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Yan, R.

Publications and source records attributed to Yan, R..

At least 55 records · Page 3Linked to original sources
bioRxiv2023

Bio-inspired mineralization collagen induce fibrocartilage regeneration after tendon-bone injury by activating Gli1+Dkk3+ progenitor cells

A fibrocartilaginous connection between the tendon and bone, plays a critical role in transferring force from muscle to bone to enable joint movement. However, due to the high mechanical stress it experiences, the enthesis is vulnerable to injury and incapable of regenerating. The spatial relationship and functional basis of the principal components of the fibrocartilage - mineral and collagen - have not been clearly elucidated, which is a significant remaining gap in reconstructing complex architectures for promoting interface tissue regeneration. Here, using three-dimensional electron tomography imaging and high-resolution two-dimensional electron microscopy, we discover that mineral particles form a continuous cross-fibrillar phase within the fibrocartilage region. By developing a "floating mineralization" system, we fabricate a three-layer hydrogel that mimics the hierarchical nano- to micro-scale structure of tendon-bone interface (TBI). The middle layer is noteworthy for its resemblance to the nanostructure of fibrocartilage and its superior ability to induce mineralized fibrochondrogenesis in vitro. Based on motor function analysis, imaging diagnosis, histological staining, immunofluorescence staining, and biomechanics performance, we demonstrate that in situ transplantation of the gradient hydrogel achieved tendon-fibrocartilage-bone synchronous regeneration and result in 68% maximum mechanical recovery at 8-week postoperation. Single-cell RNA sequencing analysis reveals that a unique atlas of in situ stem/progenitor cells is generated during the TBI healing in vivo. Notably, the bio-inspired hydrogel microenvironment drived endogenous Gli1+Dkk3+ progenitor cells, playing a key role in TBI regeneration. Therefore, we have successfully decoded and reconstructed the nanostructure of fibrocartilage, which has great potential in TBI regeneration.

bioengineering↗
bioRxiv2023

Antagonistic Neural Circuits Drive Opposing Behaviors towards the Young in Females

In many species, including mice, females show strikingly different pup-directed behaviors based on their reproductive state1,2. Naive wild female mice often kill pups while lactating females are dedicated to pup caring3,4. The neural mechanisms that mediate infanticide and its switch to maternal behaviors during motherhood remain unclear. Here, based on the hypothesis that maternal and infanticidal behaviors are supported by distinct and competing neural circuits5,6, we used the medial preoptic area (MPOA), a key site for maternal behaviors7-11, as a starting point and identified three MPOA-connected brain regions that drive differential negative pup-directed behaviors. Further functional manipulation and in vivo recording revealed that estrogen receptor alpha (Esr1) expressing cells in the principal nucleus of the bed nucleus of stria terminalis (BNSTprEsr1) are necessary, sufficient, and naturally activated during infanticide in female mice. Furthermore, MPOAEsr1 and BNSTprEsr1 neurons form reciprocal inhibition and change their excitability in opposite directions with reproductive state. The shift in balance between BNSTprEsr1 and MPOAEsr1 cell activity is likely a key mechanism for the behavioral switch during motherhood.

neuroscience↗
bioRxiv2023

Epidemiological evaluation and identification of the insect vector of soybean stay-green associated virus

In recent years, the emergence of soybean stay-green syndrome (SGS), also referred to as "zhengqing", in the Huang-Huai-Hai region of China has resulted in significant yield losses, with some areas experiencing a complete reduction in seed yield. SGS is a phenomenon characterized by the delayed senescence of soybean, resulting in stay-green leaves, flat pods, and stunted seed development at harvest. Our group was the first to identify a distinct geminivirus, named soybean stay-green associated geminivirus (SoSGV), as the causative agent of SGS by fulfilling Kochs postulate. To further understand the epidemiology of SoSGV, in this study, we collected 368 stay-green samples from 17 regions in 8 provinces including the Huang-Huai-Hai region and surrounding areas of China. The results showed that 228 samples tested positive for SoSGV (61.96%), and 96.93% of these positive samples showed severe pod deflation. Our epidemiological assessment reveals SGS caused by the SoSGV is prevalent in the fields, and it is undergoing geographical expansion and genetic differentiation. Additionally, we determined the other natural hosts grown in the Huang-Huai-Hai region of China. By capturing insects in the field and conducting laboratory vector transmission tests, we confirmed that the common brown leafhopper (Orosius orientalis) is the transmitting vector of SoSGV. With a better understanding of the epidemiology of SoSGV and its transmission, we can develop more effective strategies for managing and mitigating its impact on soybean yields.

