Biology subjects

Wang, N.

Publications and source records attributed to Wang, N..

At least 127 records · Page 7Linked to original sources

bioRxiv2024

Alteration of skin fibroblast steady state contributes to healing outcomes

Fibroblasts display complex functions associated with distinct gene expression profiles that influence matrix production and cell communications and the autonomy of tissue development and repair. Thrombospondin-2 (TSP-2), produced by fibroblasts, is a potent angiogenesis inhibitor and negatively associated with tissue repair. Single-cell (sc) sequencing analysis on WT and TSP2KO skin fibroblasts demonstrate distinct cell heterogeneity. Specifically, we found an enrichment of Sox10+ multipotent progenitor cells, identified as Schwann precursor cells, in TSP2KO fibroblasts, while fibrosis-related subpopulations decreased. Immunostaining of tissue and cells validated the increase of this Sox10+ population in KO fibroblasts. Furthermore, in silico analysis suggested enhanced pro-survival signaling, including WNT, TGF-{beta}, and PDGF-{beta}, alongside a reduced BMP4 response. Additionally, the creation of two TSP2KO NIH3T3 cell lines using the CRISPR/Cas9 technique allowed functional and signaling validation in a less complex system. Moreover, KO 3T3 cells exhibited enhanced migration and proliferation, with elevated levels of pro-regenerative molecules including TGF-{beta}3 and Wnt4, and enrichment of nuclear {beta}-catenin. These functional and molecular alterations likely contribute to improved healing and increased neurogenesis in TSP2-deficient wounds. Overall, our findings describe the heterogeneity of dermal fibroblasts and identify pro-regenerative features of TSP2KO fibroblasts.

pathology↗

bioRxiv2024

Molecular epidemiology of carbapenem-resistant hypervirulent Klebsiella pneumoniae: Risk factors and resistance mechanism of ceftazidime/avibactam in China

The high morbidity and mortality rates associated with carbapenem-resistant hypervirulent Klebsiella pneumoniae have become a global public health problem. We analyzed the whole genome sequence and epidemiological data of 81 carbapenem-resistant Klebsiella pneumoniae strains and conducted sensitivity experiments to explore the optimal concentration of carbapenem-resistant Klebsiella pneumoniae. We verified the resistance and virulence genes of carbapenem-resistant Klebsiella pneumoniae using polymerase chain reaction and compared virulence between carbapenem-resistant hypervirulent Klebsiella pneumoniae a ndcarbapenem-resistant-non-hypervirulent Klebsiella pneumoniae through Galleria mellonella assays.The prevalent types of multilocus sequence typing in our carbapenem-resistant Klebsiella pneumoniae strains were ST11 (69.14%, 56/81). ST11-K64-O1/O2v1 has become an epidemic type in our hospital, with drug-resistance genes dominated by blaKPC-2 (90.12%, 73/81). Ceftazidime/avibactam has better antibacterial effects on carbapenem-resistant Klebsiella pneumoniae, and its resistance is mainly mediated by a resistance plasmid containing the blaKPC-2 gene. 52 carbapenem-resistant hypervirulent Klebsiella pneumoniae strains carry the blaKPC-2, with a high detection rate of siderophore. Further research has shown that the genetic environment of the blaKPC-2 contains TnpR_Tn3 and ISKpn27 upstream and ISKpn6 insertion sequences downstream. Galleria mellonella revealed that the survival rate of carbapenem-resistant hypervirulent Klebsiella pneumoniae was lower than that of carbapenem-resistant-non-hypervirulent Klebsiella pneumoniae, and the survival rate of carbapenem-resistant hypervirulent Klebsiella pneumoniae-K64 was lower than that of carbapenem-resistant hypervirulent Klebsiella pneumoniae-K47.The spread of carbapenem-resistant hypervirulent Klebsiella pneumoniae strains is alarming, necessitating molecular monitoring of hypervirulent strains and strengthening the nosocomial infection prevention and control measures. Antibiotics should be used reasonably based on patients infection status and local epidemiological data. ImportanceCarbapenem-resistant Klebsiella pneumonia is a global public health concern. We conducted a molecular epidemiological analysis of 81 carbapenem-resistant hypervirulent Klebsiella pneumoniae strains from our hospital and explored the resistance mechanism of ceftazidime/avibactam. We identified the blaKPC-2 gene to be primarily responsible for carbapenem resistance in our hospital, and ST11-K64 was the dominant clone. A high-risk clone, ST307-K102, was detected, necessitating strengthened surveillance to prevent its spread. This studys findings contribute to the optimization of antimicrobial management and indicate that genomic research can assist with the tracking of hospital infection outbreaks and the improvement of infection-control measures.

