Biology subjects

Liu, Y.

Publications and source records attributed to Liu, Y..

At least 1,063 records · Page 59Linked to original sources

bioRxiv2024

Ribozyme-based biosensor for imaging gene expression in plants

Detection of gene expression in plants is critical for understanding the molecular basis of complex plant biosystems and plant responses to environmental stresses. Here, we report the development of a split ribozyme-based biosensor that enables in vivo visualization of gene expression in plants. We demonstrated the utility of this biosensor in transient expression experiments (i.e., leaf infiltration in Nicotiana benthamiana) to detect RNAs derived from transgenes and tobacco rattle virus, respectively. Furthermore, we successfully engineered a split ribozyme-based biosensor in Arabidopsis thaliana for in vivo visualization of endogenous gene expression at the cellular level. In addition, we developed a platform for easy incorporation of different reporters into the RNA biosensor.

synthetic biology↗

bioRxiv2024

Multi-View Integrative Approach For Imputing Short-Chain Fatty Acids and Identifying Key factors predicting Blood SCFA

Short-chain fatty acids (SCFAs) are the main metabolites produced by bacterial fermentation of dietary fiber within gastrointestinal tract. SCFAs produced by gut microbiotas (GMs) are absorbed by host, reach bloodstream, and are distributed to different organs, thus influencing host physiology. However, due to the limited budget or the poor sensitivity of instruments, most studies on GMs have incomplete blood SCFA data, limiting our understanding of the metabolic processes within the host. To address this gap, we developed an innovative multi-task multi-view integrative approach (M2AE, Multi-task Multi-View Attentive Encoders), to impute blood SCFA levels using gut metagenomic sequencing (MGS) data, while taking into account the intricate interplay among the gut microbiome, dietary features, and host characteristics, as well as the nuanced nature of SCFA dynamics within the body. Here, each view represents a distinct type of data input (i.e., gut microbiome compositions, dietary features, or host characteristics). Our method jointly explores both view-specific representations and cross-view correlations for effective predictions of SCFAs. We applied M2AE to two in-house datasets, which both include MGS and blood SCFAs profiles, host characteristics, and dietary features from 964 subjects and 171 subjects, respectively. Results from both of two datasets demonstrated that M2AE outperforms traditional regression-based and neural-network based approaches in imputing blood SCFAs. Furthermore, a series of gut bacterial species (e.g., Bacteroides thetaiotaomicron and Clostridium asparagiforme), host characteristics (e.g., race, gender), as well as dietary features (e.g., intake of fruits, pickles) were shown to contribute greatly to imputation of blood SCFAs. These findings demonstrated that GMs, dietary features and host characteristics might contribute to the complex biological processes involved in blood SCFA productions. These might pave the way for a deeper and more nuanced comprehension of how these factors impact human health.

bioinformatics↗

bioRxiv2024

Interpreting Sleep Activity Through Neural Contrastive Learning

Memories are spontaneously replayed during sleep, a process thought to support memory consolidation. However, capturing this replay in humans has been challenging because unlike wakefulness, sleep EEG is dominated by slow, rhythmic background activity. Moreover, each sleep stage (e.g., NREM, REM) has distinct rhythms, hindering generalisation of models trained on wake-state data. To overcome these challenges, we developed the Sleep Interpreter (SI), a neural network model that decodes memory replay from sleep EEG. In a large dataset comprising 135 participants ([~]1,000 h of overnight sleep; [~]400 h of wake), we employed a TMR-like paradigm with 15 semantically congruent cue-image pairs to tag specific memories. SI was trained separately for NREM and REM using contrastive learning to align neural patterns across wake and sleep, filtering out stage-specific background rhythms. We also examined how slow oscillations and spindle coupling influence decoding in NREM sleep. In a 15-way classification, SI achieved up to 40.02% Top-1 accuracy on unseen subjects. To test generalisability, we followed up with two independent nap experiments in separate samples and applied the trained SI model off-the-shelf. The first probed spontaneous reactivation without auditory cues, while the second used semantic-free sounds with new images. In both, SI successfully decoded reactivation during sleep that correlated with post-nap memory performance. By openly sharing our dataset and SI system, we provide a unique resource for advancing research on memory and learning during sleep, and related disorders.