microbiology↗
bioRxiv2023

Single-molecule displacement mapping unveils sign-asymmetric protein charge effects on intraorganellar diffusion

Using single-molecule displacement/diffusivity mapping (SMdM), an emerging super-resolution microscopy method, here we quantify, at nanoscale resolution, the diffusion of a typical fluorescent protein (FP) in the endoplasmic reticulum (ER) and mitochondrion of living mammalian cells. We thus show that the diffusion coefficients D in both organelles are ~40% of that in the cytoplasm, with the latter exhibiting higher spatial inhomogeneities. Moreover, we unveil that diffusions in the ER lumen and the mitochondrial matrix are markedly impeded when the FP is given positive, but not negative, net charges. Calculation shows most intraorganellar proteins as negatively charged, thus a mechanism to impede the diffusion of positively charged proteins. However, we further identify the ER protein PPIB as an exception with a positive net charge, and experimentally show that the removal of this positive charge elevates its intra-ER diffusivity. We thus unveil a sign-asymmetric protein charge effect on the nanoscale intraorganellar diffusion.

biophysics↗
bioRxiv2023

Assembly of gut-derived bacterial communities follows "early-bird" resource utilization dynamics

Diet can impact host health through changes to the gut microbiota, yet we lack mechanistic understanding linking nutrient availability and microbiota composition. Here, we use thousands of microbial communities cultured in vitro from human feces to uncover simple assembly rules and develop a predictive model of community composition upon addition of single nutrients from central carbon metabolism to a complex medium. Community membership was largely determined by the donor feces, whereas relative abundances were determined by the supplemental carbon source. The absolute abundance of most taxa was independent of the supplementing nutrient, due to the ability of fast-growing organisms to quickly exhaust their niche in the complex medium and then exploit and monopolize the supplemental carbon source. Relative abundances of dominant taxa could be predicted from the nutritional preferences and growth dynamics of species in isolation, and exceptions were consistent with strain-level variation in growth capabilities. Our study reveals that community assembly follows simple rules of nutrient utilization dynamics and provides a predictive framework for manipulating gut commensal communities through nutritional perturbations.

microbiology↗
bioRxiv2022

Structural basis for the assembly of the DNA polymerase holoenzyme from a monkeypox virus variant

The ongoing pandemic caused by a monkeypox virus (MPXV) variant has spread all over the world and raised great public health concerns. The DNA polymerase F8 of MPXV, associated with its processivity factors A22 and E4, is responsible for viral genome replication in the perinuclear sites of the infected cells as well as a critical target for developing antiviral drugs. However, the assembly and working mechanism for the DNA polymerase holoenzyme of MPXV remains elusive. Here, we present the cryo-EM structure of the DNA polymerase holoenzyme F8/A22/E4 from the 2022 West African strain at an overall resolution of 3.5 [A] and revealed the precise spatial arrangement. Surprisingly, unlike any other previously reported B-family DNA polymerase, the holoenzyme complex is assembled as a dimer of heterotrimers, of which the extra interface between the thumb domain of F8 and A22 shows a clash between A22 and substrate DNA, suggesting an auto-inhibition state. Supplying an exogenous double-stranded DNA could notably shift the hexameric form into a trimeric form, which exposes the DNA binding site of thumb domain and might represent a more active state. The structures provide a molecular basis for the design of new antiviral therapeutics that target the MPXV DNA polymerase holoenzyme.

