Biology subjects

Kim, H. J.

Publications and source records attributed to Kim, H. J..

At least 55 records · Page 3Linked to original sources

bioRxiv2023

Different Diets Modulate the Gut Microbiome Compositions and Promote the Health of Apis mellifera.

Honey bee (Apis mellifera) health is crucial for honey bee products, and effective pollination and is closely associated with gut bacteria. Various factors such as reduced habitat, temperature, disease, and diet affect the health of honey bees, by disturbing the homeostasis of the gut microbiota. In this study, high-throughput 16S rRNA gene sequencing was used to analyze the gut microbiota of Apis mellifera subjected to seven different diets. The identified microbiota in the Apis mellifera gut from all the diets consisted of Lactobacillus (62%), followed by Rhizobiaceae (21%), Snodgrassella (4%), and Erwiniaceae (4%) among other 33 genera. Based on diet types, Lactobacillus a lactic acid bacteria (LAB), dominates the microbiota with the highest relative abundance in AIGT+SAC (91%), AIGT+Soytide (88%), and AIGT+Apple juice (69%) diet groups. Bifidobacterium and Commensalibacter appeared as the second most abundant genera in AIGT+SAC and AIGT+Soytide diet groups, respectively. These bacteria are important markers for honey bee health. Considering the importance of these diets in shaping their host microbiome into a healthy status. Individual honey bee health (IHH) was observed to validate the quality and correlation between the microbiota and honey bee health. The results were consistent, indicating that Apis mellifera fed on AIGT+Soytide and AIGT+SAC diet showed the highest health expression level of vitellogenin. The group with 60%Syrup possessing Rhizobiaceae as the dominant taxa showed poor health status. This finding paved the way for establishing a link between gut microbiota and IHH under different diets.

genomics↗

bioRxiv2023

Lymphatic muscle cells are the innate pacemaker cells regulating mouse lymphatic collecting vessel contractions

Collecting lymphatic vessels (cLVs) exhibit spontaneous contractions with a pressure-dependent frequency, but the identity of the lymphatic pacemaker cell is still debated. Here we combined immunofluorescence and scRNAseq analyses with electrophysiological methods to examine the cellular constituents of the mouse cLV wall and assess whether any cell type exhibited morphological and functional processes characteristic of pacemaker cells. We employed inducible Cre (iCre) mouse models to target specific cell populations including c-kitCreERT2 to target interstitial cells of Cajal like cells; Pdgfr{beta}CreERT2to target pericyte-like cells; PdgfrCreERTMto target CD34+ adventitial cells; and Myh11CreERT2to target lymphatic muscle cells (LMCs) directly. These inducible Cre lines were crossed to the fluorescent reporter ROSA26mT/mG, the genetically encoded Ca2+ sensor GCaMP6f, and the light- activated cation channel rhodopsin2 (ChR2). Only LMCs consistently, but heterogeneously, displayed spontaneous Ca2+ events during the diastolic period of the contraction cycle, and whose frequency was modulated in a pressure-dependent manner. Further, optogenetic depolarization with ChR2 only induced propagated contractions in LMCs. Membrane potential recordings in LMCs demonstrated that the rate of diastolic depolarization significantly correlated with contraction frequency. These findings support the conclusion that LMCs, or a subset of LMCs, are responsible for mouse cLV pacemaking. ImpactLymphatic muscle cells, but not CD34+ adventitial cells, exhibited pacemaker behaviors such as pressure-dependent depolarization, pressure-dependent calcium mobilization during diastole, and propagated contraction waves induced by focal, optogenetic depolarization via enforced channel- rhodopsin2.

physiology↗

bioRxiv2023

Large-scale population genomics of Malayan pangolins reveals deep diversification and a new species

