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Biology subjects

Jiang, F.

Publications and source records attributed to Jiang, F..

At least 73 records · Page 4Linked to original sources

Dynamic functional connectivity MEG features of Alzheimer's disease

Dynamic resting state functional connectivity (RSFC) characterizes time-varying fluctuations of functional brain network activity. While many studies have investigated static functional connectivity, it has been unclear whether features of dynamic functional connectivity are associated with neurodegenerative diseases. Popular sliding-window and clustering methods for extracting dynamic RSFC have various limitations that prevent extracting reliable features to address this question. Here, we use a novel and robust time-varying dynamic network (TVDN) approach to extract the dynamic RSFC features from high resolution magnetoencephalography (MEG) data of participants with Alzheimers disease (AD) and matched controls. The TVDN algorithm automatically and adaptively learns the low-dimensional spatiotemporal manifold of dynamic RSFC and detects dynamic state transitions in data. We show that amongst all the functional features we investigated, the dynamic manifold features are the most predictive of AD. These include: the temporal complexity of the brain network, given by the number of state transitions and their dwell times, and the spatial complexity of the brain network, given by the number of eigenmodes. These dynamic features have high sensitivity and specificity in distinguishing AD from healthy subjects. Intriguingly, we found that AD patients generally have higher spatial complexity but lower temporal complexity compared with healthy controls. We also show that graph theoretic metrics of dynamic component of TVDN are significantly different in AD versus controls, while static graph metrics are not statistically different. These results indicate that dynamic RSFC features are impacted in neurodegenerative disease like Alzheimers disease, and may be crucial to understanding the pathophysiological trajectory of these diseases.

neuroscience↗

Integrated Cell Landscape and Dynamics in the Progression of Bone Repair

Bone homeostasis and repair is a systematic progress with spatiotemporal interaction of multiple cell types involved in skeletal and immune system. Precise spatiotemporal regulation of cell type-specific functions in bone repair contributes to further development of tissue engineering and regenerative medicine. Here, we utilized single-cell RNA sequencing to illustrate a map of cell landscape and dynamics in the progression of rodent bone self-healing and a perturbation by lymphoid cell-deficiency. We identified different functions of myeloid cell and lymphoid cell to osteogenesis and angiogenesis during bone repair and their mutual complementation under lymphoid cell-deficient condition. Additionally, we used CD34+ humanized reconstituted mice to reveal further insights into the mechanism of human bone homeostasis and repair. Our integrated cellular analysis of bone repair explores the functional diversity and complementation between myeloid cells and lymphoid cells during bone healing process and provides further therapeutic implications for the treatment of bone disease and degeneration following ageing.

cell biology↗

ZBTB20 is Essential for Cochlear Maturation and Hearing in Mice

The mammalian cochlear epithelium undergoes substantial remodeling and maturation before the onset of hearing. However, very little is known about the transcriptional network governing cochlear late-stage maturation and particularly the differentiation of its lateral non-sensory region. Here we establish ZBTB20 as an essential transcription factor required for cochlear terminal differentiation and maturation and hearing. ZBTB20 is abundantly expressed in the developing and mature cochlear non-sensory epithelial cells, with transient expression in immature hair cells and spiral ganglion neurons. Otocyst-specific deletion of Zbtb20 causes profound deafness with reduced endolymph potential in mice. The subtypes of cochlear epithelial cells are normally generated but their postnatal development is arrested in the absence of ZBTB20, as manifested by an immature appearance of the organ of Corti, malformation of tectorial membrane, a flattened spiral prominence, and a lack of identifiable Boettcher cells. Furthermore, these defects are related with a failure in the terminal differentiation of the non-sensory epithelium covering the outer border Claudius cells, outer sulcus root cells and spiral prominence epithelial cells. Transcriptome analysis shows ZBTB20 regulates genes coding for tectorial membrane proteins in the greater epithelial ridge, and those preferentially expressed in root cells and spiral prominence epithelium. Our results point to ZBTB20 as an essential regulator for postnatal cochlear maturation and particularly for the terminal differentiation of cochlear lateral non-sensory domain.

developmental biology↗

RNA binding protein PRRC2B mediates translation of specific proteins and regulates cell cycle progression

