Biology subjects

Chen, K.

Publications and source records attributed to Chen, K..

At least 253 records · Page 14Linked to original sources

bioRxiv2023

Multiple sequence-alignment-based RNA language model and its application to structural inference

Compared to proteins, DNA and RNA are more difficult languages to interpret because 4-letter-coded DNA/RNA sequences have less information content than 20-letter-coded protein sequences. While BERT (Bidirectional Encoder Representations from Transformers)-like language models have been developed for RNA, they are ineffective at capturing the evolutionary information from homologous sequences because unlike proteins, RNA sequences are less conserved. Here, we have developed an unsupervised Multiple sequence-alignment-based RNA language model (RNA-MSM) by utilizing homologous sequences from an automatic pipeline, RNAcmap. The resulting unsupervised, two-dimensional attention maps and one-dimensional embeddings from RNA-MSM can be directly mapped with high accuracy to 2D base pairing probabilities and 1D solvent accessibilities, respectively. Further fine-tuning led to significantly improved performance on these two downstream tasks over existing state-of-the-art techniques. We anticipate that the pre-trained RNA-MSM model can be fine-tuned on many other tasks related to RNA structure and function.

bioinformatics↗

bioRxiv2023

Cas12a/Cpf1 knock-in mice enable efficient multiplexed immune cell engineering

Cas9 transgenic animals have drastically accelerated the discovery of novel immune modulators. But due to its inability to process its own CRISPR RNAs (crRNAs), simultaneous multiplexed gene perturbations using Cas9 remains limited, especially by pseudoviral vectors. Cas12a/Cpf1, however, can process concatenated crRNA arrays for this purpose. Here, we created conditional and constitutive LbCas12a knock-in transgenic mice. With these mice, we demonstrated efficient multiplexed gene editing and surface protein knockdown within individual primary immune cells. We showed genome editing across multiple types of primary immune cells including CD4 and CD8 T cells, B cells, and bone-marrow derived dendritic cells. These transgenic animals, along with the accompanying viral vectors, together provide a versatile toolkit for a broad range of ex vivo and in vivo gene editing applications, including fundamental immunological discovery and immune gene engineering.

genetics↗

bioRxiv2023

An interpretable ML model to characterize patient-specific HLA-I antigen presentation

Personalized immunotherapy holds the promise of revolutionizing cancer prevention and treatment. However, selecting HLA-bound peptide targets that are specific to patient tumors has been challenging due to a lack of patient-specific antigen presentation models. Here, we present epiNB, a white-box, positive-example-only, semi-supervised method based on Naive Bayes formulation, with information content-based feature selection, to achieve accurate modeling using Mass Spectrometry data eluted from mono-allelic cell lines and patient-derived cell lines. In addition to achieving state-of-the-art accuracy, epiNB yields novel insights into the structural properties, such as interactions of peptide positions, that appear important for modeling personalized, tumor-specific antigen presentation. epiNB uses substantially less parameters than neural networks, does not require hyperparameter tweaking and can efficiently train and run on our web portal (https://epinbweb.streamlit.app/) or a regular PC/laptop, making it easily applicable in translational settings.

bioinformatics↗

bioRxiv2023

Phage administration with repeated intravenous doses leads to faster phage clearance in mammalian hosts

ObjectivesPhage therapy has shown a great promise for the treatment of multidrug-resistant bacterial infections. However, the lack of a thorough and organized understanding of phage-body interactions has limited its clinical application. MethodsHere, we administered different purified phages (Salmonella phage SE_SZW1, Acinetobacter phage AB_SZ6, and Pseudomonas phage PA_LZ7) intravenously to healthy animals (rats and monkeys) to evaluate the phage-induced host responses and phage pharmacokinetics (PK) with different intravenous (IV) doses in healthy animals. The plasma and the organs were sampled after different IV doses to determine the phage biodistribution, the phage-induced cytokines, and antibodies. The potential side effects of phages on animals were assessed. ResultsA non-compartment model revealed that the plasma phage titer gradually decreased over time following a single dose. Repeated doses caused that the plasma phage titer at 5 minutes dropped 2-3 Log10 compared to the first dose regardless of phage types in rats. Host innate immune responses were activated including the upregulated expression (>10-fold) of TNF- and splenic enlargement following repeated doses. Phage-specific neutralization antibodies in animals receiving phages were detected. Similar results were obtained from monkeys. ConclusionsThe mammalian bodies were well-tolerant to the administered phages. The animal responses to the phages and the phage biodistribution profiles could have a significant impact on the efficacy of phage therapy.

