参考文献

Cell-to-cell communication by exosomes controls normal and pathogenic processes1,2. Viruses can spread in exosomes and thereby avoid immune recognition3. While biogenesis,binding and uptake of exosomes are well characterized4,5,delivery of exosome cargo into the cytoplasm is poorly understood3. We report that the phosphatidylserine receptor HAVCR1 (refs. 6,7) and the cholesterol transporter NPC1 (ref. 8) participate in cargo delivery from exosomes of hepatitis A virus (HAV)-infected cells (exo-HAV) by clathrin-mediated endocytosis. Using CRISPR-Cas9 knockout technology,we show that these two lipid receptors,which interact in the late endosome9,are necessary for the membrane fusion and delivery of RNA from exo-HAV into the cytoplasm. The HAVCR1-NPC1 pathway,which Ebola virus exploits to infect cells9,mediates HAV infection by exo-HAV,which indicates that viral infection via this exosome mimicry mechanism does not require an envelope glycoprotein. The capsid-free viral RNA in the exosome lumen,but not the endosomal uncoating of HAV particles contained in the exosomes,is mainly responsible for exo-HAV infectivity as assessed by methylene blue inactivation of non-encapsidated RNA. In contrast to exo-HAV,infectivity of HAV particles is pH-independent and requires HAVCR1 or another as yet unidentified receptor(s) but not NPC1. Our findings show that envelope-glycoprotein-independent fusion mechanisms are shared by exosomes and viruses,and call for a reassessment of the role of envelope glycoproteins in infection. View Publication

Preclinical in vitro models provide an essential tool to study cancer cell biology as well as aid in translational research,including drug target identification and drug discovery efforts. For any model to be clinically relevant,it needs to recapitulate the biology and cell heterogeneity of the primary tumor. We recently developed and described a conditional reprogramming (CR) cell technology that addresses many of these needs and avoids the deficiencies of most current cancer cell lines,which are usually clonal in origin. Here,we used the CR cell method to generate a collection of patient-derived cell cultures from non-small cell lung cancers (NSCLC). Whole exome sequencing and copy number variations are used for the first time to address the capability of CR cells to keep their tumor-derived heterogeneity. Our results indicated that these primary cultures largely maintained the molecular characteristics of the original tumors. Using a mutant-allele tumor heterogeneity (MATH) score,we showed that CR cells are able to keep and maintain most of the intra-tumoral heterogeneity,suggesting oligoclonality of these cultures. CR cultures therefore represent a pre-clinical lung cancer model for future basic and translational studies. View Publication

Human-based body-on-a-chip" technology provides powerful platforms in developing models for drug evaluation and disease evaluations in phenotypic models. Induced pluripotent stem cells (iPSCs) are ideal cell sources for generating different cell types for these in vitro functional systems and recapitulation of the neuromuscular reflex arc would allow for the study of patient specific neuromuscular diseases. Regarding relevant afferent (intrafusal fibers sensory neurons) and efferent (extrafusal fibers motoneurons) cells in vitro differentiation of intrafusal fiber from human iPSCs has not been established. This work demonstrates a protocol for inducing an enrichment of intrafusal bag fibers from iPSCs using morphological analysis and immunocytochemistry. Phosphorylation of the ErbB2 receptors and S46 staining indicated a 3-fold increase of total intrafusal fibers further confirming the efficiency of the protocol. Integration of induced intrafusal fibers would enable more accurate reflex arc models and application of this protocol on patient iPSCs would allow for patient-specific disease modeling." View Publication

Targeted knockout of genes in primary human cells using CRISPR-Cas9-mediated genome-editing represents a powerful approach to study gene function and to discern molecular mechanisms underlying complex human diseases. We used lentiviral delivery of CRISPR-Cas9 machinery and conditional reprogramming culture methods to knockout the MUC18 gene in human primary nasal airway epithelial cells (AECs). Massively parallel sequencing technology was used to confirm that the genome of essentially all cells in the edited AEC populations contained coding region insertions and deletions (indels). Correspondingly,we found mRNA expression of MUC18 was greatly reduced and protein expression was absent. Characterization of MUC18 knockout cell populations stimulated with TLR2,3 and 4 agonists revealed that IL-8 (a proinflammatory chemokine) responses of AECs were greatly reduced in the absence of functional MUC18 protein. Our results show the feasibility of CRISPR-Cas9-mediated gene knockouts in AEC culture (both submerged and polarized),and suggest a proinflammatory role for MUC18 in airway epithelial response to bacterial and viral stimuli. View Publication