biochemistry↗
bioRxiv2022

A dedicated hypothalamic oxytocin circuit controls aversive social learning

To survive and thrive in a complex social group, it is essential to not only know who to approach but more importantly who to avoid. After a single defeat, mice learn to stay away from the winning aggressor for weeks. Here, we identify oxytocin neurons in the retrochiasmatic supraoptic nucleus (SOROXT) and oxytocin receptor expressing cells in the anterior subdivision of ventromedial hypothalamus, ventrolateral part (aVMHvlOXTR) as a key circuit motif for defeat-induced social avoidance learning. After defeat, aVMHvlOXTR cells drastically increase their responses to aggressor cues. This response change is functionally important as optogenetic activation of aVMHvlOXTR cells elicits time-locked social avoidance towards a benign social target whereas inactivating the cells suppresses defeat-induced social avoidance. Furthermore, OXTR in the aVMHvl is itself essential for the behavior change. Knocking out OXTR in the aVMHvl or antagonizing the receptor during defeat, but not during post-defeat social interaction, impairs defeat-induced social avoidance. aVMHvlOXTR receives its private source of oxytocin from SOROXT cells, which are highly activated by the noxious somatosensory inputs associated with defeat. Oxytocin released from SOROXT depolarizes aVMHvlOXTR cells and facilitates their synaptic potentiation, and hence, increases aVMHvlOXTR cell responses to aggressor cues. Ablating SOROXT cells impairs defeat-induced social avoidance learning whereas activating the cells promotes social avoidance after a subthreshold defeat experience. Altogether, our study reveals an essential role of SOROXT-aVMHvlOXTR circuit in defeat-induced social learning and highlights the importance of brain oxytocin system in social plasticity.

neuroscience↗
bioRxiv2022

The SARS-CoV-2 accessory protein Orf3a is not an ion channel, but does interact with trafficking proteins

The severe acute respiratory syndrome associated coronavirus 2 (SARS-CoV-2) and SARS-CoV-1 accessory protein Orf3a colocalizes with markers of the plasma membrane, endocytic pathway, and Golgi apparatus. Some reports have led to annotation of both Orf3a proteins as a viroporin. Here we show that neither SARS-CoV-2 nor SARS-CoV-1 form functional ion conducting pores and that the conductances measured are common contaminants in overexpression and with high levels of protein in reconstitution studies. Cryo-EM structures of both SARS-CoV-2 and SARS-CoV-1 Orf3a display a narrow constriction and the presence of a basic aqueous vestibule, which would not favor cation permeation. We observe enrichment of the late endosomal marker Rab7 upon SARS-CoV-2 Orf3a overexpression, and co-immunoprecipitation with VPS39. Interestingly, SARS-CoV-1 Orf3a does not cause the same cellular phenotype as SARS-CoV-2 Orf3a and does not interact with VPS39. To explain this difference, we find that a divergent, unstructured loop of SARS-CoV-2 Orf3a facilitates its binding with VPS39, a HOPS complex tethering protein involved in late endosome and autophagosome fusion with lysosomes. We suggest that the added loop enhances SARS-CoV-2 Orf3a ability to co-opt host cellular trafficking mechanisms for viral exit or host immune evasion.

biophysics↗
bioRxiv2022

Conditional forest models built using metagenomic data could accurately predict Salmonella contamination in Northeastern streams

