Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 22
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Int J Mol Sci ; 20(21)2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31671683

RESUMO

The exponential increase of patients with diabetes mellitus urges for novel therapeutic strategies to reduce the socioeconomic burden of this disease. The loss or dysfunction of insulin-producing ß-cells, in patients with type 1 and type 2 diabetes respectively, put these cells at the center of the disease initiation and progression. Therefore, major efforts have been taken to restore the ß-cell mass by cell-replacement or regeneration approaches. Implementing novel therapies requires deciphering the developmental mechanisms that generate ß-cells and determine the acquisition of their physiological phenotype. In this review, we summarize the current understanding of the mechanisms that coordinate the postnatal maturation of ß-cells and define their functional identity. Furthermore, we discuss different routes by which ß-cells lose their features and functionality in type 1 and 2 diabetic conditions. We then focus on potential mechanisms to restore the functionality of those ß-cell populations that have lost their functional phenotype. Finally, we discuss the recent progress and remaining challenges facing the generation of functional mature ß-cells from stem cells for cell-replacement therapy for diabetes treatment.

2.
Curr Opin Cell Biol ; 61: 48-55, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31377680

RESUMO

The pancreas is derived from the foregut endoderm during embryonic development. After gastrulation and endoderm germ layer formation complex morphogenetic events coupled with cell differentiation programs pattern the gut tube and induce pancreas organogenesis. This results in formation of exocrine, ductal and hormone-producing endocrine cells. Among these, endocrine cells are responsible for blood glucose homeostasis and their malfunction leads to diabetes mellitus, which cannot be stopped or reversed by the current standard treatments. Thus, intense efforts to regenerate or replace the lost or dysfunctional insulin-producing ß-cells are on the way. This depends on identifying the factors that coordinate pancreas organogenesis. Here, we highlight the contribution of canonical and non-canonical Wnt signaling branches in orchestrating endoderm formation, pancreatic morphogenesis as well as endocrine cell formation and function.

3.
Development ; 146(12)2019 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-31160421

RESUMO

Deciphering mechanisms of endocrine cell induction, specification and lineage allocation in vivo will provide valuable insights into how the islets of Langerhans are generated. Currently, it is ill defined how endocrine progenitors segregate into different endocrine subtypes during development. Here, we generated a novel neurogenin 3 (Ngn3)-Venus fusion (NVF) reporter mouse line, that closely mirrors the transient endogenous Ngn3 protein expression. To define an in vivo roadmap of endocrinogenesis, we performed single cell RNA sequencing of 36,351 pancreatic epithelial and NVF+ cells during secondary transition. This allowed Ngn3 low endocrine progenitors, Ngn3 high endocrine precursors, Fev+ endocrine lineage and hormone+ endocrine subtypes to be distinguished and time-resolved, and molecular programs during the step-wise lineage restriction steps to be delineated. Strikingly, we identified 58 novel signature genes that show the same transient expression dynamics as Ngn3 in the 7260 profiled Ngn3-expressing cells. The differential expression of these genes in endocrine precursors associated with their cell-fate allocation towards distinct endocrine cell types. Thus, the generation of an accurately regulated NVF reporter allowed us to temporally resolve endocrine lineage development to provide a fine-grained single cell molecular profile of endocrinogenesis in vivo.

4.
Dev Cell ; 49(1): 1-3, 2019 04 08.
Artigo em Inglês | MEDLINE | ID: mdl-30965032

RESUMO

How organ morphogenesis specifies cell fate and whether organ progenitors are predetermined or specified via niche signals are critical developmental biology questions. In this issue of Developmental Cell, Nyeng et al. (2019) modulate cell-cell adhesion in the pancreas and provide evidence that progenitors are plastic and instructed by niche signals.


