MBP mRNA Research Articles

Ultra-high-resolution mapping of myelin and g-ratio in a panel of Mbp enhancer-edited mouse strains using microstructural MRI

Non-invasive myelin water fraction (MWF) and g-ratio mapping using microstructural MRI have the potential to offer critical insights into brain microstructure and our understanding of neuroplasticity and neuroinflammation. By leveraging a unique panel of variably hypomyelinating mouse strains, we validated a high-resolution, model-free image reconstruction method for whole-brain MWF mapping. Further, by employing a bipolar gradient echo MRI sequence, we achieved high spatial resolution and robust mapping of MWF and g-ratio across the whole mouse brain. Our regional white matter-tract specific analyses demonstrated a graded decrease in MWF in white matter tracts which correlated strongly with myelin basic protein gene (Mbp) mRNA levels. Using these measures, we derived the first sensitive calibrations between MWF and Mbp mRNA in the mouse. Minimal changes in axonal density supported our hypothesis that observed MWF alterations stem from hypomyelination. Overall, our work strongly emphasizes the potential of non-invasive, MRI-derived MWF and g-ratio modeling for both preclinical model validation and ultimately translation to humans.

Myelin basic protein mRNA levels affect myelin sheath dimensions, architecture, plasticity, and density of resident glial cells.

Myelin Basic Protein (MBP) is essential for both elaboration and maintenance of CNS myelin, and its reduced accumulation results in hypomyelination. How different Mbp mRNA levels affect myelin dimensions across the lifespan and how resident glial cells may respond to such changes are unknown. Here, to investigate these questions, we used enhancer-edited mouse lines that accumulate Mbp mRNA levels ranging from 8% to 160% of wild type. In young mice, reduced Mbp mRNA levels resulted in corresponding decreases in Mbp protein accumulation and myelin sheath thickness, confirming the previously demonstrated rate-limiting role of Mbp transcription in the control of initial myelin synthesis. However, despite maintaining lower line specific Mbp mRNA levels into old age, both MBP protein levels and myelin thickness improved or fully normalized at rates defined by the relative Mbp mRNA level. Sheath length, in contrast, was affected only when mRNA levels were very low, demonstrating that sheath thickness and length are not equally coupled to Mbp mRNA level. Striking abnormalities in sheath structure also emerged with reduced mRNA levels. Unexpectedly, an increase in the density of all glial cell types arose in response to reduced Mbp mRNA levels. This investigation extends understanding of the role MBP plays in myelin sheath elaboration, architecture, and plasticity across the mouse lifespan and illuminates a novel axis of glial cell crosstalk.

Evaluating Gene Expression and Methylation Profiles of TCF4, MBP, and EGR1 in Peripheral Blood of Drug-Free Patients with Schizophrenia: Correlations with Psychopathology, Intelligence, and Cognitive Impairment.

Discovery and validation of new, reliable diagnostic and predictive biomarkers for schizophrenia (SCZ) are an ongoing effort. Here, we assessed the mRNA expression and DNA methylation of the TCF4, MBP, and EGR1 genes in the blood of patients with SCZ and evaluated their relationships to psychopathology and cognitive impairments. Quantitative real-time PCR and quantitative methylation-specific PCR methods were used to assess the expression level and promoter DNA methylation status of these genes in 70 drug-free SCZ patients and 72 healthy controls. The correlation of molecular changes with psychopathology and cognitive performance of participants was evaluated. We observed downregulation of TCF4 and upregulation of MBP mRNA levels in SCZ cases, relative to controls in our study. DNA methylation status at the promoter region of TCF4 demonstrated an altered pattern in SCZ as well. Additionally, TCF4 mRNA levels were inversely correlated with PANSS and Stroop total errors and positively correlated with WAIS total score and working memory, consistent with previous studies by our group. In contrast, MBP mRNA level was significantly positively correlated with PANSS and Stroop total errors and inversely correlated with WAIS total score and working memory. These epigenetic and expression signatures can help to assemble a peripheral biomarker-based diagnostic panel for SCZ.

OX40 Expression in Eosinophils Aggravates OVA-Induced Eosinophilic Gastroenteritis.

