Biology subjects

Wan, Y.

Publications and source records attributed to Wan, Y..

At least 55 records · Page 3Linked to original sources

bioRxiv2024

Novel derivatives of BCV and (S)-HPMPA inhibit orthopoxviruses and human adenoviruses more potently than BCV

BCV and tecovirimat are the only two chemical drugs that have been approved to treat smallpox and can be requested for Mpox treatment through a single-patient Emergency Investigational New Drug (EIND) application. Disappointedly, the efficacy of tecovirimat manifested in a recent clinical trial is far from being satisfactory, while the clinical efficacy of BCV is still inconclusive. Given that MPXV, variola and other emerging orthopoxviruses are posing serious threats to global health, it is urgent to develop better therapeutics. In this study, we tested the antiviral effects of three novel prodrugs, which were designed based on previously reported parent drugs, either (S)-HPMPC (cidofovir) or (S)-HPMPA. We found that one of the (S)-HPMPA-based prodrugs, ODE-(S)-HPMPA formate, exhibited significantly better anti-orthopoxvirus activity than BCV both in vitro and in vivo, which also inhibited human adenovirus type 2 and type 21 more efficiently than BCV. Most strikingly, the EC50 and EC90 of ODE-(S)-HPMPA formate against MPXV were more than 40-fold lower than those of BCV. In contrast, we observed that the anti-HSV-1 activities of the (S)-HPMPA-based prodrugs were less effective than those of the cidofovir-based prodrugs (BCV and BCV formate), especially in vivo. Moreover, we showed for the first time that cytidine and adenine analog combined therapies could provide mice with complete protection against lethal challenges of both vaccinia and HSV-1. Collectively, we propose that both the ODE-(S)-HPMPA formate and the BCV/ODE-(S)-HPMPA formate combination are worth further investigations for their potential clinical applications.

microbiology↗

bioRxiv2024

Whole-embryo Spatial Transcriptomics at Subcellular Resolution from Gastrulation to Organogenesis

Spatiotemporal patterns of gene expression underlie embryogenesis. Despite progress in single-cell genomics, mapping these patterns across whole embryos with comprehensive gene coverage and at high resolution has remained elusive. Here, we introduce a whole-embryo imaging platform using multiplexed error-robust fluorescent in-situ hybridization (weMERFISH). We quantified the expression of 495 genes in whole-mount zebrafish embryos at subcellular resolution. Integration with single-cell multiomics data generated an atlas detailing the expression of 25,872 genes and the accessibility of 294,954 chromatin regions, explorable with an online interface MERFISHEYES (beta version). We found that temporal gene expression aligns with cellular maturation and morphogenetic movements, diverse expression patterns correspond to composites of tissue-specific accessible elements, and changes in gene expression generate sharp boundaries during gastrulation. These results establish a novel approach for whole-organism spatial transcriptomics, provide a comprehensive spatially resolved atlas of gene expression and chromatin accessibility, and reveal the diversity, precision and emergence of embryonic patterns.

developmental biology↗

bioRxiv2024

Temporal-spatial transcriptomics reveals key gene regulation for grain yield and quality in wheat

Cereal grain size and quality are important agronomic traits in crop production. The development of wheat grains is underpinned by complex regulatory networks. The precise spatial and temporal coordination of diverse cell types is essential for the formation of functional compartments. To provide comprehensive spatiotemporal information about biological processes in developing wheat grain, we performed a spatial transcriptomics study during the early grain development stage from 4 to 12 days after pollination. We defined a set of tissue-specific marker genes and discovered that certain genes or gene families exhibit specific spatial expression patterns over time. Weighted gene co-expression network and motif enrichment analyses identified specific groups of genes potentially regulating wheat grain development. The embryo and surrounding endosperm specifically expressed transcription factor TaABI3-3B negatively regulates embryo and grain size. In Chinese breeding programs, a haplotype associated with higher grain weight was identified, linked to altered expression levels of TaABI3-3B. Data and knowledge obtained from the proposed study will provide pivotal insights into yield improvement and serve as important genetic information for future wheat breeding.

developmental biology↗

bioRxiv2024

Optimizing a CRISPR-Cas13d gene circuit for tunable target RNA downregulation with minimal collateral RNA cutting