Assuntos
Pâncreas , Cateninas , Diferenciação Celular , Movimento Celular , Morfogênese
5.
Mol Metab ; 24: 80-97, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30930126

RESUMO

OBJECTIVE: Hundreds of missense mutations in the coding region of PDX1 exist; however, if these mutations predispose to diabetes mellitus is unknown. METHODS: In this study, we screened a large cohort of subjects with increased risk for diabetes and identified two subjects with impaired glucose tolerance carrying common, heterozygous, missense mutations in the PDX1 coding region leading to single amino acid exchanges (P33T, C18R) in its transactivation domain. We generated iPSCs from patients with heterozygous PDX1P33T/+, PDX1C18R/+ mutations and engineered isogenic cell lines carrying homozygous PDX1P33T/P33T, PDX1C18R/C18R mutations and a heterozygous PDX1 loss-of-function mutation (PDX1+/-). RESULTS: Using an in vitro ß-cell differentiation protocol, we demonstrated that both, heterozygous PDX1P33T/+, PDX1C18R/+ and homozygous PDX1P33T/P33T, PDX1C18R/C18R mutations impair ß-cell differentiation and function. Furthermore, PDX1+/- and PDX1P33T/P33T mutations reduced differentiation efficiency of pancreatic progenitors (PPs), due to downregulation of PDX1-bound genes, including transcription factors MNX1 and PDX1 as well as insulin resistance gene CES1. Additionally, both PDX1P33T/+ and PDX1P33T/P33T mutations in PPs reduced the expression of PDX1-bound genes including the long-noncoding RNA, MEG3 and the imprinted gene NNAT, both involved in insulin synthesis and secretion. CONCLUSIONS: Our results reveal mechanistic details of how common coding mutations in PDX1 impair human pancreatic endocrine lineage formation and ß-cell function and contribute to the predisposition for diabetes.

6.
Nat Biotechnol ; 37(4): 461-468, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30936567

RESUMO

Recent single-cell RNA-sequencing studies have suggested that cells follow continuous transcriptomic trajectories in an asynchronous fashion during development. However, observations of cell flux along trajectories are confounded with population size effects in snapshot experiments and are therefore hard to interpret. In particular, changes in proliferation and death rates can be mistaken for cell flux. Here we present pseudodynamics, a mathematical framework that reconciles population dynamics with the concepts underlying developmental trajectories inferred from time-series single-cell data. Pseudodynamics models population distribution shifts across trajectories to quantify selection pressure, population expansion, and developmental potentials. Applying this model to time-resolved single-cell RNA-sequencing of T-cell and pancreatic beta cell maturation, we characterize proliferation and apoptosis rates and identify key developmental checkpoints, data inaccessible to existing approaches.


Assuntos
Diferenciação Celular/genética , Análise de Sequência de RNA/estatística & dados numéricos , Análise de Célula Única/estatística & dados numéricos , Animais , Apoptose/genética , Biotecnologia , Proliferação de Células/genética , Feminino , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/metabolismo , Funções Verossimilhança , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Modelos Biológicos , Células-Tronco Embrionárias Murinas/citologia , Células-Tronco Embrionárias Murinas/metabolismo , Linfócitos T/citologia , Linfócitos T/metabolismo , Fatores de Tempo
7.
Nat Rev Endocrinol ; 2018 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-30504925

RESUMO

Diabetes mellitus is a multifactorial disease affecting increasing numbers of patients worldwide. Progression to insulin-dependent diabetes mellitus is characterized by the loss or dysfunction of pancreatic ß-cells, but the pathomechanisms underlying ß-cell failure in type 1 diabetes mellitus and type 2 diabetes mellitus are still poorly defined. Regeneration of ß-cell mass from residual islet cells or replacement by ß-like cells derived from stem cells holds great promise to stop or reverse disease progression. However, the development of new treatment options is hampered by our limited understanding of human pancreas organogenesis due to the restricted access to primary tissues. Therefore, the challenge is to translate results obtained from preclinical model systems to humans, which requires comparative modelling of ß-cell biology in health and disease. Here, we discuss diverse modelling systems across different species that provide spatial and temporal resolution of cellular and molecular mechanisms to understand the evolutionary conserved genotype-phenotype relationship and translate them to humans. In addition, we summarize the latest knowledge on organoids, stem cell differentiation platforms, primary micro-islets and pseudo-islets, bioengineering and microfluidic systems for studying human pancreas development and homeostasis ex vivo. These new modelling systems and platforms have opened novel avenues for exploring the developmental trajectory, physiology, biology and pathology of the human pancreas.

