Biology subjects

Fan, M.

Publications and source records attributed to Fan, M..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

Inter-kingdom signaling by the Legionella autoinducer LAI-1 involves the antimicrobial guanylate binding protein GBP

The causative agent of Legionnaires disease, Legionella pneumophila, is an amoebae-resistant environmental bacterium, which replicates intracellularly in a distinct compartment, the "Legionella-containing vacuole" (LCV). L. pneumophila employs the -hydroxyketone compound LAI-1 (Legionella autoinducer-1) for intra-species and inter-kingdom signaling. LAI-1 promotes intracellular replication and inhibits the migration of mammalian cells and Dictyostelium discoideum. In this study, we revealed that LAI-1 and "clickable" azido-LAI-1 derivatives inhibit the migration of D. discoideum and localize to LCVs. Azido-LAI-1 colocalizes with the LCV markers calnexin, P4C, and AmtA, but not with mitochondrial or lipid droplet markers. Intriguingly, LAI-1 dependent inhibition of D. discoideum migration involves the single guanylate-binding protein (GBP), a member of the GBP family of large GTPases, which in metazoan organisms promote cell autonomous immunity. D. discoideum lacking GBP ({Delta}gnbp) allows more efficient intracellular replication of L. pneumophila, without apparently compromising LCV remodeling or integrity, and GBP-GFP localizes to the ER at LCV-ER membrane contact sites (MCS). However, the peri-LCV localization of LAI-1 and GBP is not mutually dependent. Synthetic LAI-1 inhibits the expansion/remodeling of LCVs (but not vacuoles harboring avirulent L. pneumophila) in a GBP-dependent manner. Taken together, the work shows that LAI-1 localizes to LCVs, and LAI-1-dependent inter-kingdom signaling involves D. discoideum GBP, which localizes to LCV-ER MCS and acts as an antimicrobial factor by restricting the intracellular growth of L. pneumophila. Author SummarySmall molecule inter-kingdom signaling between pathogens and host cells represents a crucial but only partly understood aspect of microbial virulence. The amoeba-resistant opportunistic pathogen Legionella pneumophila employs the compound LAI-1 (Legionella autoinducer-1) for intra-species and inter-kingdom signaling. In metazoan cells, the conserved and wide-spread family of guanylate-binding protein (GBP) large GTPases usually comprises several distinct paralogues, which are implicated in pathogen detection, inflammation, cell death pathways, and cell autonomous immunity. In the social amoeba Dictyostelium discoideum, only a single GBP gene of unknown function is present. Using approaches from organic chemistry, genetics, cell biology and infection biology, we reveal that GBP is involved in the inhibition of D. discoideum migration and pathogen vacuole expansion/remodeling by LAI-1 as well as in intracellular growth of L. pneumophila. This study provides a novel link between small molecule inter-kingdom signaling and GBP-dependent cell autonomous immunity.

microbiology↗

bioRxiv2024

Structure-Mechanics Principles and Mechanobiology of Fibrocartilage Pericellular Matrix: A Pivotal Role of Type V Collagen

The pericellular matrix (PCM) is the immediate microniche surrounding resident cells in various tissue types, regulating matrix turnover, cell-matrix cross-talk and disease initiation. This study elucidated the structure-mechanical properties and mechanobiological functions of the PCM in fibrocartilage, a family of connective tissues that sustain complex tensile and compressive loads in vivo. Studying the murine meniscus as the model tissue, we showed that fibrocartilage PCM contains thinner, random collagen fibrillar networks that entrap proteoglycans, a structure distinct from the densely packed, highly aligned collagen fibers in the bulk extracellular matrix (ECM). In comparison to the ECM, the PCM has a lower modulus and greater isotropy, but similar relative viscoelastic properties. In Col5a1+/D menisci, the reduction of collagen V, a minor collagen localized in the PCM, resulted in aberrant fibril thickening with increased heterogeneity. Consequently, the PCM exhibited a reduced modulus, loss of isotropy and faster viscoelastic relaxation. This disrupted PCM contributes to perturbed mechanotransduction of resident meniscal cells, as illustrated by reduced intracellular calcium signaling, as well as upregulated biosynthesis of lysyl oxidase and tenascin C. When cultured in vitro, Col5a1+/D meniscal cells synthesized a weakened nascent PCM, which had inferior properties towards protecting resident cells against applied tensile stretch. These findings underscore the PCM as a distinctive microstructure that governs fibrocartilage mechanobiology, and highlight the pivotal role of collagen V in PCM function. Targeting the PCM or its molecular constituents holds promise for enhancing not only meniscus regeneration and osteoarthritis intervention, but also addressing diseases across various fibrocartilaginous tissues.