BackgroundArchipelagos and oceanic islands often present high percentage of endemism due to rapid speciation. The Malayan pangolin is a species distributing at both mainland (southern Yunnan, China) and oceanic islands via Malayan peninsula, which may result in deep differentiation among populations. In-depth investigation of population structure and genetic consequences for such species is of vital importance for their protection and conservation, practically for the critically endangered Malayan pangolin that is suffering from poaching, illegal trade, and habitat loss. ResultsHere we carried out a large-scale population genomic analysis for Malayan pangolins, and revealed three highly distinct genetic populations in this species, two of which are now being reported for the first time. Based on multiple lines of genomic and morphological evidence, we postulate the existence of a new pangolin species (Manis_1). Genetic diversity and recent inbreeding were both at a moderate level for both Malayan pangolins and Manis_1, but mainland Malayan pangolins presented relatively lower genetic diversity, higher inbreeding and fitness cost than island populations. ConclusionsWe found extremely deep and graded differentiation in Malayan pangolins, with two newly discovered genetic populations and a new pangolin species that is closely related to the Philippine pangolin than the typical Malayan pangolin, but a distant relative of the Indian pangolin. Anthropogenic factors did not significantly weaken the basis of genetic sustainability for Malayan pangolins, but mainland Malayan pangolins should be paid more attention for conservation due to higher genetic risks than island populations.

genomics↗

bioRxiv2023

Interaction between host G3BP and viral nucleocapsid protein regulates SARS-CoV-2 replication

G3BP1/2 are paralogous proteins that promote stress granule formation in response to cellular stresses, including viral infection. G3BP1/2 are prominent interactors of the nucleocapsid (N) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the functional consequences of the G3BP1-N interaction in the context of viral infection remain unclear. Here we used structural and biochemical analyses to define the residues required for G3BP1-N interaction, followed by structure-guided mutagenesis of G3BP1 and N to selectively and reciprocally disrupt their interaction. We found that mutation of F17 within the N protein led to selective loss of interaction with G3BP1 and consequent failure of the N protein to disrupt stress granule assembly. Introduction of SARS-CoV-2 bearing an F17A mutation resulted in a significant decrease in viral replication and pathogenesis in vivo, indicating that the G3BP1-N interaction promotes infection by suppressing the ability of G3BP1 to form stress granules.

cell biology↗

bioRxiv2023

Identification of small molecule inhibitors of G3BP-driven stress granule formation

Stress granule formation is triggered by the release of mRNAs from polysomes and is promoted by the action of the paralogs G3BP1 and G3BP2. G3BP1/2 proteins bind mRNAs and thereby promote the condensation of mRNPs into stress granules. Stress granules have been implicated in several disease states, including cancer and neurodegeneration. Consequently, compounds that limit stress granule formation or promote their dissolution have potential as both experimental tools and novel therapeutics. Herein, we describe two small molecules, referred to as G3BP inhibitor a and b (G3Ia and G3Ib), designed to bind to a specific pocket in G3BP1/2 that is known to be targeted by viral inhibitors of G3BP1/2 function. In addition to disrupting co-condensation of RNA, G3BP1, and caprin 1 in vitro, these compounds inhibit stress granule formation in cells treated prior to or concurrent with stress, and dissolve pre-existing stress granules when added to cells after stress granule formation. These effects are consistent across multiple cell types and a variety of initiating stressors. Thus, these compounds represent ideal tools to probe the biology of stress granules and hold promise for therapeutic interventions designed to modulate stress granule formation.

cell biology↗

bioRxiv2023

A new Karyopherin-β2 binding PY-NLS epitope of HNRNPH2 is linked to neurodevelopmental disorders