8.
Mol Metab ; 9: 57-68, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29396371

RESUMO

OBJECTIVE: Homozygous loss-of-function mutations in the gene coding for the homeobox transcription factor (TF) PDX1 leads to pancreatic agenesis, whereas heterozygous mutations can cause Maturity-Onset Diabetes of the Young 4 (MODY4). Although the function of Pdx1 is well studied in pre-clinical models during insulin-producing ß-cell development and homeostasis, it remains elusive how this TF controls human pancreas development by regulating a downstream transcriptional program. Also, comparative studies of PDX1 binding patterns in pancreatic progenitors and adult ß-cells have not been conducted so far. Furthermore, many studies reported the association between single nucleotide polymorphisms (SNPs) and T2DM, and it has been shown that islet enhancers are enriched in T2DM-associated SNPs. Whether regions, harboring T2DM-associated SNPs are PDX1 bound and active at the pancreatic progenitor stage has not been reported so far. METHODS: In this study, we have generated a novel induced pluripotent stem cell (iPSC) line that efficiently differentiates into human pancreatic progenitors (PPs). Furthermore, PDX1 and H3K27ac chromatin immunoprecipitation sequencing (ChIP-seq) was used to identify PDX1 transcriptional targets and active enhancer and promoter regions. To address potential differences in the function of PDX1 during development and adulthood, we compared PDX1 binding profiles from PPs and adult islets. Moreover, combining ChIP-seq and GWAS meta-analysis data we identified T2DM-associated SNPs in PDX1 binding sites and active chromatin regions. RESULTS: ChIP-seq for PDX1 revealed a total of 8088 PDX1-bound regions that map to 5664 genes in iPSC-derived PPs. The PDX1 target regions include important pancreatic TFs, such as PDX1 itself, RFX6, HNF1B, and MEIS1, which were activated during the differentiation process as revealed by the active chromatin mark H3K27ac and mRNA expression profiling, suggesting that auto-regulatory feedback regulation maintains PDX1 expression and initiates a pancreatic TF program. Remarkably, we identified several PDX1 target genes that have not been reported in the literature in human so far, including RFX3, required for ciliogenesis and endocrine differentiation in mouse, and the ligand of the Notch receptor DLL1, which is important for endocrine induction and tip-trunk patterning. The comparison of PDX1 profiles from PPs and adult human islets identified sets of stage-specific target genes, associated with early pancreas development and adult ß-cell function, respectively. Furthermore, we found an enrichment of T2DM-associated SNPs in active chromatin regions from iPSC-derived PPs. Two of these SNPs fall into PDX1 occupied sites that are located in the intronic regions of TCF7L2 and HNF1B. Both of these genes are key transcriptional regulators of endocrine induction and mutations in cis-regulatory regions predispose to diabetes. CONCLUSIONS: Our data provide stage-specific target genes of PDX1 during in vitro differentiation of stem cells into pancreatic progenitors that could be useful to identify pathways and molecular targets that predispose for diabetes. In addition, we show that T2DM-associated SNPs are enriched in active chromatin regions at the pancreatic progenitor stage, suggesting that the susceptibility to T2DM might originate from imperfect execution of a ß-cell developmental program.

9.
Nat Rev Endocrinol ; 14(3): 140-162, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29348476

RESUMO

More than one-third of the worldwide population is overweight or obese and therefore at risk of developing type 2 diabetes mellitus. In order to mitigate this pandemic, safer and more potent therapeutics are urgently required. This necessitates the continued use of animal models to discover, validate and optimize novel therapeutics for their safe use in humans. In order to improve the transition from bench to bedside, researchers must not only carefully select the appropriate model but also draw the right conclusions. In this Review, we consolidate the key information on the currently available animal models of obesity and diabetes and highlight the advantages, limitations and important caveats of each of these models.

