Biology subjects

Xiao, T.

Publications and source records attributed to Xiao, T..

At least 37 records · Page 2Linked to original sources

bioRxiv2025

Crosstalk between Immune Microenvironment and Hair Follicle Cells Underlies Sexual Dimorphism in Androgenetic Alopecia

Androgenetic alopecia (AGA), also known as female pattern hair loss (FPHL) in women, is the most prevalent form of hair loss. It is characterized by progressive miniaturization of hair follicles and shortening of the anagen phase. The condition is widely attributed to genetic predisposition and androgen-mediated activation of androgen receptors. Other factors, such as the immune microenvironment, could also contribute to the pathogenesis. However, the specific mechanisms involved are still poorly understood. This study aimed to investigate the potential role of skin-resident myeloid cells in interacting with hair follicle cells under androgen stimulation, and to elucidate the sex-specific differences in dihydrotestosterone (DHT)-induced hair loss. Both female and male mice received DHT treatment, and histological examination was performed to assess DHT-induced alterations in skin morphology. Single-cell RNA sequencing (scRNA-seq) was utilized to profile skin cell populations and explore underlying mechanisms. Our results demonstrated that DHT inhibited hair regrowth in both sexes, altered skin thickness, and induced hair follicle miniaturization. scRNA-seq analysis revealed enhanced interactions between myeloid and fibroblast subpopulations, with more robust crosstalk observed in female mice. An in vitro experiment demonstrated that DHT promoted apoptosis of dermal papilla cells (DPCs) in the presence of macrophages. Treatment with polypeptides Y001 and Y002 effectively promoted hair regrowth by suppressing apoptosis signaling pathways. Our findings underscore the interactions between immune cells and hair follicular cells, particularly mediated by skin-resident myeloid cells, in the sexual dimorphism of androgenetic alopecia. The polypeptides Y001 and Y002 exhibit promising therapeutic potential by targeting apoptotic pathways, offering novel avenues for AGA treatment.

cell biology↗

bioRxiv2025

Aggressive Cholesterol Lowering Normalizes Atherosclerosis Regression in Jak2V617F Clonal Hematopoiesis

BackgroundThe Jak2V617F (Jak2VF) mutation is an important cause of both clonal hematopoiesis of indeterminate potential (CHIP) and myeloproliferative neoplasms (MPN). Mouse models of Jak2VF CHIP and MPN show accelerated atherosclerosis progression, driven by macrophage inflammasome activation. We undertook the present study to assess the hypothesis that ongoing inflammation would impede atherosclerosis resolution in Jak2VF mice. Methods and ResultsChimeric Jak2VF/WT or control WT/WT bone marrow was transplanted into Ldlr-/-mice and, following 13-16 weeks of Western diet-induced atherosclerosis progression, cholesterol was lowered either moderately (to 200-300 mg/dl) or markedly (to 100 mg/dl). With moderate cholesterol lowering, there was impaired resolution of lesions in Jak2VFMPN mice compared to controls. However, with marked cholesterol lowering, progression of lesions was halted in both Jak2VF MPN and control mice while macrophage burden was decreased and lesional collagen was increased similarly in Jak2VFMPN and control mice. Two mechanisms of low-density lipoprotein (LDL) lowering-induced suppression of inflammation in plaques were implicated: 1) reversal of increased proliferation, DNA damage and Absent in Melanoma 2 (AIM2) inflammasome activation specifically in Jak2VF macrophages and 2) markedly increased macrophage triggering receptor expressed on myeloid cells 2 (TREM2), c-myc expressing macrophages in both Jak2VF and control mice. ConclusionsAggressive LDL lowering reverses inflammasome activation and induces pro-resolving changes in macrophages in Jak2VF MPN, halting atherosclerosis progression and promoting features of plaque stabilization. These findings suggest that aggressive LDL cholesterol lowering could reverse atherosclerotic cardiovascular disease (ACVD) risk in individuals with JAK2VFCHIP or MPN.