microbiology↗

bioRxiv2024

The virulence and motility of Pseudomonas syringae pv. Actinidiae mediated by a temperature sensor HktS-HktR

Kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae (Psa) is one of the most devastating diseases of kiwifruit and can damage almost all kiwifruit varieties. The severity of the disease occurrence is closely related to the temperature. Our previous research indicated that Psa showed stronger pathogenicity and expansion ability at relatively cool temperatures, but how Psa senses environmental temperature and regulates its virulence mechanism remains unclear. In this study, 69 Histidine kinases (HK) in Psa were predicted through bioinformatics analysis, and 9 differentially expressed HK genes were identified at varying temperatures through pathogenicity detection and quantitative reverse transcription PCR (qRT-PCR). Among them, HktS as a temperature signal receiver was identified, and its response regulator (RR) HktR was determined through structure analysis and cotranscription assay. The results showed that HktR can bind to transcription factor RpoD, and RpoD bind to hrpRS promoter region, thus initiating the expression level of the type III secretion system (T3SS), which plays an important role in the pathogenesis of Psa. In addition, the motility of Psa was also regulated by HktS-HktR in a temperature-dependent manner. These findings reveal the molecular mechanism by which HktS-HktR acts as a temperature sensor to regulate bacterial virulence and motility of Psa, providing a new potential target for KBC control.

microbiology↗

bioRxiv2024

Substrate utilization and cross-feeding synergistically determine microbiome resistance to pathogen invasion

Understanding how microbiomes resist pathogen invasion remains a key challenge in natural ecosystems. Here, we combined genome-scale metabolic models with synthetic community experiments to unravel the mechanisms driving pathogen suppression. We developed curated genome-scale models for each strain, incorporating 48 common resource utilization profiles to fully capture their metabolic capacities. Trophic interactions inferred from models accurately predicted pathogen invasion outcomes, achieving an F1 score of 96% across 620 invasion tests involving diverse microbial communities and nutrient environments. Importantly, considering both substrate and metabolite features provided a more holistic understanding of pathogen suppression. In particular, cross-feeding metabolites within the native community emerged as crucial yet often overlooked predictors of community resistance, disproportionally favoring native species over invaders. This study lays the foundation for designing disease-resistant microbiomes, with broad implications for mitigating pathogen exposure in diverse environments.

ecology↗

bioRxiv2024

The Whole Proteome, Phosphoproteome, and Glycoproteome Landscape of Pan-Cancer Cell Lines Profiled by Mass Spectrometry and Reverse Phase Protein Array

Mammalian cancer cell lines are essential model systems in biomedical research. We conducted multi-level proteomics analyses on 54 widely used cancer cell lines derived from various tissue-of-origins using two prominent proteomics technologies: mass spectrometry (MS) and reverse-phase protein array (RPPA). Our analysis identified 10,088 proteins, 33,609 phosphorylation sites across 7,289 phosphoproteins, and 56,350 site-specific glycans on 16,296 glycosylation sites from 5,966 glycoproteins, along with 305 drug-relevant protein and phosphoprotein targets. Our results reveal both consistent and distinct patterns in protein expression and modification between MS and RPPA, underscoring their complementary strengths as discovery tools. Additionally, we identified protein features that distinguish tissue origins across different cell line lineages. This dataset supports model system selection for drug target-related studies in vitro and provides valuable insights into key signaling pathways. Overall, this comprehensive resource enables new opportunities for exploration in cancer biology and offers significant value to research communities focused on biomarker profiling, drug target discovery, and understanding mechanisms across diverse cancer types.

cancer biology↗

bioRxiv2024

α-Synuclein Strain Dynamics Correlate with Cognitive Shifts in Parkinson's Disease

