetics and Trans-Omics for regional Precision Medicine. Besides, the origin and genetic diversity of HM people and their phylogenetic relationship with surrounding modern and ancient populations are unknown. Here, we reported genome-wide SNPs in 52 representative Miao people and combined them with 144 HM people from 13 geographically representative populations to characterize the full genetic admixture and adaptive landscape of HM speakers. We found that obvious genetic substructures existed in geographically different HM populations and also identified one new ancestral lineage specifically exited in HM people, which spatially distributed from Sichuan and Guizhou in the North to Thailand in the South and temporally dated to at least 500 years. The sharing patterns of the newly-identified homogeneous ancestry component combined the estimated admixture times via the decay of Linkage Disequilibrium and haplotype sharing in GLOBETROTTER suggested that the modern HM-speaking populations originated from Southwest China and migrated southward recently, which is consistent with the reconstructed phenomena of linguistic and archeological documents. Additionally, we identified specific adaptive signatures associated with several important human nervous system biological functions. Our pilot work emphasized the importance of anthropologically-informed sampling and deeply genetic structure reconstruction via whole-genome sequencing in the next step in the deep Chinese population genomic diversity project (CPGDP), especially in the ethnolinguistic regions.

genetics↗

bioRxiv2021

Genomic Modules and Intramodular Network Convergency of Susceptibility and Resilience in Multimodeled Stress in Male Mice

The multifactorial etiology of stress-related disorders is a challenge in developing synchronized medical standards for treatment and diagnosis. It is largely unknown whether there exists molecular convergence in preclinical models of stress generated using disparate construct validity. Using RNA-sequencing (RNA-seq), we investigated the genomic signatures in the ventral hippocampus, which mostly regulates affective behavior, in mouse models that recapitulate the hallmarks of anxiety and depression. Chronic oral corticosterone (CORT), a model that causes a blunted endocrine response to stress, induced anxiety- and depression-like behavior in wildtype mice and mice heterozygous for the gene coding for brain-derived neurotrophic factor (BDNF) Val66Met, a variant associated with genetic susceptibility to stress. In a separate set of mice, chronic social defeat stress led to a susceptible or a resilient population, whose proportion was dependent on housing conditions, standard housing or enriched environment. A rank-rank-hypergeometric (RRHO) analysis of the RNA-seq data set across models demonstrated that in mice treated with CORT and susceptible mice raised in standard housing differentially expressed genes (DEGs) converged toward gene networks involved in similar biological functions. Weighted gene co-expression analysis generated 54 unique modules of interconnected gene hubs, two of which included a combination of all experimental groups and were significantly enriched in DEGs, whose function was consistent with that predicted in the RRHO GO analysis. This multimodel approach showed transcriptional synchrony between models of stress with hormonal, environmental or genetic construct validity shedding light on common genomic drivers that embody the multifaceted nature of stress-related disorders.

neuroscience↗

bioRxiv2021

Three-dimensional organization of chromatin associated RNAs and their role in chromatin architecture in human cells

The interphase genome is dynamically organized in the nucleus and decorated with chromatin-associated RNA (caRNA). It remains unclear whether the genome architecture modulates the spatial distribution of caRNA and vice versa. Here, we generate a resource of genome-wide RNA-DNA and DNA-DNA contact maps in human cells. These maps reveal the chromosomal domains demarcated by locally transcribed RNA, hereafter termed RNA-defined chromosomal domains. Further, the spreading of caRNA is constrained by the boundaries of topologically associating domains (TADs), demonstrating the role of the 3D genome structure in modulating the spatial distribution of RNA. Conversely, stopping transcription or acute depletion of RNA induces thousands of chromatin loops genome-wide. Activation or suppression of the transcription of specific genes suppresses or creates chromatin loops straddling these genes. Deletion of a specific caRNA-producing genomic sequence promotes chromatin loops that straddle the interchromosomal target sequences of this caRNA. These data suggest a feedback loop where the 3D genome modulates the spatial distribution of RNA, which in turn affects the dynamic 3D genome organization.

genomics↗

bioRxiv2021

Co-targeting strategy for precise, scarless gene editing with CRISPR/Cas9 and donor ssODNs in Chlamydomonas

Programmable site-specific nucleases, such as the CRISPR/Cas9 ribonucleoproteins (RNPs), have allowed creation of valuable knockout mutations and targeted gene modifications in Chlamydomonas. However, in walled strains, present methods for editing genes lacking a selectable phenotype involve co-transfection of RNPs and exogenous double-stranded DNA (dsDNA) encoding a selectable marker gene. Repair of the double-stranded DNA breaks induced by the ribonucleoproteins is usually accompanied by genomic insertion of exogenous dsDNA fragments, hindering the recovery of precise, scarless mutations in target genes of interest. In this study, we tested whether co-targeting two genes by electroporation of pairs of CRISPR/Cas9 RNPs and single-stranded oligodeoxynucleotides (ssODNs) would facilitate the recovery of precise edits in a gene of interest (lacking a selectable phenotype) by selection for precise editing of another gene (creating a selectable marker) - in a process completely lacking exogenous dsDNA. We used PPX1 (encoding protoporphyrinogen IX oxidase) as the generated selectable marker, conferring resistance to oxyfluorfen, and identified precisely, scarless edited FTSY or WDTC1 genes in [~]1% of the oxyfluorfen resistant colonies. Analysis of the target site sequences in edited mutants suggested that ssODNs were used as templates for DNA synthesis during homology directed repair, a process prone to replicative errors. The Chlamydomonas acetolactate synthase gene could also be efficiently edited to serve as an alternative selectable marker. This transgene-free strategy may allow creation of individual strains containing precise mutations in multiple target genes, to study complex cellular processes, pathways or structures. One sentence summaryCo-targeting two genes by co-electroporation of CRISPR/Cas9 RNPs and ssODN repair templates allows concomitant genome editing to create a selectable marker gene and to introduce precise modifications in another gene of interest.

