Microglia constitute a highly specialized network of tissue-resident immune cells that is important for the control of tissue homeostasis and the resolution of diseases of the CNS. Little is known about how their spatial distribution is established and maintained in vivo. Here we establish a new multicolor fluorescence fate mapping system to monitor microglial dynamics during steady state and disease. Our findings suggest that microglia establish a dense network with regional differences, and the high regional turnover rates found challenge the universal concept of microglial longevity. Microglial self-renewal under steady state conditions constitutes a stochastic process. During pathology this randomness shifts to selected clonal microglial expansion. In the resolution phase, excess disease-associated microglia are removed by a dual mechanism of cell egress and apoptosis to re-establish the stable microglial network. This study unravels the dynamic yet discrete self-organization of mature microglia in the healthy and diseased CNS.
BackgroundMicroglia reactivity is a hallmark of retinal degenerations and overwhelming microglial responses contribute to photoreceptor death. Minocycline, a semi-synthetic tetracycline analog, has potent anti-inflammatory and neuroprotective effects. Here, we investigated how minocycline affects microglia in vitro and studied its immuno-modulatory properties in a mouse model of acute retinal degeneration using bright white light exposure.MethodsLPS-treated BV-2 microglia were stimulated with 50 μg/ml minocycline for 6 or 24 h, respectively. Pro-inflammatory gene transcription was determined by real-time RT-PCR and nitric oxide (NO) secretion was assessed using the Griess reagent. Caspase 3/7 levels were determined in 661W photoreceptors cultured with microglia-conditioned medium in the absence or presence of minocycline supplementation. BALB/cJ mice received daily intraperitoneal injections of 45 mg/kg minocycline, starting 1 day before exposure to 15.000 lux white light for 1 hour. The effect of minocycline treatment on microglial reactivity was analyzed by immunohistochemical stainings of retinal sections and flat-mounts, and messenger RNA (mRNA) expression of microglia markers was determined using real-time RT-PCR and RNA-sequencing. Optical coherence tomography (OCT) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) stainings were used to measure the extent of retinal degeneration and photoreceptor apoptosis.ResultsStimulation of LPS-activated BV-2 microglia with minocycline significantly diminished the transcription of the pro-inflammatory markers CCL2, IL6, and inducible nitric oxide synthase (iNOS). Minocycline also reduced the production of NO and dampened microglial neurotoxicity on 661W photoreceptors. Furthermore, minocycline had direct protective effects on 661W photoreceptors by decreasing caspase 3/7 activity. In mice challenged with white light, injections of minocycline strongly decreased the number of amoeboid alerted microglia in the outer retina and down-regulated the expression of the microglial activation marker translocator protein (18 kDa) (TSPO), CD68, and activated microglia/macrophage whey acidic protein (AMWAP) already 1 day after light exposure. Furthermore, RNA-seq analyses revealed the potential of minocycline to globally counter-regulate pro-inflammatory gene transcription in the light-damaged retina. The severe thinning of the outer retina and the strong induction of photoreceptor apoptosis induced by light challenge were nearly completely prevented by minocycline treatment as indicated by a preserved retinal structure and a low number of apoptotic cells.ConclusionsMinocycline potently counter-regulates microgliosis and light-induced retinal damage, indicating a promising concept for the treatment of retinal pathologies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-015-0431-4) contains supplementary material, which is available to authorized users.