10.
Cell Metab ; 26(4): 620-632.e6, 2017 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-28943448

RESUMO

Chronic inflammation has been proposed to contribute to the pathogenesis of diet-induced obesity. However, scarce therapeutic options are available to treat obesity and the associated immunometabolic complications. Glucocorticoids are routinely employed for the management of inflammatory diseases, but their pleiotropic nature leads to detrimental metabolic side effects. We developed a glucagon-like peptide-1 (GLP-1)-dexamethasone co-agonist in which GLP-1 selectively delivers dexamethasone to GLP-1 receptor-expressing cells. GLP-1-dexamethasone lowers body weight up to 25% in obese mice by targeting the hypothalamic control of feeding and by increasing energy expenditure. This strategy reverses hypothalamic and systemic inflammation while improving glucose tolerance and insulin sensitivity. The selective preference for GLP-1 receptor bypasses deleterious effects of dexamethasone on glucose handling, bone integrity, and hypothalamus-pituitary-adrenal axis activity. Thus, GLP-1-directed glucocorticoid pharmacology represents a safe and efficacious therapy option for diet-induced immunometabolic derangements and the resulting obesity.


Assuntos
Dexametasona/uso terapêutico , Peptídeo 1 Semelhante ao Glucagon/uso terapêutico , Glucocorticoides/uso terapêutico , Incretinas/uso terapêutico , Inflamação/tratamento farmacológico , Obesidade/tratamento farmacológico , Animais , Peso Corporal/efeitos dos fármacos , Dexametasona/análogos & derivados , Metabolismo Energético/efeitos dos fármacos , Peptídeo 1 Semelhante ao Glucagon/análogos & derivados , Glucocorticoides/química , Glucose/metabolismo , Células HEK293 , Humanos , Hipotálamo/efeitos dos fármacos , Hipotálamo/metabolismo , Incretinas/química , Inflamação/complicações , Inflamação/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Obesos , Obesidade/complicações , Obesidade/metabolismo
11.
Development ; 144(16): 2873-2888, 2017 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-28811309

RESUMO

The pancreas is an endoderm-derived glandular organ that participates in the regulation of systemic glucose metabolism and food digestion through the function of its endocrine and exocrine compartments, respectively. While intensive research has explored the signaling pathways and transcriptional programs that govern pancreas development, much remains to be discovered regarding the cellular processes that orchestrate pancreas morphogenesis. Here, we discuss the developmental mechanisms and principles that are known to underlie pancreas development, from induction and lineage formation to morphogenesis and organogenesis. Elucidating such principles will help to identify novel candidate disease genes and unravel the pathogenesis of pancreas-related diseases, such as diabetes, pancreatitis and cancer.


Assuntos
Pâncreas/embriologia , Animais , Endoderma/embriologia , Endoderma/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Pâncreas/metabolismo , Transdução de Sinais
12.
Mol Metab ; 6(6): 524-534, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28580283

RESUMO

OBJECTIVE: The transcription factors (TF) Foxa2 and Pdx1 are key regulators of beta-cell (ß-cell) development and function. Mutations of these TFs or their respective cis-regulatory consensus binding sites have been linked to maturity diabetes of the young (MODY), pancreas agenesis, or diabetes susceptibility in human. Although Foxa2 has been shown to directly regulate Pdx1 expression during mouse embryonic development, the impact of this gene regulatory interaction on postnatal ß-cell maturation remains obscure. METHODS: In order to easily monitor the expression domains of Foxa2 and Pdx1 and analyze their functional interconnection, we generated a novel double knock-in homozygous (FVFPBFDHom) fluorescent reporter mouse model by crossing the previously described Foxa2-Venus fusion (FVF) with the newly generated Pdx1-BFP (blue fluorescent protein) fusion (PBF) mice. RESULTS: Although adult PBF homozygous animals exhibited a reduction in expression levels of Pdx1, they are normoglycemic. On the contrary, despite normal pancreas and endocrine development, the FVFPBFDHom reporter male animals developed hyperglycemia at weaning age and displayed a reduction in Pdx1 levels in islets, which coincided with alterations in ß-cell number and islet architecture. The failure to establish mature ß-cells resulted in loss of ß-cell identity and trans-differentiation towards other endocrine cell fates. Further analysis suggested that Foxa2 and Pdx1 genetically and functionally cooperate to regulate maturation of adult ß-cells. CONCLUSIONS: Our data show that the maturation of pancreatic ß-cells requires the cooperative function of Foxa2 and Pdx1. Understanding the postnatal gene regulatory network of ß-cell maturation will help to decipher pathomechanisms of diabetes and identify triggers to regenerate dedifferentiated ß-cell mass.