The invention of RNA-guided DNA cutting systems has revolutionized biotechnology. More recently, RNA-guided RNA cutting by Cas13d entered the scene as a highly promising alternative to RNA interference to engineer cellular transcriptomes for biotechnological and therapeutic purposes. Unfortunately, "collateral damage" by indiscriminate off-target cutting tampered enthusiasm for these systems. Yet, how collateral activity, or even RNA target reduction depends on Cas13d and guide RNA abundance has remained unclear due to the lack of expression-tuning studies to address this question. Here we use precise expression-tuning gene circuits to show that both nonspecific and specific, on-target RNA reduction depend on Cas13d and guide RNA levels, and that nonspecific RNA cutting from trans cleavage might contribute to on-target RNA reduction. Using RNA-level control techniques, we develop new Multi-Level Optimized Negative-Autoregulated Cas13d and crRNA Hybrid (MONARCH) gene circuits that achieve a high dynamic range with low basal on-target RNA reduction while minimizing collateral activity in human kidney cells and green monkey cells most frequently used in human virology. MONARCH should bring RNA-guided RNA cutting systems to the forefront, as easily applicable, programmable tools for transcriptome engineering in biotechnological and medical applications.

synthetic biology↗

bioRxiv2024

Protein interactions, calcium, phosphorylation, and cholesterol modulate CFTR cluster formation on membranes

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a chloride channel whose dysfunction leads to intracellular accumulation of chloride ions, dehydration of cell surfaces, and subsequent damage to airway and ductal organs. Beyond its function as a chloride channel, interactions between CFTR, ENaC, and SLC transporter family membrane proteins and cytoplasmic proteins, including calmodulin and NHERF-1, co-regulate ion homeostasis. CFTR has also been observed to form mesoscale membrane clusters. However, the biophysical mechanisms that regulate the formation of CFTR clusters are unknown. Using a combination of computational modeling and complex biochemical reconstitution assays, we demonstrate that multivalent protein-protein interactions with CFTR binding partners, calcium, and membrane cholesterol can induce CFTR cluster formation on model membranes. Phosphorylation of the intracellular domains of CFTR also promotes cluster formation in the absence of calcium, indicating that multiple mechanisms can regulate CFTR cluster formation. Our findings reveal that coupling of multivalent protein and lipid interactions promote CFTR cluster formation consistent with membrane-associated biological phase separation. SIGNIFICANCE STATEMENTMutations in the cystic fibrosis transmembrane conductance regulator (CFTR) membrane protein underlie cystic fibrosis. It is thought that molecular "hubs" of CFTR and its binding partners co-regulate ion homeostasis and that disruption of these clusters can result in disease. However, the physical basis for molecular hub formation is unclear. In this study, we present evidence that multivalent protein and lipid interactions drive the formation of mesoscale CFTR-containing clusters or "hubs" on model membranes in a manner consistent with biological phase separation. These data provide important insights into physical mechanisms that modulate CFTR membrane organization and offer a new lens for the development of corrective therapeutics.

biophysics↗

bioRxiv2024

Ancient cyanobacterial proto-circadian clock adapted to short day-night cycles ~ 0.95 billion years ago

In the early history, the Earth rotation was much faster; however, how ancient organisms adapted to the day-night cycles of that time remains unclear. We resurrected the ancestor KaiABC (anKaiABC) genes circa 0.95 billion years (Ga) ago when the daily-night cycling period was [~] 18 h. Compared with its contemporary counterpart KaiC, the anKaiC protein shows subtle structural differences, and the activities of kinase, phosphatase activities, and adenosine triphosphatase (ATPase) of anKaiC are lower. The anKaiAB proteins are less effective in regulating KaiC/anKaiC phosphorylation status. The anKaiABC system does not sustain an endogenous oscillation but it can be entrained by an 18-h light/dark cycle. The strain expressing anKaiABC shows better adaptation under 9-h light/9-h dark cycles (LD9:9) which mimic the 18-h day-night cycles. These findings suggest that the ancient cyanobacterial proto-circadian system may not be endogenous, but it conferred the capability to adapt to daily cycles [~] 0.95 Ga ago.