neuroscience↗

bioRxiv2024

Growth and defence in a unicellular microalga: the coexistence of r and K strategies

r (high reproductivity but stress-sensitive offspring) and K (low reproductivity but high stress-resistant offspring) strategies are two classical life history theories. Contrary to the belief that one species only has a single strategy (i.e., either r or K), we present experimental evidence for the coexistence of both strategies in the isogenic microalga Haematococcus lacustris. Under standard conditions, swimming vegetative cells (SVC) normally grew and divided via binary fission (r strategy) and gradually shifted into non-swimming cysts (NSC) over time. Intriguingly, unlike the prevailing notion that NSC cannot propagate under stress, they were found to reproduce via multiple fission at a barely detectable growth rate, resulting in stress-resistant, non-mobile daughter cells and demonstrating a complete life history (K strategy). Collectively, our findings indicate that H. lacustris adopts both r and K strategies throughout its life history. This research enhances the understanding of the adaptation and survival of microbial populations in changing environments.

ecology↗

bioRxiv2024

AQP1- A regulatory factor associated with brown adipose tissue silencing

The activation of non-shivering thermogenesis (NST) in brown adipose tissue (BAT) by environmental cold challenge yields strong metabolic benefit in the face of diet-induced obesity (DIO). Yet, a critical barrier to leveraging brown fat NST for therapeutic use against metabolic disease is that BAT is silenced and inactive at physiological ambient temperature conditions in humans. The mechanisms that govern this silencing process remain poorly understood. Here, we identified a putative BAT-silencing factor, aquaporin-1 (AQP1), in brown fat from wild-type (WT) mice via proteomics analysis. We generated the first BAT-specific AQP1 knockout mice (AQP1-KO) and revealed that AQP1-KO could activate NST under BAT silencing environmental conditions and that the AQP1-KO mice were significantly protected against DIO and metabolic dysfunction compared to Flox controls. We found that AQP1-KO mice on high fat diet (HFD) had reduced weight gain through reductions in fat mass, improved glucose tolerance, and increased whole body energy expenditure compared to Flox control mice. Mechanistically, we show that AQP1 ablation in mice had upregulated gene expression related to the electron transport chain (ETC) and mitochondrial translation contributing to the activation of NST under BAT environmental silenced conditions. Significance StatementNovel strategies to combat obesity-associated metabolic dysfunction are urgently needed to curb the growing obesity epidemic. Investigation of brown adipose tissue (BAT) silencing mechanisms may reveal novel therapeutic targets that when ablated, can activate BAT to increase energy expenditure and protect subjects against the metabolic dysfunction associated with obesity. We have identified Aquaporin 1 (AQP1) as a putative BAT silencer regulatory factor and show through the generation of the first BAT-specific aquaporin-1 knockout (AQP1-KO) mouse that BAT can be activated under environmental silencing conditions. We further show that these mice are protected against diet-induced obesity, with improved glucose tolerance, and increased energy expenditure. These findings highlight AQP1 as a promising therapeutic target in the emerging research field of BAT silencers.

molecular biology↗

bioRxiv2024

Fasting is required for many of the benefits of calorie restriction in the 3xTg mouse model of Alzheimer&aposs disease

Caloric restriction (CR) is a widely recognized geroprotective intervention that slows or prevents Alzheimers disease (AD) in animal models. CR is typically implemented via feeding mice a single meal per day; as CR mice rapidly consume their food, they are subject to a prolonged fast between meals. While CR has been shown to improve metabolic and cognitive functions and suppress pathological markers in AD mouse models, the specific contributions of fasting versus calorie reduction remains unclear. Here, we investigated the contribution of fasting and energy restriction to the beneficial effects of CR on AD progression. To test this, we placed 6-month-old 3xTg mice on one of several diet regimens, allowing us to dissect the effects of calories and fasting on metabolism, AD pathology, and cognition. We find that energy restriction alone, without fasting, was sufficient to improve glucose tolerance and reduce adiposity in both sexes, and to reduce A{beta} plaques and improve aspects of cognitive performance in females. However, we find that a prolonged fast between meals is necessary for many of the benefits of CR, including improved insulin sensitivity, reduced phosphorylation of tau, decreased neuroinflammation, inhibition of mTORC1 signaling, and activation of autophagy, as well as for the full cognitive benefits of CR. Finally, we find that fasting is essential for the benefits of CR on survival in male 3xTg mice. Overall, our results demonstrate that fasting is required for the full benefits of a CR diet on the development and progression of AD in 3xTg mice, and suggest that both when and how much we eat influences the development and progress of AD.