Accumulating evidence suggests that posttranscriptional control of gene expression, including RNA splicing, transport, modification, translation, and degradation, primarily relies on RNA binding proteins (RBPs). However, the functions of many RBPs remain understudied. Here, we characterized the function of a novel RBP, Proline-Rich Coiled-coil 2B (PRRC2B). Through photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation and sequencing (PAR-CLIP-seq), we identified transcriptome-wide CU- or GA-rich PRRC2B binding sites near the translation initiation codon on a specific cohort of mRNAs in HEK293T cells. These mRNAs, including oncogenes and cell cycle regulators such as CCND2 (cyclin D2), exhibited decreased translation upon PRRC2B knockdown as revealed by polysome-associated RNA-seq, resulting in reduced G1/S phase transition and cell proliferation. Antisense oligonucleotides blocking PRRC2B interactions with CCND2 mRNA decreased its translation, thus inhibiting G1/S transition and cell proliferation. Mechanistically, PRRC2B interactome analysis revealed RNA-independent interactions with eukaryotic translation initiation factors 3 (eIF3) and 4G2 (eIF4G2). The interaction with translation initiation factors is essential for PRRC2B function since the eIF3/eIF4G2-interacting defective mutant, unlike wild-type PRRC2B, failed to rescue the translation deficiency or cell proliferation inhibition caused by PRRC2B knockdown. Altogether, our findings reveal that PRRC2B is essential for efficiently translating specific proteins required for cell cycle progression and cell proliferation. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=190 SRC="FIGDIR/small/520836v2_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@cc9385org.highwire.dtl.DTLVardef@e92f55org.highwire.dtl.DTLVardef@1228c7corg.highwire.dtl.DTLVardef@1352179_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

3D spheroid-microvasculature-on-a-chip for tumor-endothelium mechanobiology interplay

In the final step of cancer metastasis, tumor cells become lodged in a distant capillary bed, where they can undergo extravasation and form a secondary tumor. While increasing evidence suggests blood/lymphatic flow and shear stress play a critical role in the tumor extravasation process, there is a lack of systematic and biomechanical approaches to recapitulate sophisticated 3D microtissue interactions within the controllable hydrodynamic microenvironment. Here, we report a simple-to-use 3D spheroid-microvasculature-on-a-chip (SMAC) model. Under static and controlled flow conditions, the SMAC recapitulates the biomechanical crosstalk between heterogeneous tumor spheroids and the endothelium in a high-throughput and quantitative manners. As an in vitro metastasis mechanobiology model, we discover 3D spheroid-induced endothelial compression and cell-cell junction degradation in the process of tumor migration and expansion. Lastly, we examine the shear stress effects on the endothelial orientation, polarization as well as the tumor spheroid expansion. Taken together, our SMAC model offers a miniaturized, cost-efficient and versatile platform for future investigation on metastasis mechanobiology, enhanced permeability and retention effect and even personalized therapeutic evaluation.

bioengineering↗

Mechanism of dual pharmacological correction and potentiation of human CFTR

Cystic fibrosis (CF) is caused by mutations in a chloride channel called the human Cystic Fibrosis Transmembrane Conductance Regulator (hCFTR). We used cryo-EM global conformational ensemble reconstruction to characterize the mechanism by which the breakthrough drug VX445 (Elexacaftor) simultaneously corrects both protein-folding and channel-gating defects caused by CF mutations. VX445 drives hCFTR molecules harboring the gating-defective G551D mutation towards the open-channel conformation by binding to a site in the first transmembrane domain. This binding interaction reverses the usual pathway of allosteric structural communication by which ATP binding activates channel conductance, which is blocked by the G551D mutation. Our ensemble reconstructions include a 3.4 [A] non-native structure demonstrating that detachment of the first nucleotide-binding domain of hCFTR is directly coupled to local unfolding of the VX445 binding site. Reversal of this unfolding transition likely contributes to its corrector activity by cooperatively stabilizing NBD1 and the transmembrane domains of hCFTR during biogenesis. SummaryCryo-EM global conformational ensemble reconstruction has been used to characterize the mechanism-of-action of a breakthrough pharmaceutical that corrects fatal protein-folding and channel-gating defects in the human cystic fibrosis transmembrane conductance regulator (CFTR).