13.
Nature ; 535(7612): 430-4, 2016 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-27398620

RESUMO

Insulin-dependent diabetes is a complex multifactorial disorder characterized by loss or dysfunction of ß-cells. Pancreatic ß-cells differ in size, glucose responsiveness, insulin secretion and precursor cell potential; understanding the mechanisms that underlie this functional heterogeneity might make it possible to develop new regenerative approaches. Here we show that Fltp (also known as Flattop and Cfap126), a Wnt/planar cell polarity (PCP) effector and reporter gene acts as a marker gene that subdivides endocrine cells into two subpopulations and distinguishes proliferation-competent from mature ß-cells with distinct molecular, physiological and ultrastructural features. Genetic lineage tracing revealed that endocrine subpopulations from Fltp-negative and -positive lineages react differently to physiological and pathological changes. The expression of Fltp increases when endocrine cells cluster together to form polarized and mature 3D islet mini-organs. We show that 3D architecture and Wnt/PCP ligands are sufficient to trigger ß-cell maturation. By contrast, the Wnt/PCP effector Fltp is not necessary for ß-cell development, proliferation or maturation. We conclude that 3D architecture and Wnt/PCP signalling underlie functional ß-cell heterogeneity and induce ß-cell maturation. The identification of Fltp as a marker for endocrine subpopulations sheds light on the molecular underpinnings of islet cell heterogeneity and plasticity and might enable targeting of endocrine subpopulations for the regeneration of functional ß-cell mass in diabetic patients.


Assuntos
Ilhotas Pancreáticas/citologia , Animais , Biomarcadores/análise , Diferenciação Celular , Linhagem da Célula/genética , Polaridade Celular , Proliferação de Células , Humanos , Resistência à Insulina , Ilhotas Pancreáticas/metabolismo , Ligantes , Camundongos , Camundongos Endogâmicos C57BL , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Via de Sinalização Wnt
14.
Ann Clin Transl Neurol ; 2(12): 1116-23, 2015 12.
Artigo em Inglês | MEDLINE | ID: mdl-26734662

RESUMO

BACKGROUND: Synthesis of clonal IgG is a consistent feature of patients with multiple sclerosis (MS). Whether oligoclonal bands (OCBs) represent unspecific disease bystanders or active components in MS pathology is an open question. The aim of this study was to develop a method to quantify and compare the reactivity of cerebrospinal fluid (CSF) antibodies from patients with and without MS. METHODS: We collected CSF from 262 patients from two different cohorts, which included 148 patients with MS and 114 with other neurological diseases (OND). We established a highly sensitive electrochemiluminescence (ECL)-based assay to measure CSF antibody reactivity against purified myelin particles and biotin anchored liposomes. The diagnostic value of the ECL score against myelin particles was assessed with receiver operating characteristic curves. RESULTS: CSF from patients with MS have higher reactivity toward purified myelin particles as compared to those with OND with OCBs. Using liposomes with defined lipid compositions and myelin particles from ceramide synthase 2 (CerS2) knockout mice, we find that some of the CSF antibody reactivity is directed against cerebrosides. CONCLUSION: The ECL-based assay system expands the currently available toolbox for the detection of autoantibodies in MS and related diseases.

15.
Cell Mol Life Sci ; 71(7): 1265-77, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24165921

RESUMO

Rapid nerve conduction requires the coating of axons by a tightly packed multilayered myelin membrane. In the central nervous system, myelin is formed from cellular processes that extend from oligodendrocytes and wrap in a spiral fashion around an axon, resulting in the close apposition of adjacent myelin membrane bilayers. In this review, we discuss the physical principles underlying the zippering of the plasma membrane of oligodendrocytes at the cytoplasmic and extracellular leaflet. We propose that the interaction of the myelin basic protein with the cytoplasmic leaflet of the myelin bilayer triggers its polymerization into a fibrous network that drives membrane zippering and protein extrusion. In contrast, the adhesion of the extracellular surfaces of myelin requires the down-regulation of repulsive components of the glycocalyx, in order to uncover weak and unspecific attractive forces that bring the extracellular surfaces into close contact. Unveiling the mechanisms of myelin membrane assembly at the cytoplasmic and extracelluar sites may help to understand how the myelin bilayers are disrupted and destabilized in the different demyelinating diseases.


