技术资料

Dynamic regulation of metabolic activities in astrocytes is critical to meeting the demands of other brain cells. During neuronal stress,lipids are transferred from neurons to astrocytes,where they are stored in lipid droplets (LDs). However,it is not clear whether and how neuron-derived lipids trigger metabolic adaptation in astrocytes. Here,we uncover an endolysosomal function that mediates neuron-astrocyte transcellular lipid signaling. We identify Tweety homolog 1 (TTYH1) as an astrocyte-enriched endolysosomal protein that facilitates autophagic flux and LD degradation. Astrocyte-specific deletion of mouse Ttyh1 and loss of its Drosophila ortholog lead to brain accumulation of neutral lipids. Computational and experimental evidence suggests that TTYH1 mediates endolysosomal clearance of ceramide 1-phosphate (C1P),a sphingolipid that dampens autophagic flux and LD breakdown in mouse and human astrocytes. Furthermore,neuronal C1P secretion induced by inflammatory cytokine interleukin-1β causes TTYH1-dependent autophagic flux and LD adaptations in astrocytes. These findings reveal a neuron-initiated signaling paradigm that culminates in the regulation of catabolic activities in astrocytes. Subject terms: Organelles,Glial biology,Lipid signalling View Publication

Immunoglobulin (Ig) class switch DNA recombination (CSR) is the crucial mechanism diversifying the biological effector functions of antibodies. Generation of double-strand DNA breaks (DSBs),particularly staggered DSBs,in switch (S) regions of the upstream and downstream CH genes involved in the specific recombination process is an absolute requirement for CSR. Staggered DSBs would be generated through deamination of dCs on opposite DNA strands by activation-induced cytidine deaminase (AID),subsequent dU deglycosylation by uracil DNA glycosylase (Ung) and abasic site nicking by apurinic/apyrimidic endonuclease. However,consistent with the findings that significant amounts of DSBs can be detected in the IgH locus in the absence of AID or Ung,we have shown in human and mouse B cells that AID generates staggered DSBs not only by cleaving intact double-strand DNA,but also by processing blunt DSB ends generated in an AID-independent fashion. How these AID-independent DSBs are generated is still unclear. It is possible that S region DNA may undergo AID-independent cleavage by structure-specific nucleases,such as endonuclease G (EndoG). EndoG is an abundant nuclease in eukaryotic cells. It cleaves single and double-strand DNA,primarily at dG/dC residues,the preferential sites of DSBs in S region DNA. We show here that EndoG can localize to the nucleus of B cells undergoing CSR and binds to S region DNA,as shown by specific chromatin immunoprecipitation assays. Using knockout EndoG(-/-) mice and EndoG(-/-) B cells,we found that EndoG deficiency resulted in a two-fold reduction in CSR in vivo and in vitro,as demonstrated by reduced cell surface IgG1,IgG2a,IgG3 and IgA,reduced secreted IgG1,reduced circle Iγ1-Cμ,Iγ3-Cμ,Iɛ-Cμ,Iα-Cμ transcripts,post-recombination Iμ-Cγ1,Iμ-Cγ3,Iμ-Cɛ and Iμ-Cα transcripts. In addition to reduced CSR,EndoG(-/-) mice showed a significantly altered spectrum of mutations in IgH J(H)-iEμ DNA. Impaired CSR in EndoG(-/-) B cells did not stem from altered B cell proliferation or apoptosis. Rather,it was associated with significantly reduced frequency of DSBs. Thus,our findings determine a role for EndoG in the generation of S region DSBs and CSR. View Publication