Background & AimsEosinophils are the main inflammatory effector cells that damage gastrointestinal tissue in eosinophilic gastrointestinal diseases (EGIDs). Activation of the OX40 pathway aggravates allergic diseases, such as asthma, but it is not clear whether OX40 is expressed in eosinophils to regulate inflammation in EGIDs. In this study, we assessed the expression and effect of OX40 on eosinophils in WT and Ox40-/- eosinophilic gastroenteritis (EGE) mice.MethodsEosinophil infiltration, ovalbumin (OVA)-specific Ig production, OX40 expression and inflammatory factor levels in the intestine and bone marrow (BM) were investigated to evaluate inflammation.ResultsWe confirmed that OVA-challenged mice produced high levels of Ox40, Mbp, Ccl11, Il5, Il4, Il13, and Il6 mRNA and a low level of Ifng mRNA in the intestine. Increased eosinophils were observed in intestinal and lymph tissues, accompanied by significantly upregulated OX40 and Type 2 cytokine production in eosinophils of EGE mice. Ox40 deficiency ameliorated OVA-induced inflammation, eosinophil infiltration, and cytokine production in the intestine. Consistently, Ox40-/ - eosinophils exhibited decreased proliferation and proinflammatory function. The stimulation of the agonistic anti-OX40 antibody, OX86, promoted the effect of OX40 on eosinophils. The present study also showed that Ox40 deficiency dampened the Traf2/6-related NF-κB signaling pathway in eosinophils.ConclusionsOX40 may play a critical role in the progress of OVA-induced EGE by promoting the maturation and function of eosinophils via the Traf2/6-related NF-κB signaling pathway.

Cognitive impairment in obese rat model: role of glial cells.

Obesity is a worldwide problem. Some studies revealed that it leads to deterioration of the cognitive function, regardless of age. explore the effect of obesity on cognitive function in a rat model of obesity highlighting the role of glial cells. twenty adult male albino rats were assigned to two groups: group I: consumed normal diet, group II: consumed high-fat diet. Body Mass Index (BMI), serum glucose, insulin, HOMA IR and lipid profile were measured. Also, hippocampal expression of Brain derived neurotrophic factor (Bdnf), synapsin, Ionized calcium binding adaptor molecule 1 (Iba), nuclear factor erythroid -related factor 2 (Nrf2), Myelin basic protein (Mbp) were measured by real-time polymerase chain reaction. The Morris Water Maze is a test used to assess spatial learning and memory capacities of rats. There was a high significant increase in lipid profile, serum glucose, insulin serum levels and HOMA-IR in obese groups with impaired Morris water maze performance compared to control group. There was a significant downregulation in hippocampal Bdnf and synapsin mRNA expression. In addition to decrease in Mbp mRNA expression (P < 0.001). This could be explained by oxidative stress through significant downregulation of Nrf2 mRNA, and inflammation observed in significant upregulation Iba mRNA gene expression in the obese group. Many factors contribute to obesity associated cognitive impairment. In our study, we figured out the crucial roles of glial cells including microglial activation and oligodendrocytes affection with other underlying mechanisms including oxidative stress and hippocampal inflammation.

Dynamic Changes of Beclin-1 in the Hippocampus of Male Mice with Vascular Dementia at Different Time Points.

This study tried to investigate the dynamic changes of Beclin-1 in the hippocampus of male mice with vascular dementia (VD) at different time points. The mouse model of VD was established by the four-vessel blocking method. Then, the VD mice were randomly divided into five groups (n = 12) according to the disease duration: the 0.1-day model group, 0.5-day model group, 1-day model group, 3-day model group, 5-day model group and 14-day model group. In addition, all surgical procedures were the same in the sham group as those in the model groups, except the mice in the sham group were not subjected to clipping. The expression of Beclin-1, LC3B, p62, Bcl-2, Bax, BACE1, GFAP, MBP and ET-1 mRNA were determined by RT-PCR; the expression of Beclin-1 was detected by Western blot and immunofluorescence; the pathological characteristics of the hippocampus were observed by haematoxylin-eosin (HE) staining; and the correlation of Beclin-1 with other VD-related proteins was analysed by Pearson's correlation. Compared with that in the sham group, the expression of Beclin-1, LC3B, Bax, BACE1, GFAP, MBP and ET-1 mRNA was increased in the VD mice at different time points (0.1day, 0.5day, 1day, 3days, 5days and 14days) (P < 0.05) and then remained relatively stable in the 0.5-day VD mice, whereas the p62 and Bcl-2 mRNA levels decreased (P < 0.05). Beclin-1 protein expression was significantly increased in the VD mice at different time points (P < 0.05). The hippocampus showed a certain degree of neuronal damage in the VD mice at different time points (P < 0.05). Additionally, certain correlations among LC3B, p62, Bcl-2, Bax, BACE1, GFAP, MBP, ET-1 and Beclin-1 were observed in this study. In conclusion, the results described above demonstrated that neuronal damage and dynamic stability of Beclin-1 expression were established in the VD male mice after 0.5day by the four-vessel blocking method.