physiology↗

bioRxiv2024

Constructing a Mouse Brain Atlas of Dendritic Microenvironments Helps Discover Hidden Associations Between Anatomical Layout, Projection Targets and Transcriptomic Profiles of Neurons

Digital brain atlases have become essential anatomical references for understanding the spatial and functional organization of brains. For mice, typical resources include the Allen Reference Atlas, the Allen Common Coordinate Framework (CCF), and their variants, like CCFv3. However, previous whole-brain atlases were constructed based on limited neuronal features, such as cell body (soma) density or average maps from collections of registered brain images, without considering the spatial organization of neuronal arbors. This study introduces a microenvironment representation that incorporates the morphological features of neighboring neurons to better quantify brain modularity. We generated a large dataset containing dendrites from 101,136 neurons across 111 mouse brains, covering 91% of non-ventricular, non-fiber-tract CCF regions, and constructed a multidimensional microenvironment feature map of the whole brain. Our findings reveal that the spatial organization of these microenvironments outperforms the CCFv3 and a state-of-the-art spatial transcriptomic cell atlas by providing complementary subregions within established regions, nearly doubling the total number of brain regions compared to CCFv3. In this way, our atlas enables the identification of previously unobserved neuron groupings or "subtypes". Our results also demonstrate that this microenvironment atlas enhances local spatial homogeneity while maintaining spatial differentiation within established CCF brain regions. For example, we found that the microenvironments of hippocampal neurons are correlated with axonal projection targets and improve the specificity of projection mapping, which implies the potential characterization of long-range axonal projections of mammalian neurons based on only local dendritic organization. The sub-parcellation of the caudoputamen (CP) aligns well with previous studies on projections, connectivity, and transcriptomics, revealing diverse input and output wiring patterns among CP subregions.

neuroscience↗

bioRxiv2024

Airway applied IVT mRNA vaccine needs specific sequence design and high standard purification that removes devastating dsRNA contaminant

The development of next-generation mucosal mRNA vaccines is promising but extremely challenging. Major efforts have been focused on optimizing delivery systems, whereas it is still unknown whether the intrinsic quality of IVT mRNA significantly impacts the potency of airway inoculated mRNA vaccines. Here, we systematically demonstrate the mucosal mRNA vaccine requires a higher standard of purification and tailor-designed sequence to fulfil its potency compared to the parenteral route inoculated counterpart. We found double strand RNA (dsRNA) contaminants are prone to trigger innate immunoreaction in the airway that activates the mRNA degradation mechanism, thereby diminishing the mRNA expression and subsequent antigen-specific immune responses. To address these challenges, we developed a strategy that combines optimized untranslated regions (UTRs) screened from endogenous genes of pulmonary cells with affinity chromatography-based purification which removes almost all the dsRNA contaminants. The optimized mRNA administered via the airway route not only demonstrates superior protein expression (30-fold increase) and reduces inflammation in the lung, but also promotes robust immunity comprising significantly elevated systemic, cellular, and mucosal immune responses, which is in stark contrast to intramuscular injected counterpart that displays less pronounced benefits. Our findings offer new insight into the development of mucosal mRNA therapeutics from an overlooked but crucial perspective of optimizing mRNA components.

synthetic biology↗

bioRxiv2024

Antipsychotic-like effects of the selective Rho-kinase 2 inhibitor KD025 in genetic and pharmacological mouse models of schizophrenia