The limited ability of cytotoxic CD8+ T cells to infiltrate solid tumors and function within the tumor microenvironment presents a major roadblock to effective immunotherapy. Ion channels and Ca2+-dependent signaling events control the activity of T cells and are implicated in the failure of immune surveillance in cancer. Reduced KCa3.1 channel activity mediates the heightened inhibitory effect of adenosine on the chemotaxis of circulating T cells from head and neck squamous cell carcinoma (HNSCC) patients. Herein,we conducted experiments that elucidate the mechanisms of KCa3.1 dysfunction and impaired chemotaxis in HNSCC CD8+ T cells. The Ca2+ sensor calmodulin (CaM) controls multiple cellular functions including KCa3.1 activation. Our data showed that CaM expression is lower in HNSCC than healthy donor (HD) T cells. This reduction was due to an intrinsic decrease in the genes encoding CaM combined to the failure of HNSCC T cells to upregulate CaM upon activation. Furthermore,the reduction in CaM was confined to the plasma membrane and resulted in decreased CaM-KCa3.1 association and KCa3.1 activity (which was rescued by the delivery of CaM). IFN$\gamma$ production,also Ca2+- and CaM-dependent,was instead not reduced in HNSCC T cells,which maintained intact cytoplasmic CaM and Ca2+ fluxing ability. Knockdown of CaM in HD T cells decreased KCa3.1 activity,but not IFN$\gamma$ production,and reduced their chemotaxis in the presence of adenosine,thus recapitulating HNSCC T cell dysfunction. Activation of KCa3.1 with 1-EBIO restored the ability of CaM knockdown HD T cells to chemotax in the presence of adenosine. Additionally,1-EBIO enhanced INF$\gamma$ production. Our data showed a localized downregulation of membrane-proximal CaM that suppressed KCa3.1 activity in HNSCC circulating T cells and limited their ability to infiltrate adenosine-rich tumor-like microenvironments. Furthermore,they indicate that KCa3.1 activators could be used as positive CD8+ T cell modulators in cancers. View Publication

Cancer is believed to arise from stem cells,but mechanisms that limit the acquisition of mutations and tumor development have not been well defined. We show that a +4 stem cell (SC) in the gastric antrum,marked by expression of Cck2r (a GPCR) and Delta-like ligand 1 (DLL1),is a label-retaining cell that undergoes predominant asymmetric cell division. This +4 antral SC is Notch1low/ Numb+ and repressed by signaling from gastrin-expressing endocrine (G) cells. Chemical carcinogenesis of the stomach is associated with loss of G cells,increased symmetric stem cell division,glandular fission,and more rapid stem cell lineage tracing,a process that can be suppressed by exogenous gastrin treatment. This hormonal suppression is associated with a marked reduction in gastric cancer mutational load,as revealed by exomic sequencing. Taken together,our results show that gastric tumorigenesis is associated with increased symmetric cell division that facilitates mutation and is suppressed by GPCR signaling. View Publication

