Biology subjects

Chai, R.

Publications and source records attributed to Chai, R..

16 recordsLinked to original sources

bioRxiv2025

Next-generation enhancer AAVs for selective interspecies targeting of midbrain dopaminergic neurons

Using single-nucleus multiomic profiling of the marmoset midbrain, we develop and benchmark enhancer-AAVs to selectively access dopamine (DA) neurons in wild-type animals without combinatorial systems. In vivo candidate screenings identified one highly specific DA enhancer, cjDAE8, in both mice and marmosets. To overcome low-level off-target (leaky) expression, a common limitation for enhancer AAVs, we engineered next-generation AAV backbones that strengthen expression while minimizing leakiness. Quantitative histology comparing natural versus antibody-amplified fluorescence defined AAV doses to achieve high labeling efficiency with greater than 90-95% DA-neuron specificity across species and injection routes. We further demonstrate applications of DA-enhancer-AAVs for (i) retrograde targeting of projection-defined DA populations in marmoset, (ii) fiber-photometric recording of divergent DA-axonal dynamics in striatal subregions, and (iii) optogenetic VTA-DA self-stimulation in mice. Our results establish a resource for cross-species DA targeting and two practical guidelines: backbone context critically shapes enhancer performance, and antibody-amplified readouts rigorously assess specificity.

neuroscience↗

bioRxiv2025

Dendritic computation for rule-based flexible categorization

A hallmark of intelligent behavior is the ability to flexibly respond to external sensory inputs based on dynamically changing rules. A central question is how neurons in the brain implement computations underlying intelligent behaviors. The neocortical pyramidal neurons use their elaborated dendritic arbors to segregate a plethora of inputs and dynamically integrate them--a process known as dendritic computation--which may play important roles in rule-dependent sensory processing. However, evidence directly linking dendritic computation with intelligent cognitive behaviors has been absent. Here we combine two-photon imaging and a rule-switching flexible categorization task in mice to show that a projectome-defined extratelencephalic (ET) cortical layer 5 (L5) neurons in the auditory cortex integrate dendritic rule information and somatic sensory input to enable rule-dependent flexible categorization. The apical dendrite and soma within the same ET neurons exhibit distinct compartmental representations for sensory and rule information, with the soma predominantly encoding sensory information and the dendrites representing inferred task rule. Simultaneous optogenetic dendritic inhibition and two-photon imaging revealed that dendritic rule coding is essential for somatic output of flexible categorization. Our findings indicate that nonlinear dendritic integration of rule and sensory information constitutes a neuronal computational mechanism underlying rule-switching flexible decision-making.

neuroscience↗

bioRxiv2024

Uncovering Ancient DNA in Petroleum: Insights into Earth Hidden Life Events and Geological History

Specific macromolecules in petroleum, preserved through geological processes from ancient organisms, are recognized as molecular fossils or geochemical markers (GMs). Our selected GMs indicate that the source rocks of Nanyang Oilfield formed in an anoxic, saline, and stratified lacustrine environment with marine influence. Contrary to science fiction notions that oil originates from ancient large animals, mainstream academia has consistently asserted that oil is derived from the organic matter of lower life forms, formed over extended geological processes, with intact DNA no longer persisting in oil post-formation. However, this study successfully extracted 3,159,020 DNA fragments from the petroleum samples using the nanoparticle affinity bead technology, followed by sequencing and classification via the mega screen method. These fragments, categorized as original in situ DNA (oriDNA), recent environmental DNA (preDNA), and paleo-environmental DNA (paeDNA), exhibit a "Genome Accumulated over Time" (GAT) pattern of "old-less, new-many". This aligns with findings from GMs while offering more specific genetic information. The analysis reveals evidence of historical events, including animal extinctions, marine invasions, ancient bird species presence, Asian Homo erectus activities, and modern human influences in preDNA. Notably, the mitogenomic data positions Asian Homo erectus closer to modern humans than to chimpanzees at the maternal basis. The absence of deamination in petroleum ancient DNA (aDNA) fragments is likely due to the anaerobic, anhydrous environment and the screening process that excludes degraded fragments. Consequently, the authenticity criteria and scope of application of traditional aDNA methods require reevaluation. Surprisingly, the near-absence of oriDNA has impeded our efforts to determine the specific biological origins of the oil. These findings position petroleum as a novel, non-skeletal source of aDNA, offering insights into ancient animal activities, geological changes, and human origins while underscoring its potential as an untapped resource for studying genetic preservation across geological timescales.