pharmacology and toxicology↗

bioRxiv2023

Social Behavior Atlas: A computational framework for tracking and mapping 3D close interactions of free-moving animals

The study of social behaviors in animals is essential for understanding their survival and reproductive strategies. However, accurately tracking and analyzing the social interactions of free-moving animals has remained a challenge. Existing multi-animal pose estimation techniques suffer from drawbacks such as the need for extensive manual annotation and difficulty in discriminating between similar-looking animals in close social interactions. In this paper, we present the Social Behavior Atlas (SBeA), a novel computational framework that solves these challenges by employing a deep learning-based video instance segmentation model, 3D pose reconstruction, and unsupervised dynamic behavioral clustering. SBeA framework also involves a multi-camera setup to prevent occlusion, and a novel approach to identify individual animals in close social interactions. We demonstrate the effectiveness of SBeA in tracking and mapping the 3D close interactions of free-moving animals using the example of genetic mutant mice, birds, and dogs. Our results show that SBeA is capable of identifying subtle social interaction abnormalities, and the models and frameworks developed can be applied to a wide range of animal species. SBeA is a powerful tool for researchers in the fields of neuroscience and ecology to study animal social behaviors with a high degree of accuracy and reliability.

neuroscience↗

bioRxiv2023

An efficient stochastic steering strategy of magnetic particles in vascular networks

One of the primary challenges of magnetic drug targeting is to achieve efficient and accurate delivery of drug particles to the desired sites in complex physiological conditions. Though a majority of drugs are delivered through intravenous administration, until now, the kinematics and dynamics of drug particles influenced by the magnetic field, vascular topology and blood flows are still less understood. In this work, a multi-physics dynamical model which captures transient particle motions in both artificial and in vivo-like 3D vascular networks manipulated by the time-varying magnetic field is developed. Based on the model, it is found that particles which perform a random walk with correlated speed and persistence (RWSP motion) inspired by the migratory motion of immune and metastasis cells have higher mobility and navigation ability in both 2D and 3D tree-like and web-like networks. Moreover, to steer particles to perform the efficient RWSP motion, a stochastic magnetic steering strategy which uses time-varying gradient magnetic field is proposed. Parameters of the steering strategy is optimized and the capability of controlling particles to achieve fast spreading and transport in the vascular networks is demonstrated. In addition, the influence of heterogeneous flows in the vascular networks on the particle steering efficiency is discussed. Overall, the numerical model and the magnetic steering strategy can be widely used in the drug delivery systems for precise medicine research.

biophysics↗

bioRxiv2023

The Alfin-like transcription factor GmAlfin09 regulates endoplasmic reticulum stress in soybean via a peroxidase GmPRDX6

Soybean is a valuable oil crop cultivated throughout the world, but also highly susceptible to environmental stressors. The development of approaches to enhancing soybean stress resistance is thus vital to improving yields. In prior studies, Alfin has been shown to serve as an epigenetic regulator of plant growth and development. No studies of Alfin have yet been reported in soybean, however. In this study, the endoplasmic reticulum (ER) stress- and reactive oxygen species (ROS)-related transcription factor GmAlfin09 was identified. Screening of genes co-expressed with GmAlfin09 unexpectedly led to the identification of the peroxidase GmPRDX6. Further analyses revealed that both GmAlfin09 and GmPRDX6 were responsive to ER stress, with GmPRDX6 localizing to the ER under stress. Promoter binding experiments confirmed the ability of GmAlfin09 to directly bind the GmPRDX6 promoter. When GmAlfin09 and GmPRDX6 were overexpressed in soybean, enhanced ER stress resistance and decreased ROS levels were observed. Together, these findings suggest that GmAlfin09 can promote the upregulation of GmPRDX6, which subsequently localizes to the ER, reduced ROS levels, promotes ER homeostasis, and helps ensure the normal growth of soybean even under ER stress. This study highlights a novel genetic target for the future molecular breeding of stress-resistant soybean cultivars. HIGHLIGHTGmAlfin09 can increase the expression of GmPRDX6 to reduce ROS level under ER stress.

plant biology↗

bioRxiv2023

Single-cell transcriptomic analyses reveal the cellular and genetic basis of aquatic locomotion in scyphozoan jellyfish

The authors have withdrawn their manuscript because the authors need to re-organize the data and writing. More experimental evidence from whole-mount ISH assay and RNAi assays will be added to support the viewpoints. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

ecology↗

bioRxiv2023

Establishment of beta cell heterogeneity via differential CpG methylation at Nnat