The normally nuclear HNRNPH2 is mutated in HNRNPH2-related X-linked neurodevelopmental disorder causing the protein to accumulate in the cytoplasm. Interactions of HNRNPH2 with its importin Karyopherin-{beta}2 (Transportin-1) had not been studied. We present a structure that shows Karyopherin-{beta}2 binding HNRNPH2 residues 204-215, a proline-tyrosine nuclear localization signal or PY-NLS that contains a typical R-X2-4-P-Y motif, 206RPGPY210, followed a new Karyopherin-{beta}2 binding epitope at 211DRP213 that make many interactions with Karyopherin-{beta}2 W373. Mutations at each of these sites decrease Karyopherin-{beta}2 binding affinities by 70-100 fold, explaining aberrant accumulation in cells and emphasizing the role of nuclear import defects in the disease. Sequence/structure analysis suggests that the new epitope C-terminal of the PY-motif, which binds Karyopherin-{beta}2 W373, is rare and thus far limited to close paralogs HNRNPH2, HNRNPH1 and HNRNPF. Karyopherin-{beta}2 W373, a HNRNPH2-binding hotspot, corresponds to W370 of close paralog Transportin-2, a site of pathological variants in patients with neurodevelopmental abnormalities, suggesting that Transportin-2-HNRNPH2/H1/F interactions may be compromised in the abnormalities. SummaryHNRNPH2 variants in HNRNPH2-related X-linked neurodevelopmental disorder aberrantly accumulate in the cytoplasm. A structure of Karyopherin-{beta}2*HNRNPH2 explains nuclear import defects of the variants, reveals a new NLS epitope that suggests mechanistic changes in pathological variants of Karyopherin-{beta}2 paralog Transportin-2.

biophysics↗

bioRxiv2022

Inferring delays in partially observed gene regulatory networks

MotivationCell function is regulated by gene regulatory networks (GRNs) defined by protein-mediated interaction between constituent genes. Despite advances in experimental techniques, we can still measure only a fraction of the processes that govern GRN dynamics. To infer the properties of GRNs using partial observation, unobserved sequential processes can be replaced with distributed time delays, yielding non-Markovian models. Inference methods based on the resulting model suffer from the curse of dimensionality. ResultsWe develop a simulation-based Bayesian MCMC method for the efficient and accurate inference of GRN parameters when only some of their products are observed. We illustrate our approach using a two-step activation model: An activation signal leads to the accumulation of an unobserved regulatory protein, which triggers the expression of observed fluorescent proteins. With prior information about observed fluorescent protein synthesis, our method successfully infers the dynamics of the unobserved regulatory protein. We can estimate the delay and kinetic parameters characterizing target regulation including transcription, translation, and target searching of an unobserved protein from experimental measurements of the products of its target gene. Our method is scalable and can be used to analyze non-Markovian models with hidden components. AvailabilityAccompanying code in R is available at https://github.com/Mathbiomed/SimMCMC. Contactjaekkim@kaist.ac.kr or kresimir.josic@gmail.com or cbskust@korea.ac.kr Supplementary informationSupplementary data are available at Bioinformatics online.

bioinformatics↗

bioRxiv2022

Expanding the epitranscriptomic RNA sequencing and modification mapping mass spectrometry toolbox with field asymmetric waveform ion mobility and electrochemical elution liquid chromatography

Post-transcriptional modifications of RNA strongly influence RNA structure and function. Recent advances in RNA sequencing and mass spectrometry (MS) methods have identified over 140 of these modifications on a wide variety of RNA species. Most next-generation sequencing approaches can only map one RNA modification at a time, and while MS can assign multiple modifications simultaneously in an unbiased manner, MS cannot accurately catalog and assign RNA modifications in complex biological samples due to limitations in fragment length and coverage depth. Thus, a facile method to identify novel RNA modifications while simultaneously locating them in the context of their RNA sequences is still lacking. We combined two orthogonal modes of RNA ion separation before mass-spectrometry identification: high-field asymmetric ion mobility separation (FAIMS) and electrochemically modulated liquid chromatography (EMLC). FAIMS RNA-MS increases both coverage and throughput, while the EMLC LC-MS orthogonally separates RNA of different length and charge. The combination of the two methods offers a broadly applicable platform to improve length and depth of MS-based RNA sequencing while providing contextual access to the analysis of RNA modifications.

biochemistry↗

bioRxiv2022

Immature Myeloid Cell Deposition in Old Bone Marrow Revealed by Single-Cell Transcriptome Analysis