1Copy number variations in the ARHGAP10 gene encoding Rho GTPase-activating protein 10 are significantly associated with schizophrenia. ARHGAP10 negatively regulates RhoA/Rho-kinase (ROCK) signaling. We previously demonstrated that fasudil, a non-selective ROCK inhibitor, exhibited antipsychotic-like effects in several mouse models of schizophrenia. ROCK has two subtypes, ROCK1 and ROCK2. ROCK1 is mainly expressed in the thymus and blood, while ROCK2 is predominantly expressed in the brain. Therefore, it is expected that like fasudil, selective ROCK2 inhibitors will exhibit antipsychotic-like effects, accompanied by a lower incidence of adverse effects due to ROCK1 inhibition. Here, we used genetic and pharmacological models of schizophrenia to investigate whether the selective ROCK2 inhibitor KD025 would show antipsychotic-like effects with a favorable adverse effect profile. Oral administration of KD025 suppressed the abnormal increase in the phosphorylation level of myosin phosphatase-targeting subunit 1, a substrate of ROCK, and ameliorated the decreased spine density of layer 2/3 pyramidal neurons in the medial prefrontal cortex of Arhgap10 S490P/NHEJ mice. Furthermore, KD025 mitigated the methamphetamine-induced impairment of visual discrimination (VD) in Arhgap10 S490P/NHEJ and wild-type mice. KD025 also reduced MK-801-induced impairments of VD, novel object recognition, and hyperlocomotion. Regarding side effects that are commonly seen with typical antipsychotics, KD025 did not affect systolic blood pressure and did not induce extrapyramidal symptoms, hyperprolactinemia, or hyperglycemia at the effective dosage in naive wild-type mice. Taken together, KD025 shows antipsychotic-like effects with a favorable adverse effect profile in genetic and pharmacological mouse models of schizophrenia.

pharmacology and toxicology↗

bioRxiv2024

Distinct duration and diet dependent lipid profiles and renal complicationsin GCK-MODY

Heterozygous inactivating mutations in the glucokinase (GCK) gene cause one of the most common types of maturity-onset diabetes of the young type 2 (MODY2), also named GCK-MODY. Studies suggest that, unlike other types of diabetes, patients with GCK-MODY do not have increased risk of diabetic complications and therefore do not typically require antihyperglycemic therapy. However, long-term outcomes of GCK-MODY on lipid profiles and chronic complications under different dietary scenarios remain unclear. Herein, using a knock-in mouse model expressing a novel MODY causing mutation GCK-Q26L (GCKMut), we examined age- and diet-related lipid profiles and diabetic complications. We found that, although GCKMut mice exhibited mild elevated blood glucose, the lipid profiles, body fat composition, and diabetic kidney disease (DKD) were initially improved in high-fat-diet (HFD) fed mice at the age of 28 weeks, supporting potential beneficial effects of GCKMut on lipid metabolism and kidney health. Unexpectedly however, those protective effects diminished by 40 weeks, and became more severe dyslipidemia and kidney injury associated with renal fibrosis and inflammation at 60-week-old mice fed with normal diet (ND) or HFD. Those findings revealed distinct duration- and diet-dependent effects of inactivating GCK mutation on lipid profiles and DKD, highlighting previously unrealized long-term chronic complications in GCK-MODY.

physiology↗

bioRxiv2024

An integrated view of the structure and function of the human 4D nucleome

The dynamic three-dimensional (3D) organization of the human genome (the "4D Nucleome") is closely linked to genome function. Here, we integrate a wide variety of genomic data generated by the 4D Nucleome Project to provide a detailed view of human 3D genome organization in widely used embryonic stem cells (H1-hESCs) and immortalized fibroblasts (HFFc6). We provide extensive benchmarking of 3D genome mapping assays and integrate these diverse datasets to annotate spatial genomic features across scales. The data reveal a rich complexity of chromatin domains and their sub-nuclear positions, and over one hundred thousand structural loops and promoter-enhancer interactions. We developed 3D models of population-based and individual cell-to-cell variation in genome structure, establishing connections between chromosome folding, nuclear organization, chromatin looping, gene transcription, and DNA replication. We demonstrate the use of computational methods to predict genome folding from DNA sequence, uncovering potential effects of genetic variants on genome structure and function. Together, this comprehensive analysis contributes insights into human genome organization and enhances our understanding of connections between the regulation of genome function and 3D genome organization in general.

genomics↗

bioRxiv2024

NMI induces chemokine release and recruits neutrophils through the activation of NF-kappaB pathway

