Biology subjects

Chen, Q.

Publications and source records attributed to Chen, Q..

At least 307 records · Page 17Linked to original sources

bioRxiv2022

Human iPSC-derived neuron of 16p11.2 deletion reveals haplotype-specific expression of MAPK3 and its contribution to variable NDD phenotypes

Recurrent proximal 16p11.2 deletion (16p11.2del) is risk factor of diverse neurodevelopmental disorders (NDDs) with variable penetrance. Although previous human induced pluripotent stem cell (hiPSC) models of 16p11.2del confirmed disrupted neuron development, it is not known which gene(s) at this interval are mainly responsible for the abnormal cellular phenotypes and how the NDD penetrance is regulated. After haplotype phasing of 16p11.2 region, we generated hiPSCs for two 16p11.2del families with distinct residual haplotypes and variable NDD phenotypes. We also differentiated the hiPSCs to cortical neural cells and demonstrated MAPK3 as a driver signal of 16p11.2 region contributing to the dysfunctions in multiple pathways related to neuron development, which leads to altered morphological or electrophysiological properties in neuron cells. Furthermore, residual haplotype-specific MAPK3 expression was identified in 16p11.2del neuron cells, associating MAPK3 down-expression with the minor allele of the residual haplotype. Ten SNPs of the residual haplotype are mapped as enhancer SNPs (enSNPs) of MAPK3, eight enSNPs were functionally validated by luciferase assays, implying enSNPs contribute to residual haplotype-specific MAPK3 expression via cis-regulation. Finally, the analyses of three different patient cohorts showed that the residual haplotype of 16p11.2del is associated with variable NDD phenotypes.

genetics↗

bioRxiv2022

Modulating hierarchical learning by high-definition transcranial alternating current stimulation at theta frequency

Considerable evidence highlights the dorsolateral prefrontal cortex (DLPFC) as a key region for hierarchical (i.e., multi-level) learning. In a previous electroencephalography (EEG) study we found that the low-level prediction errors (PEs) were encoded by frontal theta oscillations (4-7Hz), centered on right DLPFC (rDLPFC). However, the causal relationship between frontal theta oscillations and hierarchical learning remains poorly understood. To investigate this question, in the current study, participants received theta (6Hz) and sham high-definition transcranial alternating current stimulation (HD-tACS) over the rDLPFC, while performing the probabilistic reversal learning task. Behaviorally, theta tACS induced a significant reduction in accuracy for the stable environment, but not for the volatile environment, relative to the sham condition. Computationally, we implemented a combination of a hierarchical Bayesian learning and a decision model. Theta tACS induced a significant increase in low-level (i.e., probability-level) learning rate and uncertainty of low-level estimation relative to sham condition. Instead, the temperature parameter of the decision model, which represents (inverse) decision noise, was not significantly altered due to theta stimulation. These results indicate that theta frequency may modulate the (low-level) learning rate. Furthermore, environmental features (e.g., its stability) may determine whether learning is optimized as a result.

neuroscience↗

bioRxiv2022

Evidence for the digital programming of cellular differentiation: characterization of binary switches in lineage-determining transcription factors

Previous studies of the murine Ly49 and human KIR gene clusters have revealed a role for bidirectional promoters in the control of variegated gene expression. Whether or not competing promoters control other instances of cell fate determination remains an outstanding question. Although divergent transcripts within 300 bp are found in ~6% of human genes, an analysis of human transcription factor (TF) genes (1640) revealed that 33% possess stable divergent transcripts with a transcription start site (TSS) less than 300 bp upstream, with many separated by less than 30 bp, indicating an enrichment for potential binary switches in TFs. We have performed a detailed examination of putative bidirectional promoter switches in three lineage-determining TF genes: AHR, GATA3, and ROR{gamma}T. These genes also contain additional pairs of opposing promoters that would prevent simultaneous transcription of sense and antisense, and thus may represent simple on/off switches rather than probabilistic switches. In situ RNA hybridization of human tissues revealed mutually exclusive expression of sense versus antisense transcription, indicating switching between stable sense or antisense transcriptional states. Single-cell RNAseq confirmed the separate sense/antisense states, and revealed the identity of cells with active switch elements. Differential gene expression analysis of cells with antisense switch transcripts revealed an enrichment for genes found in immature/stem cells and a lack of genes associated with terminally differentiated cells. Taken together, these data indicate that there is a digital component to the differentiation program mediated by binary promoter switches in lineage-determining transcription factors.