biophysics↗

Modifying the trajectory of epicardial leads can substantially reduce MRI-induced RF heating in pediatric patients with a cardiac implantable electronic device

PurposeInfants and children with congenital heart defects, inherited arrhythmia syndromes, and congenital cardiac conduction disorders often receive epicardial implantable electronic devices. Unfortunately, once an epicardial device is implanted, the patient is no longer eligible to receive MRI exams due to an elevated risk of RF heating. Here we show that a simple modification in the trajectory of epicardial leads can substantially and reliably reduce RF heating during MRI at 1.5 T, with benefits extending to abandoned leads. MethodsElectromagnetic simulations were performed to assess RF heating of two common epicardial lead trajectories exhibiting different degrees of coupling with MRI incident electric fields. Experiments in anthropomorphic phantoms implanted with commercial cardiac implantable electronic devices (CIEDs) confirmed the findings. ResultsSimulations of an epicardial lead with a trajectory where the excess length of the lead was looped and placed on the anterior surface of the heart showed a 9-fold reduction in 0.1g-averaged SAR compared to the lead with excess length looped on the inferior surface of the heart. Repeated experiments with a commercial epicardial device confirmed the results, showing a 16-fold reduction in the average temperature rise for fully implanted systems with leads following low-SAR trajectories, and a 20-fold reduction in RF heating on an abandoned lead. ConclusionSurgical modification of epicardial lead trajectory can substantially reduce RF heating at 1.5 T, with benefits extending to abandoned leads.

biophysics↗

Artifacts can be deceiving: The actual location of deep brain stimulation electrodes differs from the artifact seen on magnetic resonance images

IntroductionDeep brain stimulation (DBS) is a common treatment for a variety of neurological and psychiatric disorders. Recent studies have highlighted the role of neuroimaging in localizing the position of electrode contacts relative to target brain areas in order to optimize DBS programming. Among different imaging methods, postoperative magnetic resonance imaging (MRI) has been widely used for DBS electrode localization; however, the geometrical distortion induced by the lead limits its accuracy. In this work, we investigated to what degree the difference between the actual location of the leads tip and the location of the tip estimated from the MRI artifact varies depending on the MRI sequence parameters such as acquisition plane and phase encoding direction, as well as the leads extracranial configuration. Accordingly, an imaging technique to increase the accuracy of lead localization was devised and discussed. MethodsWe designed and constructed an anthropomorphic phantom with an implanted DBS system following 18 clinically relevant configurations. The phantom was scanned at a Siemens 1.5 Tesla Aera scanner using a T1MPRAGE sequence optimized for clinical use and a T1TSE sequence optimized for research purposes. We varied slice acquisition plane and phase encoding direction and calculated the distance between the caudal tip of the DBS lead MRI artifact and the actual tip of the lead, as estimated from MRI reference markers. ResultsImaging parameters and lead configuration substantially altered the difference in the depth of the lead within its MRI artifact on the scale of several millimeters - with a difference as large as 4.99 millimeters. The actual tip of the DBS lead was found to be consistently more rostral than the tip estimated from the MR image artifact. The smallest difference between the tip of the DBS lead and the tip of the MRI artifact using the clinically relevant sequence (i.e., T1MPRAGE) was found with the sagittal acquisition plane and anterior-posterior phase encoding direction. Discussion/ConclusionThe actual tip of an implanted DBS lead is located up to several millimeters rostral to the tip of the leads artifact on postoperative MR images. This distance depends on the MRI sequence parameters and the DBS systems extracranial trajectory. MRI parameters may be altered to improve this localization.

neuroscience↗

Simultaneously spatiotemporal gene expression and chromatin accessibility for mouse brain development

Brain are complex biological tissues which function relies on coordinated anatomical and molecular structure comprised by a large number of specialized cells. The spatial architecture of brain which is key to the understanding of its physiological and pathological significance is formed during embryo development. However, the molecular basis for discrete neuroanatomical domains particularly in the context of spatial organization of the brain is inadequate. Here, we introduced microfluidic indexing based spatial ATAC and RNA sequencing (MISAR-seq), a method for joint profiling of chromatin accessibility and gene expression with spatial information retained in the developing mouse brain. Our study has established a direct means to spatially determine the coordination between chromatin accessibility and transcriptome, identified the chromatin potential to define cell fate determination of brain organization, and uncovered spatiotemporal regulatory principles during mammalian brain development.