The use of water contaminated with Salmonella for produce production contributes to foodborne disease burden. To reduce human health risks, there is a need for novel, targeted approaches for assessing the pathogen status of agricultural water. We investigated the utility of water microbiome data for predicting Salmonella contamination of streams used to source water for produce production. Grab samples were collected from 60 New York streams in 2018 and tested for Salmonella. Separately, DNA was extracted from the samples and used for Illumina shotgun metagenomic sequencing. Reads were trimmed and used to assign taxonomy with Kraken2. Conditional forest (CF), regularized random forest (RRF), and support vector machine (SVM) models were implemented to predict Salmonella contamination. Model performance was determined using 10-fold cross-validation repeated 10 times to quantify area under the curve (AUC) and Kappa score. Taxa identified as the most informative for accurately predicting Salmonella contamination based on conditional variable importance were compared to taxa identified by ALDEx2 as being differentially abundant between Salmonella-positive and - negative samples. CF models outperformed the other two algorithms based on AUC (0.82 - CF, 0.76 - RRF, 0.67 - SVM) and Kappa score (0.41- CF, 0.38 - RRF, 0.19 - SVM). CF and differential abundance tests both identified Aeromonas (VI = 0.32) and Tabrizicola (VI = 0.12) as the two most informative taxa for predicting Salmonella contamination. The taxa identified in this study warrant further investigation as indicators of Salmonella contamination in Northeastern freshwater streams. IMPORTANCEUnderstanding the associations between surface water microbiome composition and the presence of foodborne pathogens, such as Salmonella, can facilitate the identification of novel indicators of Salmonella contamination. This study assessed the utility of microbiome data and three machine learning algorithms for predicting Salmonella contamination of Northeastern streams. The research reported here both expanded the knowledge on the microbiome composition of surface waters and identified putative novel indicators (i.e., Aeromonas and Tabrizicola) for Salmonella in Northeastern streams. These putative indicators warrant further research to assess whether they are consistent indicators of Salmonella for regions, waterways, and years not represented in the dataset used in this study.

microbiology↗
bioRxiv2022

Structural basis for the enhanced infectivity and immune evasion of Omicron subvariants

The Omicron variants of SARS-CoV-2 have recently become the globally dominant variants of concern in the COVID-19 pandemic. At least five major Omicron sub-lineages have been characterized: BA.1, BA.2, BA.3, BA.4 and BA.5. They all possess over 30 mutations on the Spike (S) protein. Here we report the cryo-EM structures of the trimeric S proteins from the five subvariants, of which BA.4 and BA.5 share the same mutations of S protein, each in complex with the surface receptor ACE2. All three receptor binding domains of S protein from BA.2 and BA.4/BA.5 are "up", while the BA.1 S protein has two "up" and one "down". The BA.3 S protein displays increased heterogeneity, with the majority in the all "up" RBD state. The differentially preferred conformations of the S protein are consistent with their varied transmissibilities. Analysis of the well defined S309 and S2K146 epitopes reveals the underlie immune evasion mechanism of Omicron subvariants.

biochemistry↗
bioRxiv2022

In situ cryo-electron tomography reveals the asymmetric architecture of mammalian sperm axonemes

The flagella of mammalian sperm display non-planar, asymmetric beating, in contrast to the planar, symmetric beating of flagella from sea urchin sperm and unicellular organisms. The molecular basis of this difference is unclear. Here, we perform in situ cryo-electron tomography of mouse and human sperm axonemes, providing the highest resolution structural information to date. Our subtomogram averages reveal mammalian sperm- specific protein complexes within the outer microtubule doublets, the radial spokes and nexin-dynein regulatory complexes. The locations and structures of these complexes suggest potential roles in enhancing the mechanical strength of mammalian sperm axonemes and regulating dynein-based axonemal bending. Intriguingly, we find that each of the nine outer microtubule doublets is decorated with a distinct combination of sperm- specific complexes. We propose that this asymmetric distribution of proteins differentially regulates the sliding of each microtubule doublet and may underlie the asymmetric beating of mammalian sperm.

biophysics↗
bioRxiv2022

T cell-mediated development of stromal fibroblasts with an immune-enhancing chemokine profile

