Biology subjects

Tang, J.

Publications and source records attributed to Tang, J..

At least 235 records · Page 13Linked to original sources

bioRxiv2020

Antibody repertoire induced by SARS-CoV-2 spike protein immunogens

Multiple vaccine candidates against SARS-CoV-2 based on viral spike protein are under development. However, there is limited information on the quality of antibody response generated following vaccination by these vaccine modalities. To better understand antibody response induced by spike protein-based vaccines, we immunized rabbits with various SARS-CoV-2 spike protein antigens: S-ectodomain (S1+S2) (aa 16-1213), which lacks the cytoplasmic and transmembrane domains (CT-TM), the S1 domain (aa 16-685), the receptor-binding domain (RBD) (aa 319-541), and the S2 domain (aa 686-1213 as control). Antibody response was analyzed by ELISA, Surface Plasmon Resonance (SPR) against different Spike proteins in native conformation, and a pseudovirion neutralization assay to measure the quality and function of the antibodies elicited by the different Spike antigens. All three antigens (S1+S2 ectodomain, S1 domain, and RBD) generated strong neutralizing antibodies against SARS-CoV-2. Vaccination induced antibody repertoire was analyzed by SARS-CoV-2 spike Genome Fragment Phage Display Libraries (SARS-CoV-2 GFPDL), which identified immunodominant epitopes in the S1, S1-RBD and S2 domains. Furthermore, these analyses demonstrated that surprisingly the RBD immunogen elicited a higher antibody titer with 5-fold higher affinity antibodies to native spike antigens compared with other spike antigens. These findings may help guide rational vaccine design and facilitate development and evaluation of effective therapeutics and vaccines against COVID-19 disease. One Sentence SummarySARS-CoV-2 Spike induced immune response

microbiology↗

bioRxiv2020

Nucleolin is essential for rabbit hemorrhagic disease virus replication by providing a physical link in replication complex formation

Rabbit hemorrhagic disease virus (RHDV) is an important member of the Caliciviridae family and cannot be propagated in vitro, which has greatly impeded progress of investigating its replication mechanism. Construction of an RHDV replicon system has recently provided a platform for exploring RHDV replication in host cells. Here, aided by this replicon system and using two-step affinity purification, we purified the RHDV replicase and identified its associated host factors. We identified rabbit nucleolin (NCL) as a physical link required for the formation of RHDV replication complexes (RCs), by mediating the interaction between other host proteins and the viral RNA replicase, RNA-dependent RNA polymerase (RdRp). We found that RHDV RdRp uses an amino acid (aa) region spanning residues 448-478 to directly interact with NCLs RNA-recognition motif 2. We also found that the viral p16 protein uses a highly conserved region (35Cys-Ile-Arg-Ala38 or CIRA motif) to specifically bind the N-terminal region of NCL (aa 1-110) and that RHDV p23 uses a specific domain (aa 90-145) to bind NCLs RNA-recognition motif 1. Disrupting these protein-protein interactions severely weakened viral replication. Furthermore, NCL overexpression or knockdown significantly increased or severely impaired, respectively, RHDV replication. Collectively, these results indicate that the host protein NCL is essential for RHDV replication and plays a key role in the formation of RHDV RCs. The mechanisms by which NCL promotes viral replicase assembly reported here shed light on viral RC biogenesis and may inform antiviral therapies. Author summaryRabbit hemorrhagic disease virus (RHDV) is the causative agent of highly contagious and lethal hemorrhagic disease in the European rabbit, but the host factors involved in RHDV replication remain poorly understood. In the present study, we isolated RHDV replication complex (RC) for the first time and identified its main components. We found that nucleolin (NCL) plays a key role in the formation of the RHDV RC. NCL not only interacts with viral replicase (RdRp), it also specifically binds to other important host factors. In addition, we proved that NCL is necessary for RHDV replication because the level of RHDV replication is significantly affected by knocking down the NCL gene in cells. Together, our data suggest that RHDV completes its replication by hijacking NCL to recruit other viral proteins and host factors, thereby assembling the RC of RHDV.