paleontology↗

bioRxiv2024

Molecular insights into the atypical activation mechanism of GPR156 in maintaining auditory function

The class C orphan GPCR GPR156, which lacks the typical extracellular region, plays a pivotal role in auditory function through Gi2/3. Here, we demonstrate that GPR156 with high constitutive activity is essential for maintaining auditory function, and we further present two cryo-EM structures of human GPR156. The GPR156 dimer in both the apo state and Gi3 protein-coupled state adopt a TM5/6-TM5/6 interface, indicating the high constitutive activity of GPR156 in the apo state. The C-terminus plays a dual role in promoting G protein binding within G-bound subunit while preventing the G-free subunit from binding to additional G protein. These observations explain how GPCR activity is maintained through dimerization and provide a mechanistic insight into the sustained role of GPR156 in maintaining auditory function.

molecular biology↗

bioRxiv2023

A reverse-central-dogma pathway underlies ribosome-antibiotic efficacy and accelerates resistance evolution

In bacteria, the precise coordination of DNA replication, transcription and translation is mediated by dynamic interactions among the corresponding macromolecular machineries, playing a pivotal role in maintaining cellular homeostasis. Here we show that such coordination is hijacked by ribosome antibiotics to trigger secondary damage that predominantly contributes to their efficacy. Specifically, through developing a transcription dynamics profiling method, complemented by genetic and biochemical approaches, we unveil that translation inhibition disrupts transcription-translation coupling, leading to premature stalling of RNA polymerase (RNAP) at genome scale, which subsequently triggers extensive genomic instability. Moreover, mutagenic repairment of genomic lesions is mediated by heterogenous hyperactivation of SOS response, facilitating an inducible evolutionary path towards genetic resistance characterized by a unique mutation spectrum. Our findings thereby reveal a yet overlooked reverse-central-dogma pathway underlying actions of ribosome inhibitors, and establish a framework to understand antibiotic efficacy and induced mutagenesis through network disorder.

microbiology↗

bioRxiv2022

A Community Challenge to Predict Clinical Outcomes After Immune Checkpoint Blockade in Non-Small Cell Lung Cancer

PurposePredictive biomarkers of immune checkpoint inhibitors (ICIs) efficacy are currently lacking for non-small cell lung cancer (NSCLC). Here, we describe the results from the Anti-PD-1 Response Prediction DREAM Challenge, a crowdsourced initiative that enabled the assessment of predictive models by using data from two randomized controlled clinical trials (RCTs) of ICIs in first-line metastatic NSCLC. MethodsParticipants developed and trained models using public resources. These were evaluated with data from the CheckMate 026 trial (NCT02041533), according to the model-to-data paradigm to maintain patient confidentiality. The generalizability of the models with the best predictive performance was assessed using data from the CheckMate 227 trial (NCT02477826). Both trials were phase III RCTs with a chemotherapy control arm, which supported the differentiation between predictive and prognostic models. Isolated model containers were evaluated using a bespoke strategy that considered the challenges of handling transcriptome data from clinical trials. ResultsA total of 59 teams participated, with 417 models submitted. Multiple predictive models, as opposed to a prognostic model, were generated for predicting overall survival, progression-free survival, and progressive disease status with ICIs. Variables within the models submitted by participants included tumor mutational burden (TMB), programmed death ligand 1 (PD-L1) expression, and gene-expression-based signatures. The bestperforming models showed improved predictive power over reference variables, including TMB or PD-L1. ConclusionThis DREAM Challenge is the first successful attempt to use protected phase III clinical data for a crowdsourced effort towards generating predictive models for ICIs clinical outcomes and could serve as a blueprint for similar efforts in other tumor types and disease states, setting a benchmark for future studies aiming to identify biomarkers predictive of ICIs efficacy. Context summaryO_ST_ABSKey objectiveC_ST_ABSNot all patients with non-small cell lung cancer (NSCLC) eligible for immune checkpoint inhibitor (ICIs) respond to treatment, but accurate predictive biomarkers of ICIs clinical outcomes are currently lacking. This crowdsourced initiative enabled the robust assessment of predictive models using data from two randomized clinical trials of first-line ICI in metastatic NSCLC. Knowledge generatedModels submitted indicate that a combination of programmed death ligand 1 (PD-L1), tumor mutational burden (TMB), and immune gene signatures might be able to identify patients more likely to respond to ICIs. TMB and PD-L1 seemed important to predict progression-free survival and overall survival. Mechanisms including apoptosis, T-cell crosstalk, and adaptive immune resistance appeared essential to predict response. Relevance

cancer biology↗

bioRxiv2022

Somatostatin interneurons in auditory cortex regulate cortical representations and contribute to auditory perception