evolutionary biology↗

bioRxiv2024

Silicone Wire Embolization-induced Acute Retinal Artery Ischemia and Reperfusion Model in Mouse: Gene Expression Provide Insight into Pathological Processes

Acute retinal ischemia and ischemia-reperfusion injury are the primary causes of retinal neural cell death and vision loss in retinal artery occlusion (RAO). The absence of an accurate mouse model for simulating the retinal ischemic process has hindered progress in developing neuroprotective agents for RAO. We developed a unilateral pterygopalatine ophthalmic artery occlusion (UPOAO) mouse model using silicone wire embolization combined with carotid artery ligation. The survival of retinal ganglion cells and visual function were evaluated to determine the duration of ischemia. Immunofluorescence staining, optical coherence tomography, and haematoxylin and eosin staining were utilized to assess changes in major neural cell classes and retinal structure degeneration at two reperfusion durations. Transcriptomics was employed to investigate alterations in the pathological process of UPOAO following ischemia and reperfusion, highlighting transcriptomic differences between UPOAO and other retinal ischemia-reperfusion models. The UPOAO model successfully replicated the acute interruption of retinal blood supply observed in RAO. 60-minutes of Ischemia led to significant loss of major retinal neural cells and visual function impairment. Notable thinning of the inner retinal layer, especially the ganglion cell layer, was evident post-UPOAO. Temporal transcriptome analysis revealed various pathophysiological processes related to immune cell migration, oxidative stress, and immune inflammation during the non-reperfusion and reperfusion periods. A pronounced increase in microglia within the retina and peripheral leukocytes accessing the retina was observed during reperfusion periods. Comparison of differentially expressed genes (DEGs) between the UPOAO and high intraocular pressure models revealed specific enrichments in lipid and steroid metabolism-related genes in the UPOAO model. The UPOAO model emerges as a novel tool for screening pathogenic genes and promoting further therapeutic research in RAO.

neuroscience↗

bioRxiv2024

Comparison of therapeutic effects between pulsed field ablation and cryoballoon ablation in the treatment of atrial fibrillation: a systematic review and me-ta-analysis

BackgroundPulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) ablation surgery. Cryoballoon ablation (CBA), a conventional thermal ablation technique, enjoys widespread clinical application. In contrast, Pulsed field ablation (PFA) is a novel non thermal ablation technique for the treatment of atrial fibrillation (AF) patients, with safety comparable to traditional thermal ablation surgery. The present study aims to evaluate and compare the procedural efficiency and safety profiles of PFA and CBA in the management of AF. MethodWe performed a systematic search across PubMed, the Cochrane Library, and Embase databases, encompassing the literature up to February 2024, to inform our systematic review and meta-analysis. When assessing outcome indicators, the risk ratio (RR) and its corresponding 95% confidence interval (CI) were calculated for dichotomous variables. For continuous variables, the mean difference (MD) and the associated 95% CI were determined. In this context, an RR less than 1 and an MD less than 0 were considered advantageous for the PFA group. ResultIn this analysis, nine observational studies encompassing 2,875 patients with AF were included. Among these, 38% (n=1105) were treated with PFA, while 62% (n=1,770) received CBA. The results indicated that PFA was associated with a significantly shorter surgical duration compared to CBA, with a mean difference (MD) of -10.49 minutes (95% CI [-15.50, -5.49]; p<0.0001). Additionally, the PFA group exhibited a reduced risk of perioperative complications relative to the CBA group, with a risk ratio (RR) of 0.52 (95% CI 0.30-0.89; p=0.02). Nevertheless, no statistically significant differences were observed when comparing the two treatment cohorts concerning fluorescence irradiation time (MD 0.71; 95% CI [-0.45, 1.86]; p=0.23) and the recurrence of atrial arrhythmias during follow-up (RR 0.95; 95% CI 0.78-1.14; p=0.57). ConclusionThe outcomes of this investigation reveal that PFA holds a relative advantage over CBA in certain respects, notably by reducing both surgical duration and the incidence of perioperative complications. However, no significant distinction was identified between the two modalities concerning the duration of fluorescence irradiation or the rate of atrial arrhythmia recurrence. To enhance the robustness of these estimates, further research is needed, especially by incorporating additional randomized controlled trials.