molecular biology↗

bioRxiv2025

Saccades orchestrate intraocular glucose to shape visual responses in birds

Birds exhibit remarkable vision despite lacking the typical network of blood vessels in their eyes. The characteristic poses a long-standing question about how avian retinas fulfill high energy demands necessary for sight. Here we show that natural, rhythmic eye movements, known as oscillatory saccades, orchestrate intraocular metabolic dynamics and attention-guided visual processing in pigeons. In a series of integrated experiments, we monitored eye movements along with glucose levels in the eye and neuronal activity in key brain regions receiving direct input from the retina. We found that these saccades generate fluctuations in intraocular glucose concentrations, closely linked to changes in neuronal visual responses over timescales of seconds to minutes. Moreover, pharmacological manipulations that altered glucose availability and eliminated these oscillatory saccades resulted in corresponding shifts in neuronal responses, demonstrating a causal linkage between oscillatory saccades, metabolic regulation, and visual processing. These findings reveal a mechanism by which birds actively evoked saccades during attention-driven information gathering, propelling retinal metabolism and facilitating their vision in the absence of retinal vasculature. This study underscores the interplay among eye movements, metabolic regulation, and high-level visual performance, suggesting broader implications for how eye movements contribute to retinal health, attention, and visual function across species.

neuroscience↗

bioRxiv2025

Restoration of excitation/inhibition balance enhances neuronal signal-to-noise ratio and rescues social deficits in autism-associated Scn2a-deficiency

Social behavior is critical for survival and adaptation, which is profoundly disrupted in autism spectrum disorders (ASD). Social withdrawal due to information overload was often described in ASD, and it was suspected that increased basal noise, i.e., excessive background neuronal activities in the brain could be a disease mechanism. However, experimental test of this hypothesis is limited. Loss-of-function mutations (deficiency) in SCN2A, which encodes the voltage-gated sodium channel NaV1.2, have been revealed as a leading monogenic cause of profound ASD. Here, we revealed that Scn2a deficiency results in robust and multifaceted social impairments in mice. Scn2a-deficient neurons displayed an increased excitation-inhibition (E/I) ratio, contributing to elevated basal neuronal noise and diminished signal-to-noise ratio (SNR) during social interactions. Notably, the restoration of Scn2a expression in adulthood is able to rescue both SNR and social deficits. By balancing the E/I ratio and reducing basal neuronal firing, an FDA-approved GABAA receptor-positive allosteric modulator improves sociability in Scn2a-deficient mice and normalizes neuronal activities in translationally relevant human brain organoids carrying autism-associated SCN2A nonsense mutation. Collectively, our findings revealed a critical role of the NaV1.2 channel in the regulation of social behaviors, and identified molecular, cellular, and circuitry mechanisms underlying SCN2A-associated disorders. HIGHLIGHTSO_LINaV1.2 deficiency leads to pronounced social deficits in mice. C_LIO_LINaV1.2 deficiency results in an overall enhanced E/I ratio, elevated basal neuronal activity, and impaired signal-to-noise ratio. C_LIO_LIBoth the enhanced E/I ratio and impaired sociability are reversible through the restoration of NaV1.2 expression in adulthood. C_LIO_LITargeted restoration of NaV1.2 in striatum-projecting neurons rescues social impairments. C_LIO_LIGABA transmission is reduced in both mouse and human organoid models of SCN2A deficiency, and acute systemic administration of GABAA receptor-positive allosteric modulators restores sociability. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=193 HEIGHT=200 SRC="FIGDIR/small/641498v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@154a323org.highwire.dtl.DTLVardef@1a27fbaorg.highwire.dtl.DTLVardef@16fa3beorg.highwire.dtl.DTLVardef@6712c2_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical abstract: Severe Scn2a deficiency leads to a predominate decrease in GABA transmission with an overall enhanced E/I ratio, elevated basal neuronal activity, impaired SNR, and social deficits in adult NaV1.2-deficient mice.

neuroscience↗

bioRxiv2025

Intratumoral gene delivery of 4-1BBL boosts IL-12-triggered anti-glioblastoma immunity