Leaf-to-leaf systemic immune signaling known as systemic acquired resistance is poorly understood in monocotyledonous plants. Here, we characterize systemic immunity in barley (Hordeum vulgare) triggered after primary leaf infection with either Pseudomonas syringae pathovar japonica (Psj) or Xanthomonas translucens pathovar cerealis (Xtc). Both pathogens induced resistance in systemic, uninfected leaves against a subsequent challenge infection with Xtc. In contrast to systemic acquired resistance in Arabidopsis (Arabidopsis thaliana), systemic immunity in barley was not associated with NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 or the local or systemic accumulation of salicylic acid. Instead, we documented a moderate local but not systemic induction of abscisic acid after infection of leaves with Psj. In contrast to salicylic acid or its functional analog benzothiadiazole, local applications of the jasmonic acid methyl ester or abscisic acid triggered systemic immunity to Xtc. RNA sequencing analysis of local and systemic transcript accumulation revealed unique gene expression changes in response to both Psj and Xtc and a clear separation of local from systemic responses. The systemic response appeared relatively modest, and quantitative reverse transcriptionpolymerase chain reaction associated systemic immunity with the local and systemic induction of two WRKY and two ETHYLENE RESPONSIVE FACTOR (ERF)-like transcription factors. Systemic immunity against Xtc was further associated with transcriptional changes after a secondary/systemic Xtc challenge infection; these changes were dependent on the primary treatment. Taken together, bacteria-induced systemic immunity in barley may be mediated in part by WRKY and ERF-like transcription factors, possibly facilitating transcriptional reprogramming to potentiate immunity.
The human mitochondrial genome consists of a multicopy, circular dsDNA molecule of 16,569 base pairs. It encodes for 13 proteins, two ribosomal genes, and 22 tRNAs that are essential in the generation of cellular ATP by oxidative phosphorylation in eukaryotic cells. Germline mutations in mitochondrial DNA (mtDNA) are an important cause of maternally inherited diseases, while somatic mtDNA mutations may play important roles in aging and cancer. mtDNA polymorphisms are also widely used in population and forensic genetics. Therefore, methods that allow the rapid, inexpensive and accurate sequencing of mtDNA are of great interest. One such method is the Affymetrix GeneChip Human Mitochondrial Resequencing Array 2.0 (MitoChip v.2.0) (Santa Clara, CA). A direct comparison of 93 worldwide mitochondrial genomes sequenced by both the MitoChip and dideoxy terminator sequencing revealed an average call rate of 99.48% and an accuracy of > or =99.98% for the MitoChip. The good performance was achieved by using in-house software for the automated analysis of additional probes on the array that cover the most common haplotypes in the hypervariable regions (HVR). Failure to call a base was associated mostly with the presence of either a run of > or =4 C bases or a sequence variant within 12 bases up- or downstream of that base. A major drawback of the MitoChip is its inability to detect insertions/deletions and its low sensitivity and specificity in the detection of heteroplasmy. However, the vast majority of haplogroup defining polymorphism in the mtDNA phylogeny could be called unambiguously and more rapidly than with conventional sequencing.
Interleukin‐33 (IL‐33), a cytokine with pleiotropic functions, is elevated in serum of patients with hepatocellular carcinoma (HCC). This study investigated the effects of local IL‐33 expression in resected HCC on patient survival and on the immunological and molecular tumor microenvironment. Tissue of resected HCCs was stained for hematoxylin and eosin, Masson trichrome, alpha‐smooth muscle actin, IL‐33, CD8, and IL‐13 and analyzed by flow cytometry. Besides histomorphologic evaluation, the immunohistochemical stainings were analyzed for the respective cell numbers separately for tumor area, infiltrative margin, and distant liver stroma. These findings were correlated with clinical data and patient outcome. Further, gene expression of different HCC risk groups was compared using microarrays. In multivariable analysis, infiltration of HCCs by IL‐33+ cells (P = 0.032) and CD8+ cells (P = 0.014) independently was associated with prolonged patient survival. Flow cytometry demonstrated that cytotoxically active subpopulations of CD8+ cells, in particular CD8+CD62L–KLRG1+CD107a+ effector‐memory cells, are the main producers of IL‐33 in these HCC patients. Using infiltration by IL‐33+ and CD8+ cells as two separate factors, an HCC immune score was designed and evaluated that stratified patient survival (P = 0.0004). This HCC immune score identified high‐ and low‐risk patients who differ in gene expression profiles (P < 0.001). Conclusion: Infiltration of HCCs by IL‐33+ and CD8+ cells is independently associated with prolonged patient survival. We suggest that this is due to an induction of highly effective, cytotoxically active CD8+CD62L–KLRG1+CD107a+ effector‐memory cells producing IL‐33. Based on these two independent factors, we established an HCC immune score that provides risk stratification for HCC patients and can be used in the clinical setting. (Hepatology 2015;61:1957‐1967)
The Drosophila neurodegeneration gene swiss-cheese encodes a neuronal protein apparently involved in glia-neuron interaction and is homologous to human NTE, the molecular target of organophosphate-induced neuropathy. The isolated Msws/NTE gene is 96% identical to NTE. During development the Msws transcript is expressed in the embryonic respiratory system, different epithelial structures and strongly in the spinal ganglia. Postnatally, Msws mRNA is expressed in all brain areas, with an increasingly restrictive pattern. In adult mice expression is most prominent in Purkinje cells, granule cells and pyramidal neurons of the hippocampus and some large neurons in the medulla oblongata, nucleus dentatus and pons.