bioengineering↗

bioRxiv2024

KAT6A deficiency impairs cognitive functions through suppressing RSPO2/Wnt signaling in hippocampal CA3

Intellectual disability (ID) affects [~]2% of the general population and is often genetic in origin. ID-associated genes are enriched for epigenetic factors, including those encoding the largest family of histone lysine acetyltransferases (KAT5-KAT8). Among them is KAT6A, whose de novo heterozygous mutations cause KAT6A Syndrome (or Arboleda-Tham Syndrome), with ID as a common clinical feature. However, the underlying molecular mechanisms remain elusive. Here, we show that haploinsufficiency of Kat6a impairs learning and memory in mice, and specific deletion of Kat6a in excitatory neurons recapitulates the hippocampus-dependent memory deficits. Unexpectedly, KAT6A deficiency results in impaired synaptic structure and plasticity in hippocampal CA3, but not in CA1 region. Combining single-nucleus RNA-sequencing and chromatin analysis, we identify a CA3-enriched gene Rspo2, encoding a Wnt activator R-spondin 2, as a key transcriptional target of KAT6A. Moreover, deletion of Rspo2 in excitatory neurons phenocopies the loss of Kat6a, resulting in defective Wnt/{beta}-catenin signaling and synaptic plasticity in CA3, and abnormal cognitive behaviors in mice. Importantly, restoring RSPO2 expression in CA3 pyramidal neurons rescues the deficits in Wnt signaling and learning-associated behaviors in Kat6a mutant mice. Collectively, our results demonstrate that KAT6A plays a critical role in regulating synaptic plasticity and memory formation through RSPO2-mediated Wnt signaling in hippocampal CA3, shedding new light on the fundamental mechanisms of ID and providing potential therapeutic targets for the treatment of KAT6A Syndrome and related neurodevelopmental diseases.

neuroscience↗

bioRxiv2024

Post-death Vesicles of Senescent Bone Marrow Mesenchymal Stromal Polyploids Promote Macrophage Aging and Breast Cancer

Potential systemic factors contributing to aging-associated breast cancer (BC) remain elusive. Here, we reveal that the polyploid giant cells (PGCs) that contain more than two sets of genomes prevailing in aging and cancerous tissues constitute 5-10% of healthy female bone marrow mesenchymal stromal cells (fBMSCs). The PGCs can repair DNA damage and stimulate neighboring cells for clonal expansion. However, dying PGCs in advanced-senescent fBMSCs can form "spikings" which are then separated into membraned mtDNA-containing vesicles (Senescent PGC-Spiking Bodies; SPSBs). SPSB-phagocytosed macrophages accelerate aging with diminished clearance on BC cells and protumor M2 polarization. SPSB-carried mitochondrial OXPHOS components are enriched in BC of elder patients and associated with poor prognosis. SPSB-incorporated breast epithelial cells develop aggressive characteristics and PGCs resembling the polyploid giant cancer cells (PGCCs) in clonogenic BC cells and cancer tissues. These findings highlight an aging BMSC-induced BC risk mediated by SPSB-induced macrophage dysfunction and epithelial cell precancerous transition. SIGNIFICANCEMechanisms underlying aging-associated cancer risk remain unelucidated. This work demonstrates that polyploid giant cells (PGCs) in bone marrow mesenchymal stromal cells (BMSCs) from healthy female bone marrow donors can boost neighboring cell proliferation for clonal expansion. However, the dying-senescent PGCs in the advanced-senescent fBMSCs can form "spikings" which are separated into mitochondrial DNA (mtDNA)-containing spiking bodies (senescent PGC-spiking bodies; SPSBs). The SPSBs promote macrophage aging and breast epithelial cell protumorigenic transition and form polyploid giant cancer cells. These results demonstrate a new form of ghost message from dying-senescent BMSCs, that may serve as a systemic factor contributing to aging-associated immunosuppression and breast cancer risk. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/583755v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@f07b60org.highwire.dtl.DTLVardef@33ef98org.highwire.dtl.DTLVardef@1b720c8org.highwire.dtl.DTLVardef@1c9514d_HPS_FORMAT_FIGEXP M_FIG Xie et al demonstrate that the polyploid giant cells (PGCs) in the juvenile phase expansion of female bone marrow mesenchymal stromal cells (fBMSCs) can boost neighboring cell proliferation for clonal expansion. However, when fBMSCs enter to the advanced-senescent phase, the dying-senescent PGCs form "spikings" which are then separated into membraned vesicles termed Senescent PGC spiking bodies, SPSBs). The SPSBs carrying fragmented mitochondrial elements and OXPHOS proteins can be phagocytosed by macrophage and breast epithelial cells leading to macrophage aging and breast epithelial protumorigenic transition. The SPSBs are demonstrated to be a new form of post-cell death vesicle from aging BMSCs and may serve as a systemic factor contributing to aging-associated immunosuppression and breast cancer risk. C_FIG