developmental biology↗

Transcriptional circuitry of NKX2-1 and SOX1 defines an unrecognized lineage subtype of small cell lung cancer

RationaleThe current molecular classification of small cell lung cancer (SCLC) based on expression of four lineage transcription factors still leaves its major subtype SCLC-A as a heterogeneous group, necessitating more precise characterization of lineage subclasses. ObjectivesTo refine the current SCLC classification with epigenomic profiles and to identify features of the re-defined SCLC subtypes. MethodsWe performed unsupervised clustering of epigenomic profiles on 25 SCLC cell lines. Functional significance was evaluated by cell growth, apoptosis and xenograft using CRISPR-Cas9-mediated deletion. The specific cistromic profiles by ChIP-seq and its functional transcriptional partners using co-immunoprecipitation followed by mass spectrometry were determined. Rb1fl/flTrp53fl/fl and Rb1fl/flNkx2-1fl/fl mouse models were engineered to explore the function of Nkx2-1 in tumor initiation and differentiation. H3K27ac profiles were analyzed to reveal 6 human SCLC specimen and 20 mice tumors epigenomic landscapes. Measurements and Main ResultsWe identified an epigenomic subclusters of the major SCLC-A subtype, named SCLC-A and SCLC-A{sigma}. SCLC-A was characterized by the presence of a super-enhancer at the NKX2-1 locus, which was observed in human SCLC specimens and a murine SCLC model. We found NKX2-1, a dual lung and neural lineage factor, is uniquely relevant in SCLC-A. We further found maintenance of this neural identity in SCLC-A is mediated by collaborative transcriptional activity with another neuronal transcriptional factor SOX1. ConclusionsWe comprehensively describe an additional epigenomic heterogeneity of the major SCLC-A subtype, and define SCLC-A subtype by the core regulatory circuitry representing NKX2-1 and SOX1 super-enhancers and their functional collaborations to maintain neuronal linage state.

molecular biology↗

Cohesin mutation sensitizes cancer cells to anti-PD-1 therapy through endogenous retrovirus-mediated PD-L1 upregulation

Immune checkpoint therapy shows impressive and durable clinical responses in cancer patients, but the genetic determinants that enable cancer cells to respond to anti-PD-1 therapy are still elusive. Herein, we identified that NIPBL deficiency promotes endogenous retrovirus (ERV) expression in tumour cells, which in turn inactivates CD8+ tumour-infiltrating lymphocytes (TILs) via the PD-L1/PD-1 inhibitory checkpoint pathway. Mechanistically, NIPBL deficiency impairs DNMT1 transcription, preventing DNMT1 from suppressing ERV expression in tumour cells; ERVs stimulate PD-L1 expression by inducing the STAT2-IRF9 complex, a downstream event of double-stranded RNA (dsRNA)-MAVS-IRF3 signalling, and thereby suppress CD8 TIL-mediated immunity. An anti-PD-1 monoclonal antibody achieved remarkable therapeutic effects in Nipbl-deficient syngeneic tumour models and improved host survival by eliciting an antitumour memory immune response. Cancer patients harbouring mutations of cohesin subunits and regulators plus DNMT1 had significantly better responses to anti-PD-1 therapy than their non-mutated counterparts did. Our study reveals a novel mechanism by which cohesin complex deregulation stimulates ERV expression by impairing DNMT1 expression and fosters an immunosuppressive tumour microenvironment by activating the PD-L1/PD-1 inhibitory checkpoint.