A promising strategy to limit cholera severity involves blockers mimicking the canonical cholera toxin ligand (CT) ganglioside GM1. However,to date the efficacies of most of these blockers have been evaluated in noncellular systems that lack ligands other than GM1. Importantly,the CT B subunit (CTB) has a noncanonical site that binds fucosylated structures,which in contrast to GM1 are highly expressed in the human intestine. Here we evaluate the capacity of norbornene polymers displaying galactose and/or fucose to block CTB binding to immobilized protein-linked glycan structures and also to primary human and murine small intestine epithelial cells (SI ECs). We show that the binding of CTB to human SI ECs is largely dependent on the noncanonical binding site,and interference with the canonical site has a limited effect while the opposite is observed with murine SI ECs. The galactose-fucose polymer blocks binding to fucosylated glycans but not to GM1. However,the preincubation of CT with the galactose-fucose polymer only partially blocks toxic effects on cultured human enteroid cells,while preincubation with GM1 completely blocks CT-mediated secretion. Our results support a model whereby the binding of fucose to the noncanonical site places CT in close proximity to scarcely expressed galactose receptors such as GM1 to enable binding via the canonical site leading to CT internalization and intoxication. Our finding also highlights the importance of complementing CTB binding studies with functional intoxication studies when assessing the efficacy inhibitors of CT. View Publication

BACKGROUND/OBJECTIVE A subset of neovascular age-related macular degeneration (nvAMD) subjects appears to be refractory to the effects of anti-VEGF treatment and require frequent intravitreal injections. The vascular phenotype of the choroidal neovascular (CNV) lesions may contribute to the resistance. Animal studies of CNV lesions have shown that cells originating from bone marrow are capable of forming varying cell types in the lesions. This raised the possibility of a similar cell population in human nvAMD subjects. MATERIALS AND METHODS Blood draws were obtained from subjects with active nvAMD while patients were receiving standard of care anti-VEGF injections. Subjects were classified as refractory or non-refractory to anti-VEGF treatment based on previous number of injections in the preceding 12 months. Peripheral blood mononuclear cells (PBMCs) were isolated and CD34-positive cells purified using magnetic bead sorting. The isolated cells were expanded in StemSpan SFEM media to increase cell numbers. After expansion,the cells were split and plated in either endothelial or mesenchymal promoting conditions. Phenotype analysis was performed via qPCR. RESULTS There was no significant difference in the number of PBMCs and CD34-positive cells between refractory and non-refractory nvAMD subjects. The growth pattern distribution between endothelial and mesenchymal media conditions were very similar between refractory and non-refractory subjects. qPCR and immunostaining demonstrated positive expression of endothelial markers in endothelial media,and markers such as NG2 and $\alpha$SMA in mesenchymal media. However,analysis of subsequent samples from AMD subjects demonstrated high variability in both the numbers and differentiation properties of this cell population. CONCLUSIONS CD34+ cells can be isolated from nvAMD subjects and show both endothelial and pericyte-like characteristics after differentiation in certain media conditions. However,nvAMD subjects show high variability in both numbers of cells and differentiation characteristics in repeat sampling. This variability highlights the importance of taking multiple samples from nvAMD subjects for any clinical trials focused on biomarkers for the disease. View Publication

The COVID-19 pandemic urgently needs therapeutic and prophylactic interventions. Here,we report the rapid identification of SARS-CoV-2-neutralizing antibodies by high-throughput single-cell RNA and VDJ sequencing of antigen-enriched B cells from 60 convalescent patients. From 8,558 antigen-binding IgG1+ clonotypes,14 potent neutralizing antibodies were identified,with the most potent one,BD-368-2,exhibiting an IC50 of 1.2 and 15 ng/mL against pseudotyped and authentic SARS-CoV-2,respectively. BD-368-2 also displayed strong therapeutic and prophylactic efficacy in SARS-CoV-2-infected hACE2-transgenic mice. Additionally,the 3.8 {\AA} cryo-EM structure of a neutralizing antibody in complex with the spike-ectodomain trimer revealed the antibody's epitope overlaps with the ACE2 binding site. Moreover,we demonstrated that SARS-CoV-2-neutralizing antibodies could be directly selected based on similarities of their predicted CDR3H structures to those of SARS-CoV-neutralizing antibodies. Altogether,we showed that human neutralizing antibodies could be efficiently discovered by high-throughput single B cell sequencing in response to pandemic infectious diseases. View Publication