cancer biology↗

bioRxiv2024

Blocker-SELEX: A Structure-guided Strategy for Developing Inhibitory Aptamers Disrupting Undruggable Transcription Factor Interactions

Despite the well-established significance of transcription factors (TFs) in pathogenesis, their utilization as pharmacological targets has been limited by the inherent challenges associated with modulating their protein-protein and protein-DNA interactions. The lack of defined small-molecule binding pockets and the nuclear localization of TFs do not favor the use of small-molecule inhibitors, or neutral antibodies, in blocking TF interactions. Aptamers are short oligonucleotides exhibiting high affinity and specificity for a diverse range of targets. Large molecular weights, expansive blocking surfaces and efficient cellular internalization make aptamers a compelling molecular tool for use as traditional TF interaction modulators. Here, we report a structure-guided design strategy called Blocker-SELEX to develop inhibitory aptamers (iAptamer) that selectively block TF interactions. Our approach led to the discovery of iAptamers that cooperatively disrupts SCAF4/SCAF8-RNA Polymerase II (RNAP2) interactions, thereby dysregulating RNAP2-dependent gene expression and splicing and, in turn, leading to the impairment of cell proliferation. This approach was further applied to develop iAptamers to efficiently block WDR5-MYC interaction with a nexus in cancer. Taken together, our study highlights the potential of Blocker-SELEX in developing iAptamers that effectively disrupt potentially pathogenic TF interactions with attendant implications for iAptamers as chemical tools for use in the study of biological functions of TF interactions, but also for potential use in nucleic acids drug discovery.

biochemistry↗

bioRxiv2023

Comprehensive Multi-Omic Analysis Reveals Distinct Molecular Features in Early and Advanced Stages of Hepatocellular Carcinoma

Hepatocellular Carcinoma (HCC) is a serious primary solid tumor that is prevalent worldwide. Due to its high mortality rate, it is crucial to explore both early diagnosis and advanced treatment for HCC. In recent years, multi-omic approaches have emerged as promising tools to identify biomarkers and investigate molecular mechanisms of biological processes and diseases. In this study, we performed proteomics, phosphoproteomics, metabolomics, and lipidomics to reveal the molecular features of early- and advanced-stage HCC. The data obtained from these omics were analyzed separately and then integrated to provide a comprehensive understanding of the disease. The multi-omic results unveiled intricate biological pathways and interaction networks underlying the initiation and progression of HCC. Moreover, we proposed specific potential biomarker panels for both early- and advanced-stage HCC by overlapping our data with CPTAC database, and deduced novel insights and mechanisms related to HCC origination and development.