-Synuclein (-syn) strains can serve as discriminators between Parkinsons disease (PD) and related -synucleinopathies. The relationship between -syn strain dynamics and clinical performance as patients transition from normal cognition (NC) to cognitive impairment (CI) is not known. Here, we show that the biophysical properties and neurotoxicity of -syn strains change as PD cognitive status transitions from NC to mild cognitive impairment (PD-MCI) and dementia (PD-D). Both cross-sectional and longitudinal analyses reveal distinct -syn strains in PD patients correlating to their level of cognitive impairment. Machine learning (ML) was employed to achieve high classification accuracy. The combination of thioflavin T (ThT) maximal fluorescence intensity (mfi), max slope of rise curve (forming rate), lag time (tlag), 20% time (t20), and half-time (t50), dynamic light scattering (DLS) (peak number, [1/2] peak size, [1/2] peak intensity) and neurotoxicity together with demographic variables for model training yielded superior performance (89[~]99% accuracy in the 4- and 2- classification schema) compared to individual features alone in classifying cognitive status. For the longitudinal study, DLS peak number emerged as the strongest predictor of cognitive transition (HR = 0.12, P = 0.002), with the optimal predictive model combining DLS peak number, sex, education, DLS peak 1 size, and DLS peak 2 polydispersity achieving high accuracy (C-index of [~]93%). This study presents evidence that individuals with PD have different -syn strains correlating to their cognitive status and highlights the potential of -syn strain dynamics to guide future diagnosis, management, and stratification of PD patients. One Sentence SummaryDistinct features of -syn strains change with cognitive decline in Parkinsons disease and AI-based analysis incorporating these combined characteristics serves as a powerful tool for PD clinical stratification.

neuroscience↗

bioRxiv2024

16S rRNA gene sequencing for bacterial identification and infectious disease diagnosis

16S rRNA gene sequence is the most common housekeeping genetic marker to study bacterial phylogeny and taxonomy. Therefore, 16S rRNA gene sequencing has the potential to identify novel bacteria and diagnose bacteria. This study compared 16S rRNA gene sequencing with conventional PCR for bacterial identification and disease diagnosis. The bacterial community in healthy and diseased hosts was analyzed by 16S rRNA gene sequencing. 16S rRNA gene sequencing is more sensitive than conventional PCR in detecting bacteria. Moreover, 16S rRNA gene sequencing is adequate to identify novel bacteria. 16S rRNA gene sequencing demonstrated that most pathogenic bacteria persist in diseased or healthy hosts in different abundance. Pathogenic bacteria, such as well-known chicken pathogen Avibacterium paragallinarum, Ornithobacterium rhinotracheale, and Gallibacterium anatis, were identified as indicator species of diseased samples. Alpha diversity analysis showed that the healthy group species is significantly higher than in the diseased groups. Beta diversity analysis also demonstrated differences between healthy and infected groups. The study concluded that 16S rRNA gene sequencing is a more sensitive method for detecting pathogens, and microbiota analysis can distinguish between healthy and diseased samples. Eventually, 16S rRNA gene sequencing has represented the potential in human and animal clinical diagnosis and novel bacterial identification.

microbiology↗

bioRxiv2024

Engineered Whole Lungs for Tissue Biology

End-stage lung disease and lung cancer significantly contribute to global mortality, necessitating new research strategies for studying pulmonary biology. Here, we present an engineered whole-lung tissue model used to evaluate the effects of cellular communities on tissue organization and alveolar barrier function. Engineered lungs were grown ex vivo on decellularized whole-lung matrices as structurally biomimetic, bioactive scaffolds. Histologic architecture of engineered lungs improved with the addition of alveolar macrophages, coming to resemble neonatal lung. Incorporating alveolar macrophages maximized the differentiation of native-like cellular communities, including alveolar type I-like epithelium, bronchioalveolar stem cells, microvascular endothelium, and pericytes. Cell-cell signaling in engineered lungs showed activation of developmental and inflammatory pathways, including WNT, Notch, and FGF signaling pathways. Engineered lungs containing alveolar macrophages showed a 668% improvement in measured alveolar barrier function. This work demonstrates the potential utility of engineered lung models for studying principles of tissue biology and pulmonary regeneration.