In the mammalian neocortex, somatostatin (SOM)-expressing GABAergic interneurons serve as a critical circuit component, receiving diverse inputs and targeting various types of cortical neurons. However, their role in perception and cognition remains not well understood. In this study, we employed cell-type specific imaging and perturbation during an auditory perceptual decision task to investigate the contribution of SOM interneurons. Two-photon calcium imaging revealed that auditory cortex (ACx) SOM interneurons exhibit not only frequency-selective responses but also selectivity to categorical choices. Simultaneous optogenetic inactivation and two-photon imaging revealed that SOM interneurons refine the frequency discriminability of auditory cortical neurons and contribute to their selectivity to the categorical decision boundary. Moreover, bilateral chemogenetic inactivation of ACx SOM interneurons impaired behavior-level perceptual categorization. Our findings provide a mechanistic understanding on the functional significance of SOM interneurons in auditory cortical processing and perceptual categorization, linking cell-type specific cortical circuit computations with perceptual functions.

neuroscience↗

bioRxiv2022

Multifaceted role of RIMBP2 in promoting hearing in murine cochlear hair cells

In peripheral, the mammalian cochlea is a remarkable sensory apparatus, owning to its outer and inner hair cells (OHCs and IHCs) that amplify and transmit auditory signals to the brain, respectively. Rab3-interacting molecular (RIM) binding protein 2 (RIMBP2) is widely expressed in receptor cells and neurons, specifically in the active zones for exocytosis of synaptic vesicles (SVs), but its exact functions in the cochlea are not very well understood. We therefore generated a Rimbp2 knockout mouse model (Rimbp2-/-), which exhibited severely impaired hearing with not only elevated hearing thresholds but also increased latencies and reduced amplitudes in the Wave I of their auditory brainstem responses (ABRs). Consistent with the threshold elevation, we found significant loss of OHCs, likely through apoptosis, in the Rimbp2-/- cochlea. Consistent with changes observed in the ABR Wave I, we found greatly reduced exocytosis, both spontaneously and upon stimulation, in Rimbp2-/- IHCs. Specifically, our patch-clamp analysis on IHCs and postsynaptic spiral ganglion neurons (SGNs) revealed not only reduced readily releasable pool (RRP) of SVs but also reduced sustained release rate, along with complete blockade of fast endocytosis, in Rimbp2-/- IHCs. Lastly, with immunostaining of whole-mounted cochleae, we found that while the number of ribbon synapses in Rimbp2-/- IHCs was unchanged, their localization moved subtly but significantly towards the basal pole of IHCs. Taken together, we uncovered an unexpected role of RIMBP2 for OHC survival and a more extensive role in promoting IHC exocytosis than previously believed.

neuroscience↗

bioRxiv2021

Fatigue Metabolites of Large Yellow Croaker and Construction of Swimming Model

A trend in large yellow croaker (Larimichthys crocea) aquaculture is to establish new production sites that are suitable for extreme weather conditions. However, continuous and strong currents can harm fish welfare. To determine the location of the net cage, it is necessary to assess the swimming ability of large yellow croaker. Currently, our research on large yellow croakers is focusing on behavior analysis. This article investigates the effect of swimming large yellow croakers on metabolites in the body by examining the preferred speed of the group and the endurance swimming ability of single-tailed fish. We evaluated the factors that influence the large yellow croakers swimming fatigue by quantifying the content of metabolites and constructed the endurance swimming model using those results. Various results showed large yellow croaker populations tend to grow in low-velocity environments, and this matches their traditional habitat. The samples were taken at different swimming times at a flow rate of 0.35 m/s. According to the results of the metabolite content determination, blood glucose levels is closely related to swimming ability in large yellow croakers. The content of liver glycogen, which regulates blood glucose concentration, decreases in a certain linear relationship. The endurance swimming model of large yellow croaker was constructed according to the changes of liver glycogen content. The goals of this article are to provide a deeper understanding of the physiological characteristics of large yellow croaker swimming, and to provide a reference for choosing fishing and cage sites for large yellow croaker.

animal behavior and cognition↗

bioRxiv2021

Heterogeneity and molecular programming of progenitors for motor neurons and oligodendrocytes