cancer biology↗

bioRxiv2023

Scalable bio-platform to recover critical metals fromcomplex waste sources

Chemical methods for extraction and refinement of technologically critical rare earth elements (REEs) are energy intensive, hazardous, and environmentally destructive. Current bio-based extraction systems rely on extremophilic organisms and generate many of the same detrimental effects as chemical methodologies. The mesophilic methylotrophic bacterium Methylobacterium extorquens AM1 was previously shown to grow using electronic waste by naturally acquiring REEs to power methanol metabolism. Here we show that growth using electronic waste as a sole REE source is scalable up to 10 L with consistent metal yields, without the use of harsh acids or high temperatures. Addition of organic acids increases REE leaching in a nonspecific manner. REE-specific bioleaching can be engineered through the overproduction of REE-binding ligands (called lanthanophores) and pyrroloquinoline quinone. REE bioaccumulation increases with leachate concentration and is highly specific. REEs are stored intracellularly in polyphosphate granules, and genetic engineering to eliminate exopolyphosphatase activity increases metal accumulation, confirming the link between phosphate metabolism and biological REE use. Finally, we report the innate ability of M. extorquens to grow using other complex REE sources including pulverized smart phones, demonstrating the flexibility and potential for use as a recovery platform for these critical metals.

bioengineering↗

bioRxiv2023

The Legionella autoinducer LAI-1 is delivered by outer membrane vesicles to promote inter-bacterial and inter-kingdom signaling

Legionella pneumophila is an environmental bacterium, which replicates in amoeba but also in macrophages, and causes a life-threatening pneumonia called Legionnaires disease. The opportunistic pathogen employs the -hydroxyketone compound LAI-1 (Legionella autoinducer-1) for intra-species and inter-kingdom signaling. LAI-1 is produced by the autoinducer synthase LqsA, but it is not known, how LAI-1 is released by the pathogen. Here, we use a V. cholerae luminescence reporter strain and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to detect bacteria-produced and synthetic LAI-1. Ectopic production of LqsA in E. coli generated LAI-1, which partitions to outer membrane vesicles (OMVs), and slightly reduces OMV size. These E. coli OMVs trigger luminescence of the V. cholerae reporter strain and inhibit the migration of Dictyostelium discoideum amoeba. Overexpression of lqsA in L. pneumophila under the control of strong stationary phase promoters (PflaA or P6SRNA), but not under control of its endogenous promoter (PlqsA), produces LAI-1, which is detected in purified OMVs. These L. pneumophila OMVs trigger luminescence of the Vibrio reporter strain and inhibit D. discoideum migration. L. pneumophila OMVs are smaller upon overexpression of lqsA or upon addition of LAI-1 to growing bacteria, and therefore, LqsA affects OMV production. The overexpression of lqsA but not a catalytically inactive mutant promotes intracellular replication of L. pneumophila in macrophages, indicating that intracellularly produced LA1-1 modulates the interaction in favour of the pathogen. Taken together, we provide evidence that L. pneumophila LAI-1 is secreted through OMVs and promotes inter-bacterial communication as well as interactions with eukaryotic host cells. Originality - Significance StatementInter-kingdom signaling involving low molecular weight bacterial compounds that are detected by eukaryotic cells represents an important, yet incompletely understood aspect of pathogen-host interactions. In many cases, the small signaling molecules are produced in only little amounts, their secretion mechanism is not known, and their effects on eukaryotic host cells are barely studied. Here, we reveal that the -hydroxyketone compound LAI-1 of L. pneumophila is released from the bacteria by outer membrane vesicles, which promote inter-bacterial communication as well as inter-kingdom signaling.

microbiology↗

bioRxiv2023

StructuralDPPIV: A novel deep learning model based on atom-structure for predicting dipeptidyl peptidase-IV inhibitory peptides

MotivationDiabetes is a chronic metabolic disorder that has been a major cause of blindness, kidney failure, heart attacks, stroke, and lower limb amputation across the world. To alleviate the impact of diabetes, researchers have developed the next generation of anti-diabetic drugs, known as dipeptidyl peptidase IV inhibitory peptides (DPP-IV-IPs). However, the discovery of these promising drugs has been restricted due to the lack of effective peptide-mining tools. ResultsHere, we presented StructuralDPPI V, a deep learning model designed for DPP-IV-IP identification, which takes advantage of both molecular graph features in amino acid and sequence information. Experimental results on the independent test dataset and two wet experiment datasets show that our model outperforms the other state-of-art methods. Moreover, to better study what StructuralDPPIV learns, we used CAM technology and perturbation experiment to analyze our model, which yielded interpretable insights into the reasoning behind prediction results. AvailabilityThe project code is available at https://github.com/WeiLab-BioChem/Structural-DPP-IV. Contactweileyi@sdu.edu.cn, ran.su@tju.edu.cn

bioinformatics↗

bioRxiv2023

Acetylated dietary protein contributes to the acetylome in cells via KARS-mediated intra-translational deposition of acetyl-lysine in nascent protein