The standard of care in high-grade gliomas has remained unchanged in the past 20 years. Efforts to replicate effective immunotherapies in non-cranial tumors have led to only modest therapeutical improvements in glioblastoma (GB). Here, we demonstrate that intratumoral administration of recombinant interleukin-12 (rIL-12) promotes local cytotoxic CD8POS T cell accumulation and conversion into an effector-like state, resulting in a dose-dependent survival benefit in preclinical GB mouse models. This tumor-reactive CD8 T cell response is further supported by intratumoral rIL-12-sensing dendritic cells (DCs) and is accompanied by the co-stimulatory receptor 4-1BB expression on both cell types. Given that DCs and CD8POS T cells are functionally suppressed in the tumor microenvironments of de novo and recurrent glioma patients, we tested whether anti-tumor response at the rIL-12-inflamed tumor site could be enhanced with 4-1BBL, the ligand of 4-1BB. 4-1BBL was delivered using an adeno-associated virus (AAV) vector targeting GFAP-expressing cells and resulted in prolonged survival of rIL-12 treated GB-bearing mice. This study establishes that tumor antigen-specific CD8 T cell activity can be directed using an AAV-vector-mediated gene therapy approach, effectively enhancing anti-GB immunity.

cancer biology↗

bioRxiv2024

Delineation of Single-cell Altas Provides New Insights for Development of Coronary Artery Lesions in Kawasaki Disease: Bad and Good Signaling Molecules

BackgroundKawasaki Disease (KD) is a vasculitis syndrome featured with a high and persistent fever and mainly affects children under 5 years of age. It is the leading cause of acquired heart disease in the form of coronary artery lesions (CALs) for children in developed countries. Most KD can be relieved with the high-dosage Intravenous immunoglobulin (IVIG) therapy, but a small proportion develop CALs after IVIG treatment. MethodsWe performed the single-cell RNA sequencing for the peripheral blood mononuclear cells (PBMCs) from three KD non-CAL patients whose samples were acquired before and after IVIG treatment and three KD CAL patients whose samples were acquired only after IVIG treatment. Cell-to-cell communication patterns were also analyzed in KD CAL and non-CAL patients ResultsOverall cell expression feature analyses show immunoglobulin and adaptive immunity related genes are upregulated in KD CAL patients while B cell activation related genes are downregulated in them. Pseudo-time analyses demonstrate that both KD non-CAL patients before treatment and KD CAL patients after treatment have a dysregulated B cell developmental trajectory while the former has a mixed T and B lineage and the latter has a mixed monocyte and B lineage. The early elevated expression of SPI1 could partly explain the dysregulated B cell development in KD CAL patients. Cell communication analyses propose a disorder cell communication pattern in KD non-CAL patients before treatment and some persistent bad cell-to-cell signals in KD CAL patients after treatment. There are four signaling molecules, APP, CCL, and MCH-II, whose expression is significantly increased in the CD14 and CD16 monocytes of KD CAL patients, where the expression of RESISTIN is significantly increased in those KD non-CAL patients. ConclusionsOur results suggest that APP, CCL, and MCH-II might be the bad signals for indicating the possible development of CAL while RESISTIN is a good one for protecting from CAL.

immunology↗

bioRxiv2024

Principles of nutrition-dependent root-microbiome engineering for regulating crop yield via live microbial inoculants

As the second genome, host-associated microbiota can enhance the functions of host immune systems, improve host nutrient availability and acquisition capacity, and increase host resistance to abiotic stress. Constructing host-associated microbiomes by applying various bioinoculants has become an attractive tool for promoting human health and increasing food production. However, despite their promising properties, the efficacy of bioinoculants vary significantly in actual field and clinical practices. Understanding the global design principles that shape the outcomes of interactions between bioinoculants and target host-microbiome symbionts remains a considerable challenge. In this study, we used a wheat production system as a case study to quantitatively understand how soil nutrient status impacts the establishment of host-microbiome interaction networks and their subsequent interactions with external bioinoculants. We found that soil organic carbon, one of the most general soil properties for global crop productivity and resilience, could affect the outcome of bioinoculant applications in wheat production systems, which led to functional instability in bioinoculant application outcomes. The results of this study significantly improved our understanding of the global design principles of nutrition-dependent root-microbiome engineering for regulating crop yield via the application of live microbial inoculants and provide theoretical guidance for bioinoculant applications in agricultural practice.