cancer biology↗

Beneficial Effects of Celastrol on Immune Balance by Modulating Gut Microbiota in Dextran Sodium Sulfate-Induced Ulcerative Colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease caused by multi-factors including colonic inflammation and microbiota dysbiosis. Previous studies have indicated that Celastrol (CSR) has strong anti-inflammatory and immune-inhibitory effects. Here, we investigated the effects of CSR on colonic inflammation and the mucosal immunity in an experimental colitis model, and addressed the mechanism by which CSR preforms the protective effect. We characterized the therapeutic effects and the potential mechanism of CSR in treating UC using histological staining, intestinal permeability assay, cytokine assay, flow cytometry, fecal microbiota transplantation (FMT), 16S rRNA sequencing, untargeted metabolomics, and cell differentiation approaches. CSR administration significantly ameliorated DSS-induced colitis, as evidenced by the recovery of body weight and colon length, decreased disease activity index (DAI) score, as well as decreased intestinal permeability. CSR down-regulated the secretion of proinflammatory cytokines, upregulated the anti-inflammatory mediators, and improved the balances of Treg/Th1 and Treg/Th17 to maintain colonic immune homeostasis. However, the protective effects of CSR disappeared when the antibiotic cocktail was applied to deplete the gut microbiota, and the gut microbiota-mediated effect was confirmed by FMT. Furthermore, CSR treatment increased the gut microbiota diversity and composition, and raised the metabolic productions of pyruvate and adenosine, which probably involve in gut microbiota mediated protective effect. In conclusion, CSR ameliorates colonic inflammation in a gut microbiota-dependent manner. The underlying protective mechanism is associated with the rectified Treg/Th1 and Treg/Th17 balance, and increased pyruvate and adenosine production. The study provided the solid evidence that CSR might be a promising therapeutic drug for UC.

microbiology↗

Analyzing the Perceptual Attributes of Electro-tactile Stimuli as Function of Various Signal Properties

This study is designed to determine the proper electrical signals that induce various perceptual qualities. These perceptions are chosen from a wide range of feelings, comfort and even surface qualities such as smoothness or flatness. The goal is to derive the relationship between the electrical signal properties (i.e. voltage, frequency and duty cycle) and the perceived qualities which are understood by human observers and reveal any pattens in their reports. A total of 144 measurements are collected from 8 participants. The results are analyzed using numerous statistical methods. In the end, the governing factors are identified and a signal with specific properties is is determined for each of the perception qualities. A great number of plots are included in this study to facilitate the process of choosing the appropriate signal for each factor.

bioinformatics↗

Printed Texts Tracking and Following for a Finger-Wearable Electro-Braille System Through Opto-electrotactile Feedback

This paper presents our recent development on a portable and refreshable text reading and sensory substitution system for the blind or visually impaired (BVI), called Finger-eye. The system mainly consists of an opto-text processing unit and a compact electro-tactile based display that can deliver text-related electrical signals to the fingertip skin through a wearable and Braille-dot patterned electrode array and thus delivers the electro-stimulation based Braille touch sensations to the fingertip. To achieve the goal of aiding BVI to read any text not written in Braille through this portable system, in this work, a Rapid Optical Character Recognition (R-OCR) method is firstly developed for real-time processing text information based on a Fisheye imaging device mounted at the finger-wearable electrotactile display. This allows real-time translation of printed text to electro-Braille along with natural movement of users fingertip as if reading any Braille display or book. More importantly, an electro-tactile neuro-stimulation feedback mechanism is proposed and incorporated with the R-OCR method, which facilitates a new opto-electrotactile feedback based text line tracking control approach that enables text line following by user fingertip during reading. Multiple experiments were designed and conducted to test the ability of blindfolded participants to read through and follow the text line based on the opto-electrotactile-feedback method. The experiments show that as the result of the opto-electrotactile-feedback, the users were able to maintain their fingertip within a 2mm distance of the text while scanning a text line. This research is a significant step to aid the BVI users with a portable means to translate and follow to read any printed text to Braille, whether in the digital realm or physically, on any surface.

bioinformatics↗

Myosin-driven Nucleation of Actin Filaments Drives Stereocilia Development Critical for Hearing