Aging causes dysfunction of innate immunity, although hematopoietic stem cells of aged bone marrow (BM) show an increased differentiation potential to myeloid lineage cells. The alteration of cellular heterogeneity and intercellular communications between BM immune cells may provide important clues to understanding age-dependent immune dysfunction. Here, we provide a deep single-cell transcriptomic analysis of total immune cell populations of young and old BM. We identified the well-organized differentiation status of 11 myeloid/lymphoid lineage cell populations and age-dependent alterations in the proportions of cells. The neutrophil lineages showed the most prominent alteration by aging, and subclustering of neutrophils indicated that the specific immature neutrophils are increased in old BM. In addition, we identified age-dependent alterations in secretory phenotypes associated with a decline in innate immunity and immune cell differentiation. Among these secretory phenotypes, SPP1 could be suggested as a representative signal that triggers myeloid skewing and immature neutrophil deposition in aged BM. Collectively, these results provide a novel link between the altered immune cell proportions in BM and age-dependent dysregulation of innate immunity.

bioinformatics↗

bioRxiv2022

Selective enrichment of plasma cell-free messenger RNA in cancer-associated extracellular vesicles

Extracellular vesicles (EVs) have been shown as key mediators of extracellular small RNA transport. However, carriers of cell-free messenger RNA (cf-mRNA) in human biofluid and their association with cancer remain poorly understood. Here, we performed a transcriptomic analysis of size-fractionated plasma from lung cancer, liver cancer, multiple myeloma, and healthy donors. Morphology and size distribution analysis showed the successful separation of medium and small EVs and non-vesicular carriers. We developed a strategy to purify and sequence ultra-low amounts of cf-mRNA from vesicular and non-vesicular subpopulations with the implementation of RNA spike-ins to control for technical variability and to normalize for intrinsic drastic differences in the amount of cf-mRNA carried in each plasma fraction. We found that the majority of cf-mRNA was enriched and protected in EVs with remarkable stability in RNase-rich environments. We observed specific enrichment patterns of cancer-associated cf-mRNA in each vesicular and non-vesicular subpopulation. The EV-enriched differentiating genes were associated with specific biological pathways, such as immune systems, liver function, and toxic substance regulation in lung cancer, liver cancer, and multiple myeloma, respectively. Our results suggest that dissecting the complexity of EVs subpopulations illuminates their biological significance and offers a promising liquid biopsy approach.

genomics↗

bioRxiv2022

Npas4-mediated dopaminergic regulation of fear memory states

Amygdala circuitry encodes associations between conditioned stimuli and aversive unconditioned stimuli, and also controls fear expression (Pape and Pare, 2010). However, whether and how irrelevant information for unpaired conditioned stimuli (CS-) is discretely processed, and how it was influenced by stress remain unknown. CS- memory is retrievable immediately after fear conditioning, but then becomes silent after memory consolidation in mice. Synaptic pathway from the lateral to the anterior basal amygdala gates the expression of CS- memory, depending upon Npas4-mediated Drd4 synthesis. The upregulation of Npas4-Drd4 axis, which is precluded by corticosterone, shifts functional states of neural engrams for CS- memory toward silent states and limits its retrievability. In here, we demonstrate the cellular and molecular mechanisms regulating the functional states of neural engrams, which can be switched or maintained, supporting discriminative memory.

neuroscience↗

bioRxiv2022

Proximal dendritic localization of NALCN channels underlies tonic and burst firing in nigral dopaminergic neurons

In multipolar nigral dopamine (DA) neurons, the highly excitable proximal dendritic compartments (PDCs) and two Na+-permeable leak channels, TRPC3 and NALCN, play a key role in pacemaking. However, the causal link between them is unknown. Here we report that the proximal dendritic localization of NALCN underlies pacemaking and burst firing in DA neurons. Our morphological analysis of nigral DA neurons reveals that TRPC3 is ubiquitously expressed in the whole somatodendritic compartment, but NALCN is localized within the PDCs. Blocking either TRPC3 or NALCN channels abolished pacemaking. However, only blocking NALCN, not TRPC3, degraded burst discharges. Furthermore, local glutamate uncaging readily induced burst discharges within the PDCs, compared with other parts of the neuron, and NALCN channel inhibition dissipated burst generation, indicating the importance of NALCN to the high excitability of PDCs. Therefore, we conclude that PDCs serve as a common base for tonic and burst firing in nigral DA neurons.