developmental biology↗

bioRxiv2022

Red blood cell dynamics in extravascular biological tissues modelled as canonical disordered porous media

The dynamics of blood flow in the smallest vessels and passages of the human body, where the cellular character of blood becomes prominent, plays a dominant role in the transport and exchange of solutes. Recent studies have revealed that the micro-haemodynamics of a vascular network is underpinned by its interconnected structure, and certain structural alterations such as capillary dilation and blockage can substantially change blood flow patterns. However, for extravascular media with disordered microstructure (e.g., the porous intervillous space in the placenta), it remains unclear how the mediums structure affects the haemodynamics. Here, we simulate cellular blood flow in simple models of canonical porous media representative of extravascular biological tissue, with corroborative microfluidic experiments performed for validation purposes. For the media considered here, we observe three main effects: first, the relative apparent viscosity of blood increases with the structural disorder of the medium; second, the presence of red blood cells (RBCs) dynamically alters the flow distribution in the medium; third, increased structural disorder of the medium can promote a more homogeneous distribution of RBCs. Our findings contribute to a better understanding of the cellscale haemodynamics that mediates the relationship linking the function of certain biological tissues to their microstructure.

biophysics↗

bioRxiv2022

The columnar structure of human telomeric chromatin suggests mechanisms for telomere maintenance

Telomeres, the ends of eukaryotic chromosomes, play pivotal roles in ageing and cancer and are targets of DNA damage and response. However, little is known about the structure and organization of telomeric chromatin at the molecular level. We used electron microscopy and single-molecule magnetic tweezers to characterize well-defined telomeric chromatin fibers of kilobasepair length. The cryo-EM structure of the compact telomeric tetranucleosome revealed a novel columnar folding, unusually short nucleosome repeat length of [~]132bp and the role of the histone N-terminal tails in stabilizing this structure. This is the first near-high resolution structure of chromatin with a native DNA sequence. The columnar structure exposes the DNA, making them susceptible to DNA damage. The telomeric tetranucleosome also exists in an alternative well-defined state, with one nucleosome open, accessible to protein factors. This suggests that protein factors, which plays a role in maintaining telomeres, can bind to telomeric chromatin in its compact heterochromatic form. The features of the telomeric chromatin structure reveals important insights of significant relevance for telomere function in vivo that provides information on mechanisms of nucleosome recognition by chromatin factors

molecular biology↗

bioRxiv2022

Neural plate progenitors give rise to both anterior and posterior pituitary cells

The pituitary is the master neuroendocrine gland, which regulates body homeostasis. It consists of the anterior pituitary/adenohypophysis (AH), which harbors hormones producing cells and the posterior pituitary/neurohypophysis (NH), which relays the direct passage of hormones from the brain to the periphery. It is widely accepted that the AH originates from the oral ectoderm (Rathkes pouch) whereas the neural ectoderm contributes to the NH. Using single cell transcriptomics of the zebrafish pituitary we characterized cyp26b1-positive pituicyte of the NH and prop1-positive adenohypophyseal progenitors. We found that these cell types expressed common markers implying lineage relatedness. Genetic tracing revealed that in contrast to the prevailing dogma, neural plate precursors of both zebrafish (her4.3+) and mouse (Sox1+) contribute to both the neurohypophyseal and adenohypophyseal cells. We further show that pituicytes and prop1+ progenitors reside in close anatomical proximity and pituicyte-derived RA-degrading enzyme Cyp26b1 fine-tunes differentiation of prop1+ progenitors into hormone-producing cells. These results challenge the notion that AH cells are exclusively derived from non-neural ectoderm and demonstrate that a cross-talk between neuro- and adeno-hypophyseal cells fine-tunes the development of pituitary neuroendocrine cells.

developmental biology↗

bioRxiv2022

Radiation therapy promotes unsaturated fatty acids to maintain survival of glioblastoma