Assuntos
Membrana Celular/metabolismo , Modelos Biológicos , Proteína Básica da Mielina/metabolismo , Bainha de Mielina/fisiologia , Sequência de Aminoácidos , Membrana Celular/ultraestrutura , Doenças Desmielinizantes/metabolismo , Doenças Desmielinizantes/patologia , Dados de Sequência Molecular , Proteína Básica da Mielina/química , Proteína Proteolipídica de Mielina/metabolismo , Proteína Proteolipídica de Mielina/fisiologia , Bainha de Mielina/química , Bainha de Mielina/ultraestrutura , Oligodendroglia/citologia , Oligodendroglia/metabolismo , Alinhamento de Sequência
16.
Proc Natl Acad Sci U S A ; 110(8): 3143-8, 2013 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-23382229

RESUMO

During the development of the central nervous system (CNS), oligodendrocytes wrap their plasma membrane around axons to form a multilayered stack of tightly attached membranes. Although intracellular myelin compaction and the role of myelin basic protein has been investigated, the forces that mediate the close interaction of myelin membranes at their external surfaces are poorly understood. Such extensive bilayer-bilayer interactions are usually prevented by repulsive forces generated by the glycocalyx, a dense and confluent layer of large and negatively charged oligosaccharides. Here we investigate the molecular mechanisms underlying myelin adhesion and compaction in the CNS. We revisit the role of the proteolipid protein and analyze the contribution of oligosaccharides using cellular assays, biophysical tools, and transgenic mice. We observe that differentiation of oligodendrocytes is accompanied by a striking down-regulation of components of their glycocalyx. Both in vitro and in vivo experiments indicate that the adhesive properties of the proteolipid protein, along with the reduction of sialic acid residues from the cell surface, orchestrate myelin membrane adhesion and compaction in the CNS. We suggest that loss of electrostatic cell-surface repulsion uncovers weak and unspecific attractive forces in the bilayer that bring the extracellular surfaces of a membrane into close contact over long distances.


Assuntos
Sistema Nervoso Central/metabolismo , Bainha de Mielina/metabolismo , Eletricidade Estática , Animais , Membrana Celular/metabolismo , Células Cultivadas , Bicamadas Lipídicas , Camundongos , Oligodendroglia/metabolismo , Ligação Proteica
17.
J Cell Sci ; 124(Pt 3): 447-58, 2011 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-21242314

RESUMO

The transfer of antigens from oligodendrocytes to immune cells has been implicated in the pathogenesis of autoimmune diseases. Here, we show that oligodendrocytes secrete small membrane vesicles called exosomes, which are specifically and efficiently taken up by microglia both in vitro and in vivo. Internalisation of exosomes occurs by a macropinocytotic mechanism without inducing a concomitant inflammatory response. After stimulation of microglia with interferon-γ, we observe an upregulation of MHC class II in a subpopulation of microglia. However, exosomes are preferentially internalised in microglia that do not seem to have antigen-presenting capacity. We propose that the constitutive macropinocytotic clearance of exosomes by a subset of microglia represents an important mechanism through which microglia participate in the degradation of oligodendroglial membrane in an immunologically 'silent' manner. By designating the capacity for macropinocytosis and antigen presentation to distinct cells, degradation and immune function might be assigned to different subtypes of microglia.