Not provided. View Publication

BACKGROUND Transplantation of enteric neural stem cells (ENSC) holds promise as a potential therapy for enteric neuropathies,including Hirschsprung disease. Delivery of transplantable cells via laparotomy has been described,but we propose a novel,minimally invasive endoscopic method of cell delivery. METHODS Enteric neural stem cells for transplantation were cultured from dissociated gut of postnatal donor mice. Twelve recipient mice,including Ednrb(-/-) mice with distal colonic aganglionosis,underwent colonoscopic injection of ENSC under direct vision using a 30-gauge Hamilton needle passed through a rigid cystoureteroscope. Cell engraftment,survival,and neuroglial differentiation were studied 1-4 weeks after the procedure. KEY RESULTS All recipient mice tolerated the procedure without complications and survived to sacrifice. Transplanted cells were found within the colonic wall in 9 of 12 recipient mice with differentiation into enteric neurons and glia. CONCLUSIONS & INFERENCES Endoscopic injection of ENSC is a safe and reliable method for cell delivery,and can be used to deliver a large number of cells to a specific area of disease. This minimally invasive endoscopic approach may prove beneficial to future human applications of cell therapy for neurointestinal disease. View Publication

Cyclic dinucleotide (CDN) agonists of stimulator of interferon genes (STING) are a promising class of immunotherapeutics that activate innate immunity to increase tumour immunogenicity. However,the efficacy of CDNs is limited by drug delivery barriers,including poor cellular targeting,rapid clearance and inefficient transport to the cytosol where STING is localized. Here,we describe STING-activating nanoparticles (STING-NPs)-rationally designed polymersomes for enhanced cytosolic delivery of the endogenous CDN ligand for STING,2'3' cyclic guanosine monophosphate-adenosine monophosphate (cGAMP). STING-NPs increase the biological potency of cGAMP,enhance STING signalling in the tumour microenvironment and sentinel lymph node,and convert immunosuppressive tumours to immunogenic,tumoricidal microenvironments. This leads to enhanced therapeutic efficacy of cGAMP,inhibition of tumour growth,increased rates of long-term survival,improved response to immune checkpoint blockade and induction of immunological memory that protects against tumour rechallenge. We validate STING-NPs in freshly isolated human melanoma tissue,highlighting their potential to improve clinical outcomes of immunotherapy. View Publication

Embryonic stem cells (ESC) have two main characteristics: they can be indefinitely propagated in vitro in an undifferentiated state and they are pluripotent,thus having the potential to differentiate into multiple lineages. Such properties make ESCs extremely attractive for cell based therapy and regenerative treatment applications. However for its full potential to be realized the cells have to be differentiated into mature and functional phenotypes,which is a daunting task. A promising approach in inducing cellular differentiation is to closely mimic the path of organogenesis in the in vitro setting. Pancreatic development is known to occur in specific stages,starting with endoderm,which can develop into several organs,including liver and pancreas. Endoderm induction can be achieved by modulation of the nodal pathway through addition of Activin A in combination with several growth factors. Definitive endoderm cells then undergo pancreatic commitment by inhibition of sonic hedgehog inhibition,which can be achieved in vitro by addition of cyclopamine. Pancreatic maturation is mediated by several parallel events including inhibition of notch signaling; aggregation of pancreatic progenitors into 3-dimentional clusters; induction of vascularization; to name a few. By far the most successful in vitro maturation of ESC derived pancreatic progenitor cells have been achieved through inhibition of notch signaling by DAPT supplementation. Although successful,this results in low yield of the mature phenotype with reduced functionality. A less studied area is the effect of endothelial cell signaling in pancreatic maturation,which is increasingly being appreciated as an important contributing factor in in-vivo pancreatic islet maturation. The current study explores such effect of endothelial cell signaling in maturation of human ESC derived pancreatic progenitor cells into insulin producing islet-like cells. We report a multi-stage directed differentiation protocol where the human ESCs are first induced towards endoderm by Activin A along with inhibition of PI3K pathway. Pancreatic specification of endoderm cells is achieved by inhibition of sonic hedgehog signaling by Cyclopamine along with retinoid induction by addition of Retinoic Acid. The final stage of maturation is induced by endothelial cell signaling achieved by a co-culture configuration. While several endothelial cells have been tested in the co-culture,herein we present our data with rat heart microvascular endothelial Cells (RHMVEC),primarily for the ease of analysis. View Publication