PurposeRadiation therapy (RT) is essential for the management of glioblastoma (GBM). However, GBM frequently relapses within the irradiated margins, thus suggesting that RT might stimulate mechanisms of resistance that limits its efficacy. GBM is recognized for its metabolic plasticity, but whether RT-induced resistance relies on metabolic adaptation remains unclear. MethodsWe analyzed in vitro extracellular flux and profiled targeted metabolites as well as free fatty acids in two syngenic models of glioblastomas 24hrs post RT. Metabolic adaptation of irradiated GBM were confirmed in vivo by mass spectrometry imaging. The role of the fatty acid synthase (FASN) in RT-induced lipid metabolites was assessed by genetical and pharmacological inhibition of Fasn in irradiated GBM cells. The impact of FASN-mediated lipids on endoplasmic reticulum (ER) stress and apoptosis of irradiated GBM cells were performed by transmission electronic microscopy, western blot, clonogenic assay and flow cytometry. Inhibition of FASN combined with focal RT was assessed in mice. Analysis of a public dataset of GBM patients was performed to correlate preclinical findings. ResultsHere, we show in vitro and in vivo that irradiated GBM tumors switch their metabolic program to accumulate lipids, especially unsaturated fatty acids. This resulted in an increase formation of lipid droplets to prevent ER stress. We uncovered that FASN is critical for lipid accumulation of irradiated GBM and demonstrate that genetic suppression and pharmacological inhibition of FASN lead to mitochondrial dysfunction and apoptosis. Combination of FASN inhibition with focal RT improved the median survival of GBM-bearing mice. Supporting the translational value of these findings, retrospective analysis of the GLASS consortium dataset of matched GBM patients revealed an enrichment in lipid metabolism signature in recurrent GBM compared to primary. ConclusionsOverall, these results demonstrate that RT drives GBM resistance by generating a lipogenic environment permissive to GBM survival. Targeting lipid metabolism might be required to develop more effective anti-GBM strategies.

cell biology↗

bioRxiv2022

Peritoneal autoantibody landscape in endometriosis

Women with endometriosis have a profound association with autoimmunity. An excess of autoantigens in the peritoneal cavity resulting from retrograde menstruation could lead to inflammation and pathologic autoimmunity. Using a native-conformation protein array, proteome-wide analysis of autoantibodies (AAbs) against 1623 proteins were profiled in peritoneal fluids (PF) of 25 women with endometriosis and 25 endometriosis-negative women. 46% of endometriotic women have five or more AAbs. Diverse cognate autoantigens were identified and corresponding AAbs against proteins involved in implantation, B-cell activation/development, and aberrant migration and mitogenicity. AAbs recognizing tumour suppressor protein p53 were the most frequent at 35% and were targeted against native and citrullinated p53 forms. Further, unsupervised hierarchical clustering and integrative pathway analysis, we observed clusters of endometriosis-associated infertile women with 60% positive for two or more AAbs which are involved in PDGF, TGF-{beta}, RAC1/PAK1/p38/MMP2 signaling, LAT2/NTAL/LAB-mediated calcium mobilisation and integrin-mediated cell adhesion. Together, our data identifies peritoneal autoimmunity in a significant subset of women with endometriosis, with diverse impact on infertility and disease pathophysiology.

immunology↗

bioRxiv2022

Selective detection of m6A derived from mRNA using the Phospho-tag m6A assay

N6-methyladenosine (m6A) is a modified nucleotide found in mRNA, ribosome RNA (rRNA) and small nuclear RNA (snRNA). m6A in mRNA has important roles in regulating mRNA stability, splicing, and other processes. Numerous studies have described m6A as a dynamic modification using mass spectrometry-based quantification of m6A in mRNA samples prepared from different cellular conditions. However, these results have been questioned based on the finding that the mRNA purification protocols often result in varying levels of rRNA contamination. Additionally, mRNA purification protocols disproportionately enrich for the 3 ends of mRNA, a region that is enriched in m6A. To address these problems, we developed the Phospho-tag m6A assay, a highly efficient method for quantifying m6A specifically from mRNA. In this assay, a series of selective RNase digestion steps is performed, which results in m6A from rRNA and snRNA being liberated as m6A monophosphate, while m6A from mRNA is mostly liberated as m6A nucleoside. m6A levels are normalized to transcript levels, using m7G monophosphate liberated by yDcpS decapping enzyme as a surrogate for mRNA levels. Notably, this approach uses total cellular RNA, rather than purified mRNA, which simplifies the steps for m6A detection and overcomes the 3-end biases associated with mRNA purification. Overall, the Phospho-tag m6A provides a simple and efficient method for quantification of mRNA-derived m6A from total RNA samples.