Neutrophils are essential components of the innate immune system, playing a pivotal role in immune responses. These cells rapidly migrate to sites of inflammation or tissue injury, facilitating pathogen clearance and tissue repair. The chemotactic signaling network regulating neutrophil recruitment is complex and not fully understood, particularly regarding damage-associated molecular patterns (DAMPs). In our previous research, we identified NMI as a DAMP that activates dendritic cells and macrophages, amplifying inflammatory responses and contributing to both acute and chronic inflammation. In this study, we investigated the role of NMI in neutrophil recruitment. We purified and characterized a recombinant murine NMI protein, ensuring endotoxin removal while preserving biological activity. In vivo experiments demonstrated that NMI enhances neutrophil recruitment in both a murine air pouch model and an acute peritonitis model, mediated by macrophage-derived chemokines. In vitro assays revealed a concentration-dependent increase in neutrophil migration induced by NMI, facilitated by chemokine secretion and subsequent migration through the CXCR2 receptor. Importantly, we established that NMI activates chemokine expression via the NF-{kappa}B signaling pathway. These findings provide insights into the mechanisms of NMI-induced neutrophil migration, enhancing our understanding of neutrophil recruitment during inflammation.

immunology↗

bioRxiv2024

Structural insights into terminal arabinosylation biosynthesis of the mycobacterial cell wall arabinan

The emergence of drug-resistant strains exacerbates the global challenge of tuberculosis caused by Mycobacterium tuberculosis (Mtb). Central to the pathogenicity of Mtb is its complex cell envelope, which serves as a barrier against both immune system and pharmacological attacks. Two key components of this envelope, arabinogalactan (AG) and lipoarabinomannan (LAM) are complex polysaccharides that contain integral arabinan domains important for cell wall structural and functional integrity. The arabinofuranosyltransferase AftB terminates the synthesis of these arabinan domains by catalyzing the addition of {beta}-(1[->]2)-linked terminal arabinofuranose residues. Here, we present the cryo-EM structures of Mycobacterium chubuense AftB in its apo and donor substrate analog-bound form, determined to 2.9 [A] and 3.4 [A] resolution, respectively. Our structures reveal that AftB has a GT-C fold transmembrane (TM) domain comprised of eleven TM helices and a periplasmic cap domain. AftB has an irregular tube-shaped cavity that bridges the two proposed substrate binding sites. By integrating structural analysis, biochemical assays, and molecular dynamics simulations, we elucidate the molecular basis of the reaction mechanism of AftB and propose a model for catalysis.

biochemistry↗

bioRxiv2024

Mechanistic studies of mycobacterial glycolipid biosynthesis by the mannosyltransferase PimE

Tuberculosis (TB), exceeded in mortality only by COVID-19 among global infectious diseases, is caused by Mycobacterium tuberculosis (Mtb). The pathogenicity of Mtb is largely attributed to its complex cell envelope, which includes a class of glycolipids called phosphatidyl-myo-inositol mannosides (PIMs), found uniquely in mycobacteria and its related corynebacterineae. These glycolipids maintain the integrity of the mycobacterial cell envelope, regulate its permeability, and mediate host-pathogen interactions. PIMs consist of a phosphatidyl-myo-inositol core decorated with one to six mannose residues and up to four acyl chains. The mannosyltransferase PimE catalyzes the transfer of the fifth PIM mannose residue from a polyprenyl phosphate-mannose (PPM) donor. This step in the biosynthesis of higher-order PIMs contributes to the proper assembly and function of the mycobacterial cell envelope; however, the structural basis for substrate recognition and the catalytic mechanism of PimE remain poorly understood. Here, we present the cryo-electron microscopy (cryo-EM) structures of PimE from Mycobacterium abscessus captured in its apo form and in a product-bound complex with the reaction product Ac1PIM5 and the by-product polyprenyl phosphate (PP), determined at 3.0 [A] and 3.5 [A], respectively. The structures reveal the active site within a distinctive binding cavity that accommodates both donor and acceptor substrates/products. Within the cavity, we identified residues involved in substrate coordination and catalysis, which we confirmed through in vitro enzymatic assays and further validated by in vivo complementation experiments. Molecular dynamics simulations were applied to identify the access pathways and the dynamics involved in substrate binding. Integrating structural, biochemical, genetic, and computational experiments, our study provides comprehensive insights into how PimE functions, opening potential avenues for development of novel anti-TB therapeutics.