microbiology↗

bioRxiv2020

Hypoxia Depletes Contaminating CD45+ Hematopoietic Cells from Bone Marrow Stromal Cell (BMSC) Cultures: Methods for BMSC Culture Purification

Culture expanded bone marrow stromal cells (BMSCs) are easily isolated, can be grown rapidly en masse, and contain both skeletal stem cells (SSCs) and multipotent mesenchymal progenitors (MMPs). Despite this functional heterogeneity, BMSC cultures continue to be utilized for many applications due to the lack of definitive and universally accepted markers to prospectively identify and purify SSCs. Isolation of BMSCs is widely based on their adherence to tissue culture plastic; however, this method poses unique challenges when working with murine models. In particular, hematopoietic cell contamination is a significant impediment during the isolation or murine BMSCs. Several strategies to reduce hematopoietic contamination have been developed with varying levels of success. In this study, we found that up to 60% of cells isolated in standard BMSC cultures expressed the hematopoietic marker CD45. Remarkably, when cultured at a physiological oxygen tension of 1% O2, there was a 10-fold reduction in hematopoietic cells associated with a concomitant increase in PDGFR+ expressing stromal cells. This finding was due, in part, to a differential response of the two populations to low oxygen tension, or hypoxia. Specifically, in standard tissue culture conditions of 21% O2, CD45+ hematopoietic cells showed increased proliferation coupled with no observable changes in cell death when compared to their counterparts grown at 1% O2. In contrast, PDGFR+ stromal cells responded to hypoxia by increasing proliferation and exhibiting a 10-fold decrease in cell death. In summary, we describe a simple and reliable method exploiting the divergent biological response of hematopoietic and stromal cells to hypoxia to significantly increase the PDGFR+ stromal cell population in murine BMSC cultures.

cell biology↗

bioRxiv2020

Robust gene expression-based classification of cancers without normalization

Binary classification using gene expression data is commonly used to stratify cancers into molecular subgroups that may have distinct prognoses and therapeutic options. A limitation of many such methods is the requirement for comparable training and testing data sets. Here, we describe and demonstrate a self-training implementation of probability ratio-based classification prediction score (PRPS-ST) that facilitates the porting of existing classification models to other gene expression data sets. We demonstrate its robustness through application to two binary classification problems in diffuse large B-cell lymphoma using a diverse variety of gene expression data types and normalization methods.

bioinformatics↗

bioRxiv2020

IDseq - An Open Source Cloud-based Pipeline and Analysis Service for Metagenomic Pathogen Detection and Monitoring

BackgroundMetagenomic next generation sequencing (mNGS) has enabled the rapid, unbiased detection and identification of microbes without pathogen-specific reagents, culturing, or a priori knowledge of the microbial landscape. mNGS data analysis requires a series of computationally intensive processing steps to accurately determine the microbial composition of a sample. Existing mNGS data analysis tools typically require bioinformatics expertise and access to local server-class hardware resources. For many research laboratories, this presents an obstacle, especially in resource limited environments. FindingsWe present IDseq, an open source cloud-based metagenomics pipeline and service for global pathogen detection and monitoring (https://idseq.net). The IDseq Portal accepts raw mNGS data, performs host and quality filtration steps, then executes an assembly-based alignment pipeline which results in the assignment of reads and contigs to taxonomic categories. The taxonomic relative abundances are reported and visualized in an easy-to-use web application to facilitate data interpretation and hypothesis generation. Furthermore, IDseq supports environmental background model generation and automatic internal spike-in control recognition, providing statistics which are critical for data interpretation. IDseq was designed with the specific intent of detecting novel pathogens. Here, we benchmark novel virus detection capability using both synthetically evolved viral sequences, and real-world samples, including IDseq analysis of a nasopharyngeal swab sample acquired and processed locally in Cambodia from a tourist from Wuhan, China, infected with the recently emergent SARS-CoV-2. ConclusionThe IDseq Portal reduces the barrier to entry for mNGS data analysis and enables bench scientists, clinicians, and bioinformaticians to gain insight from mNGS datasets for both known and novel pathogens.

bioinformatics↗

bioRxiv2020

Risperidone-induced changes in DNA methylation from peripheral blood in first-episode schizophrenia parallel neuroimaging and cognitive phenotype

Today, second generation anti-psychotics such as clozapine and risperidone are the favored treatment for schizophrenia. Yet, the absence of relevant biomarkers that can decode their neurobiological effect shackles our ability to accurately predict and track response to treatment. While researchers have investigated DNA methylation as a biomarker for schizophrenia risk, none have performed a systematic analysis of the effect of antipsychotics upon DNA methylation. We hypothesize that disease-related methylation changes occur before treatment, and that acute antipsychotic treatment may affect DNA methylation. We designed a longitudinal DNA methylation study to estimate risperidones effect on DNA methylation and how changes in DNA methylation might influence risperidones therapeutic effect on behavioral and neuroimaging phenotypes. Thirty-eight patients with first-episode drug-naive schizophrenia (FES) and 38 demographically-matched individuals (healthy controls) participated. We identified brain related pathways enriched in 8,204 FES-associated methylation sites. Risperidone administration altered methylation in 6,143 CpG DNA sites. Post-treatment FES associated with methylation in 6760 CpG sites. Majority of the DNA methylation changes were treatment effect in the overall CpG sites, the FES associated CpG sites, and risperidone associated CpG sites, except for the post-treatment FES associated CpG sites. There were 590 DNA methylation cites normalized by risperidone treatment. The methylation changes of these 590 CpG sites were related to alterations in symptom severity, spontaneous neurophysiological activity, and cognitive function. To our knowledge, this is the first longitudinal methylation study of drug treatment effect and side effect in psychiatric disorders to include parallel studies of neuroimaging and cognitive phenotypes. We identified FES-associated CpG sites not confounded by drug treatment as potential SCZ biomarkers. The normalization effect of risperidone monotherapy suggests that DNA methylation changes may serve as a predictive biomarker for treatment effect. The constructed methylation-phenotype network revealed a relationship between methylation and a wide range of biological and psychological variables.

pharmacology and toxicology↗

bioRxiv2020

Swine Promyelocytic Leukemia Isoform II Inhibits Pseudorabies Virus Infection by Suppressing Viral Gene Transcription in PML-NBs

Promyelocytic leukaemia nuclear bodies (PML-NBs) possess an important intrinsic antiviral activity against -herpesvirus infection. PML is the structural backbone of NBs, comprising different isoforms. However, the contribution of each isoform to -herpesvirus restriction is not well understood. Here, we report the role of PML-NBs and swine PML (sPML) isoforms in pseudorabies virus (PRV) infection in its natural host swine cells. We found that sPML-NBs exhibit an anti-PRV activity in the context of increasing the expression level of endogenous sPML. Of four sPML isoforms cloned and examined, only isoform sPML-II/IIa, not sPML-I and IVa, expressed in a sPML knockout cells inhibits PRV infection. Both the unique 7b region of sPML-II and sumoylation-dependent normal formation of PML-NBs are required. 7b possesses a transcriptional repression activity and suppresses viral gene transcription during PRV infection with the cysteine residue 589 and 599 being critically involved. We conclude that sPML-NBs inhibit PRV infection by repressing viral gene transcription through the 7b region of sPML-II. IMPORTANCEPML-NBs are nuclear sites that mediate the antiviral restriction of -herpesvirus gene expression and replication. However, the contrition of each PML isoform to this activity of PML-NBs is not well characterized. Using PRV and its natural host swine cells as a system, we have discovered that the unique C-terminus of sPML isoform II is required for PML-NBs to inhibit PRV infection by directly engaging in repression of viral gene transcription. Our study not only confirms in swine cells that PML-NBs have an anti-viral function, but also presents a mechanism to suggest that PML-NBs inhibit viral infection in an isoform specific manner.

immunology↗

bioRxiv2020

The genomic landscapes of individual melanocytes from human skin

Every cell in the human body has a unique set of somatic mutations, yet it remains difficult to comprehensively genotype an individual cell. Here, we developed solutions to overcome this obstacle in the context of normal human skin, thus offering the first glimpse into the genomic landscapes of individual melanocytes from human skin. We comprehensively genotyped 133 melanocytes from 19 sites across 6 donors. As expected, sun-shielded melanocytes had fewer mutations than sun-exposed melanocytes. However, within sun-exposed sites, melanocytes on chronically sun-exposed skin (e.g. the face) displayed a lower mutation burden than melanocytes on intermittently sun-exposed skin (e.g. the back). Melanocytes located adjacent to a skin cancer had higher mutation burdens than melanocytes from donors without skin cancer, implying that the mutation burden of normal skin can be harnessed to measure cumulative sun damage and skin cancer risk. Moreover, melanocytes from healthy skin commonly harbor pathogenic mutations, likely explaining the origins of the melanomas that arise in the absence of a pre-existing nevus. Phylogenetic analyses identified groups of related melanocytes, suggesting that melanocytes spread throughout skin as fields of clonally related cells, invisible to the naked eye. Overall, our study offers an unprecedented view into the genomic landscapes of individual melanocytes, revealing key insights into the causes and origins of melanoma.

genomics↗

bioRxiv2020

Anti-cancer Drug Synergy Prediction in Understudied Tissues using Transfer Learning

MotivationExploring an exponentially increasing yet more promising space, high-throughput combinatorial drug screening has advantages in identifying cancer treatment options with higher efficacy without degradation in terms of safety. A key challenge is that accumulated number of observations in in-vitro drug responses varies greatly among different cancer types, where some tissues (such as bone and prostate) are understudied than the others. Thus, we aim to develop a drug synergy prediction model for understudied data-poor tissues as overcoming data scarcity problem. ResultsWe collected a comprehensive set of genetic, molecular, phenotypic features for cancer cell lines from six different databases. We developed a drug synergy prediction model based on deep neural networks to integrate multi-modal input and utilize transfer learning from data-rich tissues to data-poor tissues. We showed improved accuracy in predicting drug synergy in understudied tissues without enough drug combination screening data nor after-treatment transcriptome. Our synergy prediction model can be used to rank synergistic drug combinations in understudied tissues and thus help prioritizing future in-vitro experiments. Availability and ImplementationOur algorithm will be publicly available via https://github.com/yejinjkim/drug-synergy-prediction

bioinformatics↗

bioRxiv2020

Bcl6 Preserves the Suppressive Function of Regulatory T Cells during Tumorigenesis

During tumorigenesis, tumor infiltrating regulatory T (Treg) cells restrict the function of effector T cells in tumor microenvironment and thereby promoting tumor growth. The anti-tumor activity of effector T cells can be therapeutically unleashed, and is now being exploited for the treatment of various types of human cancers. However, the immune suppressive function of Treg cells remains a major hurdle to broader effectiveness of tumor immunotherapy. In this article, we reported that the deletion of Bcl6 specifically in Treg cells led to stunted tumor growth, which was caused by impaired Treg cell responses. Notably, Bcl6 is essential in maintaining the lineage stability of Treg cells in tumor microenvironment. Meanwhile, we found that the absence of follicular regulatory T (Tfr) cells, which is a result of Bcl6 deletion in Foxp3+ cells, was dispensable for tumor control. Importantly, the increased Bcl6 expression in Treg cells is associated with poor prognosis of human colorectal cancer and lymph node metastasis of skin melanoma. Furthermore, Bcl6 deletion in Treg cells exhibits synergistic effects with immune checkpoint blockade therapy. Collectively, these results indicate that Bcl6 actively participates in regulating Treg cell immune responses during tumorigenesis and can be exploited as a therapeutic target of anti-tumor immunity.

immunology↗

bioRxiv2020

The npBAF to nBAF Chromatin Switch Regulates Cell Cycle Exit in the Developing Mammalian Cortex

Nervous system development is orchestrated by tightly-regulated progenitor cell divisions, followed by differentiation at precise but varying times across different regions. As progenitors exit the cell cycle, they initiate a subunit switch of the mSWI/SNF or npBAF complex to generate neuron-specific nBAF complexes. These chromatin regulatory complexes play dosage-sensitive roles in neural development and are frequently mutated in neurodevelopmental disorders. Here we manipulated the timing of BAF subunit exchange in the developing mouse brain and find that deletion of the npBAF subunit BAF53a blocks progenitor proliferation, leading to impaired neurogenesis. We show that npBAF complexes regulate cell cycle progression by antagonizing Polycomb complexes to promote chromatin accessibility at cell cycle and NPC identity genes. Replacement of the actin-related protein, Actl6a (BAF53a) by the neuron-specific actin-related protein, Actl6b (BAF53b), but not other regulators of proliferation, rescues progenitors by promoting neuronal differentiation. We propose that the function of the npBAF to nBAF chromatin switch is to control progenitor cell cycle exit and promote synchronous neural differentiation.

developmental biology↗

bioRxiv2020

The regulation of mammalian maternal-to-embryonic transition by Eukaryotic translation initiation factor 4E

Genetic and inhibitor studies show expression of eukaryotic translation initiation factor 4E (eIF4E) was required for the successful maternal-to-embryonic transition of mouse embryos. eIF4E was in both gametes and in the cytoplasm and pro-nuclei soon after fertilization, and at each stage of early development. Knockout (Eif4e-/-) by PiggyBac (PB) [Act-RFP] transposition caused peri-implantation embryonic lethality due to the failure of embryos to form a pluripotent epiblast. Maternal stores of eIF4E supported development up to the 2-4-cell stage after which new expression occurred from both alleles. Inhibition of the maternally acquired stores of eIF4E (4EGI-1 inhibitor) resulted in a developmental block at the 2-4-cell stage. 4E-BP1 is a hypophosphorylation-dependent negative regulator of eIF4E. mTOR activity was required for 4E-BP1 phosphorylation and inhibiting 4EGI-1 retarded embryo development. eIF4E expression and activity is regulated at key embryonic transitions in the mammalian embryo and is essential for successful transition to embryonic control of development. Significance StatementeIF4E is recognized as the rate-limiting factor for CAP-dependent translation. This work used a combination of a gene knockout model, selective pharmacological inhibition and expression analyses to investigate the expression and function of Eif4e in the early mouse embryo. It provides compelling evidence for the essential role of Eif4E in the normal processes of early mammalian embryo development, including the formation of the pluripotent epiblast and the maternal-embryonic transition. The unexpected evidence for a growth deficit in mice hypomorphic for Eif4e will be a key area of future investigation. It also provides for the first time a powerful demonstration of the utility of the PB [Act-RFP] transposon mouse model for analyzing the molecular regulation of early mammalian embryo development.

developmental biology↗

bioRxiv2019

Dihydroartemisinin-loaded Magnetic Nanoparticles for Enhanced Chemodynamic Therapy

Recently, chemodynamic therapy (CDT) has represented a new approach for cancer treatment with low toxicity and side effects. Nonetheless, it has been a challenge to improve the therapeutic effect through increasing the amount of reactive oxygen species (ROS). Herein, we increased the amount of ROS agents in the Fenton-like reaction by loading dihydroartemisinin (DHA) which was an artemisinin (ART) derivative containing peroxide groups, into magnetic nanoparticles (MNP), thereby improving the therapeutic effect of CDT. Blank MNP were almost non-cytotoxic, whereas three MNP loading ART-based drugs, MNP-ART, MNP-DHA, and MNP-artesunate (MNP-AS), all showed significant killing effect on breast cancer cells (MCF-7 cells), in which MNP-DHA were the most potent. Whats more, the MNP-DHA showed high toxicity to drug-resistant breast cancer cells (MCF-7/ADR cells), demonstrating its ability to overcome multidrug resistance (MDR). The study revealed that MNP could produce ferrous ions under the acidic condition of tumor microenvironment, which catalyzed DHA to produce large amounts of ROS, leading to cell death. Further experiments also showed that the MNP-DHA had significant inhibitory effect on another two aggressive breast cancer cell lines (MDA-MB-231 and MDA-MB-453 cells), which indicated that the great potential of MNP-DHA for the treatment of intractable breast cancers.

bioengineering↗

bioRxiv2019

Downregulation of GPR183 on Infection Restricts the Early Infection and Intracellular Survival of Mycobacterium tuberculosis in Macrophage

GPR183/EBI2 is a key chemotactic receptor for the positioning of B cells in lymphoid organs, and also for the migration of T cells and other immune cells. Here, we demonstrate that the downregulation of GPR183 in macrophage induced during Mtb infection restrains the bacterial early infection and intracellular survival. Overexpression of GPR183 or stimulation with its natural ligand favors Mtb survival in macrophage, while treatment with its antagonist represses both Mtb early infection and intracellular survival. With mutational analysis, we find that substitution of Asp-73, Arg-83, Tyr-112, Tyr-256 abolished the promotive effect of GPR183 on Mtb early infection and survival in macrophage. In conclusion, we demonstrated that beside the known role of chemotaxis receptor, GPR183 also functions directly in the interaction between macrophage and Mtb in a cell-autonomous way.

microbiology↗

bioRxiv2019

Rapid disruption of the cortical microcirculation after mild traumatic brain injury

Traumatic brain injury (TBI) is a major source of cognitive deficits affecting millions annually. The bulk of human injuries are mild, causing little or no macroscopic damage to neural tissue, yet can still lead to long-term neuropathology manifesting months or years later. Although the cellular stressors that ultimately lead to chronic pathology are poorly defined, one notable candidate is metabolic stress due to reduced cerebral blood flow (CBF), which is common to many forms of TBI. Here we used high-resolution in vivo intracranial imaging in a rodent injury model to characterize deficits in the cortical microcirculation during both acute and chronic phases after mild TBI. We found that CBF dropped precipitously during immediate post-injury periods, decreasing to less than half of baseline levels within minutes and remaining suppressed for 1.5-2 hours. Repeated time-lapse imaging of the cortical microvasculature revealed further striking flow deficits in the capillary network, where 18% of vessels were completely occluded for extended periods after injury, and an additional >50% showed substantial stoppages. Decreased CBF was paralleled by extensive vasoconstriction that is likely to contribute to loss of flow. Our data indicate a major role for vascular dysfunction in even mild forms of TBI, and suggest that acute post-injury periods may be key therapeutic windows for interventions that restore flow and mitigate metabolic stress.

neuroscience↗

bioRxiv2019

Neutrophil-mediated dynamic capillary stalls in ischemic penumbra: persistent traffic jams after reperfusion contribute to injury

Ever since the introduction of thrombolysis and the subsequent expansion of endovascular treatments for acute ischemic stroke, it remains to be identified why the actual outcomes are less favorable despite recanalization. Here, by high spatio-temporal resolution imaging of capillary circulation in mice, we introduce the pathological phenomenon of dynamic flow stalls in cerebral capillaries, occurring persistently in the salvageable penumbra after recanalization. These stalls, which are distinct from permanent cellular plugs that can lead to no-flow, were temporarily and repetitively occurring in the capillary network, impairing the overall circulation like small focal traffic jams. In vivo microscopy in the ischemic penumbra revealed leukocytes traveling through capillary lumen or getting stuck, while red blood cell flow was being disturbed in the neighboring segments, within 3 hours after stroke onset. Stall dynamics could be modulated, by injection of an anti-Ly6G antibody specifically targeting neutrophils. By decreasing the number and duration of stalls, we were able to improve the blood flow in the penumbra within 2-24 hours after reperfusion, increase capillary oxygenation, decrease cellular damage and improve functional outcome. Thereby the dynamic microcirculatory stall phenomenon contributes to the ongoing penumbral injury and is a potential hyperacute stage mechanism adding on previous observations of detrimental effects of activated neutrophils in ischemic stroke.\n\nSignificanceThis work provides in vivo evidence that, even in perfused capillaries, abnormal capillary flow patterns in the form of dynamic stalls can contribute to ongoing tissue injury in the salvageable penumbra in very early hours of cerebral ischemia. These events resembling micro traffic jams in a complex road network, are mediated by passage of neutrophils through the microcirculation and persist despite recanalization of the occluded artery.

neuroscience↗

bioRxiv2019

The consequences of mixed-species malaria parasite co-infections in mice and mosquitoes for disease severity, parasite fitness, and transmission success

The distributions of human malaria parasite species overlap in most malarious regions of the world, and co-infections involving two or more malaria parasite species are common. Little is known about the consequences of interactions between species during co-infection for disease severity and parasite transmission success. Anti-malarial interventions can have disproportionate effects on malaria parasite species, and may locally differentially reduce the number of species in circulation. Thus, it is important to have a clearer understanding of how the interactions between species affect disease and transmission dynamics. Controlled competition experiments using human malaria parasites are impossible, and thus we assessed the consequences of mixed-species infections on parasite fitness, disease severity, and transmission success using the rodent malaria parasite species Plasmodium chabaudi, P. yoelii yoelii, and P. vinckei lentum. We compared the fitness of individual species within single species and co-infections in mice. We also assessed the disease severity of single versus mixed infections in mice by measuring mortality rates, anaemia, and weight loss. Finally, we compared the transmission success of parasites in single or mixed species infections by quantifying oocyst development in Anopheles stephensi mosquitoes. We found that co-infections of P. yoelii with either P. vinckei or P. chabaudi led to a dramatic increase in infection virulence, with 100% mortality observed in mixed species infections, compared to no mortality for P. yoelii and P. vinckei single infections, and 40% mortality for P. chabaudi single infections. The increased mortality in the mixed infections was associated with an inability to clear parasitaemia, with the non-P. yoelii parasite species persisting at higher parasite densities than in single infections. P. yoelii growth was suppressed in all mixed infections compared to single infections. Transmissibility of P. vinckei and P. chabaudi to mosquitoes was also reduced in the presence of P. yoelii in co-infections compared to single infections. The increased virulence of co-infections containing P. yoelii (reticulocyte restricted) and P. chabaudi or P. vinckei (predominantly normocyte restricted) may be due to parasite cell tropism and/or immune modulation of the host. We explain the reduction in transmission success of species in co-infections in terms of inter-species gamete incompatibility.

microbiology↗

bioRxiv2019

Partial loss of CFIm25 causes aberrant alternative polyadenylation and learning deficits

We previously showed that NUDT21-spanning copy-number variations (CNVs) are associated with intellectual disability (Gennarino et al., 2015). However, the patients CNVs also included other genes. To determine if reduced NUDT21 function alone can cause disease, we generated Nudt21+/- mice to mimic the human state of decreased expression. We found that although these mice have 50% reduced Nudt21 mRNA, they only have 30% less of its cognate protein, CFIm25. Despite this partial protein-level compensation, the Nudt21+/- mice have learning deficits and cortical hyperexcitability. Further, to determine the molecular mechanism driving neural dysfunction, we partially inhibited NUDT21 in human stem cell-derived neurons to reduce CFIm25 by 30%. This reduction in CFIm25 was sufficient to induce misregulated alternative polyadenylation (APA) and protein levels in hundreds of genes, dozens of which cause intellectual disability when mutated. Altogether, these results indicate that disruption of NUDT21-regulated APA events in the brain can cause intellectual disability.

genomics↗