Neurogenesis persists in the adult brain subventricular zone where neural stem/progenitor cells (NSPCs) lie close to brain endothelial cells (BECs). We show in mouse that BECs produce bone morphogenetic proteins (BMPs). Coculture of embryonic and adult NSPCs with BECs activated the canonical BMP/Smad pathway and reduced their proliferation. We demonstrate that coculture with BECs in the presence of EGF and FGF2 induced a reversible cell cycle exit of NSPCs (LeX+) and an increase in the amount of GFAP/LeX-expressing progenitors thought to be stem cells. Levels of the phosphatidylinositol phosphatase PTEN were upregulated in NSPCs after coculture with BECs,or treatment with recombinant BMP4,with a concomitant reduction in Akt phosphorylation. Silencing Smad5 with siRNA or treatment with Noggin,a BMP antagonist,demonstrated that upregulation of PTEN in NSPCs required BMP/Smad signaling and that this pathway regulated cell cycle exit of NSPCs. Therefore,BECs may provide a feedback mechanism to control the proliferation of NSPCs. View Publication

Recent studies have demonstrated that cancer stem cells play an important role in the pathobiology of head and neck squamous cell carcinomas (HNSCC). However,little is known about functional interactions between head and neck cancer stem-like cells (CSC) and surrounding stromal cells. Here,we used aldehyde dehydrogenase activity and CD44 expression to sort putative stem cells from primary human HNSCC. Implantation of 1,000 CSC (ALDH+CD44+Lin-) led to tumors in 13 (out of 15) mice,whereas 10,000 noncancer stem cells (ALDH-CD44-Lin-) resulted in 2 tumors in 15 mice. These data demonstrated that ALDH and CD44 select a subpopulation of cells that are highly tumorigenic. The ability to self-renew was confirmed by the observation that ALDH+CD44+Lin- cells sorted from human HNSCC formed more spheroids (orospheres) in 3-D agarose matrices or ultra-low attachment plates than controls and were serially passaged in vivo. We observed that approximately 80% of the CSC were located in close proximity (within 100-μm radius) of blood vessels in human tumors,suggesting the existence of perivascular niches in HNSCC. In vitro studies demonstrated that endothelial cell-secreted factors promoted self-renewal of CSC,as demonstrated by the upregulation of Bmi-1 expression and the increase in the number of orospheres as compared with controls. Notably,selective ablation of tumor-associated endothelial cells stably transduced with a caspase-based artificial death switch (iCaspase-9) caused a marked reduction in the fraction of CSC in xenograft tumors. Collectively,these findings indicate that endothelial cell-initiated signaling can enhance the survival and self-renewal of head and neck CSC. View Publication

One important function of endothelial cells in glioblastoma multiforme (GBM) is to create a niche that helps promote self-renewal of cancer stem-like cells (CSLC). However,the underlying molecular mechanism for this endothelial function is not known. Since activation of NOTCH signaling has been found to be required for propagation of GBM CSLCs,we hypothesized that the GBM endothelium may provide the source of NOTCH ligands. Here,we report a corroboration of this concept with a demonstration that NOTCH ligands are expressed in endothelial cells adjacent to NESTIN and NOTCH receptor-positive cancer cells in primary GBMs. Coculturing human brain microvascular endothelial cells (hBMEC) or NOTCH ligand with GBM neurospheres promoted GBM cell growth and increased CSLC self-renewal. Notably,RNAi-mediated knockdown of NOTCH ligands in hBMECs abrogated their ability to induce CSLC self-renewal and GBM tumor growth,both in vitro and in vivo. Thus,our findings establish that NOTCH activation in GBM CSLCs is driven by juxtacrine signaling between tumor cells and their surrounding endothelial cells in the tumor microenvironment,suggesting that targeting both CSLCs and their niche may provide a novel strategy to deplete CSLCs and improve GBM treatment. View Publication