Medulloblastoma (MB),the most frequent malignant childhood brain tumor,can arise from cellular malfunctions during hindbrain development. Here we generate humanized models for Sonic Hedgehog (SHH)-subgroup MB via MYCN overexpression in primary human hindbrain-derived neuroepithelial stem (hbNES) cells or iPSC-derived NES cells,which display a range of aggressive phenotypes upon xenografting. iPSC-derived NES tumors develop quickly with leptomeningeal dissemination,whereas hbNES-derived cells exhibit delayed tumor formation with less dissemination. Methylation and expression profiling show that tumors from both origins recapitulate hallmarks of infant SHH MB and reveal that mTOR activation,as a result of increased Oct4,promotes aggressiveness of human SHH tumors. Targeting mTOR decreases cell viability and prolongs survival,showing the utility of these varied models for dissecting mechanisms mediating tumor aggression and demonstrating the value of humanized models for a better understanding of pediatric cancers. View Publication

Hematopoietic clones with leukemogenic mutations arise in healthy people as they age,but progression to acute myeloid leukemia (AML) is rare. Recent evidence suggests that the microenvironment may play an important role in modulating human AML population dynamics. To investigate this concept further,we examined the combined and separate effects of an oncogene (c-MYC) and exposure to IL3,GM-CSF and SCF on the experimental genesis of a human AML in xenografted immunodeficient mice. Initial experiments showed that normal human CD34+ blood cells transduced with a lentiviral MYC vector and then transplanted into immunodeficient mice produced a hierarchically organized,rapidly fatal and serially transplantable blast population,phenotypically and transcriptionally similar to human AML cells,but only in mice producing IL3,GM-CSF and SCF transgenically,or in regular mice in which the cells were exposed to IL3 or GM-CSF delivered using a co-transduction strategy. In their absence,the MYC+ human cells produced a normal repertoire of lymphoid and myeloid progeny in transplanted mice for many months but,upon transfer to secondary mice producing the human cytokines,the MYC+ cells rapidly generated AML. Indistinguishable diseases were also obtained efficiently from both primitive (CD34+CD38-) and late (GMPs) cells. These findings underscore the critical role that these cytokines can play in activating a malignant state in normally differentiating human hematopoietic cells in which MYC expression has been deregulated. They also introduce a robust experimental model of human leukemogenesis to further elucidate key mechanisms involved and test strategies to suppress them. View Publication

Scleroderma (SSc) is an autoimmune connective tissue disease characterized by immune dysregulation,vasculopathy,and fibrosis. We have previously demonstrated that low Fli1 expression in SSc fibroblasts and endothelial cells plays an important role in SSc pathogenesis. Cells of myeloid and lymphoid origin also express Fli1 and are dysregulated in patients with SSc,playing key roles in disease pathogenesis. However,the role for immune Fli1 in SSc is not yet clear. Our aim was to elucidate whether Fli1 contributes to the immune dysregulation seen in SSc. Comparison of the expression of Fli1 in monocytes,B- and T-cell fractions of PBMCs isolated from SSc patients and healthy controls (HC),showed an increase in Fli1 levels in monocytes. We used siRNA transfected human myeloid cells and mouse peritoneal macrophages obtained from Fli1 flox/flox LysMCre+/+ mice,and found that markers of alternative macrophage activation were increased with Fli1 deletion. Coculture of Fli1-deficient myeloid cells and primary human or mouse fibroblasts resulted in a potent induction of collagen type I,independent of TGF$\beta$ upregulation. We next analyzed global gene expression profile in response to Fli1 downregulation,to gain further insight into the molecular mechanisms of this process and to identify differentially expressed genes in myeloid cells. Of relevance to SSc,the top most upregulated pathways were hallmark IFN-$\gamma$ and IFN-$\alpha$ response. Additionally,several genes previously linked to SSc pathogenesis and fibrosis in general were also induced,including CCL2,CCL7,MMP12,and CXCL10. ANKRD1,a profibrotic transcription co-regulator was the top upregulated gene in our array. Our results show that Fli1-deficient myeloid cells share key features with cells from SSc patients,with higher expression of profibrotic markers and activation of interferon responsive genes,thus suggesting that dysregulation of Fli1 in myeloid cells may contribute to SSc pathogenesis. View Publication