Stromal fibroblasts reside in inflammatory tissues that are characterized by either immune suppression or immune activation, but whether these cells adapt to these contrasting microenvironments is not known. Cancer-associated fibroblasts (CAFs) mediate immune quiescence by producing the chemokine CXCL12 that coats cancer cells to suppress T cell infiltration. We examined whether CAFs can adopt an immune-promoting chemokine profile. Single-cell RNA-sequencing of CAFs from mouse pancreatic adenocarcinomas identified a sub-population with decreased expression of CXCL12 and increased expression of the T cell-attracting chemokine, CXCL9, that was expanded when tumors were infiltrated with T cells. Conditioned media from activated CD8+ T cells containing TNF and IFN{gamma} converted the chemokine profile of stromal fibroblasts from a CXCL12+/CXCL9- immune suppressive phenotype into a CXCL12-/CXCL9+ immune-activating phenotype. Studies with recombinant cytokines showed that TNF acted synergistically with IFN{gamma} to induce CXCL9 expression, and alone was mainly responsible for suppressing CXCL12 expression. This coordinated chemokine switch demonstrates that stromal fibroblasts have a phenotypic plasticity that allow their adaptation to contrasting immune tissue microenvironments. SummaryIt is unclear whether and how stromal fibroblasts adapt and contribute to varying tissue microenvironments. This study shows immune-suppressive cancer-associated fibroblasts (CAFs) have the capacity to develop an immune-promoting chemokine profile in response to cytokines from infiltrating T cells.

immunology↗
bioRxiv2022

An intergeneric recombinant geminivirus causes soybean stay-green disease

Soybean is one of the most valuable legume crops in the world with high nutritional value. Recently, the outbreak of soybean stay-green syndrome has swept the soybean production in the Huang-Huai-Hai region of China, resulting in huge yield losses, which has become an epidemic and prominent problem in soybean production. However, the cause of the stay-green syndrome remains obscure. Here, we report a novel intergeneric recombinant geminivirus which causes soybean stay-green symptoms. Viral small RNA-based screening identified a new recombinant geminvirus from field soybean stay-green samples. The complete genome sequence of the virus contains 2762 nucleotide (nt) and appears to be an intergeneric recombinant virus in which protein coding for coat protein (V1) is similar to member of genus Mastrevirus, whereas proteins coding for V2, C2, C3 are most similar to those of viruses in the Maldovirus genus, and C1 and C4 are most similar to virus in genus Begomovirus. Inoculation of the infectious clone of the recombinant geminivirus through Agrobacterium rhizogenes causes typical soybean stay-green syndrome which resembles field symptoms including delayed leaf senescence, flat pods and abnormal seeds. The recombinant geminivirus can be detected in seed coat but not in cotyledon and embryo, thus failing to be transmitted by seeds. Moreover, the genome variation and epidemiological dynamic analysis were also carried out to help the continuous epidemiological surveillance of this emerging geminivirus. Collectively, this new geminivirus is tentatively named soybean stay-green associated virus (SoSGV). Our determination of the causal agent of soybean stay-green disease will bolster efforts to develop effective management strategies to control this prevalent disease in the field.

microbiology↗
bioRxiv2022

The bladder microbiome, metabolome, cytokines, and phenotypes in patients with systemic lupus erythematosus

Background and aimsEmerging studies reveal a unique bacterial community in the human bladder, with alteration of composition associated to disease states. Systemic lupus erythematosus (SLE) is a complex autoimmune disease that is characterized by frequent impairment of the kidney. Here, we explored the bladder microbiome, metabolome, and cytokine profiles in SLE patients, as well as correlations between microbiome and metabolome, cytokines, and disease profiles. Methods and materialsWe recruited a cohort of 50 SLE patients and 50 individually matched asymptomatic controls. We used transurethral catheterization to collect urine samples, 16S rRNA gene sequencing to profile bladder microbiomes, and LC-MS/MS to perform untargeted metabolomic profiling. ResultsCompared to controls, SLE patients possessed a unique bladder microbial community and increased alpha diversity. These differences were accompanied by differences in urinary metabolomes, cytokines, and patients disease profiles. The SLE-enriched genera, including Bacteroides, were positively correlated with several SLE-enriched metabolites, including olopatadine. The SLE-depleted genera, such as Pseudomonas, were negatively correlated to SLE-depleted cytokines, including IL-8. Alteration of the bladder microbiome was associated with disease profile. For example, the genera Megamonas and Phocaeicola were negatively correlated with serum complement C3, and Streptococcus was positively correlated with IgG. ConclusionsOur present study reveals associations between the bladder microbiome and the urinary metabolome, cytokines, and disease phenotypes. Our results could help identify biomarkers for SLE.