Aims/hypothesisBeta cells within the pancreatic islet represent a heterogenous population wherein individual sub-groups of cells make distinct contributions to the overall control of insulin secretion. These include a subpopulation of highly-connected hub cells, important for the propagation of intercellular Ca2+ waves. Functional subpopulations have also been demonstrated in human beta cells, with an altered subtype distribution apparent in type 2 diabetes. At present, the molecular mechanisms through which beta cell hierarchy is established are poorly understood. Changes at the level of the epigenome provide one such possibility which we explore here by focussing on the imprinted gene neuronatin (Nnat), which is required for normal insulin synthesis and secretion. MethodsSingle cell RNA-seq datasets were examined using Seurat 4.0 and ClusterProfiler running under R. Transgenic mice expressing eGFP under the control of the Nnat enhancer/promoter regions were generated for fluorescence-activated cell (FAC) sorting of beta cells and downstream analysis of CpG methylation by bisulphite and RNA sequencing, respectively. Animals deleted for the de novo methyltransferase, DNMT3A from the pancreatic progenitor stage were used to explore control of promoter methylation. Proteomics was performed using affinity purification mass spectrometry and Ca2+ dynamics explored by rapid confocal imaging of Cal-520 and Cal-590. Insulin secretion was measured using Homogeneous Time Resolved Fluorescence Imaging. ResultsNnat mRNA was differentially expressed in a discrete beta cell population in a developmental stage- and DNA methylation (DNMT3A)-dependent manner. Thus, pseudo-time analysis of embryonic data sets demonstrated the early establishment of Nnat-positive and negative subpopulations during embryogenesis. NNAT expression is also restricted to a subset of beta cells across the human islet that is maintained throughout adult life. NNAT+ beta cells also displayed a discrete transcriptome at adult stages, representing a sub-population specialised for insulin production, reminiscent of recently-described "{beta}HI" cells and were diminished in db/db mice. Hub cells were less abundant in the NNAT+ population, consistent with epigenetic control of this functional specialization. Conclusions/interpretationThese findings demonstrate that differential DNA methylation at Nnat represents a novel means through which beta cell heterogeneity is established during development. We therefore hypothesise that changes in methylation at this locus may thus contribute to a loss of beta cell hierarchy and connectivity, potentially contributing to defective insulin secretion in some forms of diabetes. Research in contextWhat is already known about this subject? - Neuronatin (Nnat/NNAT) is an imprinted gene in humans and mice and is required for glucose-stimulated insulin secretion in vivo - Pancreatic beta cells are functionally heterogeneous with specific highly-connected subpopulations known to coordinate islet wide Ca2+ dynamics - Functional subpopulations have been described in human beta cells and their distribution is altered in type 2 diabetes What is the key question? - Does NNAT mark a discrete subpopulation of functional beta cells and which epigenetic pathways coordinate its formation and maintenance? What are the new findings? - A subpopulation of NNAT+ beta cells is established prior to the first week of postnatal life in mice via de novo DNA methylation at the Nnat promoter - NNAT+ beta cells are transcriptionally highly differentiated and appear to be functionally specialised for insulin production, possibly corresponding to recently-described "{beta}HI" and "CD63hi" beta cells. NNAT is expressed in a subset of beta cells across the human islet, and its deficiency in human beta cells diminishes glucose-stimulated insulin secretion - NNAT+ cells are likelier to belong to the population of follower, rather than hub cells, consistent with a role in insulin production rather than glucose detection How might this impact on clinical practice in the foreseeable future? - Epigenome-modifying compounds may provide a way of enhancing beta cell function and the ensemble behaviour of the islet to stimulate insulin secretion

cell biology↗

bioRxiv2023

Self-supervised learning on millions of pre-mRNA sequences improves sequence-based RNA splicing prediction

RNA splicing is an important post-transcriptional process of gene expression in eukaryotic cells. Predicting RNA splicing from primary sequences can facilitate the interpretation of genomic variants. In this study, we developed a novel self-supervised pre-trained language model, SpliceBERT, to improve sequence-based RNA splicing prediction. Pre-training on pre-mRNA sequences from vertebrates enables SpliceBERT to capture evolutionary conservation information and characterize the unique property of splice sites. SpliceBERT also improves zero-shot prediction of variant effects on splicing by considering sequence context information, and achieves superior performance for predicting branchpoint in the human genome and splice sites across species. Our study highlighted the importance of pre-training genomic language models on a diverse range of species and suggested that pre-trained language models were promising for deciphering the sequence logic of RNA splicing.

bioinformatics↗

bioRxiv2023

Pro-myelinating Clemastine administration improves recording performance of chronically implanted microelectrodes and nearby neuronal health