N6-acetyl-L-lysine residue is abundant in dietary protein but less is known about its potential influences on the diet-consumers. We herein report that KARS mediates intra- translational deposition of diet-derived N6-acetyl-L-lysine in nascent proteins to contribute the acetylome in cells. Acetylated dietary protein is a direct source of N6-acetyl-L-lysine that can widely and substantially contribute the acetylome in multiple organs of mice. By analyzing the co-crystal structure of Lysyl-tRNA synthetase (KARS) in complex with N6- acetyl-L-lysyl-AMP and pyrophosphate, together with in vitro biochemical assays, we learned that KARS can utilize N6-acetyl-L-lysine to produce N6-acetyl-L-lysyl-AMP and transfers the N6-acetyl-L-lysyl-moiety to lysine cognate tRNA to generate N6-acetyl-L- lysyl-tRNA, which introduces N6-acetyl-L-lysine into growing nascent polypeptide and intra-translationally results in protein acetylation. This undocumented protein modification mechanism is inherently different from post-translational modification (PTM) and termed as intra-translational modification (ITM). ITM can functionally mimic PTM mechanisms to deposit acetylation in histones to decondense chromatin. It can also modify PTM- inaccessible regions that are buried inside and functionally important to proteins. ITM is expected to extend the repertoire of acetylome and improve our understandings in protein modification modes in cells.

biochemistry↗

bioRxiv2022

Covalent Disruptor of YAP-TEAD Association Suppresses Defective Hippo Signaling

The transcription factor TEAD, together with its coactivator YAP/TAZ, is a key transcriptional modulator of the Hippo pathway. Activation of TEAD transcription by YAP has been implicated in a number of malignancies, and this complex represents a promising target for drug discovery. However, both YAP and its extensive binding interfaces to TEAD have been difficult to address using small molecules, mainly due to a lack of druggable pockets. TEAD is post-translationally modified by palmitoylation that targets a conserved cysteine at a central pocket, which provides an opportunity to develop cysteine-directed covalent small molecules for TEAD inhibition. Here, we employed covalent fragment screening approach followed by structure-based design to develop an irreversible TEAD inhibitor MYF-03-69. Using a range of in vitro and cell-based assays we demonstrated that through a covalent binding with TEAD palmitate pocket, MYF-03-69 disrupts YAP-TEAD association, suppresses TEAD transcriptional activity and inhibits cell growth of Hippo signaling defective malignant pleural mesothelioma (MPM). Further, a cell viability screening with a panel of 903 cancer cell lines indicated a high correlation between TEAD-YAP dependency and the sensitivity to MYF-03-69. Transcription profiling identified the upregulation of proapoptotic BMF gene in cancer cells that are sensitive to TEAD inhibition. Further optimization of MYF-03-69 led to an in vivo compatible compound MYF-03-176, which shows strong antitumor efficacy in MPM mouse xenograft model via oral administration. Taken together, we disclosed a story of the development of covalent TEAD inhibitors and its high therapeutic potential for clinic treatment for the cancers that are driven by TEAD-YAP alteration.

cancer biology↗

bioRxiv2021

HIF-dependent expression of creatine kinase brain isoform (CKB) promotes breast cancer metastasis, and blocking creatine kinase activity with cyclocreatine impairs invasion and improves the efficacy of conventional chemotherapies