Large scale purification of endothelial cells is of great interest as it could improve tissue transplantation,reperfusion of ischemic tissues and treatment of pathologies in which an endothelial cell dysfunction exists. In this study,we describe a novel genetic approach that selects for endothelial cells from differentiating embryonic stem (ES) cells. Our strategy is based on the establishment of ES-cell clones that carry an integrated puromycin resistance gene under the control of a vascular endothelium-specific promoter,tie-1. Using EGFP as a reporter gene,we first confirmed the endothelial specificity of the tie-1 promoter in the embryoid body model and in cells differentiated in 2D cultures. Subsequently,tie-1-EGFP ES cells were used as recipients for the tie-1-driven puror transgene. The resulting stable clones were expanded and differentiated for seven days in the presence of VEGF before puromycin selection. As expected,puromycin-resistant cells were positive for EGFP and also expressed several endothelial markers,including CD31,CD34,VEGFR-1,VEGFR-2,Tie-1,VE-cadherin and ICAM-2. Release from the puromycin selection resulted in the appearance of alpha-smooth muscle actin-positive cells. Such cells became more numerous when the population was cultured on laminin-1 or in the presence of TGF-beta1,two known inducers of smooth muscle cell differentiation. The hypothesis that endothelial cells or their progenitors may differentiate towards a smooth muscle cell phenotype was further supported by the presence of cells expressing both CD31 and alpha-smooth muscle actin markers. Finally,we show that purified endothelial cells can incorporate into the neovasculature of transplanted tumors in nude mice. Taken together,these results suggest that application of endothelial lineage selection to differentiating ES cells may become a useful approach for future pro-angiogenic and endothelial cell replacement therapies. View Publication

Resting CD4+ T cells are primary targets of early HIV infection events in vivo,but do not readily support HIV replication in vitro. This barrier to infection can be overcome by exposing resting CD4+ T cells to endothelial cells (ECs). ECs line blood vessels and direct T cell trafficking into inflamed tissues. Cell trafficking pathways have been shown to have overlapping roles in facilitating HIV replication,but their relevance to EC-mediated enhancement of HIV susceptibility in resting CD4+ T cells has not previously been examined. We characterized the phenotype of primary human resting CD4+ T cells that became productively infected with HIV when cocultured with primary human blood and lymphatic ECs. The infected CD4+ T cells were primarily central memory cells enriched for high expression of the integrins LFA-1 and VLA-4. ICAM-1 and VCAM-1,the cognate ligands for LFA-1 and VLA-4,respectively,were expressed by the ECs in the coculture. Blocking LFA-1 and VLA-4 on resting CD4+ T cells inhibited infection by 65.4%-96.9%,indicating that engagement of these integrins facilitates EC-mediated enhancement of productive HIV infection in resting CD4+ T cells. The demonstration that ECs influence cellular HIV susceptibility of resting memory CD4+ T cells through cell trafficking pathways engaged during the transmigration of T cells into tissues highlights the physiological relevance of these findings for HIV acquisition and opportunities for intervention. View Publication

We report a paracrine effect whereby endothelial cells (ECs) promote the cancer stem cell (CSC) phenotype of human colorectal cancer (CRC) cells. We showed that,without direct cell-cell contact,ECs secrete factors that promoted the CSC phenotype in CRC cells via Notch activation. In human CRC specimens,CD133 and Notch intracellular domain-positive CRC cells colocalized in perivascular regions. An EC-derived,soluble form of Jagged-1,via ADAM17 proteolytic activity,led to Notch activation in CRC cells in a paracrine manner; these effects were blocked by immunodepletion of Jagged-1 in EC-conditioned medium or blockade of ADAM17 activity. Collectively,ECs play an active role in promoting Notch signaling and the CSC phenotype by secreting soluble Jagged-1. View Publication