Mechanistic Target of Rapamycin Regulates the Oligodendrocyte Cytoskeleton during Myelination.

During differentiation, oligodendrocyte precursor cells (OPCs) extend a network of processes that make contact with axons and initiate myelination. Recent studies revealed that actin polymerization is required for initiation of myelination whereas actin depolymerization promotes myelin wrapping. Here, we used primary OPCs in culture isolated from neonatal rat cortices of both sexes and young male and female mice with oligodendrocyte-specific deletion of mechanistic target of rapamycin (mTOR) to demonstrate that mTOR regulates expression of specific cytoskeletal targets and actin reorganization in oligodendrocytes during developmental myelination. Loss or inhibition of mTOR reduced expression of profilin2 and ARPC3, actin polymerizing factors, and elevated levels of active cofilin, which mediates actin depolymerization. The deficits in actin polymerization were revealed in reduced phalloidin and deficits in oligodendrocyte cellular branching complexity at the peak of morphologic differentiation and a delay in initiation of myelination. We further show a critical role for mTOR in expression and localization of myelin basic protein (Mbp) mRNA and MBP protein to the cellular processes where it is necessary at the myelin membrane for axon wrapping. Mbp mRNA transport deficits were confirmed by single molecule RNA FISH. Moreover, expression of the kinesin family member 1B, an Mbp mRNA transport protein, was reduced in CC1+ cells in the mTOR cKO and in mTOR inhibited oligodendrocytes undergoing differentiation in vitro These data support the conclusion that mTOR regulates both initiation of myelination and axon wrapping by targeting cytoskeletal reorganization and MBP localization to oligodendrocyte processes.SIGNIFICANCE STATEMENT Myelination is essential for normal CNS development and adult axon preservation and function. The mechanistic target of rapamycin (mTOR) signaling pathway has been implicated in promoting CNS myelination; however, there is a gap in our understanding of the mechanisms by which mTOR promotes developmental myelination through regulating specific downstream targets. Here, we present evidence that mTOR promotes the initiation of myelination through regulating specific cytoskeletal targets and cellular process expansion by oligodendrocyte precursor cells as well as expression and cellular localization of myelin basic protein.

Effect of propofol on myelin basic protein expression and myelination of oligodendrocytes in neonatal SD rats

To investigate the effects of different doses of propofol on myelin basic protein (MBP) synthesis and myelination of oligodendrocytes in neonatal SD rats. A total of 57 neonatal SD rats (7 days old) were randomly divided into control group (n=13), vehicle (fat emulsion) group (n=5), and 25, 50 and 100 mg/kg propofol groups (n=13 in each group). Eight hours after a single intraperitoneal injection of propofol or the vehicle, the rats were examined for expressions of mbp mRNA, caspase-3 mRNA, cleaved caspase-3 and MBP in the brain tissues using qPCR and Western blotting. Immunofluorescence assay was used to detect the apoptosis of the oligodendrocytes at 8 h after the injection and the myelination of the corpus callosum and internal capsule at 24 h. Compared with the control group, the neonatal rats with propofol injections showed significantly down-regulated expressions of mbp mRNA and MBP protein in the brain tissue (P &lt; 0.05). Propofol dose-dependently increased the transcription level of caspase-3 and the protein levels of cleaved caspase-3 at 8 h after the injection (P &lt; 0.05). Propofol injection significantly increased the apoptosis of the oligodendrocytes, and the effect was significantly stronger in 50 and 100 mg/kg groups than in 25 mg/kg group (P &lt; 0.05). At 24 h after propofol injection, myelin formation was significantly decreased in the corpus callosum of the neonatal rats in 100 mg/kg propofol group and in the internal capsule in 50 and 100 mg/kg groups (P &lt; 0.05). In neonatal SD rats, propofol can dose-dependently promote oligodendrocyte apoptosis, decrease MBP expressions in the brain, and suppress myelin formation in the corpus callosum and the internal capsule.