The oxygen-responsive Hypoxia Inducible Factor (HIF)-1 promotes several steps of the metastatic cascade. A hypoxic gene signature is enriched in triple negative breast cancers (TNBCs) and correlates with poor patient survival. Since inhibiting the HIF transcription factors with small molecules is challenging, we sought to identify genes downstream of HIF-1 that could be targeted to block invasion and metastasis. Creatine kinase brain isoform (CKB) was identified as a highly differentially expressed gene in a screen of HIF-1 wild type and knockout mammary tumor cells derived from a transgenic model of metastatic breast cancer. CKB is a cytosolic enzyme that reversibly catalyzes the phosphorylation of creatine, generating phosphocreatine (PCr) in the forward reaction, and regenerating ATP in the reverse reaction. Creatine kinase activity is inhibited by the creatine analog cyclocreatine (cCr). Loss and gain of function genetic approaches were used in combination with cCr therapy to define the contribution of CKB expression or creatine kinase activity to cell proliferation, migration, invasion, and metastasis in ER-negative breast cancers. CKB was necessary for cell invasion in vitro and strongly promoted tumor growth and metastasis in vivo. Similarly, cyclocreatine therapy repressed cell migration, cell invasion, formation of invadopodia, and lung metastasis. Moreover, in common TNBC cell line models, the addition of cCr to conventional cytotoxic chemotherapy agents was either additive or synergistic to repress tumor cell growth.

cancer biology↗

bioRxiv2021

Disruption of Brachypodium Lichenase Alters Metabolism of Mixed-linkage Glucan and Starch

Mixed-linkage glucan (MLG), which is widely distributed in grasses, is a polysaccharide highly abundant in cell walls of grass endosperm and young vegetative tissues. Lichenases are enzymes that hydrolyze MLG first identified in MLG-rich lichens. In this study, we identify a gene encoding a lichenase we name Brachypodium distachyon LICHENASE 1 (BdLCH1), which is highly expressed in the endosperm of germinating seeds and coleoptiles and at lower amounts in mature shoots. RNA in situ hybridization showed that BdLCH1 is primarily expressed in chlorenchyma cells of mature leaves and internodes. Disruption of BdLCH1 resulted in an eight-fold increase in MLG content in senesced leaves. Consistent with the in situ hybridization data, immunolocalization results showed that MLG was not removed in chlorenchyma cells of lch1 mutants as it was in wild type and implicate the BdLCH1 enzyme in removing MLG in chlorenchyma cells in mature vegetative tissues. We also show that MLG accumulation in lch1 mutants was resistant to dark induced degradation, and eight-week-old lch1 plants showed a faster rate of starch breakdown than wild type in darkness. Our results suggest a role for BdLCH1 in modifying the cell wall to support highly metabolically active cells.

plant biology↗

bioRxiv2020

Deep learning and automated Cell Painting reveal Parkinson's disease-specific signatures in primary patient fibroblasts

Drug discovery for diseases such as Parkinsons disease are impeded by the lack of screenable cellular phenotypes. We present an unbiased phenotypic profiling platform that combines automated cell culture, high-content imaging, Cell Painting, and deep learning. We applied this platform to primary fibroblasts from 91 Parkinsons disease patients and matched healthy controls, creating the largest publicly available Cell Painting image dataset to date at 48 terabytes. We use fixed weights from a convolutional deep neural network trained on ImageNet to generate deep embeddings from each image and train machine learning models to detect morphological disease phenotypes. Our platforms robustness and sensitivity allow the detection of individual-specific variation with high fidelity across batches and plate layouts. Lastly, our models confidently separate LRRK2 and sporadic Parkinsons disease lines from healthy controls (receiver operating characteristic area under curve 0.79 (0.08 standard deviation)), supporting the capacity of this platform for complex disease modeling and drug screening applications.

cell biology↗

bioRxiv2020

Single-cell immune landscape of human recurrent spontaneous abortion

Successful pregnancy in placental mammals substantially depends on the establishment of maternal immune tolerance to the semi-allogenic fetus. Disorders in this process are tightly associated with adverse pregnancy outcomes including recurrent spontaneous abortion (RSA). However, an in-depth understanding of the disorders from the aspect of systematic and decidual immune environment in RSA remains largely lacking. In this study, we utilized single-cell RNA-sequencing to comparably analyze the cellular and molecular signatures of decidual and peripheral leukocytes in normal and RSA pregnancies at the early stage of gestation. Integrative analysis identified 22 distinct cell clusters in total, and a dramatic difference in leukocyte subsets and molecular properties in RSA cases was revealed. Specifically, the cytotoxic properties of CD8T effector, NK, and MAIT cells in peripheral blood indicated apparently enhanced immune inflammatory status, and the subpopulation proportions and ligand-receptor interactions of the decidual leukocyte subsets demonstrated preferential immune activation in RSA patients. The molecular features, spatial distribution and the developmental trajectories of five decidual NK (dNK) subsets were illustrated. The proportion of a dNK subset responsible for fetal protection was reduced, while the ratio of another dNK subset with cytotoxic and immune-active signature was significantly increased. Notably, a unique pro-inflammatory CD56+CD16+ dNK subpopulation was substantially accumulated in RSA decidua. These findings reveal a comprehensive cellular and molecular atlas of decidual and peripheral leukocytes in human early pregnancy, which provides an in-depth insight into the immune pathogenesis for early pregnancy loss.