microbiology↗

bioRxiv2024

Impaired experience-dependent inter-areal network connectivity across the visual cortex in Fmr1 KO mice

Fragile X syndrome (FX) is the most prevalent inheritable form of autism spectrum disorder (ASD), characterized by hypersensitivity, difficulty in habituating to new sensory stimuli, and intellectual disability. Individuals with FX often experience visual perception and learning deficits. Visual experience leads to the emergence of the familiarity-evoked theta band oscillations in the primary visual cortex (V1) and the lateromedial area (LM) of mice. These theta oscillations in V1 and LM are synchronized with each other, providing a mechanism of sensory multi-areal binding. However, how this multi-areal binding and the corresponding theta oscillations are altered in FX is not known. Using iDISCO whole brain clearing with light-sheet microscopy, we quantified immediate early gene Fos expression in V1 and LM, identifying deficits in experience-dependent neural activity in FX mice. We performed simultaneous in vivo recordings with silicon probes in V1 and LM of awake mice and channelrhodopsin-2-assisted circuit mapping (CRACM) in acute brain slices to examine the neural activity and strength of long-range synaptic connections between V1 and LM in both wildtype (WT) and Fmr1 knockout (KO) mice, the model of FX, before and after visual experience. Our findings reveal synchronized familiarity-evoked theta oscillations in V1 and LM, the increased strength of V1[->]LM functional and synaptic connections, which correlated with the corresponding changes of presynaptic short-term plasticity in WT mice. The LM oscillations were attenuated in FX mice and correlated with impaired functional and synaptic connectivity and short-term plasticity in the feedforward (FF) V1[->]LM and feedback (FB) LM[->]V1 pathways. Finally, using 4Pi single-molecule localization microscopy (SMLM) in thick brain tissue, we identified experience-dependent changes in the density and shape of dendritic spines in layer 5 pyramidal cells of WT mice, which correlated with the functional synaptic measurements. Interestingly, there was an increased dendritic spine density and length in naive FX mice that failed to respond to experience. Our study provides the first comprehensive characterization of the role of visual experience in triggering inter-areal neural synchrony and shaping synaptic connectivity in WT and FX mice.

neuroscience↗

bioRxiv2024

Omicron-specific ultra-potent SARS-CoV-2 neutralizing antibodies targeting the N1/N2 loop of Spike N-terminal domain

A multitude of functional mutations continue to emerge on the N-terminal domain (NTD) of the spike protein in SARS-CoV-2 Omicron subvariants. Understanding the immunogenicity of Omicron NTD and the properties of antibodies elicited by it is crucial for comprehending the impact of NTD mutations on viral fitness and guiding vaccine design. In this study, we find that most of NTD-targeting antibodies isolated from individuals with BA.5/BF.7 breakthrough infection (BTI) are ancestral (wildtype or WT)-reactive and non-neutralizing. Surprisingly, we identified five ultra-potent neutralizing antibodies (NAbs) that can only bind to Omicron but not WT NTD. Structural analysis revealed that they bind to a unique epitope on the N1/N2 loop of NTD and interact with the receptor-binding domain (RBD) via the light chain. These Omicron-specific NAbs achieve neutralization through ACE2 competition and blockage of ACE2-mediated S1 shedding. However, BA.2.86 and BA.2.87.1, which carry insertions or deletions on the N1/N2 loop, can evade these antibodies. Together, we provided a detailed map of the NTD-targeting antibody repertoire in the post-Omicron era, demonstrating their vulnerability to NTD mutations enabled by its evolutionary flexibility, despite their potent neutralization. These results highlighted the importance of considering the immunogenicity of NTD in vaccine design. Author SummaryCOVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to be a major global public health concern four years after its emergence. The N-terminal domain (NTD) is a critical component of the spike glycoprotein, which is pivotal for SARS-CoV-2 cellular entry and serves as a primary target for antibody therapeutics and vaccine development. Characterizing the properties of antibodies elicited by NTD of Omicron sublineages is crucial for understanding viral evolution and guiding vaccine design. Here, we show that Omicron infection after vaccination induces majorly non-neutralizing NTD antibodies. Still, we identified a class of ultra-potent neutralizing antibodies (NAbs) which specifically bind to the NTD of Omicron sublineages. These NAbs neutralize the virus by competing with ACE2 and blocking ACE2-mediated S1 shedding. Structural analyses reveal that these antibodies target a unique epitope on the N1/N2 loop of NTD, and intriguingly interact with the receptor-binding domain (RBD) of spike glycoprotein. This class of NAbs with the special binding pattern, are escaped by BA.2.86 and BA.2.87.1 sublineages, shedding light on the role of recently emerged mutations in the N1/N2 loop of NTD. Our findings provide fresh insights into the immunogenicity of Omicron NTD, highlighting its capacity for antibody evasion due to its evolutionary flexibility. This underscores the importance of carefully considering the NTD component in vaccine design.