The RBP2-H1/JARID1B nuclear protein belongs to the ARID family of DNA-binding proteins and is a potential tumor suppressor that is lost during melanoma development. As we have recently shown, one physiological function of RBP2-H1/JARID1B is to exert cell cycle control via maintenance of active retinoblastoma protein. We now add new evidence that RBP2-H1/JARID1B can also directly regulate gene transcription in a reporter assay system, either alone or as part of a multimolecular complex together with the developmental transcription factors FOXG1b and PAX9. In melanoma cells, chromatin immunoprecipitation combined with promoter chip analysis (ChIP-on-chip) suggests a direct binding of re-expressed RBP2-H1/JARID1B to a multitude of human regulatory chromosomal elements (promoters, enhancers and introns). Among those, a set of 23 genes, including the melanoma relevant genes CDK6 and JAG-1 could be confirmed by cDNA microarray analyses to be differentially expressed after RBP2-H1/JARID1B re-expression. In contrast, in nonmelanoma HEK 293 cells, RBP2-H1/JARID1B overexpression only evokes a minor transcriptional response in cDNA microarray analyses. Because the transcriptional regulation in melanoma cells is accompanied by an inhibition of proliferation, an increase in caspase activity and a partial cell cycle arrest in G1/0, our data support an anti-tumorigenic role of RBP2-H1/JARID1B in melanocytic cells. ' 2007 Wiley-Liss, Inc.Key words: melanoma; transcription; gene expression; retinoblastoma protein binding protein; apoptosisIn 1999, our group detected a gene transcript suppressed by UV-B in normal human melanocytes (Acc. No. AF087481, 1 ). Based on its homology to the previously described RBP2, 2 this new gene was termed retinoblastoma binding protein 2-homolog 1 (RBP2-H1). Subsequent expression studies revealed a frequent loss of RBP2-H1 in the majority of advanced and metastatic melanomas in vivo and in many melanoma cell lines, whereas benign melanocytic tumors, normal tissues and other cancer types mostly retain RBP2-H1. 1,3 Recently, we showed that RBP2-H1 has a tumor suppressive activity partly due to binding and stabilization of hypophosphorylated retinoblastoma protein (pRb) leading to maintenance of pRb-mediated cell cycle control. 4 As a result of truncation studies, we located the pRb-binding activity of RBP2-H1 to its C-term, containing a homolog region of the non-T/E1A-pRb binding domain known from other retinoblastoma binding proteins like RBP2. 5 Moreover, RBP2-H1 and its splicing variants PLU-1 and RBBP2H1a contain further well-conserved domains known to be involved in direct gene regulation and chromatin homeostasis, e.g. 3 PHD motifs and the ARID (AT-rich interacting) DNA-binding domain. [6][7][8][9] Although the 3 splicing variants show a cDNA sequence homology of more than 98%, RBP2-H1 differs from PLU-1 and RBBP2H1a by an additional exon encoding a region with strong homology to chromosomal ALU repeats. Thus, previously reported differences in tissue expression (PLU-1 shows a restricted expre...
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