Intracortical microelectrodes have become a useful tool in neuroprosthetic applications in the clinic and to understand neurological disorders in basic neurosciences. Many of these brain-machine interface technology applications require successful long-term implantation with high stability and sensitivity. However, the intrinsic tissue reaction caused by implantation remains a major failure mechanism causing loss of recorded signal quality over time. Oligodendrocytes remain an underappreciated intervention target to improve chronic recording performance. These cells can accelerate action potential propagation and provides direct metabolic support for neuronal health and functionality. However, implantation injury causes oligodendrocyte degeneration and leads to progressive demyelination in surrounding brain tissue. Previous work highlighted that healthy oligodendrocytes are necessary for greater electrophysiological recording performance and the prevention of neuronal silencing around implanted microelectrodes over chronic implantation. Thus, we hypothesize that enhancing oligodendrocyte activity with a pharmaceutical drug, Clemastine, will prevent the chronic decline of microelectrode recording performance. Electrophysiological evaluation showed that the promyelination Clemastine treatment significantly elevated the signal detectability and quality, rescued the loss of multi-unit activity, and increased functional interlaminar connectivity over 16-weeks of implantation. Additionally, post-mortem immunohistochemistry showed that increased oligodendrocyte density and myelination coincided with increased survival of both excitatory and inhibitory neurons near the implant. Overall, we showed a positive relationship between enhanced oligodendrocyte activity and neuronal health and functionality near the chronically implanted microelectrode. This study shows that therapeutic strategy that enhance oligodendrocyte activity is effective for integrating the functional device interface with brain tissue over chronic implantation period. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/526463v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@1a729d0org.highwire.dtl.DTLVardef@1aa3f8aorg.highwire.dtl.DTLVardef@31b231org.highwire.dtl.DTLVardef@a9dd39_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2023

The Master Database of All Possible RNA Sequences and Its Integration with RNAcmap for RNA Homology Search

Recent success of AlphaFold2 in protein structure prediction relied heavily on co-evolutionary information derived from homologous protein sequences found in the huge, integrated database of protein sequences (Big Fantastic Database). In contrast, the existing nucleotide databases were not consolidated to facilitate wider and deeper homology search. Here, we built a comprehensive database by including the noncoding RNA sequences from RNAcentral, the transcriptome assembly and metagenome assembly from MG-RAST, the genomic sequences from Genome Warehouse (GWH), and the genomic sequences from MGnify, in addition to NCBIs nucleotide database (nt) and its subsets. The resulting MARS database (Master database of All possible RNA sequences) is 20-fold larger than NCBIs nt database or 60-fold larger than RNAcentral. The new dataset along with a new split-search strategy allows a substantial improvement in homology search over existing state-of-the-art techniques. It also yields more accurate and more sensitive multiple sequence alignments (MSA) than manually curated MSAs from Rfam for the majority of structured RNAs mapped to Rfam. The results indicate that MARS coupled with the fully automatic homology search tool RNAcmap will be useful for improved structural and functional inference of noncoding RNAs.

bioinformatics↗

bioRxiv2023

Unraveling the causal genes and transcriptomic determinants of human telomere length

Telomere length (TL) shortening is a pivotal indicator of biological aging and is associated with many human diseases. The genetic determinates of human TL have been widely investigated, however, most existing studies were conducted based on adult tissues which are heavily influenced by lifetime exposure. Based on the analyses of terminal restriction fragment (TRF) length of telomere, individual genotypes, and gene expressions on 166 healthy placental tissues, we systematically interrogated TL-modulated genes and their potential functions. We found that placental TL is relatively longer across human tissues and which maintenance is mostly connected to genes responsible for alternative lengthening of telomeres. Trans-ancestral TL genome-wide association studies (GWASs) on 644,553 individuals identified 20 novel genetic associations and provided increased polygenic determination of human TL. Next, we integrated the powerful TL GWAS with placental expression quantitative trait locus (eQTL) mapping to prioritize 31 likely causal genes, among which 4 were functionally validated, including MMUT, RRM1, KIAA1429, and YWHAZ. Finally, modeling transcriptomic signatures and TRF-based TL improved the prediction performance of human TL. This study deepened our understanding of causal genes and transcriptomic determinants of human TL, promoting the mechanistic research on fine-grained TL regulation.