physiology↗

bioRxiv2024

Rapid in situ mutation detection in extracellular vesicle-DNA

A PCR- and sequencing-free mutation detection assay facilitates cancer diagnosis and reduces over-reliance on specialized equipment. This benefit was highlighted during the pandemic when high demand for viral nucleic acid testing often sidelined mutation analysis. This shift led to substantial challenges for patients on targeted therapy in tracking mutations. Here, we report a 30-minute DNA mutation detection technique using Cas12a-loaded liposomes in a microplate reader, a fundamental laboratory tool. CRISPR-Cas12a complex and fluorescence-quenching (FQ) probes are introduced into tumor-derived extracellular vesicles (EV) through membrane fusion. When CRISPR-RNA hybridizes with the DNA target, activated Cas12a can trans-cleave FQ probes, resulting in fluorescence signals for the quantification of DNA mutation. Future advancements in multiplex and high-throughput mutation detection using this assay will streamline self-diagnosis and treatment monitoring at home.

bioengineering↗

bioRxiv2024

TDP-43 loss induces extensive cryptic polyadenylation in ALS/FTD

Nuclear depletion and cytoplasmic aggregation of the RNA-binding protein TDP-43 is the hallmark of ALS, occurring in over 97% of cases. A key consequence of TDP-43 nuclear loss is the de-repression of cryptic exons. Whilst TDP-43 regulated cryptic splicing is increasingly well catalogued, cryptic alternative polyadenylation (APA) events, which define the 3 end of last exons, have been largely overlooked, especially when not associated with novel upstream splice junctions. We developed a novel bioinformatic approach to reliably identify distinct APA event types: alternative last exons (ALE), 3UTR extensions (3Ext) and intronic polyadenylation (IPA) events. We identified novel neuronal cryptic APA sites induced by TDP-43 loss of function by systematically applying our pipeline to a compendium of publicly available and in house datasets. We find that TDP-43 binding sites and target motifs are enriched at these cryptic events and that TDP-43 can have both repressive and enhancing action on APA. Importantly, all categories of cryptic APA can also be identified in ALS and FTD post mortem brain regions with TDP-43 proteinopathy underlining their potential disease relevance. RNA-seq and Ribo-seq analyses indicate that distinct cryptic APA categories have different downstream effects on transcript and translation. Intriguingly, cryptic 3Exts occur in multiple transcription factors, such as ELK1, SIX3, and TLX1, and lead to an increase in wild-type protein levels and function. Finally, we show that an increase in RNA stability leading to a higher cytoplasmic localisation underlies these observations. In summary, we demonstrate that TDP-43 nuclear depletion induces a novel category of cryptic RNA processing events and we expand the palette of TDP-43 loss consequences by showing this can also lead to an increase in normal protein translation.

neuroscience↗

bioRxiv2023

Activating SRC/MAPK signaling via 5-HT1A receptor contributes to the effect of vilazodone on improving thrombocytopenia

Thrombocytopenia caused by long-term radiotherapy and chemotherapy exists in cancer treatment. Previous research demonstrates that 5-Hydroxtrayptamine (5-HT) and its receptors induces the formation of megakaryocytes (MKs) and platelets. However, the relationships between 5-HT1A receptor (5-HTR1A) and MKs is unclear so far. We screened and investigated the mechanism of vilazodone as a 5-HTR1A partial agonist in promoting MK differentiation and evaluated its therapeutic effect in thrombocytopenia. We employed a drug screening model based on machine learning (ML) to screen the megakaryocytopoiesis activity of VLZ. The effects of Vilazodone (VLZ) on megakaryocytopoiesis were verified in HEL and Meg-01 cells. Tg (itga2b: eGFP) zebrafish was performed to analyze the alterations in thrombopoiesis. Moreover, we established a thrombocytopenia mice model to investigate VLZ administration accelerates platelet recovery and function. We carried out network pharmacology, Western blot and immunofluorescence to demonstrate the potential targets and pathway of VLZ. VLZ has been predicted to have a potential biological action. Meanwhile, VLZ administration promotes MK differentiation and thrombopoiesis in cells and zebrafish models. Progressive experiments showed that VLZ has a potential therapeutic effect on radiation-induced thrombocytopenia in vivo. The network pharmacology and associated mechanism study indicated that SRC and MAPK signaling are both involved in the processes of megakaryopoiesis facilitated by VLZ. Furthermore, the expression of 5-HTR1A during megakaryocyte differentiation is closely related to the activation of SRC and MAPK. Our findings demonstrated that the expression of 5-HTR1A on MK, VLZ could bind to the 5-HTR1A receptor and further regulate the SRC/MAPK signaling pathway to facilitate megakaryocyte differentiation and platelet production, which provides new insights into the alternative therapeutic options for thrombocytopenia.