The assembly and maintenance of actin-based mechanosensitive stereocilia in the cochlea is critical for lifelong hearing. Myosin-15 (MYO15) is hypothesized to modulate stereocilia height by trafficking actin regulatory proteins to their tip compartments, where actin polymerization must be precisely controlled during development. We identified a mutation (p.D1647G) in the MYO15 motor-domain that initially maintained trafficking, but caused progressive hearing loss by stunting stereocilia growth, revealing an additional function for MYO15. Consistent with its maintenance of tip trafficking in vivo, purified p.D1647G MYO15 modestly reduced actin-stimulated ATPase activity in vitro. Using ensemble and single-filament fluorescence in vitro assays, we demonstrated that wild-type MYO15 directly accelerated actin filament polymerization by driving nucleation, whilst p.D1647G MYO15 blocked this activity. Collectively, our studies suggest direct actin nucleation by MYO15 at the stereocilia tip is necessary for elongation in vivo, and that this is a primary mechanism disrupted in DFNB3 hereditary human hearing loss.

cell biology↗

Structural basis for tunable control of actin dynamics by myosin-15 in mechanosensory stereocilia

The motor protein myosin-15 is necessary for the development and maintenance of mechanosensory stereocilia, and myosin-15 mutations cause profound deafness. In a companion study, we report that myosin-15 nucleates actin filament ("F-actin") assembly and identify a progressive hearing loss mutation (p.D1647G, "jordan") which disrupts stereocilia elongation by inhibiting actin polymerization. Here, we present cryo-EM structures of myosin-15 bound to F-actin, providing a framework for interpreting deafness mutations and their impacts on myosin-stimulated actin assembly. Rigor myosin-15 evokes conformational changes in F-actin yet maintains flexibility in actins D-loop, which mediates inter-subunit contacts, while the jordan mutant locks the D-loop in a single conformation. ADP-bound myosin-15 also locks the D-loop, which correspondingly blunts actin-polymerization stimulation. We propose myosin-15 enhances polymerization by bridging actin protomers, regulating nucleation efficiency by modulating actins structural plasticity in a myosin nucleotide-state dependent manner. This tunable regulation of actin polymerization could be harnessed to precisely control stereocilium height.

biophysics↗

High activity and high functional connectivity are mutually exclusive in resting state zebrafish and human brains

Active neurons impact cell types with which they are functionally connected. Both activity and functional connectivity are heterogeneous across the brain, but the nature of their relationship is not known. Here we employ brain-wide calcium imaging at cellular resolution in larval zebrafish to record spontaneous activity of >12,000 neurons in the forebrain. By classifying their activity and functional connectivity into three levels (high, medium, low), we find that highly active neurons have low functional connections and highly connected neurons are of low activity. Intriguingly, deploying the same analytical methods on functional magnetic resonance imaging (fMRI) data from the resting state human brain, we uncover a similar relationship between activity and functional connectivity, that is, regions of high activity are non-overlapping with those of high connectivity. These findings reveal a previously unknown and evolutionarily conserved brain organizational principle that have implications for understanding disease states and designing artificial neuronal networks.

neuroscience↗

Time-varying Dynamic Network Model For Dynamic Resting State Functional Connectivity in fMRI and MEG imaging

Dynamic resting state functional connectivity (RSFC) characterizes fluctuations that occurs over time in functional brain networks. Existing methods to extract dynamic RSFCs, such as sliding-window and clustering methods, have various limitations due to their inherent non-adaptive nature and high-dimensionality including an inability to reconstruct brain signals, insufficiency of data for reliable estimation, insensitivity to rapid changes in dynamics, and a lack of generalizability across multimodal functional imaging datasets. To overcome these deficiencies, we develop a novel and unifying time-varying dynamic network (TVDN) framework for examining dynamic resting state functional connectivity. TVDN includes a generative model that describes the relation between low-dimensional dynamic RSFC and the brain signals, and an inference algorithm that automatically and adaptively learns to detect dynamic state transitions in data and a low-dimensional manifold of dynamic RSFC. TVDN is generalizable to handle multimodal functional neuroimaging data (fMRI and MEG/EEG). The resulting estimated low-dimensional dynamic RSFCs manifold directly links to the frequency content of brain signals. Hence we can evaluate TVDN performance by examining whether learnt features can reconstruct observed brain signals. We conduct comprehensive simulations to evaluate TVDN under hypothetical settings. We then demonstrate the application of TVDN with real fMRI and MEG data, and compare the results with existing benchmarks. Results demonstrate that TVDN is able to correctly capture the dynamics of brain activity and more robustly detect brain state switching both in resting state fMRI and MEG data.

bioengineering↗