bioengineering↗

bioRxiv2024

Targeting an Olfactory Receptor Mitigates High Residual Platelet Reactivity and Arterial Thrombosis Through Actin Cytoskeleton Depolymerization

BackgroundDespite antiplatelet therapy, some patients remain at high risk for ischemic events due to medication non-responsiveness or High Residual Platelet Reactivity (HRPR). Our goal was to target an orphan G-Protein-Coupled Receptor (GPCR) on platelets belonging to the olfactory receptor family as a new antithrombotic strategy. MethodsUsing an engineered reporter cell line expressing Olfactory Receptor 2L13 (OR2L13) that was recently identified as an orphan GPCR to limit platelet reactivity, we performed a high-throughput screen (HST) of non-odorant bioactive compounds with counter-screen validation, followed by studies to determine changes in platelet function in healthy subjects and in patients with coronary artery disease and peripheral artery disease. Phospho-proteomics identified key signal transduction pathways, and a variety of ex vivo assays and in vivo functional studies examined the impact of an identified non-odorant compound on platelet signaling, platelet biomechanics, and thrombosis. ResultsWe identified 6 ligands specific for OR2L13 that function as receptor agonists, leading to the suppression of platelet aggregation and -granule exocytosis via P2Y12, PAR1, Thromboxane Receptor (TxR) and glycoprotein VI (GPVI) receptors, suggesting involvement of common downstream mediator. The lead OR2L13 agonist identified phosphorylates heat shock protein 27 (HSP27) and depolymerizes the platelet filamentous actin cytoskeleton which was further confirmed in a clot retraction assay (CCF0054500 clot area 70.6 vs. vehicle clot area 5.2, P<0.0001). This anti-thrombotic effect of the OR2L13 agonist was reversed by a HSP27 inhibitor (clot area 3.6, P<0.0001). In a murine cremaster arterial injury model, platelet accumulation at the injury site was reduced by 88.9% by the lead OR2L13 agonist compared to vehicle (P<0.0003) without altering fibrin generation in vivo, or interfering with the coagulation cascade, and without impairing the protective mechanism of platelet hemostasis. ConclusionWe describe and characterize the first non-olfactory tool to target an olfactory receptor for the purpose of inhibiting platelet activation and thrombosis through downstream HSP27 in a comprehensive investigation using a first-of-its kind platelet inhibitor targeting an orphan platelet GPCR.

physiology↗

bioRxiv2024

Gestational arsenite exposure alters maternal postpartum heart size and induces Ca2+ handling dysregulation in cardiomyocytes

Cardiovascular disease is the leading cause of mortality in the US. Studies suggest a role for environmental exposures in the etiology of cardiovascular disease, including exposure to arsenic through drinking water. Arsenic exposure during pregnancy has been shown to have effects on offspring, but few studies have examined impacts on maternal cardiovascular health. While our prior work documented the detrimental effect of arsenic on the maternal heart during pregnancy, our current study examines the effect of gestational arsenic exposure on the maternal heart postpartum. Timed-pregnant wild-type (C57BL/6J) mice were exposed to 0, 100 or 1000 {micro}g/L sodium arsenite (NaAsO2) via drinking water from embryonic day 2.5 (E2.5) until parturition. Postpartum heart structure and function was assessed via transthoracic echocardiography and gravimetric measurement. Hypertrophic markers were probed via qRT-PCR and western blot. Isolated cardiomyocyte Ca2+-handling and contraction were also assessed, and expression of proteins associated with Ca2+ handling and contraction. Interestingly, we found that exposure to either 100 or 1000 {micro}g/L sodium arsenite increased postpartum heart size at P12 vs. non-exposed postpartum controls. At the cellular level, we found altered cardiomyocyte Ca2+-handling and contraction. We also found altered expression of key contractile proteins, including -Actin and cardiac myosin binding protein C (cMyBP-c). Together, these findings suggest that gestational arsenic exposure impacts the postpartum maternal heart, possibly inducing long-term cardiovascular changes. Furthermore, these findings highlight the importance of reducing arsenic exposure during pregnancy, and the need for more research on the impact of arsenic and other environmental exposures on maternal heart health and adverse pregnancy events. New & NoteworthyGestational exposure to sodium arsenite at environmentally relevant doses (100 and 1000 {micro}g/L) increases postpartum heart size, and induces dysregulated Ca2+ homeostasis and impaired shortening in isolated cardiomyocytes. This is the first study to demonstrate that gestational arsenic exposure impacts postpartum heart structure and function beyond the exposure period.