biochemistry↗

bioRxiv2024

Proteogenomic Characterization of Primary Oral Squamous Cell Carcinomas Unveils the Extracellular Matrix Remodeling and Immunosuppressive Microenvironment Linked with Lymph Node Metastasis

Oral squamous cell carcinoma (OSCC) is an increasingly prevalent malignancy worldwide. This study aims to understand molecular alterations associated with lymph node metastasis of OSCC in order to improve treatment strategies. We analyzed a cohort of 46 patients with primary OSCC, including 10 with lymph node metastasis and 36 without. Using a comprehensive multi-omics approach--encompassing genomic, transcriptomic, proteomic, epigenetic, single-cell, and spatial analyses--we integrated data to delineate the molecular landscape of OSCC in the context of lymph node metastasis. Our genomic analysis identified significant mutations in key genes within the MAPK, TGF-{beta}, and WNT signaling pathways, which are essential for tumor development. The proteogenomic analysis highlighted pathways critical for lymph node dissemination and factors contributing to an immunosuppressive tumor microenvironment. Elevated levels of POSTN were found to reorganize the extracellular matrix (ECM), interact with TGF-{beta}, disrupt cell cycle regulation, and suppress the immune response by reducing VCAM1 activity. Integrated analyses of single-cell and spatial transcriptome data revealed that cancer-associated fibroblasts (CAFs) secrete TGF-{beta}1/2, promoting cancer cell metastasis through epithelial-mesenchymal transition (EMT). Our integrated multi-omics analysis provides a detailed understanding of molecular mechanisms driving lymph node metastasis of OSCC. These insights could lead to more precise diagnostics and targeted treatments.

cancer biology↗

bioRxiv2024

The transcription factor ZmbZIP75 promotes both grain filling and kernel dehydration in maize

Selecting both high-yield and low-kernel-moisture varieties is essential for modern maize production, but relevant breeding efforts are hindered by a lack of valuable regulatory genes. Here, we demonstrate that the transcription factor (TF) basic leucine zipper 75 (ZmbZIP75) promotes grain yield and reduces kernel moisture in maize. Knockout of ZmbZIP75 results in defective grain filling and kernel dehydration, whereas ZmbZIP75 overexpression confers increased grain yield per plant and decreased kernel moisture without altering plant architecture. Mechanistically, during the grain filling stage, ZmbZIP75 is transcriptionally induced by maternal-derived basal abscisic acid (ABA) and directly activates multiple core starch synthesis-related genes and key TFs, thereby promoting grain filling and final yield. In the late stage of kernel development, high concentrations of zygotic ABA enhance ZmbZIP75 phosphorylation through SnRK2.10. The phosphorylated ZmbZIP75 subsequently transactivates and interacts with TF VP1 to synergistically promote kernel dehydration. This study thus highlights the potential of ZmbZIP75 for engineering both high-yield and low-kernel-moisture varieties to meet the demands of high-efficient maize production. IN A NUTSHELLO_ST_ABSBackgroundC_ST_ABSHigh grain yield in maize is generally associated with elevated kernel moisture at harvest, which is the main limiting factor for modern maize production. Therefore, it is of importance to select varieties with both high-yield and low-kernel-moisture. These traits are largely controlled by grain filling and kernel dehydration, two tightly connected processes during maize kernel development. Abscisic acid (ABA) is well-documented for its vital role in grain filling and dehydration maturation. However, the molecular mechanisms by which ABA coordinates these two processes remain unclear. QuestionWhat are the regulatory factors involved, and how do they mediate ABA signaling to coordinate grain filling and dehydration maturation in maize? FindingsZmbZIP75 is transcriptionally induced by ABA and directly activates multiple core starch synthesis-related genes and key TFs in developing maize endosperm, thereby promoting grain filling. In developing embryo, ABA enhances ZmbZIP75 phosphorylation via SnRK2.10. The phosphorylated ZmbZIP75 then transactivates and interacts with VP1 to synergistically promote kernel dehydration. Moreover, ZmbZIP75 overexpression confers increased grain yield and reduced kernel moisture in maize. Next stepsWhile ZmbZIP75 is directly phosphorylated to mediate ABA signaling during dehydration maturation, ZmbZIP75 is transcriptionally induced by ABA during grain filling. We plan to identify upstream factors that mediate ABA signaling to regulate ZmbZIP75 expression, thereby enhancing our understanding of ABA-promoted grain filling in maize.