pharmacology and toxicology↗

bioRxiv2023

HGNNPIP: A Hybrid Graph Neural Network framework for Protein-protein Interaction Prediction

A deep understanding of Protein-protein interactions (PPIs) can provide comprehensive insights into many biological functions, thereby facilitating drug target identification and novel therapeutic design. Recent developments in artificial intelligence (AI)-driven computational methods have enabled the discovery of previously uncharacterized PPIs from large-scale interactome datasets. Almost all existing machine learning methods rely on Subcellular Localization (SL) to construct balanced datasets based on positive interactions to achieve predictions. Despite high fitting accuracy, the generalization ability of these models is questionable. To solve this problem, we analyzed existing methods and found that the high false positives in these methods are due to the bias in data distribution caused by SL. Therefore, we proposed a new strategy for negative instance sampling in PPI prediction and developed a Hybrid Graph Neural Network framework for Protein-protein Interaction Prediction (HGNNPIP). The experimental results showed that HGNNPIP works well on six benchmark datasets. Comparison analysis demonstrated that our model outperformed the other four existing methods. We also used HGNNPIP to explore the molecular contacts involved in the rice-pathogen interaction system. In vivo experiments confirmed multiple regulations related to disease resistance in rice. In summary, this study provides new insights into establishing a computational framework for PPI prediction with high reliability.

bioinformatics↗

bioRxiv2023

Cortical spheroids show strain-dependent cell viability loss and neurite disruption following sustained compression injury

Sustained compressive injury (SCI) in the brain is observed in numerous injury and pathological scenarios, including tumors, ischemic stroke, and traumatic brain injury-related tissue swelling. Sustained compressive injury is characterized by tissue loading over time, and currently, there are few in vitro models suitable to study neural cell responses to strain-dependent sustained compressive injury. Here, we present an in vitro model of sustained compressive neural injury via centrifugation. Spheroids were made from neonatal rat cortical cells seeded at 4000 cells/spheroid and cultured for 14 days in vitro. A subset of spheroids was centrifuged at 209 or 419 rad/s for 2 minutes. Modeling the physical compression of the spheroids via finite element analyses, we found that spheroids centrifuged at 209 and 419 rad/s experienced pressures of 38 kPa and 149 kPa, respectively, and compressive strains of 18% and 35%, respectively. Quantification of LIVE-DEAD assay and Hoechst 33342 nuclear staining showed that centrifuged spheroids exhibited significantly higher DNA damage than control spheroids at 2, 8, and 24 hours post-injury. Immunohistochemistry of {beta}3-tubulin networks at 2, 8, and 24 hours post-centrifugation injury showed increasing degradation of microtubules over time with increasing compressive strain. Our findings show that cellular injuries occur as a result of specific levels and timings of sustained compressive tissue strains. This experimental compressive injury model provides an in vitro platform to examine cellular injury to gain insights into brain injury that could be targeted with therapeutic strategies.

bioengineering↗

bioRxiv2023

Oligodendroglial precursors orchestrate immune network instigating early demyelination in experimental autoimmune encephalomyelitis

The immunomodulatory cellular network that triggers early inflammation and demyelination, the key steps in multiple sclerosis (MS) pathogenesis remains poorly characterized. Here, we demonstrate that overactivation of Wnt pathway promotes pathological transformation of oligodendrocyte precursor cells (OPCs) to replicate pathological OPCs in human MS. In mouse experimental autoimmune encephalomyelitis (EAE), pathological OPCs attract CD4+ T-helper 1 (Th1) cells into the spinal cord and brain through CC-chemokine ligand 4 (CCL4), whilst OPCs cooperate with Th1 cells inducing transformation of cytotoxic macrophages that execute early demyelination. Simultaneously, Th1 cells and cytotoxic macrophages upregulate Wnt signaling and CCL4 expression in OPCs, thus exerting positive feedback onto the OPC-immune cascade and establishing a vicious cycle propagating EAE pathogenesis. Breaking this cascade by targeting CCL4 reduces immune cell infiltration, alleviates demyelination, and attenuates EAE severity. Our findings demonstrate a closely coordinated network of OPCs and immune cells therefore providing an alternative insight into MS pathophysiology.

neuroscience↗

bioRxiv2023

Pan-genome and Haplotype Map of Cultivars and Their Wild Ancestors Provides Insights into Adaptive Evolution of Cassava (Manihot esculenta Crantz)

Cassava is the most important starch sources, a tropical model crop. We constructed nearly T2T genomes of cultivar AM560, wild ancestors FLA4047 and W14, pan-genome of 24 representatives and a clarified evolutionary tree with 486 accessions. Comparison of SVs and SNVs between the ancestors and cultivated cassavas revealed predominant expansion, contraction of genes and gene families. Significantly selective sweeping occurred in the cassava genomes in 122 footprints with 1,519 candidate domestication genes. We identified selective mutations in MeCSK and MeFNR3 promoting photoreaction associated with MeNADP-ME of C4 assimilation in modern cassava. Co-evolved retardation of floral primordia and initiation of storage roots arose from MeCOL5 mutants with altered bindings to MeFT1, MeFT2 and MeTFL2. MebHLHs evolved to regulate the biosynthesis, transport and endogenous remobilization of cyanogenic glucosides, with new functionalities of MeMATE1, MeGTR in selected sweet cassava. These findings enhanced comprehensive knowledge and database on the evolution and breeding of cassava. HIGHLIGHTSO_LIThree nearly T2T cassava genomes of cultivar AM560 and its wild ancestors FLA4047 and W14. C_LIO_LIA species-level cassava panSV haplotype map across 346,322 structural variations over 31,362 gene families and 96,032,008 SNPs and InDels variations globally and a clarified evolutionary tree with 486 accessions. C_LIO_LISelective mutations in MeCSK and MeFNR3 promoted photoreaction associated with MeNADP-ME of C4 assimilation shaped the C3-C4 intermediate photosynthesis of modern cassava. C_LIO_LICoevolution of floral primordia contrary to initiated storage root is pivotal for the domestication of cassava, and arose from MeCOL5 mutants altered the binding with MeFT1, MeFT2 (SP6A), and MeTFL2. C_LI

systems biology↗

bioRxiv2023

A Zinc finger (ZnF) transcription factor exerts its multifaceted function through ZnF-regulated phase separation

Zinc finger (ZnF) transcription factors (TFs) consist of ZnF-containing DNA-binding domains (DBDs) and intrinsically disordered region (IDR)-containing activation domains (ADs). Recent studies have suggested that liquid-liquid phase separation (LLPS) is the fundamental mechanism underlying human health and disease, with ZnF TFs activating gene expression through the LLPS capacity of their IDR-containing ADs. However, little is known about how the well-folded DBD of ZnF TFs is involved in their LLPS mechanism. GATA3 is one of the most frequently mutated genes in breast cancer, and its encoded protein GATA3, which contains two ZnFs (ZnF1 and ZnF2) in its DBD, is a master regulator of immunity. Here, we show that GATA3 undergoes LLPS in cells and in vitro, and its DBD plays an important regulatory role. Mechanistically, ZnF2 in the DBD contains two arginine amino acids (R329 and R330) that provide critical charges to regulate GATA3 LLPS and DNA binding by generating multivalent electrostatic interactions. Functionally, we demonstrated that ZnF2-regulated GATA3 LLPS is the mechanism underlying the multifaceted function of GATA3 in breast cancer development and immune regulation, where aberrant GATA3 LLPS caused by artificial or breast cancer-associated ZnF2-defective mutations by reducing Suv39H1 protein stability showed significantly reduced potential in promoting breast cancer development and exhibited remarkably enhanced capacities for activating type I interferon signaling. Since ZnF is a common feature in the DBDs of ZnF TFs, by describing GATA3 as a proof-of-principle, our data suggest that ZnF-regulated LLPS may be a general mechanism underlying the multifaceted function of ZnF TFs in human health and disease.

cancer biology↗

bioRxiv2023

LSM14B is essential for mitochondrial clustering in the oocyte meiosis

As oocyte meiotic maturation, they undergo two successive meiotic M phases, notably lacking an intervening interphase phase. During these M phases, oocytes remain transcriptionally quiescent, and we now know that "translational repressed mRNAs" are stored in a structure called the mitochondria associated ribonucleoprotein domain (MARDO). LSM14B is one of the abundant proteins of MARDO, and is predicted to bind mRNA, but its function(s) remain elusive. Here, we demonstrate that LSM14B functions to promote MARDO assembly in mouse oocytes. We also found that LSM14B knockout female mice are infertile, and show that the knockout oocytes fail to enter meiosis II, instead entering an aberrant interphase-like stage. Finally, we show that the failure of oocyte maturation results from decreased expression of Cyclin B1. Our study has revealed that the RNA-binding protein LSM14B modulates MARDO assembly and is essential for oocyte meiotic maturation.

developmental biology↗

bioRxiv2023

IS1-related large-scale deletion of chromosomal regions harbouring oxygen-insensitive nitroreductase gene nfsB causes nitrofurantoin heteroresistance in Escherichia coli

Nitrofurantoin is a broad-spectrum first-line antimicrobial used for managing uncomplicated urinary tract infection. Loss-of-function mutations in chromosomal genes nfsA, nfsB, and ribE of Escherichia coli are known to reduce nitrofurantoin susceptibility. Here, we report monoclonal nitrofurantoin heteroresistance in E. coli and a novel genetic mechanism associated with this phenomenon. Subpopulations with reduced nitrofurantoin susceptibility in cultures of two E. coli blood strains were identified using population analysis profiling. Four colonies of each strain growing on agar with 0.5xMIC nitrofurantoin were sub-cultured in broth with 0.5xMIC nitrofurantoin (n=2) or without nitrofurantoin (n=2). Moreover, one colony of each strain growing without nitrofurantoin exposure was selected as a reference for genomic comparison. Whole-genome sequencing of all isolates were conducted on Illumina and Nanopore MinION systems. Both strains had a nitrofurantoin MICs of 64 mg/L. The proportion of cells grown at 0.5xMIC was two and 99 per million, respectively, which is distinct to that of a homogeneously susceptible or resistant isolate. All isolates grown at 0.5xMIC had 11-66 kbp deletions in chromosomal regions harbouring nfsB, and all these deletions were immediately adjacent to IS1-family insertion sequences. Although this study is limited to E. coli and nitrofurantoin, our findings suggest IS1-associated genetic deletion represents a hitherto unrecognised mechanism of heteroresistance that could compromise infection management and impact conventional antimicrobial susceptibility testing. Impact statementNitrofurantoin is widely used for treating and preventing urinary tract infection. Prevalence of nitrofurantoin resistance generally is low in E. coli. Here, we report nitrofurantoin heteroresistance in two E. coli blood strains and attribute this phenotype to IS1-associated deletion of chromosomal regions harbouring oxygen-insensitive nitroreductase gene nfsB. Our discoveries demonstrate a novel genetic mechanism of heteroresistance and suggest detecting nitrofurantoin heteroresistance in E. coli urinary isolates for improving prescribing. Data summaryWhole-genome sequencing reads and genome assemblies generated in this study have been deposited under BioProject PRJEB58678 in the European Nucleotide Archive (ENA). Accession numbers are listed in Supplementary Table 1. Previously generated Illumina whole-genome sequencing reads of parental isolates EC0026B and EC0880B are available under ENA accessions ERR3142418 and ERR3142524, respectively.

microbiology↗