genetics↗

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

An efficient context-aware approach for whole slide image classification

Computational pathology for gigapixel whole slide images (WSIs) at slide-level is helpful in disease diagnosis and remains challenging. We propose a context-aware approach termed WSI Inspection via Transformer (WIT) for slide-level classification via holistically modeling dependencies among patches on the WSI. WIT automatically learns feature representation of WSI by aggregating features of all image patches. We evaluate classification performance of WIT along with state-of-the-art baseline method. WIT achieved an accuracy of 82.1% (95% CI, 80.7% - 83.3%) in the detection of 32 cancer types on the TCGA dataset, 0.918 (0.910 - 0.925) in diagnosis of cancer on the CPTAC dataset and 0.882 (0.87 - 0.890) in the diagnosis of prostate cancer from needle biopsy slide, outperforming the baseline by 31.6%, 5.4% and 9.3%, respectively. WIT can pinpoint the WSI regions that are most influential for its decision. WIT represents a new paradigm for computational pathology, facilitating the development of effective tools for digital pathology.

pathology↗

bioRxiv2023

ATP-releasing SWELL1 channel in spinal microglia contributes to neuropathic pain

Following peripheral nerve injury, extracellular ATP-mediated purinergic signaling is crucial for spinal cord microglia activation and neuropathic pain. However, the mechanisms of ATP release remain poorly understood. Here, we show that volume-regulated anion channel (VRAC) is an ATP-releasing channel and is activated by inflammatory mediator sphingosine-1-phosphate (S1P) in microglia. Mice with microglia-specific deletion of Swell1 (also known as Lrrc8a), a VRAC essential subunit, had reduced peripheral nerve injury-induced increase in extracellular ATP in spinal cord. The mutant mice also exhibited decreased spinal microgliosis, dorsal horn neuronal hyperactivity, and both evoked and spontaneous neuropathic pain-like behaviors. We further performed high-throughput screens and identified an FDA-approved drug dicumarol as a novel and potent VRAC inhibitor. Intrathecal administration of dicumarol alleviated nerve injury-induced mechanical allodynia in mice. Our findings suggest that ATP-releasing VRAC in microglia is a key spinal cord determinant of neuropathic pain and a potential therapeutic target for this debilitating disease.

physiology↗

bioRxiv2023

Structure of the ISW1a complex bound to the dinucleosome

Nucleosomes are basic repeating units of chromatin, and form regularly spaced arrays in cells. Chromatin remodelers alter the positions of nucleosomes, and are vital in regulating chromatin organization and gene expression. Here we report the cryoEM structure of chromatin remodeler ISW1a complex bound to the dinucleosome. Each subunit of the complex recognizes a different nucleosome. The motor subunit binds to the mobile nucleosome and recognizes the acidic patch through two arginine residues, and the DNA-binding module interacts with the entry DNA at the nucleosome edge. This nucleosome-binding mode provides the structural basis for linker DNA sensing of the motor. Notably, the Ioc3 subunit recognizes the disk face of the adjacent nucleosome through the H4 tail, the acidic patch and the nucleosomal DNA, which is important for the spacing activity in vitro, and for nucleosome organization and cell fitness in vivo. Together, these findings support the nucleosome spacing activity of ISW1a, and add a new mode of nucleosome remodeling in the context of a chromatin environment.

biochemistry↗

bioRxiv2022

Androgen-mediated TGFβ expression suppresses anti-tumor neutrophil response in bone metastatic prostate cancer

Prostate Cancer (PCa) bone metastases are associated with spinal cord compression, fracture, bone pain and death. Despite advances in the medical therapy for localized disease, metastatic disease is incurable and osseous progression is largely dictated by tumor-stromal interactions in the bone microenvironment. We showed previously that tumor bone neutrophils are tumoricidal to PCa but lose their cytotoxic potential as the tumor progresses. However, there have been no studies to date to clinically define and characterize neutrophils throughout the prostate cancer disease spectrum to determine their biomarker potential. Using patient peripheral blood polymorphonuclear neutrophils (PMNs), we identify that PCa progression dictates PMN properties, including viability, cell surface markers and gene expression. However, the majority of PMNs elicited an anti-tumor response ex vivo demonstrating that PMN cytotoxicity is cell autonomous and independent of PCa disease stage. In fact, we identify a novel role for androgen regulation, i.e., androgen deprivation therapy (ADT), in suppressing PMN cytotoxicity via altered transforming growth factor beta receptor I (T{beta}RI). Using preclinical models, we found that high dose testosterone/bipolar androgen therapy (BAT) and genetic or pharmacologic T{beta}RI inhibition combined with standard ADT rescued the androgen-associated suppression and restored PMN anti-tumor immune response. This combination provided a therapeutic strategy more impactful than ADT alone, in bone metastatic prostate cancer (BM-PCa). These studies: 1) highlight a necessity for both molecular and functional characterization of PMNs per cancer type and 2) reveals the ability to program PMN immune response for successful targeting of BM-PCa.

cancer biology↗