immunology↗

bioRxiv2024

Oriented nucleosome binding by the pioneer factor ELF2

Pioneer transcription factors are DNA-binding proteins that can bind to nucleosomes in closed chromatin regions, exposing enhancers and promoters of genes for transcription. The action of these factors underpin stem cell pluripotency, cell reprogramming and differentiation. ELF2 is an ETS family pioneer factor that has a strong preference for oriented binding on nucleosomes at a composite head-to-tail dimeric sequence motif with a 2 bp spacing between the GGAA core elements. In this study, we investigated the interaction between ELF2 and a nucleosome using single-particle cryo-electron microscopy (cryo-EM). The ELF2-nucleosome structure shows two ELF2 proteins bound to the nucleosome cooperatively at superhelical location +4. The recognition [a]4 helices of both ELF2 monomers dock into the major groove at the core GGAA motifs and unwrap approximately four helical turns of the DNA from the surface of the nucleosome. The unwrapping almost completely exposes one histone H2A:H2B dimer, which dissociates in a subset of particles to form an ELF2-bound hexasome. ChIP-seq combined with genome-wide motif mapping indicates that all unmethylated high-affinity ELF2 double motifs are occupied, indicating that ELF2 is able to use its binding energy to function as a pioneer factor both in vitro and in vivo. ELF2 binding is highly enriched downstream of transcription start sites (TSS) of highly expressed genes, with the motifs oriented in such a way that the TSS becomes accessible upon ELF2 binding. This mechanism is essential for cells, as mutation of ELF2 motifs result in decreased cell proliferation. Taken together, our results indicate that ELF2 can use its binding energy to open chromatin in an oriented fashion, facilitating nucleosome positioning and transcription initiation at transcription start sites.

biochemistry↗

bioRxiv2024

Humoral immunogenicity comparison of XBB and JN.1 in human infections

The continuous evolution of SARS-CoV-2, particularly the emergence of the BA.2.86/JN.1 lineage replacing XBB lineages, necessitates re-evaluation of current vaccine compositions. Here, we provide a comprehensive analysis of the humoral immune response to XBB and JN.1 human exposures, emphasizing the need for JN.1-lineage-based boosters. We demonstrate the antigenic distinctiveness of XBB and JN.1 lineages in SARS-CoV-2-naive individuals but not in those with prior vaccinations or infections, and JN.1 infection elicits superior plasma neutralization titers against its subvariants. We highlight the strong immune evasion and receptor binding capability of KP.3, supporting its foreseeable prevalence. Extensive analysis of the BCR repertoire, isolating [~]2000 RBD-specific monoclonal antibodies (mAbs) with their targeting epitopes characterized by deep mutational scanning (DMS), underscores the systematic superiority of JN.1-elicited memory B cells (MBCs). Notably, Class 1 IGHV3-53/3-66-derived neutralizing antibodies (NAbs) contribute majorly within wildtype (WT)-reactive NAbs against JN.1. However, KP.2 and KP.3 evade a substantial subset of them, even those induced by JN.1, advocating for booster updates to KP.3 for optimized enrichment. JN.1-induced Omicron-specific antibodies also demonstrate high potency across all Omicron lineages. Escape hotspots of these NAbs have mainly been mutated in Omicron RBD, resulting in higher immune barrier to escape, considering the probable recovery of previously escaped NAbs. Additionally, the prevalence of broadly reactive IGHV3-53/3-66- encoding antibodies and MBCs, and their capability of competing with all Omicron-specific NAbs suggests their inhibitory role on the de novo activation of Omicron-specific naive B cells, potentially explaining the heavy immune imprinting in mRNA-vaccinated individuals. These findings delineate the evolving antibody response to Omicron antigenic shift from XBB to JN.1, and highlight the importance of developing JN.1 lineage, especially KP.3-based vaccine boosters, to enhance humoral immunity against current and future SARS-CoV-2 variants.