plant biology↗

bioRxiv2024

Microbiome and climate: Skin microbial diversity and community functions of Polypedates megacephalus (Anura: Rhacophoridae) associated with bioclimate

The microbiome inhabiting animal skin plays a crucial role in host fitness by influencing both the composition and function of microbial communities. Environmental factors, including climate, significantly impact microbial diversity and the functional attributes of these communities. However, it remains unclear how specific climatic factors affect amphibian skin microbial composition, community function, and the relationship between these two aspects. Given that amphibians are poikilotherms, and thus more susceptible to temperature fluctuations, understanding these effects is particularly important. Here, we investigated the skin microbiome of the rhacophorid tree frog Polypedates megacephalus across different climatic regimes using 16S rRNA gene sequencing. Skin swab samples were collected from nine populations of P. megacephalus adults in the Guangxi region, China. The majority of the core microbiota were found to belong to the genus Pseudomonas. Our findings indicate that microbial community diversity, composition, and function are associated with changes in climatic conditions. Specifically, the taxonomic and functional diversity of the skin microbiome increased in response to greater climate variability, particularly in temperature fluctuations. Additionally, the functional attributes of microbial communities changed in parallel with shifts in community diversity and composition, suggesting that environmental filtering driven by climate changes negatively impacts microbial community functional redundancy. These results highlight the critical influence of climatic factors on amphibian skin microbiomes and offer new insights into how microbial composition and function contribute to host adaptation in varying environmental conditions. IMPORTANCEThis study is important in understanding the association between climate variability, microbial diversity, and host adaptation in amphibians, particularly vulnerable to environmental changes due to their poikilothermic nature. Amphibians rely on their skin microbiome for key functions like disease resistance, yet little is known about how climate fluctuations impact these microbial communities. By analyzing the microbiome of Polypedates megacephalus across different climatic regimes, our analysis reveals that while climate variability enhances microbial diversity, it reduces functional redundancy. These findings highlight the potential ecological consequences of climate change and emphasize the need to integrate microbiome health into amphibian conservation strategies.

microbiology↗

bioRxiv2024

Decreased GABA levels during development result in increased connectivity in the larval zebrafish tectum

{gamma}-aminobutyric acid (GABA) is an abundant neurotransmitter that plays multiple roles in the vertebrate central nervous system (CNS). In the early developing CNS, GABAergic signaling acts to depolarize cells. It mediates several aspects of neural development, including cell proliferation, neuronal migration, neurite growth, and synapse formation, as well as the development of critical periods. Later in CNS development, GABAergic signaling acts in an inhibitory manner when it becomes the predominant inhibitory neurotransmitter in the brain. This behavior switch occurs due to changes in chloride/cation transporter expression. Abnormalities of GABAergic signaling appear to underlie several human neurological conditions, including seizure disorders. However, the impact of reduced GABAergic signaling on brain development has been challenging to study in mammals. Here we take advantage of zebrafish and light sheet imaging to assess the impact of reduced GABAergic signaling on the functional circuitry in the larval zebrafish optic tectum. Zebrafish have three gad genes: two gad1 paralogs known as gad1a and gad1b, and gad2. The gad1b and gad2 genes are expressed in the developing optic tectum. Null mutations in gad1b significantly reduce GABA levels in the brain and increase electrophysiological activity in the optic tectum. Fast light sheet imaging of genetically encoded calcium indicator (GCaMP)-expressing gab1b null larval zebrafish revealed patterns of neural activity that were different than either gad1b-normal larvae or gad1b-normal larvae acutely exposed to pentylenetetrazole (PTZ). These results demonstrate that reduced GABAergic signaling during development increases functional connectivity and concomitantly hyper-synchronization of neuronal networks. Significance StatementUnderstanding the impact of reduced GABAergic signaling on vertebrate brain development and function will help elucidate the etiology of seizure initiation and propagation and other neurological disorders due to the altered formation of neural circuits. Here, we used fast light sheet imaging of larval zebrafish that neuronally expressed a genetically encoded calcium indicator (GCaMP) to assess the impact of reduced GABA levels through null mutation of gad1b during brain development. We show that reduced GABA levels during development result in increased functional connectivity in the brain.

neuroscience↗