Laquinimod Treatment Improves Myelination Deficits at the Transcriptional and Ultrastructural Levels in the YAC128 Mouse Model of Huntington Disease.

Laquinimod, an immunomodulatory agent under clinical development for Huntington disease (HD), has recently been shown to confer behavioural improvements that are coupled with prevention of atrophy of the white matter (WM)-rich corpus callosum (CC) in the YAC128 HD mice. However, the nature of the WM improvements is not known yet. Here we investigated the effects of laquinimod on HD-related myelination deficits at the cellular, molecular and ultrastructural levels. We showed that laquinimod treatment improves motor learning and motor function deficits in YAC128 HD mice, and confirmed its antidepressant effect even at the lowest dose used. In addition, we demonstrated for the first time the beneficial effects of laquinimod on myelination in the posterior region of the CC where it reversed changes in myelin sheath thickness and rescued Mbp mRNA and protein deficits. Furthermore, the effect of laquinimod on myelin-related gene expression was not region-specific since the levels of the Mbp and Plp1 transcripts were also increased in the striatum. Also, we did not detect changes in immune cell densities or levels of inflammatory genes in 3-month-old YAC128 HD mice, and these were not altered with laquinimod treatment. Thus, the beneficial effects of laquinimod on HD-related myelination abnormalities in YAC128 HD mice do not appear to be dependent on its immunomodulatory activity. Altogether, our findings describe the beneficial effects of laquinimod treatment on HD-related myelination abnormalities and highlight its therapeutic potential for the treatment of WM pathology in HD patients.

A novel long noncoding RNA lnc158 promotes the differentiation of mouse neural precursor cells into oligodendrocytes by targeting nuclear factor-IB.

Long noncoding RNAs have been implicated in oligodendrocyte myelination and oligodendrocyte maturation, but their roles in normal oligodendrocyte differentiation are not fully defined. Here, we report a novel nonprotein-coding RNA, named lnc158, discovered in mouse oligodendrocytes identified in subependymal ventricular zone tissue by single-cell RNA sequencing. Lnc158 is an endogenous antisense transcript of nuclear factor-IB (NFIB) and complementary to 3' untranslated region of NFIB mRNA. NFIB is a member of the nuclear factor-I family and is essential in the development of many organs such as brains and lungs. We found that lnc158 transcripts serve a biological function by regulating the transcription level of the NFIB coding gene in neural stem cells. Overexpression of lnc158 increased the expression of NFIB mRNA and knockdown of lnc158 decreased the expression of NFIB mRNA, suggesting that NFIB is regulated positively by lnc158. Further analyses showed that overexpression of lnc158 in neural stem cells induced a modest increase in CNP, MBP, MAG, and OSP mRNA level, and enhanced induction of differentiation along the lineage of oligodendrocytes. These results together imply that lnc158 positively modulates the transcription level of NFIB mRNA, leading to the enhanced induction of oligodendrocytes.

The 3'UTRs of Myelin Basic Protein mRNAs Regulate Transport, Local Translation and Sensitivity to Neuronal Activity in Zebrafish.

Formation of functional myelin sheaths within the central nervous system depends on expression of myelin basic protein (MBP). Following process extension and wrapping around axonal segments, this highly basic protein is required for compaction of the multi-layered membrane sheath produced by oligodendrocytes. MBP is hypothesized to be targeted to the membrane sheath by mRNA transport and local translation, which ensures that its expression is temporally and spatially restricted. The mechanistic details of how this might be regulated are still largely unknown, in particular because a model system that allows this process to be studied in vivo is lacking. We here show that the expression of the zebrafish MBP orthologs, mbpa and mbpb, is developmentally regulated, and that expression of specific mbpa isoforms is restricted to the peripheral nervous system. By analysis of transgenic zebrafish, which express a fluorescent reporter protein specifically in myelinating oligodendrocytes, we demonstrate that both mbpa and mbpb include a 3’UTR sequence, by which mRNA transport and translation is regulated in vivo. Further functional analysis suggests that: (1) the 3’UTRs delay the onset of protein expression; and that (2) several regulatory elements contribute to targeting of the mbp mRNA to the myelin sheath. Finally, we show that a pharmacological compound known to enhance neuronal activity stimulates the translation of Mbp in zebrafish in a 3’UTR-dependent manner. A similar effect was obtained following stimulation with a TrkB receptor agonist, and cell-based assays further confirmed that the receptor ligand, BDNF, in combination with other signals reversed the inhibitory effect of the 3’UTR on translation.