immunology↗

bioRxiv2024

A generalized framework to identify SARS-CoV-2 broadly neutralizing antibodies

Monoclonal antibodies (mAbs) targeting the SARS-CoV-2 receptor-binding domain (RBD) are used to treat and prevent COVID-19. However, the rapid evolution of SARS-CoV-2 drives continuous escape from therapeutic mAbs. Therefore, the ability to identify broadly neutralizing antibodies (bnAbs) against future variants is needed. Here, we use deep mutational scanning (DMS) to predict viral RBD evolution and to select for mAbs neutralizing both existing and prospective variants. A retrospective analysis of 1,103 SARS-CoV-2 wildtype-elicited mAbs shows that this method can increase the probability of identifying effective bnAbs against the XBB.1.5 strain from 1% to 40% in an early pandemic setup. Among these bnAbs, BD55-1205 exhibited potent activity against all tested variants. Cryo-EM structural analyses revealed the receptor mimicry of BD55-1205, explaining its broad reactivity. Delivery of mRNA-LNPs encoding BD55-1205-IgG in mice resulted in ~5,000 serum NT50 against XBB.1.5, HK.3.1, and JN.1 variants. Combining bnAb identification using viral evolution prediction with the versatility of mRNA delivery technology can enable rapid development of next-generation antibody-based countermeasures against SARS-CoV-2 and potentially other pathogens with pandemic potential.

immunology↗

bioRxiv2024

Escalation of intravenous fentanyl self-administration and assessment of withdrawal behavior in male and female mice

BackgroundThe rise in overdose deaths from synthetic opioids, especially fentanyl, necessitates the development of preclinical models to study fentanyl use disorder (FUD). While there has been progress with rodent models, additional translationally relevant models are needed to examine excessive fentanyl intake and withdrawal symptoms. MethodsThe study performed intravenous self-administration (IVSA) of fentanyl in male and female C57BL/6J mice for 14 days. Mechanical pain sensitivity during withdrawal was assessed using the von Frey test. Anxiety-like behavior was evaluated via the open field test one-week into abstinence and incubation of craving for fentanyl was assessed four weeks into abstinence. ResultsBoth male and female mice demonstrated a significant escalation in fentanyl intake over the 14 days of self-administration, with significant front-loading observed in the final days of self-administration. Increased mechanical pain sensitivity was present from 36- to 48-hour into withdrawal and increased anxiety-like behavior was found 1 week into abstinence. Four weeks into abstinence, mice showed significantly higher active lever pressing than the final self-administration session prior to abstinence. ConclusionsThe study establishes a translationally relevant mouse model of IVSA of fentanyl, effectively encapsulating critical aspects of FUD, including escalation of drug intake, front-loading behavior, withdrawal symptoms, and prolonged craving for drug into abstinence. This model offers a robust basis for further exploration into behavioral and neurobiological mechanisms involved in fentanyl dependence and potential therapeutic strategies.

neuroscience↗

bioRxiv2024

Spike N354 glycosylation augments SARS-CoV-2 fitness for human adaptation through multiple mechanisms