neuroscience↗

bioRxiv2022

A novel meiotic protein required for homolog pairing and regulation of synapsis in C. elegans

Interactions between chromosomes and LINC (Linker of Nucleoskeleton and Cytoskeleton) complexes in the nuclear envelope (NE) promote homolog pairing and synapsis during meiosis. By tethering chromosomes to cytoskeletal motors, these connections lead to rapid, processive chromosome movements along the NE. This activity is usually mediated by telomeres, but in the nematode Caenorhabditis elegans special chromosome regions called "Pairing Centers" (PCs) have acquired this meiotic function. Through a genetic screen for mutations that cause meiotic nondisjunction, we discovered an uncharacterized meiosis-specific NE protein, MJL-1 (MAJIN-Like-1) that is essential for interactions between PCs and LINC complexes. MJL-1 colocalizes with PCs and LINC complexes during pairing and synapsis. Mutations in MJL-1 disrupt these interactions and eliminate active chromosome movements. mjl-1 mutants display promiscuous nonhomologous synapsis, reduced clustering of PCs, and severely impaired homolog pairing. MJL-1 likely interacts directly with SUN-1 and DNA-binding proteins to connect PCs to the LINC complex. Similarities in the molecular architecture of chromosome-LINC complex attachments between C. elegans and other organisms suggest that these connections may play previously unrecognized roles during meiosis across eukaryotes.

cell biology↗

bioRxiv2022

Comprehensive Characterisation of Fetal and Mature Retinal Cell Identity to Assess the Fidelity of Retinal Organoids

Characterizing cell identity in complex tissues such as the human retina is essential for studying its development and disease. While retinal organoids derived from pluripotent stem cells have been widely used to model development and disease of the human retina, there is a lack of studies that have systematically evaluated molecular and cellular fidelity of the organoids derived from various culture protocols in recapitulating their in vivo counterpart. To this end, we performed an extensive meta-atlas characterisation of cellular identities of the human eye, covering a wide range of developmental stages. The resulting map uncovered previously unknown biomarkers of major retinal cell types and those associated with cell-type specific maturation. Using our retinal cell identity map from the fetal and adult tissues, we systematically assessed the fidelity of the retinal organoids to mimic the human eye, enabling us to comprehensively benchmark the current protocols for retinal organoid generation.

systems biology↗

bioRxiv2022

7-UP: generating in silico CODEX from a small set of immunofluorescence markers

Multiplex immunofluorescence (mIF) assays multiple protein biomarkers on a single tissue section. Recently, high-plex CODEX (co-detection by indexing) systems enable simultaneous imaging of 40+ protein biomarkers, unlocking more detailed molecular phenotyping, leading to richer insights into cellular interactions and disease. However, high-plex imaging can be slower and more costly to collect, limiting its applications, especially in clinical settings. We propose a machine learning framework, 7-UP, that can computationally generate in silico 40-plex CODEX at single-cell resolution from a standard 7-plex mIF panel by leveraging cellular morphology. We demonstrate the usefulness of the imputed biomarkers in accurately classifying cell types and predicting patient survival outcomes. Furthermore, 7-UPs imputations generalize well across samples from different clinical sites and cancer types. 7-UP opens the possibility of in silico CODEX, making insights from high-plex mIF more widely available.

bioinformatics↗

bioRxiv2022

SPACE-GM: geometric deep learning of disease-associated microenvironments from multiplex spatial protein profiles.

Multiplexed immunofluorescence imaging enables high-dimensional molecular profiling at subcellular resolution. However, learning disease-relevant cellular environments from these rich imaging data is an open challenge. We developed SPAtial CEllular Graphical Modeling (SPACE-GM), a geometric deep learning framework that flexibly models tumor microenvironments (TMEs) as cellular graphs. We applied SPACE-GM to 658 head-and-neck and colorectal human cancer samples assayed with 40-plex immunofluorescence imaging to identify spatial motifs associated with cancer recurrence and patient survival after immunotherapy. SPACE-GM is substantially more accurate in predicting patient outcomes than previous approaches for modeling spatial data using neighborhood cell-type compositions. Computational interpretation of the disease-relevant microenvironments identified by SPACE-GM generates insights into the effect of spatial dispersion of tumor cells and granulocytes on patient prognosis.