Dual role of the RNA helicase DDX5 in post-transcriptional regulation of myelin basic protein in oligodendrocytes.

In the central nervous system, oligodendroglial expression of myelin basic protein (MBP) is crucial for the assembly and structure of the myelin sheath. MBP synthesis is tightly regulated in space and time, particularly at the post-transcriptional level. We have identified the DEAD-box RNA helicase DDX5 (also known as p68) in a complex with Mbp mRNA in oligodendroglial cells. Expression of DDX5 is highest in progenitor cells and immature oligodendrocytes, where it localizes to heterogeneous populations of cytoplasmic ribonucleoprotein (RNP) complexes associated with Mbp mRNA in the cell body and processes. Manipulation of the amount of DDX5 protein inversely affects the level of MBP. We present evidence that DDX5 is involved in post-transcriptional regulation of MBP protein synthesis, with implications for oligodendroglial development. In addition, knockdown of DDX5 results in an increased abundance of MBP isoforms containing exon 2 in immature oligodendrocytes, most likely by regulating alternative splicing of Mbp Our findings contribute to the understanding of the complex nature of MBP post-transcriptional control in immature oligodendrocytes where DDX5 appears to affect the abundance of MBP proteins via distinct but converging mechanisms.

Effect of CCR3 gene knockout on eosinophils in mice

Objective:To investigate the effect of CCR3 gene knockout on the proliferation, maturation and apoptosis of eosinophils (EOS) in mice. Method:Bone marrow cells from CCR3 gene knockout mice (experimental group) and wild-type mice (control group) were cultured in vitro and induced differentiation into mature EOS. EOS proliferation was observed by cell counting.Expression of degranulation protein mRNA was detected by qRT-PCR. EOS apoptosis was detected by Annexin V-FITC/PI double staining method. Result:①The number of cells on the 0-14 day of EOS cultured in vitro showed that the number of cells in the experimental group was less than that in the control group at tenth, twelfth, fourteenth days, and the proliferation was slower, the difference was statistically significant (P<0.01). ②The test results of EOS cells apoptosis showed that, under the condition of containing 10 ng/ml IL-5 or no IL-5, the apoptosis rate of EOS cells in experimental group was higher than that in normal control group, the difference between both groups was statistically significant (P<0.01). ③The expression results of ECP, EPO, MBP mRNA in EOS showed that the expression levels of ECP, EPO, MBP mRNA in the experimental group compared with the normal control group were reduced in varying degrees, the difference between both groups was statistically significant (P<0.05). Conclusion:Knockout CCR3 gene can inhibit the proliferation and maturation of EOS and promote its apoptosis, which provides a theoretical basis for CCR3 as a target gene to treat allergic rhinitis.

Acanthamoeba-mediated cytopathic effect correlates with MBP and AhLBP mRNA expression

BackgroundIn recent years, the concern of Acanthamoeba keratitis has increased since the infection is often associated with contact lens use. Partial 18S rRNA genotypic identification of Acanthamoeba isolates is important to correlate with pathophysiological properties in order to evaluate the degree of virulence. This is the first report of genotypic identification for clinical isolates of Acanthamoeba from corneal scrapings of keratitis in Malaysia. This study is also the first to correlate the mRNA expression of MBP and AhLBP as virulent markers for axenic strains of Acanthamoeba.ResultsIn this study, ten clinical isolates were obtained from corneal scrapings. Rns genotype and intra-genotypic variation at the DF3 region of the isolates were identified. Results revealed that all clinical isolates belonged to the T4 genotype, with T4/6 (4 isolates), T4/2 (3 isolates), T4/16 (2 isolates) and one new genotype T4 sequence (T4/36), being determined. The axenic clinical isolates were cytopathogenic to rabbit corneal fibroblasts. MBP and AhLBP mRNA expression are directly correlated to Acanthamoeba cytopathic effect.ConclusionsAll ten Malaysian clinical isolates were identified as genotype T4 which is predominantly associated with AK. Measuring the mRNA expression of Acanthamoeba virulent markers could be useful in the understanding of the pathogenesis of Acanthamoeba keratitis.