Selective pressures have given rise to a number of SARS-CoV-2 variants during the prolonged course of the COVID-19 pandemic. Recently evolved variants differ from ancestors in additional glycosylation within the spike protein receptor-binding domain (RBD). Details of how the acquisition of glycosylation impacts viral fitness and human adaptation are not clearly understood. Here, we dissected the role of N354-linked glycosylation, acquired by BA.2.86 sub-lineages, as a RBD conformational control element in attenuating viral infectivity. The reduced infectivity could be recovered in the presence of heparin sulfate, which targets the "N354 pocket" to ease restrictions of conformational transition resulting in a "RBD-up" state, thereby conferring an adjustable infectivity. Furthermore, N354 glycosylation improved spike cleavage and cell-cell fusion, and in particular escaped one subset of ADCC antibodies. Together with reduced immunogenicity in hybrid immunity background, these indicate a single spike amino acid glycosylation event provides selective advantage in humans through multiple mechanisms. HIGHLIGHTSN354 glycosylation acts as a conformational control element to modulate infectivity Reduced infectivity could be recovered by altered binding mode of heparin sulfate N354 glycosylation improved fusogenicity and conferred escape from ADCC antibodies N354 glycosylation reduced immunogenicity and conferred immune evasion

microbiology↗

bioRxiv2023

Glial swip-10 expression controls systemic mitochondrial function, oxidative stress, and neuronal viability via copper ion homeostasis

Cuprous copper (Cu(I)) is an essential cofactor for enzymes supporting many cellular functions including mitochondrial respiration and suppression of oxidative stress. Neurons are particularly dependent on these pathways, with multiple neurodegenerative diseases, including Alzheimers disease (AD), Parkinsons disease, associated with their dysfunction. Key features of Cu(I) contributions to neuronal health in vivo remain to be defined, owing largely to the complex processes involved in Cu(I) production, intracellular transport, and systemic redistribution. Here, we provide genetic and pharmacological evidence that swip-10 is a critical determinant of systemic Cu(I) levels in C. elegans, with deletion leading to systemic deficits in mitochondrial respiration, production of oxidative stress, and neurodegeneration. These phenotypes can be reproduced in wild-type worms by Cu(I)-specific chelation and offset in swip-10 mutants by growth on the Cu(I) enhancing molecule elesclomol, as well as by glial expression of wildtype swip-10. MBLAC1, the most closely related mammalian ortholog to swip-10, encodes for a pre-mRNA processing enzyme for H3 histone, a protein whose actions surprisingly include an enzymatic capacity to produce Cu(I) via the reduction of Cu(II). Moreover, genome-wide association studies and post-mortem molecular studies implicate reductions of MBLAC1 expression in risk for AD with cardiovascular disease comorbidity. Consistent with these studies, we demonstrate that the deposition of {beta}-amyloid plaques, an AD pathological hallmark, in worms engineered to express human A{beta}1-42, is greatly exaggerated by mutation of swip-10. Together, these studies identify a novel glial-expressed, and pathway for Cu(I) production that may be targeted for the treatment of AD and other neurodegenerative diseases. Significance StatementDevastating neurodegenerative diseases such as Alzheimers disease, and Parkinsons disease are associated with disruptions in copper (Cu) homeostasis. Alterations in Cu(I) give rise to increased oxidative stress burden, mitochondrial and metabolic dysfunction, and can accelerate production and/or potentiate toxicity of disease-associated protein aggregates. Here, using the model system Caenorhabditis elegans, we establish a role for the gene swip-10 in systemic Cu(I) homeostasis. Perturbation of this pathway in worms recapitulates biochemical, histological, and pathological features seen in human neurodegenerative disease. We reveal that these changes can be suppressed pharmacologically and arise when swip-10 expression is eliminated from glial cells. Our work implicates swip-10 and orthologs as key players in Cu(I) homeostasis that may be exploitable to treat multiple neurodegenerative diseases.

neuroscience↗

bioRxiv2023

Human iPSC-derived microglia sense and dampen hyperexcitability of cortical neurons carrying the epilepsy-associated SCN2A-L1342P mutation