pharmacology and toxicology↗

bioRxiv2024

ADENYLATE CYCLASE 3 MEDIATES CAROTID BODY ACTIVATION AND AUTONOMIC DYSFUNCTION IN A SLEEP APNEA MODEL

Patients with obstructive sleep apnea (OSA) experience chronic intermittent hypoxia (CIH). OSA patients and CIH-treated rodents exhibit autonomic dysfunction, characterized by overactive sympathetic nervous system and hypertension, mediated through hyperactive carotid body (CB) chemoreflex. Activation of olfactory receptor 78 (Olfr78) by hydrogen sulfide (H2S) is implicated in CB activation and autonomic responses to CIH, but the downstream signaling pathways remain unknown. Given that odorant receptor signaling is coupled to adenylyl cyclase 3 (Adcy3), we hypothesized that Adcy3-dependent cAMP contributes to CB and autonomic responses to CIH. Our findings show that CIH increases cAMP levels in the CB, a response absent in Adcy3, Cth, and Olfr78 null mice. CBs from Cth and Olfr78 mutant mice lacked persulfidation response to CIH, indicating that Adcy3 activation by CIH requires Olfr78 activation by H2S. CIH also enhanced glomus cell Ca2+ influx, an effect absent in Cnga2 and Adcy3 mutants, suggesting that CIH-induced cAMP mediates enhanced Ca2+ responses through cyclic nucleotide-gated channels. Furthermore, Adcy3 null mice did not exhibit neither CB activation nor autonomic dysfunction by CIH. These results demonstrate that Adcy3-dependent cAMP is a downstream signaling pathway to H2S/Olfr78, mediating CIH-induced CB activation and autonomic dysfunction.

physiology↗

bioRxiv2024

Genetic-Dependent Brain Signatures of Resilience: Interactions among Childhood Abuse, Genetic Risks and Brain Function

Resilience to emotional disorders is critical for adolescent mental health, especially following childhood abuse. Yet, brain signatures of resilience remain undetermined due to the differential susceptibility of the brains emotion processing system to environmental stresses. Analyzing brains responses to angry faces in a longitudinally large-scale adolescent cohort (IMAGEN), we identified two functional networks related to the orbitofrontal and occipital regions as candidate brain signatures of resilience. In girls, but not boys, higher activation in the orbitofrontal-related network was associated with fewer emotional symptoms following childhood abuse, but only when the polygenic burden for depression was high. This finding defined a genetic-dependent brain (GDB) signature of resilience. Notably, this GDB signature predicted subsequent emotional disorders in late adolescence, extending into early adulthood and generalizable to another independent prospective cohort (ABCD). Our findings underscore the genetic modulation of resilience-brain connections, laying the foundation for enhancing adolescent mental health through resilience promotion.

neuroscience↗

bioRxiv2024

Genetic code expansion reveals site-specific lactylation in living cells reshapes protein function

Still in its infancy, the functions of lactylation remain elusive. To address this, we established a comprehensive workflow for lactylation studies that integrates the discovery of lactylation sites with proteomics, the expression of site-specifically lactylated proteins in living cells via genetic code expansion (GCE), and the evaluation of the resulting biological consequences. Specifically, we developed a wet-and-dry-lab combined proteomics strategy, and identified highly conserved lactylation at ALDOA-K147. Driven by its potential biological significance, we site-specifically expressed this lactylated ALDOA in mammalian cells and interrogated the biological changes. We discovered that it not only inhibited enzyme activity but also elicited gain-of-function effects----it dramatically reshaped the functionality of ALDOA by improving stability, enhancing nuclear translocation and affecting gene expression. Further, we demonstrated broad applicability of this workflow to study distinct histone lactylation sites. Together, we anticipate its wide uses in elucidating causative links between site-specific lactylation and target-centric or cell-wide changes.