Dynein/dynactin regulate anterograde Mbp mRNA transport in oligodendrocytes to promote myelination

Dynein/dynactin regulate anterograde Mbp mRNA transport in oligodendrocytes to promote myelination

Neuroglial alterations in the zebrafish brain exposed to cadmium chloride.

Cadmium is an extremely toxic heavy metal that widely occurs in industrial workplaces with various hazardous effects on brain functions. The cytotoxic effects of cadmium chloride (CdCl2 ) on the neuroglial components of the zebrafish brain were analysed by detecting the glial fibrillary acidic protein (GFAP) expression and the mRNA levels of myelin genes mbp, mpz and plp1 in adult specimens exposed to cadmium for 2, 7 and 16 days. A significant decrease in the GFAP protein by Western blotting experiments was observed after 2 days of treatment, reaching 55% after 16 days. No change was observed in the mRNA levels. Using immunohistochemistry, a reduction in GFAP-positive structures was revealed with a progressive trend in all the brains at 2, 7 and 16 days of treatment. In particular, a considerable reduction in GFAP-positive fibres, with a different course, was observed in the ventricle areas and at the pial surface and in blood vessels after 16 days. Our experiments also showed a structural and chemical alteration of myelin and upregulation of mpz mRNA levels, the oligodendrocyte gene that is upregulated in experiments of neuronal injury, but not of plp1 and mbp mRNA levels, other myelin structural genes. These data confirm the toxic action of cadmium on the zebrafish brain. This action is time-dependent and involves the glial cells, key components of the protection and function of nerve cells, hence the basis for many neurological diseases. Copyright © 2016 John Wiley & Sons, Ltd.

Liver X Receptors differentially modulate central myelin gene mRNA levels in a region-, age- and isoform-specific manner

Liver X Receptors (LXRs) α and β are nuclear receptors able to bind oxidative forms of cholesterol. They play important roles in the central nervous system (CNS), through their implication in a large variety of physiological and pathological processes among which modulation of cholesterol homeostasis and inflammation. Besides, we recently revealed their crucial role in myelination and remyelination in the cerebellum. Given the pleiotropic effects of such receptors on CNS functioning, we studied here the influence of LXRs on myelin gene mRNA accumulation in the major myelinated regions of the CNS in vivo.We show that both LXR isoforms differentially affect mRNA amount of myelin genes (PLP and MBP) in highly myelinated structures such as spinal cord, corpus callosum, optic nerve and cerebellum. In the adult, LXR activation by the synthetic agonist TO901317 significantly increases myelin gene mRNA amount in the cerebellum but not in the other regions studied. Invalidation of the sole LXRβ isoform leads to decreased PLP and MBP mRNA levels in all the structures except the spinal cord, while the knock out of both isoforms (LXR dKO) decreases myelin gene mRNA amounts in all the regions tested except the corpus callosum. Interestingly, during myelination process (post-natal day 21), both cerebellum and optic nerve display a decrease in myelin gene mRNA levels in LXR dKO mice. Concomitantly, PLP and MBP mRNA accumulation in the spinal cord is increased. Relative expression level of LXR isoforms could account for the differential modulation of myelin gene expression in the CNS.Altogether our results suggest that, within the CNS, each LXR isoform differentially influences myelin gene mRNA levels in a region- and age-dependant manner, participating in the fine regulation of myelin gene expression.