Neuronal hyperexcitability is a hallmark of seizures. It has been recently shown in rodent models of seizures that microglia, the brains resident immune cells, can respond to and modulate neuronal excitability. However, how human microglia interacts with human neurons to regulate hyperexcitability mediated by epilepsy-causing genetic mutation found in human patients remains unknown. The SCN2A genetic locus is responsible for encoding the voltage-gated sodium channel Nav1.2, recognized as one of the leading contributors to monogenic epilepsies. Previously, we demonstrated that the recurring Nav1.2-L1342P mutation identified in patients with epilepsy leads to hyperexcitability in a hiPSC-derived cortical neuron model from a male donor. While microglia play an important role in the brain, these cells originate from a different lineage (yolk sac) and thus are not naturally present in hiPSCs-derived neuronal culture. To study how microglia respond to diseased neurons and influence neuronal excitability, we established a co-culture model comprising hiPSC-derived neurons and microglia. We found that microglia display altered morphology with increased branch length and enhanced calcium signal when co-cultured with neurons carrying the Nav1.2-L1342P mutation. Moreover, the presence of microglia significantly lowers the action potential firing of neurons carrying the mutation. Interestingly, we further demonstrated that the current density of sodium channels in neurons carrying the epilepsy-associated mutation was reduced in the presence of microglia. Taken together, our work reveals a critical role of human iPSCs-derived microglia in sensing and dampening hyperexcitability mediated by an epilepsy-causing mutation present in human neurons, highlighting the importance of neuron-microglia interactions in human pathophysiology. Significance StatementSeizure studies in mouse models have highlighted the role of microglia in modulating neuronal activity, particularly in the promotion or suppression of seizures. However, a gap persists in comprehending the influence of human microglia on intrinsically hyperexcitable neurons carrying epilepsy-associated pathogenic mutations. This research addresses this gap by investigating human microglia and their impact on neuronal functions. Our findings demonstrate that microglia exhibit dynamic morphological alterations and calcium fluctuations in the presence of neurons carrying an epilepsy-associated SCN2A mutation. Furthermore, microglia suppressed the excitability of diseased hyperexcitable neurons, suggesting a potential beneficial role. This study underscores the role of microglia in the regulation of abnormal neuronal activity, providing insights into therapeutic strategies for neurological conditions associated with hyperexcitability.

neuroscience↗

bioRxiv2023

Interfacial water confers transcription factors with dinucleotide specificity

Transcription factors bind to DNA by recognizing specific bases within their binding motifs. Binding to each DNA mononucleotide within the motif often contributes independently to total binding energy. However, some transcription factors (TFs) can bind to DNA more specifically than predicted by this model, by directly recognizing DNA dinucleotides. To understand this process, we have solved the structures of the basic helix-loop-helix protein MYF5, and the homeodomain protein BARHL2 together with DNA containing a set of dinucleotides that have different affinities to the proteins at high resolution (< 1 [A]). We observe that dinucleotides can be recognized either enthalpically by an extensive water network that connects the adjacent bases to the TF, or entropically by formation of a hydrophobic patch that maintains water mobility at the protein-DNA interface. The two distinct thermodynamic signatures of the two equally optimal sites also confer differential temperature sensitivity to the optimal sites, with implications for thermal regulation of gene expression. Our results uncover the enigma of how TFs can recognize more complex local features than mononucleotides, and demonstrate that water-mediated recognition is important in predicting affinities of macromolecules from their sequence.

biochemistry↗

bioRxiv2023

Antigenicity and infectivity characterization of SARS-CoV-2 BA.2.86

The recently identified SARS-CoV-2 variant, BA.2.86, which carries a substantial number of Spike mutations, has raised a global alarm. An immediate assessment of its antigenic properties and infectivity is necessary. Here, we reveal the distinct antigenicity of BA.2.86 compared with previous variants including XBB.1.5. BA.2.86 significantly evades convalescent plasma from XBB breakthrough infection (BTI) and reinfections. Key mutations that mediate the enhanced resistance include N450D, K356T, L452W, A484K, V483del, and V445H on the RBD, while BA.2.86s NTD mutations and E554K on SD1 also largely contribute. However, we found that BA.2.86 pseudovirus exhibits compromised efficiency of infecting HEK293T-hACE2 cells compared to XBB.1.5 and EG.5, which may be caused by K356T, V483del, and E554K, and could potentially limit BA.2.86s transmissibility. In sum, it appears that BA.2.86 has traded its infectivity for higher immune evasion during long-term host-viral evolution. Close attention should be paid to monitoring additional mutations that could improve BA.2.86s infectivity.

immunology↗