molecular biology↗

bioRxiv2024

Reactive Oxygen species dependent increase in H3K27 acetylation by intermittent hypoxia is regulated by H3S28 phosphorylation

Histones play a crucial role in regulating gene expression through post -translational modifications (PTMS) which include acetylation, methylation and phosphorylation. We have previously identified histone 3 acetylation (H3Kac) and methylation (H3Kme) as an early epigenetic mechanism associated with intermittent hypoxia (IH), a hallmark feature of sleep apnea. The goal of the present study was to determine the molecular mechanisms underlying IH increased H3 acetylation. IH-induced H3 acetylation was blocked by an antioxidant. Conversely, reactive oxygen species (ROS) mimetics, increased H3 acetylated protein expression similar to IH, suggesting a role for ROS. Trichostatin A (TSA), an HDAC (histone deacetylase) inhibitor mimicked IH-induced H3 acetylation under normoxic conditions, while pharmacological blockade of p300/CBP (HAT, histone acetylase) with CTK7A abolished IH-induced H3 acetylation. These results suggest that interplay between HATs and HDACs regulate ROS-dependent H3 acetylation by IH. Lysine 27 (H3K27) on H3 was one of the lysines specifically acetylated by IH and this acetylation was associated with dephsophorylation of H3 at serine 28 (H3S28). Inhibition of S28 dephosphorylation by protein phosphatase inhibitors (PIC or Calyculin A), prevented H3K27 acetylation by IH. Conversely, inhibiting K27 acetylation with CTK7A, increased S28 phosphorylation in IH-exposed cells. These findings highlight the intricate balance between H3 acetylation and phosphorylation in response to IH, shedding light on epigenetic mechanism regulating gene expression. (Supported by NIH-PO1-HL90554).

cell biology↗

bioRxiv2024

Metapipeline-DNA: A Comprehensive Germline & Somatic Genomics Nextflow Pipeline

SummaryThe price, quality and throughout of DNA sequencing continue to improve. Algorithmic innovations have allowed inference of a growing range of features from DNA sequencing data, quantifying nuclear, mitochondrial and evolutionary aspects of both germline and somatic genomes. To automate analyses of the full range of genomic characteristics, we created an extensible Nextflow meta-pipeline called metapipeline-DNA. Metapipeline-DNA analyzes targeted and whole-genome sequencing data from raw reads through pre-processing, feature detection by multiple algorithms, quality-control and data- visualization. Each step can be run independently and is supported robust software engineering including automated failure-recovery, robust testing and consistent verifications of inputs, outputs and parameters. Metapipeline-DNA is cloud-compatible and highly configurable, with options to subset and optimize each analysis. Metapipeline-DNA facilitates high-scale, comprehensive analysis of DNA sequencing data. AvailabilityMetapipeline-DNA is an open-source Nextflow pipeline under the GPLv2 license and is available at https://github.com/uclahs-cds/metapipeline-DNA.

bioinformatics↗

bioRxiv2024

Genetic Architecture and Analysis Practices of Circulating Metabolites in the NHLBI Trans-Omics for Precision Medicine (TOPMed) Program

Circulating metabolite levels partly reflect the state of human health and diseases and can be impacted by genetic determinants. Hundreds of loci associated with circulating metabolites have been identified; however, most findings focus on predominantly European ancestry or single-study analyses. Leveraging the rich metabolomics resources generated by the NHLBI Trans-Omics for Precision Medicine (TOPMed) Program, we harmonized and accessibly cataloged 1,729 circulating metabolites among 25,058 ancestrally diverse samples. We provided a set of reasonable strategies for outlier and imputation handling to process metabolite data. Following the practical analysis framework, we further performed a genome-wide association analysis on 1,135 selected metabolites using whole genome sequencing data from 16,359 individuals passing the quality control filters, and discovered 1,778 independent loci associated with 667 metabolites. Among 108 novel locus-metabolite pairs, we detected not only novel loci within previously implicated metabolite associated genes but also novel genes (such as GAB3 and VSIG4 located in the X chromosome) that have putative roles in metabolic regulation. In the sex-stratified analysis, we revealed 85 independent locus-metabolite pairs with evidence of sexual dimorphism, including well-known metabolic genes such as FADS2, D2HGDH, SUGP1, UTG2B17, strongly supporting the importance of exploring sex difference in the human metabolome. Taken together, our study depicted the genetic contribution to circulating metabolite levels, providing additional insight into the understanding of human health.