The pMN domain is a restricted domain in the ventral spinal cords, defined by the expression of olig2 gene. The fate determination of pMN progenitors is highly temporally and spatially regulated, with motor neurons and oligodendrocyte progenitor cells (OPCs) developing sequentially. Insight into the heterogeneity and molecular programs of pMN progenitors is currently lacking. With the zebrafish model, we identified multiple states of neural progenitors using single-cell sequencing: proliferating progenitors, common progenitors for both motor neurons and OPCs, and restricted precursors for either motor neurons or OPCs. We found specific molecular programs for neural progenitor fate transition, and manipulations of representative genes in the motor neuron or OPC lineage confirmed their critical role in cell fate determination. The transcription factor NPAS3 is necessary for the development of the OPC lineage and can interact with many known genes associated with schizophrenia. Deciphering progenitor heterogeneity and molecular mechanisms for these transitions will elucidate the formation of complex neuron-glia networks in the central nervous system during development, and understand the basis of neurodevelopmental disorders.

neuroscience↗

bioRxiv2020

Extensive MET alterations confer clinical response to MET inhibitors in gliomas

Activating alterations of the MET gene are well-characterized oncogenic drivers, and MET inhibitors could successfully treat several tumor types with MET alterations, including gliomas with PTPRZ1-MET fusion. However, the full diversity and prevalence of MET alterations in gliomas are still lacking to accurately identify a subset of patients likely to benefit from MET inhibitor treatment. Here, we interrogated genomic profiles of 1,351 gliomas, and further identify 60 cases harboring MET alterations, including MET fusions and various MET exon skipping events. MET RNA alterations, but not MET amplification, are highly enriched in the secondary glioblastomas (sGBM) with significantly worse prognosis. Further molecular analysis has shown that MET RNA alterations acting an additive effects of MET overexpression are induced in the course of glioma evolution. In vitro and clinical studies indicate cells and patients harboring MET alterations have better response to MET inhibitors. Collectively, these data suggest that a subgroup of gliomas harboring MET alterations likely to have benefit from MET-targeted therapy.

neuroscience↗

bioRxiv2020

Chinese Glioma Genome Atlas (CGGA): A Comprehensive Resource with Functional Genomic Data for Chinese Glioma Patients

Gliomas are the most common and malignant intracranial tumours in adults. Recent studies have shown that functional genomics greatly aids in the understanding of the pathophysiology and therapy of glioma. However, comprehensive genomic data and analysis platforms are relatively limited. In this study, we developed the Chinese Glioma Genome Atlas (CGGA, http://www.cgga.org.cn), a user-friendly data portal for storage and interactive exploration of multi-dimensional functional genomic data that includes nearly 2,000 primary and recurrent glioma samples from Chinese cohorts. CGGA currently provides access to whole-exome sequencing (286 samples), messenger RNA sequencing (1,018 samples) and microarray (301 samples), DNA methylation microarray (159 samples), and microRNA microarray (198 samples) data, as well as detailed clinical data (e.g., WHO grade, histological type, critical molecular genetic information, age, sex, chemoradiotherapy status and survival data). In addition, we developed an analysis tool to allow users to browse mutational, mRNA/microRNA expression, and DNA methylation profiles and perform survival and correlation analyses of specific glioma subtypes. CGGA greatly reduces the barriers between complex functional genomic data and glioma researchers who seek rapid, intuitive, and high-quality access to data resources and enables researchers to use these immeasurable data sources for biological research and clinical application. Importantly, the free provision of data will allow researchers to quickly generate and provide data to the research community.

genomics↗

bioRxiv2019

THOC1 deficiency leads to late-onset nonsyndromic hearing loss through p53-mediated hair cell apoptosis

Apoptosis of cochlear hair cells is a key step towards age-related hearing loss. Although numerous genes have been implicated in the genetic causes of late-onset, progressive hearing loss, few show direct links to the proapoptotic process. By genome-wide linkage analysis and whole exome sequencing, we identified a heterozygous p.L183V variant in THOC1 as the probable cause of the late-onset, progressive, non-syndromic hearing loss in a large dominant family. Thoc1, a member of the conserved multisubunit THO/TREX ribonucleoprotein complex, is highly expressed in mouse and zebrafish hair cells. The Thoc1 mutant zebrafish generated by gRNA-Cas9 system lacks the C-startle response, indicative of the hearing dysfunction. Both Thoc1 mutant and knockdown zebrafish have greatly reduced hair cell numbers, while the latter can be rescued by embryonic microinjection of human wild-type THOC1 mRNA but to significantly lesser degree by the p.L183V mutant mRNA. The Thoc1 deficiency resulted in marked apoptosis in zebrafish hair cells. Consistently, transcriptome sequencing of the mutants showed significantly increased gene expression in the p53-associated signaling pathway. Depletion of p53 or applying the p53 inhibitor Pifithrin- significantly rescued the hair cell loss in the Thoc1 knockdown zebrafish. Our results suggested that THOC1 deficiency lead to late-onset, progressive hearing loss through p53-mediated hair cell apoptosis. This is to our knowledge the first human disease associated with THOC1 mutations and may shed light on the molecular mechanism underlying the age-related hearing loss.\n\nSignificance StatementFor the first time, we found that THOC1 deficiency leads to late-onset nonsyndromic hearing loss. Furthermore, we revealed the hypomorphic THOC1 induced p53-mediated hair cell apoptosis. This is to our knowledge the first human disease associated with THOC1 mutations and may shed light on the molecular mechanism underlying the age-related hearing loss.