molecular biology↗

bioRxiv2022

Site-specific validation and quantification of RNA 2'-O-methylation by qPCR with RNase H

RNA 2'-O-methylation, one of the most abundant modifications on RNAs, is crucial for diverse intracellular biological processes. In the past several years, several high-throughput screening methods have been developed, resulting in the identification of thousands of new 2'-O-methylation (Nm) sites. However, due to the high variability in these high-throughput methods, accurate and rapid low-throughput validation assays are needed to confirm and quantify the 2'-O-methylation status of screened candidate sites. Although several low-throughput Nm site detection methods have been reported, precise location and quantitative assays are still challenging to achieve. Based on the characteristic that RNase H would be inhibited by Nm modification, we developed Nm-VAQ (site-specific 2'-O-methylation (Nm) Validation and Absolute Quantification resolution). In this study, with multiple tests of reagents and conditions, Nm-VAQ was established with a chimera probe of RNA/DNA, RNase H site-specific cleavage, and qRT-PCR, which demonstrated precise absolute quantification of modification ratios and methylation copy numbers. With the help of Nm-VAQ, the 2'-O-methylation status of 5 sites in rRNA was evaluated.

biochemistry↗

bioRxiv2022

Protein Lactylation and Metabolic Regulation of the Zoonotic Parasite Toxoplasma gondii

The biology of Toxoplasma gondii, the causative pathogen of one of the most wide-spread parasitic diseases remains poorly understood. Lactate, which is derived from glucose metabolic pathways, is considered to be not only an energy source in a variety of organisms including Toxoplasma gondii, but also a regulatory molecule that participates in gene activation and protein functioning. Lysine lactylation is a type of posttranslational modifications (PTMs) that was recently associated with chromatin remodeling, but lysine lactylation of histone and non-histone proteins has not yet been studied in T. gondii. To examine the prevalence and function of lactylation in T. gondii parasites, we mapped the lactylome of proliferating tachyzoite cells and found 1964 lactylation sites on 955 proteins in the T. gondii RH strain. The lactylated proteins were distributed in multiple subcellular compartments and were closely related to a wide variety of biological processes, including mRNA splicing, glycolysis, aminoacyl-tRNA biosynthesis, RNA transport, and multiple signaling pathways. We also performed chromatin immunoprecipitation sequencing (ChIP-seq) analysis with a lactylation specific antibody, the results revealed that histone H4K12la and H3K14la were enriched in the promoter and exon regions of Toxoplasma gondii genes associated with microtubule-based movement and cell invasion. We further confirmed the de-lactylase activity of histone deacetylase TgHDACs 2, 3, and 4, and that treatment with anti-histone acetyltransferase (TgMYST-A) antibodies profoundly reduced protein lactylation in the parasites. This study offers the first dataset of the global lactylation proteome and provides a basis for further dissection of the functional biology of Toxoplasma gondii.

microbiology↗

bioRxiv2022

Membrane stretching activates calcium-permeability of putative fission yeast Pkd2 channel