bioinformatics↗

bioRxiv2024

Msh3 and Pms1 Set Neuronal CAG-repeat Migration Rate to Drive Selective Striatal and Cortical Pathogenesis in HD Mice

Modifiers of Huntingtons disease (HD) include mismatch repair (MMR) genes; however, their underlying disease-altering mechanisms remain unresolved. Knockout (KO) alleles for 9 HD GWAS modifiers/MMR genes were crossed to the Q140 Huntingtin (mHtt) knock-in mice to probe such mechanisms. Four KO mice strongly (Msh3 and Pms1) or moderately (Msh2 and Mlh1) rescue a triad of adult-onset, striatal medium-spiny-neuron (MSN)-selective phenotypes: somatic Htt DNA CAG-repeat expansion, transcriptionopathy, and mHtt protein aggregation. Comparatively, Q140 cortex also exhibits an analogous, but later-onset, pathogenic triad that is Msh3-dependent. Remarkably, Q140/homozygous Msh3-KO lacks visible mHtt aggregates in the brain, even at advanced ages (20-months). Moreover, Msh3-deficiency prevents striatal synaptic marker loss, astrogliosis, and locomotor impairment in HD mice. Purified Q140 MSN nuclei exhibit highly linear age-dependent mHtt DNA repeat expansion (i.e. repeat migration), with modal-CAG increasing at +8.8 repeats/month (R2=0.98). This linear rate is reduced to 2.3 and 0.3 repeats/month in Q140 with Msh3 heterozygous and homozygous alleles, respectively. Our study defines somatic Htt CAG-repeat thresholds below which there are no detectable mHtt nuclear or neuropil aggregates. Mild transcriptionopathy can still occur in Q140 mice with stabilized Htt 140-CAG repeats, but the majority of transcriptomic changes are due to somatic repeat expansion. Our analysis reveals 479 genes with expression levels highly correlated with modal-CAG length in MSNs. Thus, our study mechanistically connects HD GWAS genes to selective neuronal vulnerability in HD, in which Msh3 and Pms1 set the linear rate of neuronal mHtt CAG-repeat migration to drive repeat-length dependent pathogenesis; and provides a preclinical platform for targeting these genes for HD suppression across brain regions. One Sentence SummaryMsh3 and Pms1 are genetic drivers of sequential striatal and cortical pathogenesis in Q140 mice by mediating selective CAG-repeat migration in HD vulnerable neurons.

neuroscience↗

bioRxiv2024

Rod-shaped microglia interact with neuronal dendrites to regulate cortical excitability in TDP-43 related neurodegeneration

Motor cortical hyperexcitability is well-documented in the presymptomatic stage of amyotrophic lateral sclerosis (ALS). However, the mechanisms underlying this early dysregulation are not fully understood. Microglia, as the principal immune cells of the central nervous system, have emerged as important players in sensing and regulating neuronal activity. Here we investigated the role of microglia in the motor cortical circuits in a mouse model of TDP-43 neurodegeneration (rNLS8). Utilizing multichannel probe recording and longitudinal in vivo calcium imaging in awake mice, we observed neuronal hyperactivity at the initial stage of disease progression. Spatial and single-cell RNA sequencing revealed that microglia are the primary responders to motor cortical hyperactivity. We further identified a unique subpopulation of microglia, rod-shaped microglia, which are characterized by a distinct morphology and transcriptional profile. Notably, rod-shaped microglia predominantly interact with neuronal dendrites and excitatory synaptic inputs to attenuate motor cortical hyperactivity. The elimination of rod-shaped microglia through TREM2 deficiency increased neuronal hyperactivity, exacerbated motor deficits, and further decreased survival rates of rNLS8 mice. Together, our results suggest that rod-shaped microglia play a neuroprotective role by attenuating cortical hyperexcitability in the mouse model of TDP-43 related neurodegeneration.

neuroscience↗