genetics↗

bioRxiv2021

Evaluation of solvents used for fabrication of microphysiological systems

Microphysiological systems (MPSs) have shown great promise for the advancement of drug discovery and toxicological tests, and as an alternative to animal models. However, although several chips and systems have been reported, some important issues are yet to be addressed, such as the use of polydimethylsiloxane (PDMS). Cyclo olefin polymers (COPs) have advantages over other thermoplastic materials, but most COP-based MPSs use solvent bonding during fabrication, which can affect any cells they are used to culture. This study uses a photobonding process with vacuum ultraviolet (UVU) to produce MPSs without the need for solvents such as cyclohexane, dichloromethane, and toluene. This is then used for comparison to investigate the effects of solvents on cell cultures. Quantitative immunofluorescent assays show that the coating efficiencies of extracellular matrix proteins, such as Matrigel and collagen I, are reduced on solvent-treated COP surfaces, compared with those prepared using VUV photobonding. Furthermore, SH-SY5Y neuroblastoma cells are used to evaluate cytotoxicity. This shows that solvent-MPSs induce apoptosis, but VUV-MPSs do not. These results provide insights into solvent bonding for MPS fabrication so that undesirable reactions can be avoided. Moreover, this work may be used to standardize MPS protocols and establish good manufacturing practices.

bioengineering↗

bioRxiv2021

Functional dynamic genetic effects on gene regulation are specific to particular cell types and environmental conditions

Genetic effects on gene expression and splicing can be modulated by cellular and environmental factors; yet interactions between genotypes, cell type and treatment have not been comprehensively studied together. We used an induced pluripotent stem cell system to study multiple cell types derived from the same individuals and exposed them to a large panel of treatments. Cellular responses involved different genes and pathways for gene expression and splicing processes, and were also highly variable across cell types and treatments. For thousands of genes, we identified variable allelic expression across contexts, and characterized different types of gene-environment interactions. Many of these GxE genes are associated with complex traits. We characterized promoter functional and evolutionary features that distinguish genes with elevated allelic imbalance mean and variance. More than 47% of the genes with dynamic regulatory interactions were missed by GTEx, but we identified them using a suitable allelic imbalance study design. This indicates the importance of exploring multiple treatments to reveal previously unrecognized regulatory loci that may be important for disease.

genomics↗

bioRxiv2020

In vitro nonalcoholic fatty liver disease model with cyclo-olefin-polymer-based microphysiological systems

Nonalcoholic fatty liver disease (NAFLD) is one of the common chronic liver conditions, whose treatment involves curing patients without liver transplantation. Understanding the mechanism of NAFLD initiation and progression would enable development of new diagnostic tools and drugs; however, until now, the underlying mechanisms of this condition remain largely unknown owing to the lack of experimental settings that can simplify the complicated NAFLD process in vitro. Microphysiological systems (MPSs) have long been used to recapture human pathophysiological conditions in vitro for applications in drug discovery. However, polydimethylsiloxane (PDMS) has been used in most of these MPSs as the structural material; it absorbs hydrophobic molecules, such as free fatty acids (FFAs), which are the key components that initiate NAFLD. Therefore, the current PDMS-based MPSs cannot be directly applied to in vitro NALFD modeling. In this work, we present an in vitro NAFLD model with an MPS made of cyclo-olefin polymer (COP), namely COP-MPS, to prevent absorption of FFAs. We demonstrated induction of the NAFLD-like phenotype in HepaRG hepatocyte-like cells cultured in the COP-MPS by introducing FFAs. The FFAs induced lipid accumulation in the HepaRG cells, resulting in inactivation of the apoptotic cells. We believe that the proposed COP-MPS can contribute toward investigations of NAFLD mechanisms and identification of new drugs to prevent the progression of liver disease and avoid liver transplantation.

bioengineering↗

bioRxiv2020

Large-scale single-cell analysis reveals critical immune characteristics of COVID-19 patients

Dysfunctional immune response in the COVID-19 patients is a recurrent theme impacting symptoms and mortality, yet the detailed understanding of pertinent immune cells is not complete. We applied single-cell RNA sequencing to 284 samples from 205 COVID-19 patients and controls to create a comprehensive immune landscape. Lymphopenia and active T and B cell responses were found to coexist and associated with age, sex and their interactions with COVID-19. Diverse epithelial and immune cell types were observed to be virus-positive and showed dramatic transcriptomic changes. Elevation of ANXA1 and S100A9 in virus-positive squamous epithelial cells may enable the initiation of neutrophil and macrophage responses via the ANXA1-FPR1 and S100A8/9-TLR4 axes. Systemic upregulation of S100A8/A9, mainly by megakaryocytes and monocytes in the peripheral blood, may contribute to the cytokine storms frequently observed in severe patients. Our data provide a rich resource for understanding the pathogenesis and designing effective therapeutic strategies for COVID-19. HIGHLIGHTSO_LILarge-scale scRNA-seq analysis depicts the immune landscape of COVID-19 C_LIO_LILymphopenia and active T and B cell responses coexist and are shaped by age and sex C_LIO_LISARS-CoV-2 infects diverse epithelial and immune cells, inducing distinct responses C_LIO_LICytokine storms with systemic S100A8/A9 are associated with COVID-19 severity C_LI

genomics↗