genetics↗

bioRxiv2019

TeraVR Empowers Precise Reconstruction of Complete 3-D Neuronal Morphology in the Whole Brain

Neuron morphology is recognized as a key determinant of cell type, yet the quantitative profiling of a mammalian neurons complete three-dimensional (3-D) morphology remains arduous when the neuron has complex arborization and long projection. Whole-brain reconstruction of neuron morphology is even more challenging as it involves processing tens of teravoxels of imaging data. Validating such reconstructions is extremely laborious. We developed TeraVR, an open-source virtual reality annotation system, to address these challenges. TeraVR integrates immersive and collaborative 3-D visualization, interaction, and hierarchical streaming of teravoxel-scale images. Using TeraVR, we produced precise 3-D full morphology of long-projecting neurons in whole mouse brains and developed a collaborative workflow for highly accurate neuronal reconstruction.

neuroscience↗

bioRxiv2018

An Atlas of Human and Murine Genetic Influences on Osteoporosis

Osteoporosis is a common debilitating chronic disease diagnosed primarily using bone mineral density (BMD). We undertook a comprehensive assessment of human genetic determinants of bone density in 426,824 individuals, identifying a total of 518 genome-wide significant loci, (301 novel), explaining 20% of the total variance in BMD--as estimated by heel quantitative ultrasound (eBMD). Next, meta-analysis identified 13 bone fracture loci in ~1.2M individuals, which were also associated with BMD. We then identified target genes from cell-specific genomic landscape features, including chromatin conformation and accessible chromatin sites, that were strongly enriched for genes known to influence bone density and strength (maximum odds ratio = 58, P = 10-75). We next performed rapid throughput skeletal phenotyping of 126 knockout mice lacking eBMD Target Genes and showed that these mice had an increased frequency of abnormal skeletal phenotypes compared to 526 unselected lines (P < 0.0001). In-depth analysis of one such Target Gene, DAAM2, showed a disproportionate decrease in bone strength relative to mineralization. This comprehensive human and murine genetic atlas provides empirical evidence testing how to link associated SNPs to causal genes, offers new insights into osteoporosis pathophysiology and highlights opportunities for drug development.

genomics↗

bioRxiv2017

Insm1a regulates motor neuron development in zebrafish

Insulinoma-associated1a (Insm1a) is a zinc-finger transcription factor playing a series of functions in cell formation and differentiation of vertebrate central and peripheral nervous systems and neuroendocrine system. However, its roles on the development of motor neuron have still remained uncovered. Here, we provided evidences that insmla was a vital regulator of motor neuron development and provide a mechanistic understanding of how it contributes to this process. Firstly, we showed the localization of insmla in spinal cord and primary motor neurons (PMNs) of zebrafish embryos by in situ hybridization and imaging analysis of transgenic reporter line Tg(insmla: mCherry) ntu805. Then we demonstrated that the deficiency of insmla in zebrafish larvae lead to the defects of PMNs development, including the reduction of caudal primary motor neurons (CaP) and middle primary motor neurons (MiP), the excessive branching of motor axons, and the disorganized distance between adjacent CaPs. Additionally, knockout of insm1 impaired motor neuron differentiation in the spinal cord. Locomotion analysis showed that insmla-null zebrafish significantly reduced the swimming activity. Furthermore, we proved that the insmla loss of function significantly decreased the transcripts levels of both olig2 and nkx6.1. Microinjection of olig2 and nkx6.1 mRNA rescued the motor neuron defects in insmla deficient embryos. Taken together, these data indicate that insmla regulates the motor neuron development, at least in part, through modulation of the expressions of olig2 and nkx6.1.

developmental biology↗