Pkd2 is the fission yeast homolog of polycystins. This putative ion channel localizes to the plasma membrane. It is required for the expansion of cell volume during interphase growth and cytokinesis, the last step of cell division. However, the channel activity of Pkd2 remains untested. Here, we examined the calcium permeability and mechanosensitivity of Pkd2 through in vitro reconstitution and calcium imaging of the pkd2 mutant cells. Pkd2 was translated and inserted into the lipid bilayer of giant unilamellar vesicles using a cell-free expression system. The reconstituted Pkd2 permeated calcium when the membrane was stretched via hypo-osmotic shock. In vivo, inactivation of Pkd2 through a temperature-sensitive mutation pkd2-B42 reduced the average intracellular calcium level by 34%. Compared to the wild type, the hypomorphic mutation pkd2-81KD reduced the amplitude of hypo-osmotic shock-triggered calcium spikes by 59%. During cytokinesis, mutations of pkd2 reduced by 60% the calcium spikes that accompany the cell separation and the ensuing membrane stretching. We concluded that fission yeast polycystin Pkd2 allows calcium influx when activated by membrane stretching, representing a likely mechanosensitive channel that contributes to the cytokinetic calcium spikes.

cell biology↗

bioRxiv2022

A Standardized Ontology for Naming tRNA-derived RNAs Based on Molecular Origin

Small RNAs processed from transfer RNA are recognized to have regulatory functions distinct from protein synthesis. This rapidly advancing field has led to a constellation of transcript nomenclatures. Building upon the accepted tRNA naming system and linking tRNA-derived small RNAs to their molecular sources, we propose an improved nomenclature. Facilitated by the tDRnamer system, it will promote inter-study comparisons leveraging a biologically-rooted nomenclature for this emerging class of intriguing regulators.

bioinformatics↗

bioRxiv2022

Reconstruction of the cell pseudo-space from single-cell RNA sequencing data with scSpace

Tissues are highly complicated with spatial heterogeneity in gene expression. However, the cutting-edge single-cell RNA-seq technology eliminates the spatial information of individual cells, which contributes to the characterization of cell identities. Herein, we propose single-cell spatial position associated co-embeddings (scSpace), an integrative algorithm to distinguish spatially variable cell subclusters by reconstructing cells onto a pseudo-space with spatial transcriptome references (Visium, STARmap, Slide-seq, etc.). We demonstrated that scSpace can define biologically meaningful cell subpopulations neglected by single-cell RNA-seq or spatially resolved transcriptomics. The use of scSpace to uncover the spatial association within single-cell data, reproduced, the hierarchical distribution of cells in the brain cortex and liver lobules, and the regional variation of cells in heart ventricles and the intestinal villus. scSpace identified cell subclusters in intratelencephalic neurons, which were confirmed by their biomarkers. The application of scSpace in melanoma and Covid-19 exhibited a broad prospect in the discovery of spatial therapeutic markers.

bioinformatics↗

bioRxiv2022

Humanization and Expression of IgG and IgM Antibodies in Plants as Potential Diagnostic Reagents for Valley Fever

Monoclonal antibodies (mAbs) are important proteins used in many life science applications, from diagnostics to therapeutics. High demand for mAbs for different applications urges the development of rapid and reliable recombinant production platforms. Plants provide a quick and inexpensive system for producing recombinant mAbs. Moreover, when paired with an established platform for mAb discovery, plants can easily be tailored to produce mAbs of different isotypes against the same target. Here, we demonstrate that a hybridoma-generated mouse mAb against chitinase 1 (CTS1), an antigen from Coccidioides spp., can be biologically engineered for use with serologic diagnostic test kits for coccidioidomycosis (Valley Fever) using plant expression. The original mouse IgG was modified and recombinantly produced in plants as IgG and IgM isotypes with human kappa, gamma, and mu constant regions. The two mAb isotypes produced in plants were shown to maintain target antigen recognition to CTS1 using similar reagents as the Food and Drug Administration (FDA)-approved Valley Fever diagnostic kits. As none of the currently approved kits provide antibody dilution controls, humanization of antibodies that bind to CTS1, a major component of the diagnostic antigen preparation, may provide a solution to the lack of consistently reactive antibody controls for Valley Fever diagnosis. Furthermore, our work provides a foundation for reproducible and consistent production of recombinant mAbs engineered to have a specific isotype for use in diagnostic assays.

immunology↗

bioRxiv2022

High-resolution Ribosome Profiling Reveals Translational Selectivity for Transcripts in Bovine Preimplantation Embryo Development