microbiology↗
bioRxiv2021

The dual role of N6-methyladenosine on mouse maternal RNAs and 2-cell specific RNAs revealed by ULI-MeRIP sequencing

N6-methyladenosine (m6A) and its regulatory components play critical roles in various developmental processes in mammals(1-5). However, the landscape and function of m6A in the maternal-to-zygotic transition (MZT) remain unclear due to limited materials. Here, by developing an ultralow-input MeRIP-seq method, we revealed the dynamics of the m6A RNA methylome during the MZT process in mice. We found that more than 1/3 maternal decay and 2/3 zygotic mRNAs were modified by m6A. Moreover, m6As are highly enriched in the RNA of transposable elements MTA and MERVL, which are highly expressed in oocytes and 2-cell embryos, respectively. Notably, maternal depletion of Kiaa1429, a component of the m6A methyltransferase complex, leads to a reduced abundance of m6A-marked maternal RNAs, including both genes and MTA, in GV oocytes, indicating m6A-dependent regulation of RNA stability in oocytes. Interestingly, when the writers were depleted, some m6A-marked 2-cell specific RNAs, including Zscan4 and MERVL, appeared normal at the 2-cell stage but failed to be decayed at later stages, suggesting that m6A regulates the clearance of these transcripts. Together, our study uncovered that m6As function in context-specific manners during MZT, which ensures the transcriptome stability of oocytes and regulates the stage specificity of zygotic transcripts after fertilization. One Sentence Summarym6A RNA methylation stabilizes the maternal RNAs in mouse oocytes and degrades the 2-cell specific RNAs in the cleavage-stage embryos.

developmental biology↗
bioRxiv2021

The endoplasmic reticulum adopts two distinct tubule forms

The endoplasmic reticulum (ER) is a versatile organelle with diverse functions. Through super-resolution microscopy, we show that the peripheral ER in the mammalian cell adopts two distinct forms of tubules. Whereas an ultrathin form, R1, is consistently covered by ER-membrane curvature-promoting proteins, e.g., Rtn4 in the native cell, in the second form, R2, Rtn4 and analogs are arranged into two parallel lines at a conserved separation of [~]105 nm over long ranges. The two tubule forms together account for [~]90% of the total tubule length in the cell, with either one being dominant in different cell types. The R1-R2 dichotomy and the final tubule geometry are both co-regulated by Rtn4 (and analogs) and the ER sheet-maintaining protein Climp63, which respectively define the edge curvature and lumen height of the R2 tubules to generate a ribbon-like structure of well-defined width. Accordingly, the R2 tubule width correlates positively with the Climp63 intralumenal size. The R1 and R2 tubules undergo active remodeling at the second/sub-second time scales as they differently accommodate proteins, with the former effectively excluding ER-luminal proteins and ER-membrane proteins with large intraluminal domains. We thus uncover a dynamic structural dichotomy for ER tubules with intriguing functional implications.

cell biology↗
bioRxiv2021

CryoEM structure of the EBV ribonucleotide reductase BORF2 and mechanism of APOBEC3B inhibition

Viruses use a plethora of mechanisms to evade immune responses. A new example is neutralization of the nuclear DNA cytosine deaminase APOBEC3B by the Epstein-Barr virus (EBV) ribonucleotide reductase subunit BORF2. Cryo-EM studies of APOBEC3B-BORF2 complexes reveal a large >1000 [A]2 binding surface comprised of multiple structural elements from each protein, which effectively blocks the APOBEC3B active site from accessing single-stranded DNA substrates. Evolutionary optimization is suggested by unique insertions in BORF2 absent from other ribonucleotide reductases and preferential binding to APOBEC3B relative to the highly related APOBEC3A and APOBEC3G enzymes. An atomic understanding of this novel pathogen-host interaction may contribute to the development of drugs that block the interaction and liberate the natural antiviral activity of APOBEC3B. One-Sentence SummaryThese studies show how a conserved viral nucleotide metabolism protein is repurposed to inhibit a potent antiviral factor.

microbiology↗