immunology↗

bioRxiv2020

BNIP3 phosphorylation by JNK1/2 promotes mitophagy via enhancing its stability under hypoxia

Mitophagy is an important metabolic mechanism that modulates mitochondrial quality and quantity by selectively removing damaged or unwanted mitochondria. BNIP3, a mitochondrial outer membrane protein, is a mitophagy receptor that mediates mitophagy under various stresses, particularly hypoxia, since BNIP3 is a hypoxia-responsive protein. However, the underlying mechanisms that regulate BNIP3 and thus mediate mitophagy under hypoxic conditions remain elusive. Here, we demonstrate that in hypoxia JNK1/2 phosphorylates BNIP3 at Ser 60/Thr 66, which hampers proteasomal degradation of BNIP3 and drives mitophagy by facilitating the direct binding of BNIP3 to LC3, while PP1/2A represses mitophagy by dephosphorylating BNIP3 and triggering its proteasomal degradation. These findings reveal the intrinsic mechanisms cells use to regulate mitophagy via the JNK1/2-BNIP3 pathway in response to hypoxia. Thus, the JNK1/2-BNIP3 signaling pathway strongly links mitophagy to hypoxia and may be a promising therapeutic target for hypoxia-related diseases.

cell biology↗

bioRxiv2020

Loss of O-GlcNAcylation on MeCP2 Thr 203 Leads to Neurodevelopmental Disorders

Mutations of the X-linked methyl-CpG-binding protein 2 (MECP2) gene in humans are responsible for most cases of Rett syndrome (RTT), an X-linked progressive neurological disorder. While genome-wide screens in clinical trials reveal several putative RTT-associated mutations on MECP2, their causative relevance regarding the functional regulation of MeCP2 on the etiologic sites at the protein level require more evidence. In this study, we demonstrate that MeCP2 is dynamically modified by O-linked-{beta}-N-acetylglucosamine (O-GlcNAc) at threonine 203 (T203), an etiologic site in RTT patients. Disruption of the O-GlcNAcylation of MeCP2 specifically at T203 impairs dendrite development and spine maturation in cultured hippocampal neurons, and disrupts neuronal migration, dendritic spine morphogenesis and dysfunction of synaptic transmission in the developing and juvenile mouse cerebral cortex. Mechanistically, genetic disruption of O-GlcNAcylation at T203 on MeCP2 decreases neuronal activity-induced induction of Bdnf transcription. Our study highlights the critical role of MeCP2 T203 O-GlcNAcylation in neural development and synaptic transmission potentially via BDNF.

neuroscience↗

bioRxiv2020

Myelin water imaging depends on white matter fiber orientation in the human brain

The multiexponential T2 decay of the magnetic resonance imaging (MRI) signal from cerebral white matter can be separated into short components sensitive to myelin water and long components related to intra- and extracellular water. In this study we investigated to what degree the myelin water fraction (MWF) depends on the angle between white matter fibers and the main magnetic filed. Maps of MWF were acquired using multi echo CPMG and GRASE sequences. The CPMG sequence was acquired with a TR of 1073 ms, 1500 ms and 2000 ms. The fiber orientation was mapped with diffusion tensor imaging. By angle-wise pooling the voxels across the brains white matter, an orientation dependent MWF curve was generated. We found that MWF varied between 25% and 35% across different fiber orientations. The orientation dependency of the MWF is characterized by a dipole-dipole interaction model. Furthermore, the selection of the TR influences the orientation dependent and global white matter MWF. White matter fiber orientation induces a strong systematic bias on the estimation of MWF. This finding has important implications for future research and the interpretation of MWI results in previously published studies.

biophysics↗