Assuntos
Exossomos/metabolismo , Microglia/fisiologia , Oligodendroglia/metabolismo , Animais , Transporte Biológico , Genes MHC da Classe II , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Pinocitose/fisiologia , Linfócitos T/imunologia , Linfócitos T/metabolismo
18.
Biophys J ; 101(11): 2713-20, 2011 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-22261060

RESUMO

Rapid conduction of nerve impulses requires coating of axons by myelin sheaths, which are multilamellar, lipid-rich membranes produced by oligodendrocytes in the central nervous system. To act as an insulator, myelin has to form a stable and firm membrane structure. In this study, we have analyzed the biophysical properties of myelin membranes prepared from wild-type mice and from mouse mutants that are unable to form stable myelin. Using C-Laurdan and fluorescence correlation spectroscopy, we find that lipids are tightly organized and highly ordered in myelin isolated from wild-type mice, but not from shiverer and ceramide synthase 2 null mice. Furthermore, only myelin lipids from wild-type mice laterally segregate into physically distinct lipid phases in giant unilamellar vesicles in a process that requires very long chain glycosphingolipids. Taken together, our findings suggest that oligodendrocytes exploit the potential of lipids to self-segregate to generate a highly ordered membrane for electrical insulation of axons.


Assuntos
Lipídeos de Membrana/metabolismo , Modelos Biológicos , Bainha de Mielina/metabolismo , Animais , Difusão , Ácidos Graxos/análise , Lipídeos de Membrana/química , Membranas/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Mutantes Neurológicos , Esfingolipídeos/metabolismo , Extratos de Tecidos
19.
J Biol Chem ; 286(1): 787-96, 2011 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-20978131

RESUMO

Myelin formation is a multistep process that is controlled by a number of different extracellular factors. During the development of the central nervous system (CNS), oligodendrocyte progenitor cells differentiate into mature oligodendrocytes that start to enwrap axons with myelin membrane sheaths after receiving the appropriate signal(s) from the axon or its microenvironment. The signals required to initiate this process are unknown. Here, we show that oligodendrocytes secrete small membrane vesicles, exosome-like vesicles, into the extracellular space that inhibit both the morphological differentiation of oligodendrocytes and myelin formation. The inhibitory effects of exosome-like vesicles were prevented by treatment with inhibitors of actomyosin contractility. Importantly, secretion of exosome-like vesicles from oligodendrocytes was dramatically reduced when cells were incubated by conditioned neuronal medium. In conclusion, our results provide new evidence for small and diffusible oligodendroglial-derived vesicular carriers within the extracellular space that have inhibitory properties on cellular growth. We propose that neurons control the secretion of autoinhibitory oligodendroglial-derived exosomes to coordinate myelin membrane biogenesis.


Assuntos
Membrana Celular/metabolismo , Exossomos/metabolismo , Bainha de Mielina/fisiologia , Oligodendroglia/citologia , Actomiosina/metabolismo , Animais , Camundongos , Bainha de Mielina/metabolismo , Fosforilação , Ratos
20.
J Cell Biol ; 189(2): 223-32, 2010 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-20404108

RESUMO

Oligodendrocytes secrete vesicles into the extracellular space, where they might play a role in neuron-glia communication. These exosomes are small vesicles with a diameter of 50-100 nm that are formed within multivesicular bodies and are released after fusion with the plasma membrane. The intracellular pathways that generate exosomes are poorly defined. Because Rab family guanosine triphosphatases (GTPases) together with their regulators are important membrane trafficking organizers, we investigated which Rab GTPase-activating proteins interfere with exosome release. We find that TBC1D10A-C regulate exosome secretion in a catalytic activity-dependent manner. We show that Rab35 is the target of TBC1D10A-C and that the inhibition of Rab35 function leads to intracellular accumulation of endosomal vesicles and impairs exosome secretion. Rab35 localizes to the surface of oligodendroglia in a GTP-dependent manner, where it increases the density of vesicles, suggesting a function in docking or tethering. These findings provide a basis for understanding the biogenesis and function of exosomes in the central nervous system.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Exossomos/metabolismo , Proteínas Ativadoras de GTPase/metabolismo , Oligodendroglia/fisiologia , Proteínas rab de Ligação ao GTP/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Cálcio/metabolismo , Linhagem Celular , Membrana Celular/metabolismo , Exocitose/fisiologia , Proteínas Ativadoras de GTPase/genética , Humanos , Camundongos , Oligodendroglia/citologia , Técnicas de Patch-Clamp , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas rab de Ligação ao GTP/genética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA