Biology subjects

Xu, C.

Publications and source records attributed to Xu, C..

At least 235 records · Page 13Linked to original sources

bioRxiv2022

Multiplex Epigenome Editing of MECP2 to Rescue Rett Syndrome Neurons

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by loss-of-function heterozygous mutations of Methyl CpG-binding Protein 2 (MECP2) on the X chromosome in girls. Reactivation of the silent wild-type MECP2 allele from the inactive X chromosome (Xi) represents a promising therapeutic opportunity for female patients with RTT. Here, we applied a multiplex epigenome editing approach to reactivate MECP2 from Xi in RTT human embryonic stem cells (hESCs) and derived neurons. Demethylation of the MECP2 promoter by dCas9-Tet1 with target sgRNA reactivated MECP2 from Xi in RTT hESCs without detectable off-target effects at the transcriptional level. Neurons derived from methylation-edited RTT hESCs maintained MECP2 reactivation and reversed the smaller soma size and electrophysiological abnormalities, two hallmarks of RTT. In RTT neurons, insulation of the methylation edited MECP2 locus by dCpf1-CTCF with target CRISPR RNA enhanced MECP2 reactivation and rescued RTT-related neuronal defects, providing a proof-of-concept study for epigenome editing to treat RTT and potentially other dominant X-linked diseases. One-Sentence SummaryReactivation of MECP2 from the inactive X chromosome by multiplex epigenome editing rescues Rett syndrome neurons in vitro.

physiology↗

bioRxiv2022

Genome-wide association study highlights escape from aphids by delayed growth in Arabidopsis thaliana

Field studies have shown that plant phenological and architectural traits often explain substantial variation in herbivory. Although plant genes involved in physical and chemical defense are well studied, less is known about the genetic basis underlying effects of plant growth traits on herbivory. Here, we conducted a genome-wide association study (GWAS) of aphid abundance in a field population of Arabidopsis thaliana. This field GWAS detected a significant peak on the third chromosome of A. thaliana. Out of candidate genes near this significant genomic region, a mutant of a ribosomal gene (AT3G13882) exhibited slower growth and later flowering than a wild type under laboratory conditions. A no-choice assay with the turnip aphid, Lipaphis erysimi, found that aphids were unable to successfully establish on the mutant. These findings suggest the potential role of growth-related genes in altering herbivore abundance.

ecology↗

bioRxiv2022

DeepCCI: a deep learning framework for identifying cell-cell interactions from single-cell RNA sequencing data

With the rapid development of high throughput single-cell RNA sequencing (scRNA-seq) technologies, it is of high importance to identify Cell-cell interactions (CCIs) from the ever-increasing scRNA-seq data. However, limited by the algorithmic constraints, current computational methods based on statistical strategies ignore some key latent information contained in scRNA-seq data with high sparsity and heterogeneity. To address the issue, here, we developed a deep learning framework named DeepCCI to identify meaningful CCIs from scRNA-seq data. Applications of DeepCCI to a wide range of publicly available datasets from diverse technologies and platforms demonstrate its ability to predict significant CCIs accurately and effectively.

bioinformatics↗

bioRxiv2022

Dynamic changes in the transcriptome of oocytes during adolescent-onset PCOS in mice

(1) Background: This study aimed to explore temporal changes in the transcriptome of oocytes in an adolescent-onset polycystic ovarian syndrome (PCOS) mouse model. (2) Methods: An adolescent-onset PCOS mouse model was established using DHEA. Genes with a similar expression trend over time were identified using trend analysis. KEGG pathway enrichment analysis and gene regulatory network diagrams were examined for signaling pathways to identify potential hub genes related to the pathogenesis of PCOS. (3) Results: Four main trends of gene expression were extracted, of which six combinations of Venn diagrams were generated. Differentially expressed genes were mainly enriched in oxidative phosphorylation, cell cycle, P53 signaling pathway. Cell cycle-related genes (Skp1, Ccnb1, Orc1 and 5, Wee2, Mapk3, Cdc20) were abnormally down-regulated in the DHEA group. Ptges3 was the top1 DEGs at the initial stage of PCOS modeling. (4) Conclusion: This study provides a novel insight into the altered transcriptome of oocytes from PCOS mice. mtDNA-related genes and Cell cycle-related genes play the most important role in the development of PCOS. Ptges3 was the one of the top DEGs which was up-regulated in DHEA group at the initial stage of modeling, which suggested it may play an important role in the early stage of PCOS.

genetics↗

bioRxiv2022

Orphan quality control shapes network dynamics and gene expression

All eukaryotes require intricate protein networks to translate developmental signals into accurate cell fate decisions. Mutations that disturb crucial interactions between network components often result in disease, but how the composition and dynamics of complex networks are established is unknown. Here, we identify the tumor suppressor E3 ligase UBR5 as a quality control enzyme that helps degrade unpaired subunits of multiple transcription factors that operate within a single network. By constantly turning over orphan subunits, UBR5 forces cells to continuously replenish network components through new protein synthesis. The resulting cycles of transcription factor synthesis and degradation allow cells to effectively execute the gene expression program, while remaining susceptible to environmental signals. We conclude that orphan quality control plays an essential role in establishing the dynamics of protein networks, which may explain the conserved need for protein degradation in transcription and offers unique opportunities to modulate gene expression in disease.

biochemistry↗

bioRxiv2022

A tissue injury repair pathway distinct but parallel to host pathogen defense

Pathogen infection and tissue injury are universal insults that disrupt homeostasis. Innate immunity senses microbial infections and induces interferons (IFNs) to activate resistance mechanisms. Applying unbiased phylogenetic analysis, we show that interleukin-24 (IL24) is among the closest evolutionary homologs to the IFN family and shares a common ancestral origin. However, in contrast to IFNs, IL24 induction occurs specifically in barrier epithelial progenitors after injury and is independent of microbiome or adaptive immunity. Surprisingly, Il24 ablation impedes not only epidermal proliferation and re-epithelialization, but also capillary and fibroblast regeneration within the dermal wound bed. Conversely, ectopic Il24 induction in homeostatic epidermis triggers global epithelial-mesenchymal tissue repair responses. Mechanistically, sustained Il24 expression depends upon both IL24 receptor/STAT3 signaling and also hypoxia-stabilized HIF1, which converge following injury. Thus, parallel to the IFN-mediated innate immune sensing of pathogens to resolve infections, epithelial stem cells sense injury signals to orchestrate IL24-mediated tissue repair.

immunology↗

bioRxiv2022

A novel brain penetrant PDGFRα inhibitor HY-008 is effective against glioblastoma

BackgroundGlioblastoma multiforme (GBM) is the most common primary intracranial malignant tumor in adults, with poor prognosis and high recurrence. Routine treatments of GBM show unsatisfactory efficiency in improving patients survival because of limited area of surgical resection and drug resistance. New therapeutic agents are needed to improve GBM treatment efficiency, but the blood-brain barrier (BBB) permeability is a major hurdle. Here, we report HY-008 as a promising therapeutic drug targeting PDGFR signaling with high BBB permeability and efficient inhibiting effects both in vitro and in vivo. MethodsThrough structural modification and medicinal chemistry efforts, HY-007 and HY-008 were developed. The brain and plasma pharmacokinetic profiles of these two compounds were assessed. The inhibitory efficiency of HY-007 and HY-008 on GBM cell survival and PDGFR signaling were evaluated. The efficacy of HY-007 and HY-008 as a single agent or HY-008 in combination with temozolomide (TMZ) was investigated using transformed mouse astrocyte and glioma stem-like cell (GSC) orthotopic xenograft models. ResultsHY-007 and HY-008 both had good brain permeability and desirable PK profiles with mild hERG inhibition, while HY-008 is more brain permeable than HY-007. In vitro, HY-007 and HY-008 both significantly inhibited viability of the established GBM cells with PDGF-A overexpression and transformed mouse astrocytes with PDGF-A/PDGFR overexpression by targeting the PDGFR signaling activated Erk1/2 and Akt. In vivo, HY-007 and HY-008 both effectively inhibited orthotopic GBM tumor xenograft growth and prolonged the survival of mice, and HY-008 showed less toxicity and better therapeutic effect. In addition, HY-008 increased sensitivity of TMZ, exhibited treatment efficiency both as a single agent and in combination with TMZ, providing significant survival benefits for GBM tumor xenograft-bearing mice. ConclusionsOur data demonstrate that HY-008 is a promising therapeutic agent in GBM treatment and a combination HY-008 with TMZ could serves as a potential efficient therapeutic option for improving GBM clinical treatment.

cancer biology↗

bioRxiv2022

Selection and adaptive introgression guided the complex evolutionary history of European common bean

Domesticated crops have been disseminated by humans over vast geographic areas. After 1492, the common bean (Phaseolus vulgaris L.) was introduced in Europe. Here, we combine whole-genome profiling, metabolic fingerprinting and phenotypic characterisation, and we show that the first common bean cultigens successfully introduced into Europe were of Andean origin, after Francisco Pizarros expedition to northern Peru in 1529. We show that hybridisation, selection and recombination have shaped the genomic diversity of the European common bean in parallel with political constraints. There is clear evidence of adaptive introgression into the Mesoamerican-derived European genotypes, with 44 Andean introgressed genomic segments shared by more than 90% of European accessions and distributed across all chromosomes except PvChr11. Genomic scans for signatures of selection highlight the role of genes relevant to flowering and environmental adaptation, suggesting that introgression has been crucial for the dissemination of this tropical crop to the temperate regions of Europe.

genomics↗

bioRxiv2022

A NOVEL UNBIASED SEED-BASED RNAi SCREEN IDENTIFIES SMALL RNAs THAT INHIBIT ANDROGEN SIGNALING AND PROSTATE CANCER CELL GROWTH

Blocking androgen receptor signaling is the mainstay of therapy for advanced prostate cancer (PCa). However, acquired resistance to single agents targeting this pathway results in the development of lethal castration resistant PCa. Combination therapy approaches represent a promising strategy for the treatment of advanced disease. Here we explore a therapeutic strategy for PCa based on the ability of sh/siRNAs to function essentially as miRNAs and, via seed sequence complementarity, induce RNA interference of numerous targets simultaneously. We developed a library that contained shRNAs with all possible seed sequence combinations to identify those ones that most potently reduce cell growth and viability when expressed in PCa cells. Validation of some of these RNAi sequences indicated that the toxic effect is associated with seed sequence complementarity to the 3-UTR of AR coregulatory and essential genes. In fact, expression of siRNAs containing the identified toxic seed sequences led to global inhibition of AR-mediated gene expression and reduced expression of cell cycle genes. When tested in mice, the toxic shRNAs also inhibited castration resistant PCa and exhibited therapeutic efficacy in pre-established tumors. This multi-targeted RNAi approach may be a promising therapeutic strategy for PCa.

cancer biology↗

bioRxiv2022

Cancer-associated SMARCAL1 loss-of-function mutations promote alternative lengthening of telomeres and tumorigenesis in telomerase-negative glioblastoma cells

Telomere maintenance mechanisms are a hallmark of cancer and are required to enable the replicative immortality of malignant cells. While most cancers activate the enzyme telomerase for telomere maintenance, a subset of cancers (~10-15%) use telomerase-independent mechanisms termed alternative lengthening of telomeres (ALT). ALT is characterized by elevated replication stress at telomeres, telomere synthesis via homology directed-repair mechanisms, and is frequently associated with mutations in the ATRX gene. Because ALT is absent in non-malignant proliferating cells, therapeutic strategies targeting ALT-mediated telomere synthesis is an area of significant translational and clinical interest. We previously showed that a subset of adult GBM patients with ATRX-expressing ALT-positive tumors harbored loss-of-function mutations in the SMARCAL1 gene. SMARCAL1 is an annealing helicase involved in replication fork remodeling and the resolution of replication stress. In this study, we used a patient-derived ALT-positive GBM cell line with native SMARCAL1 deficiency to investigate the role of SMARCAL1 in ALT-mediated telomere synthesis and gliomagenesis in vivo. Our results show that inducible rescue of SMARCAL1 expression suppresses ALT indicators and inhibits de novo telomere synthesis in GBM and osteosarcoma cells, suggesting that SMARCAL1 deficiency plays a functional role in ALT induction in cancers that natively lack SMARCAL1 function. Further, SMARCAL1-deficient ALT-positive cells can be serially propagated in vivo in the absence of detectable telomerase activity, suggesting that the SMARCAL1-deficient ALT phenotype maintains telomeres in a manner that promotes tumorigenesis. In summary, we show that SMARCAL1 loss-of-function mutations are permissive to ALT and promote gliomagenesis. We also established isogenic model systems that permit the dynamic modulation of ALT activity, which will be valuable for future studies aimed at understanding the molecular mechanisms of ALT and for identifying novel anti-cancer therapeutics that target the ALT phenotype.

cancer biology↗

bioRxiv2022

Structural and mechanistic insights into inhibition of the type I-F CRISPR-Cas surveillance complex by AcrIF4

CRISPR-Cas system provides prokaryotes with protection against mobile genetic elements (MGEs) such as phages. In turn, phages deploy anti-CRISPR (Acr) proteins to evade this immunity. AcrIF4, an Acr targeting the type I-F CRISPR-Cas system, has been reported to bind the crRNA-guided surveillance (Csy) complex. However, it remains controversial whether AcrIF4 inhibits target DNA binding to the Csy complex. Here, we present structural and mechanistic studies into AcrIF4, exploring its unique anti-CRISPR mechanism. While the Csy-AcrIF4 complex displays decreased affinity for target DNA, it is still able to bind the DNA. Structural and functional analyses of the Csy-AcrIF4-dsDNA complex revealed that AcrIF4 binding prevents rotation of the helical bundle (HB) of Cas8f induced by dsDNA binding, therefore resulting in failure of Cas2/3 recruitment and DNA cleavage. Overall, our study provides an interesting example of attack on the nuclease recruitment event by an Acr, but not conventional mechanisms of blocking binding of target DNA.

molecular biology↗

bioRxiv2022

Intestinal lamina propria supports acquired eTreg suppressor function

The intestinal immune system must maintain tolerance to commensal microbiota and self antigens whilst defending against invading pathogens. Recognising how homeostasis is established and maintained in a complex immune environment such as the gut is critical to understanding how to re-establish tolerance once broken in inflammatory disorders. Peripherally induced regulatory T cells (Tregs) play a key role in homeostasis. In intestinal tissue, Tregs work in concert with a diverse network of cells but which cellular interactions occur to instruct Treg adaptation and acquisition of distinct Treg suppressor function is not clear. We used two-photon in vivo live imaging and NICHE-seq [1] to deep phenotype Helicobacter hepaticus (Hh)-specific Tregs with shared specificity but distinct spatially compartmentalised functions in the tissue. We show transcriptionally distinct central Treg (cTreg) and effector Treg (eTreg) populations in lymphoid versus gut tissue. The lamina propria (LP), and not embedded lymphoid aggregates (LA), is the key location of acquired immune suppressor eTreg function. Tregs recruited to the LP compartment are the dominant interacting cell type and acquired a more effector Treg profile with upregulation of Areg, Gzmb, Icos, Tigit, Tnfrsf4 (OX40), and Tnfrsf18 (GITR). We identify IL-1{beta}+ macrophages, CD206+ macrophages, and ILC2 in the LP niche as the key players governing Treg survival and function. In contrast, LA, dominated by interactions with ILC3s and populations of IL-6+ DCs, are equipped to tip the balance towards a pro-inflammatory response. By functionally isolating the gut tissue from secondary lymphoid organs, we show that eTregs maintain their phenotype in the context of inflammatory insult. Blocking their key effector molecule, IL-10, results in locally differentiated Th17 cell proliferation without overt inflammation due to local IL-10 independent mechanisms that constrain inflammation. Our results reveal a previously unrecognised spatial mechanism of tolerance, and demonstrate how knowledge of local interactions can guide cell function and potentially be manipulated for the next generation of tolerance-inducing therapies.

immunology↗

bioRxiv2022

Detecting frequency-dependent selection through the effects of genotype similarity on fitness components

Frequency-dependent selection (FDS) drives an evolutionary regime that maintains or disrupts polymorphisms. Despite the increasing feasibility of genetic association studies on fitness components, there are a few methods to uncover the loci underlying FDS. Based on a simplified model of pairwise genotype-genotype interactions, we propose a linear regression that can infer FDS from observed fitness. The key idea behind our method is the inclusion of genotype similarity as a pseudo-trait in selection gradient analysis. Single-locus analysis of Arabidopsis and damselfly data could detect known negative FDS on visible polymorphism that followed Mendelian inheritance with complete dominance. By extending the singlelocus analysis to genome-wide association study (GWAS), our simulations showed that the regression coefficient of genotype similarity can distinguish negative or positive FDS without confounding other forms of balancing selection. Field GWAS of the branch number further revealed that negative FDS, rather than positive FDS, was enriched among the top-scoring single nucleotide polymorphisms (SNPs) in Arabidopsis thaliana. These results showed the wide applicability of our method for FDS on both visible polymorphism and genome-wide SNPs. Our study provides an effective method for selection gradient analysis to understand the maintenance or loss of polymorphism.

evolutionary biology↗

bioRxiv2022

Pathway and mechanism of tubulin folding mediated by TRiC/CCT conjugated with its ATPase cycle revealed by cryo-EM

The eukaryotic chaperonin TRiC/CCT assists the folding of about 10% of cytosolic proteins through an ATP-driven conformational cycle, and the essential cytoskeleton protein tubulin is the obligate substrate of TRiC. Here, we present an ensemble of cryo-EM structures of human TRiC throughout its ATPase cycle, with three of them revealing endogenously engaged tubulin in different folding stages. Our structural and XL-MS analyses suggested a gradual upward translocation and stabilization of tubulin within the TRiC chamber accompanying TRiC ring closure. Remarkably, in the closed TRiC-tubulin-S3 map resolved to 3.1-[A]-resolution, we captured a near-natively folded tubulin. We found the near-natively folded tubulin engaging through its N and C domains mainly with the A and I domains of the CCT3/6/8 subunits through electrostatic and hydrophilic interactions, while the tubulin I domain was found to remain dynamic. Moreover, we also showed the potential role of TRiC C-terminal tails in substrate stabilization and folding. Our study delineates the pathway and molecular mechanism of TRiC-mediated tubulin folding conjugated with TRiC ATPase cycle, and may also inform the design of therapeutic agents targeting TRiC-tubulin interactions.

biochemistry↗

bioRxiv2022

Neutralization of Omicron BA.4/BA.5 and BA.2.75 by Booster Vaccination or BA.2 Breakthrough Infection Sera

Many new Omicron sub-lineages have been reported to evade neutralizing antibody response, including BA.2, BA.2.12.1, BA.4 and BA.5. Most recently, another emerging sub-lineage BA.2.75 has been reported in multiple countries. In this study, we constructed a comprehensive panel of pseudoviruses (PsVs), including wild-type, Delta, BA.1, BA.1.1, BA.2, BA.3, BA.2.3.1, BA.2.10.1, BA.2.12.1, BA.2.13, BA.2.75 and BA.4/BA.5, with accumulate coverage reached 91% according to the proportion of sequences deposited in GISAID database since Jan 1st, 2022. We collected serum samples from healthy adults at day14 post homologous booster with BBIBP-CorV, or heterologous booster with ZF2001, primed with two doses of BBIBP-CorV, or from convalescents immunized with three-dose inactivated vaccines prior to infection with Omicron BA.2, and tested their neutralization activity on this panel of PsVs. Our results demonstrated that all Omicron sub-lineages showed substantial evasion of neutralizing antibodies induced by vaccination and infection, although BA.2.75 accumulated the largest number of mutations in its spike, BA.4 and BA.5 showed the strongest serum escape. However, BA.2 breakthrough infection could remarkably elevated neutralization titers against all different variants, especially titers against BA.2 and its derivative sub-lineages.

immunology↗

bioRxiv2022

Novel Viroid-like RNAs Naturally Infect a Filamentous Fungus

Viroids have been found to naturally infect only plants, resulting in big losses for some crops, but whether viroids or viroid-like RNAs naturally infect non-plant hosts remains unknown. Here we report the existence of a set of exogenous, single-stranded circular RNAs, ranging in size between 157-450 nucleotides (nt), isolated from the fungus Botryosphaeria dothidea and nominated Botryosphaeria dothidea circular RNAs (BdcRNAs). BdcRNA(s) replicate autonomously in the nucleus via a rolling-circle replication mechanism following symmetric pathways with distribution patterns depending on strand polarity and species. BdcRNAs can modulate to different degrees specific biological traits (e.g., alter morphology, decrease growth rate, attenuate virulence, and increase or decrease tolerance to osmotic stress and oxidative stress) of the host fungus by regulating related metabolic pathways. Overall, BdcRNA(s) have genome characteristics similar to those of viroids and exhibit pathogenic effects on the fungal hosts. These novel viroid-like RNAs infecting fungi are proposed to be termed as mycoviroids. BdcRNA(s) may be regarded as additional inhabitants at the frontier of life in terms of genomic complexity, and represent a new class of acellular entities endowed with regulatory functions, and novel epigenomic carriers of biological information. Significance statementSeveral viroids have been transfected into unicellular and filamentous fungi to assess whether they can replicate, but no natural infections of fungi with viroid or viroid-like RNAs have been reported before. Here we describe a set of exogenous circular RNAs (cRNAs) in a phytopathogenic fungus. These cRNAs display molecular and biological features which might represent a new class of viroid-like cRNAs endowed with regulatory functions, and novel epigenomic carriers of biological information. This is the first report of infectious viroid-like RNAs (or exogenous small cRNAs) in a life kingdom (fungi) other than plants. We also present a subcellular analysis of cRNAs in a fungus for the first time and provide useful understanding in how cRNAs replicate, move, and are distributed in fungal cells.

microbiology↗

bioRxiv2022

Modeling the Cell Cycle Response to Carbon and Nitrogen deprivation in Caulobacter Populations

Caulobacter crescentus inhabits a wide range of aquatic ecosystems, including environments with poor nutrients. It undergoes an asymmetrical cell division cycle, generating a pair of daughter cells with distinct motility and replicative potentials. Caulobacter populations have the flexibility to save energy by halting chromosome replication and reduce intraspecific competition by settling in different places in environments. The control mechanisms underlying Caulobacter cell development have been well studied under nutrient-rich conditions, however, its mechanism of response to stressful changes is not fully understood. Here we present a mathematical model to analyze the starvation responses in Caulobacter. We investigate several known starvation signaling pathways to study how these pathways influence cell cycle development and explain experimental observations of starved Caulobacter populations. We also apply a new parameterization strategy to mathematical modeling of biological systems, whose diverse communities have to be robust with many parameter variations, while still having accurate control to maintain regular cell cycle dynamics. Our model demonstrates that the guanine-based second messenger, c-di-GMP (cdG), plays important roles to immediately arrest the cell cycle of Caulobacter under nutrient deprivation; however, it is not sufficient to cause the robust arrest. Our model suggests there should be unknown pathway(s) reducing the levels of CtrA under starvation condition, which results in a significant delay in cytokinesis of starved stalked Caulobacter cells.

bioinformatics↗

bioRxiv2022

Specialized neuronal modules for economic and single-attribute choice in the orbitofrontal cortex

An important component of biological intelligence lies in the capacity to learn and execute various cognitive tasks. This ability may be facilitated by a neural system comprising functionally dissociable neuronal modules. Within the orbitofrontal cortex (OFC) lies a neural circuit that supports economic decision-making across diverse contexts. To investigate the functional specialization of this circuit, we compared the neural activity of OFC neurons in rhesus monkeys during multi-attribute choice (MC) and single-attribute choice (SC) tasks. In MC, the monkeys made subjective tradeoffs between competing attributes, whereas in SC, choices were deterministic based on a single attributes value. Neuronally, in MC, OFC neurons primarily encoded offer value, chosen value, and choice in goods space. Upon transitioning from MC to SC, a significant portion of MC-modulated neurons disengaged, while a separate set of neurons emerged to encode SC-related variables in a spatial reference frame. Notably, we observed the clustering of value-encoding neurons in MC but not SC. In essence, our findings suggest that choice tasks involving different mental processes are represented by dissociable neuronal modules within the OFC.

neuroscience↗