bioinformatics↗

bioRxiv2022

Overexpressing eukaryotic elongation factor 1 alpha (eEF1A) proteins to promote corticospinal axon repair after injury

Although protein synthesis is hypothesized to have a pivotal role in axonal repair after central nervous system (CNS) injury, the role of core components of the protein synthesis machinery has not been examined. Notably, some elongation factors possess non-canonical functions that may further impact axonal repair. Here, we examined whether overexpressing eukaryotic elongation factor 1 alpha (eEF1A) proteins enhances the collateral sprouting of corticospinal tract (CST) neurons after unilateral pyramidotomy, along with the underlying molecular mechanisms. Compared with axonal regeneration from injured neurons, axonal sprouting from uninjured neurons occurs spontaneously after injury and may represent a more accessible form of axonal repair for clinical translation. We found that overexpressing eEF1A1, eEF1A2 or both proteins in CST neurons increased the levels of pS6, an indicator for mTOR activity, in neuronal somas. In contrast, the levels of pSTAT3 and pAKT were not increased. Strikingly, overexpressing eEF1A2 alone, but neither eEF1A1 alone nor both factors simultaneously, increased protein synthesis and actin rearrangement in CST neurons. While eEF1A1 overexpression only slightly enhanced CST sprouting across the midline into the denervated side in the cervical spinal after pyramidotomy, eEF1A2 overexpression substantially enhanced this sprouting. Surprisingly, co-overexpression of both eEF1A1 and eEF1A2 led to a sprouting phenotype similar to wild-type controls, suggesting an antagonistic effect of overexpressing both proteins. These data provide the first evidence that overexpressing a core component of the translation machinery, eEF1A2, enhances CST sprouting, likely by a combination of increased protein synthesis, mTOR signaling and actin cytoskeleton rearrangement.

neuroscience↗

bioRxiv2022

A murine model of hnRNPH2-related neurodevelopmental disorder recapitulates clinical features of human disease and reveals a mechanism for genetic compensation of HNRNPH2

Mutations in HNRNPH2 cause an X-linked neurodevelopmental disorder with a phenotypic spectrum that includes developmental delay, intellectual disability, language impairment, motor function deficits, and seizures. More than 90% of patients with this disorder have a missense mutation within or adjacent to the nuclear localization signal (NLS) of hnRNPH2, although the specific pathogenic consequences of these mutations have not been examined. Here we found that hnRNPH2 NLS mutations result in reduced interaction with the nuclear transport receptor Kap{beta}2 in vitro and in cultured human cells. These mutations also cause modest accumulation of hnRNPH2 in the cytoplasm, suggesting that mislocalization of the protein might contribute to pathogenesis. We generated two knock-in mouse models with human-equivalent mutations in the endogenous mouse gene Hnrnph2, as well as Hnrnph2 knockout (KO) mice, and subjected them to extensive phenotyping. Mutant knock-in mice displayed a spectrum of phenotypes that recapitulated aspects of the human disorder, including reduced survival in males, craniofacial abnormalities, impaired motor and cognitive functions, and increased susceptibility to audiogenic seizures. Mutant knock-in male mice developed more severe phenotypes than female mice, likely due to differences in X-chromosome gene dosage. In contrast, two independent lines of Hnrnph2 KO mice showed no detectable phenotypes. Notably, KO mice had upregulated expression of Hnrnph1, a close paralog of Hnrnph2, whereas mutant Hnrnph2 knock-in mice failed to upregulate Hnrnph1. Thus, genetic compensation by Hnrnph1 might be sufficient to counteract the loss of hnRNPH2. These findings suggest that the pathogenesis of HNRNPH2-related disorder in humans may be driven by a toxic gain of function or a complex loss of HNRNPH2 function with impaired compensation by HNRNPH1. The mutant knock-in mice described here are an important resource for preclinical studies to assess the potential benefit of either gene replacement or therapeutic knockdown of mutant hnRNPH2.

neuroscience↗