Glycogen synthase kinase 3 is part of the molecular machinery regulating the adaptive response to LPS stimulation in microglial cells

Repeated stimulation of TLR4 signaling by lipopolysaccharide (LPS) in microglia induces a state of tolerance/sensitization consisting in the reprogramming of the expression of pro-inflammatory genes in favor of anti-inflammatory ones. The molecular mechanisms underlying this adaptive response are far to be elucidated. Glycogen synthase kinase 3 (GSK3) has emerged as crucial regulator of TLR signaling, mediating the balance between pro- and anti-inflammatory functions in both periphery and central nervous system. The present study extends this notion identifying GSK3 as part of the molecular machinery regulating the LPS-adaptive response in microglial cells, by using primary microglial cultures and organotypic hippocampal slices (OHSCs). We found that lithium chloride (LiCl), a widely used GSK3 inhibitor and the mainstay treatment for bipolar disorder, reinforced the LPS adaptive response by enhancing both downregulation of pro-inflammatory genes (inducible nitric oxide synthase, interleukin 1β, interleukin 6, tumor necrosis factor α), and upregulation of genes typically associated to anti-inflammatory functions (interleukin 10 and MRC1). The effects of GSK3 inhibition were mimicked by Wnt3a, added exogenously, and reversed by Inhibitor of Wnt-Response-1-endo, a pharmacological disruptor of the canonical Wnt/β-catenin pathway, and GW9662, a selective peroxisome proliferator activated receptor γ antagonist, suggesting that these two pathways are involved in the regulation of LPS-tolerance/sensitization by GSK. Finally, LiCl treatment of OHSCs enhanced the protective functional consequences of the microglial adaptive response to LPS on oligodendrocyte maturation, as indicated by MBP mRNA upregulation. These results further indicate GSK3 as key component in the orchestration of neuroinflammation and target for neuroprotective strategies.

SncRNA715 Inhibits Schwann Cell Myelin Basic Protein Synthesis.

Myelin basic proteins (MBP) are major constituents of the myelin sheath in the central nervous system (CNS) and the peripheral nervous system (PNS). In the CNS Mbp translation occurs locally at the axon-glial contact site in a neuronal activity-dependent manner. Recently we identified the small non-coding RNA 715 (sncRNA715) as a key inhibitor of Mbp translation during transport in oligodendrocytes. Mbp mRNA localization in Schwann cells has been observed, but has not been investigated in much detail. Here we could confirm translational repression of Mbp mRNA in Schwann cells. We show that sncRNA715 is expressed and its levels correlate inversely with MBP in cultured Schwann cells and in the sciatic nerve in vivo. Furthermore we could reduce MBP protein levels in cultured Schwann cells by increasing the levels of the inhibitory sncRNA715. Our findings suggest similarities in sncRNA715-mediated translational repression of Mbp mRNA in oligodendrocytes and Schwann cells.

Oligodendroglial Argonaute protein Ago2 associates with molecules of the Mbp mRNA localization machinery and is a downstream target of Fyn kinase.

Oligodendrocytes myelinate neuronal axons in the central nervous system (CNS) facilitating rapid transmission of action potentials by saltatory conduction. Myelin basic protein (MBP) is an essential component of myelin and its absence results in severe hypomyelination in the CNS of rodents. Mbp mRNA is not translated immediately after exit from the nucleus in the cytoplasm, but is transported to the plasma membrane in RNA transport granules in a translationally silenced state. We have previously identified the small non-coding RNA 715 (sncRNA715) as an inhibitor of Mbp translation associated with RNA granules. Argonaute (Ago) proteins and small RNAs form the minimal core of the RNA induced silencing complex and together recognize target mRNAs to be translationally inhibited or degraded. Recently, tyrosine phosphorylation of Ago2 was reported to be a regulator of small RNA binding. The oligodendroglial non-receptor tyrosine kinase Fyn is activated by neuronal signals and stimulates the translation of Mbp mRNA at the axon-glial contact site. Here we analyzed the expression of Ago proteins in oligodendrocytes, if they associate with Mbp mRNA transport granules and are tyrosine phosphorylated by Fyn. We show that all Ago proteins (Ago1-4) are expressed by oligodendrocytes and that Ago2 colocalizes with hnRNP A2 in granular cytoplasmic structures. Ago2 associates with hnRNP A2, Mbp mRNA, sncRNA715 and Fyn kinase and is tyrosine phosphorylated in response to Fyn activity. Our findings suggest an involvement of Ago2 in the translational regulation of Mbp. The identification of Ago proteins as Fyn targets will foster further research to understand in more molecular detail how Fyn activity regulates Mbp translation.