High resolution ribosome fractionation and low-input ribosome profiling of bovine oocytes and preimplantation embryos has enabled us to define the translational landscapes of early embryo development at an unprecedented level. We analyzed the transcriptome, polysome- and non-polysome-bound RNA profiles of bovine oocytes (GV and MII stage) and early embryos at 2-, 8-cell, morula, and blastocyst stage, and revealed four modes of translational selectivity: i. selective translation of non-abundant mRNAs, ii. active, but modest translation of a selection of highly expressed mRNAs, iii. translationally suppressed abundant to moderately abundant mRNAs, and iv. mRNAs associated specifically with monosomes. A strong translational selection of low abundance mRNAs encoding protein components involved in metabolic pathways and lysosome was found throughout bovine oocyte and preimplantation development. In particular, genes encoding components involved in mitochondrial function were prioritized for translation. Notably, transcripts encoding proteins regulating chromatin modifications selectively translated in oocytes. We found that the translational dynamics largely reflects transcriptional profiles in oocytes and 2-cell embryos, but observed marked shift in translational control in 8-cell embryos associated with the main phase of embryonic genome activation. Subsequently, transcription and translation become better synchronized in morulae and blastocysts. Together, these data reveal a unique spatiotemporal translational regulation that accompanies bovine preimplantation development. Significance StatementTranslational control during preimplantation embryo development is poorly understood, mostly due to the scarcity of samples and the corresponding inability to analyze low quantities of these materials. By developing a low-input method, we have been able to explore the transcriptome, polysome- and non-polysome-bound RNA profiles of bovine oocytes (GV and MII stage) and preimplantation embryos at 2-, 8-cell, morula, and blastocyst stages. We reveal four different modes of translational selectivity, plus novel temporal regulatory mechanisms during early embryo development. The spatiotemporal translation dynamics of bovine oocytes and preimplantation embryos offer an entirely new insight into mammalian embryo development research and new possibilities for improving efficiency of assisted reproduction technologies (ARTs).

developmental biology↗

bioRxiv2022

Microglial Piezo1 senses Aβ fibrils stiffness to restrict Alzheimer's disease

The pathology of Alzheimers disease (AD) is associated with the extracellular amyloid-{beta} (A{beta}) plaques that perturb the mechanical properties of brain tissue. Microglia sense and integrate biochemical cues in their local microenvironment, intimate linking with AD progress. However, neither the microglial mechanosensing pathway nor its impact on AD pathogenesis is well studied. Here, we showed that the mechanosensitive ion channel Piezo1 is increased in microglia upon stiffness stimuli of A{beta} fibrils. The upregulation of Piezo1 in A{beta} plaque-associated microglia was observed in AD mouse models and human patients. Microglia lacking Piezo1 disturbed microglial clustering, phagocytosis, and compaction of A{beta} plaques, resulting in the exacerbation of A{beta} and neurodegenerative pathologies in AD. Conversely, pharmacological activation of Piezo1 ameliorated brain A{beta} burden and cognitive impairment in the 5xFAD mouse. Together, our results reveal Piezo1, as a mechanosensor of A{beta} fibrils stiffness in microglia, could represent a promising therapeutic target for AD.

neuroscience↗

bioRxiv2022

Cytosolic peptide accumulation activates the NLRP1 and CARD8 inflammasomes

NLRP1 and CARD8 are related sensors that form inflammasomes, but the danger signals that they detect are not fully established. These proteins undergo autoproteolysis, generating repressive N-terminal (NT) and inflammatory C-terminal (CT) fragments. The proteasome- mediated degradation of the NT releases the CT from autoinhibition, but the CT is then sequestered in a complex with the full-length sensor and DPP9. Here, we show that cytosolic peptide accumulation activates these inflammasomes. We found that a diverse array of peptides accelerates NT degradation, and those with N-terminal XP sequences also destabilize the ternary complexes. Peptides interfere with many biological processes, including protein folding. We show that unrelated agents that disrupt protein folding also induce NT degradation, but do not cause inflammasome activation because DPP9 sequesters the CT fragments in the absence of XP peptides. Overall, these results indicate that NLRP1 and CARD8 detect protein misfolding that is associated with peptide accumulation.

immunology↗