In the past decade, several groups have reported that microRNAs (miRNAs) can participate in the regulation of tau protein at different levels, including its expression, alternative splicing, ...phosphorylation, and aggregation. These observations are significant, since the abnormal regulation and deposition of tau is associated with nearly 30 neurodegenerative disorders. Interestingly, miRNA profiles go awry in tauopathies such as Alzheimer's disease, progressive supranuclear palsy, and frontotemporal dementia. Understanding the role and impact of miRNAs on tau biology could therefore provide important insights into disease risk, diagnostics, and perhaps therapeutics. In this Perspective article, we discuss recent advances in miRNA research related to tau. While proof-of-principle studies hold promise, physiological validation remains limited. To help fill this gap, we describe herein a pure tauopathy mouse model deficient for the miR-132/212 cluster. This miRNA family is strongly downregulated in human tauopathies and shown to regulate tau
in vitro
and
in vivo
. No significant differences in survival, motor deficits or body weight were observed in PS19 mice lacking miR-132/212. Age-specific effects were seen on tau expression and phosphorylation but not aggregation. Moreover, various miR-132/212 targets previously implicated in tau modulation were unaffected (GSK-3β, Foxo3a, Mapk1, p300) or, unexpectedly, reduced (Mapk3, Foxo1, p300, Calpain 2) in miR-132/212-deficient PS19 mice. These observations highlight the challenges of miRNA research in living models, and current limitations of transgenic tau mouse models lacking functional miRNA binding sites. Based on these findings, we finally recommend different strategies to better understand the role of miRNAs in tau physiology and pathology.
Neurodegenerative disorders are defined by neuronal loss and often associated with dementia. Understanding the multifactorial nature of cognitive decline is of particular interest. Cell loss is ...certainly a possibility but also an early imbalance in the complex gene networks involved in learning and memory. The small (~22nt) non-coding microRNAs play a major role in gene expression regulation and have been linked to neuronal survival and cognition. Interestingly, changes in microRNA signatures are associated with neurodegenerative disorders. In this review, we explore the role of three microRNAs, namely miR-132, miR-124 and miR-34, which are dysregulated in major neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and Huntington's disease. Interestingly, these microRNAs have been associated with both memory impairment and neuronal survival, providing a potential common molecular mechanism contributing to dementia.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The abnormal regulation of amyloid-β (Aβ) metabolism (e.g., production, cleavage, clearance) plays a central role in Alzheimer's disease (AD). Among endogenous factors believed to participate in AD ...progression are the small regulatory non-coding microRNAs (miRs). In particular, the miR-132/212 cluster is severely reduced in the AD brain. In previous studies we have shown that miR-132/212 deficiency in mice leads to impaired memory and enhanced Tau pathology as seen in AD patients. Here we demonstrate that the genetic deletion of miR-132/212 promotes Aβ production and amyloid (senile) plaque formation in triple transgenic AD (3xTg-AD) mice. Using RNA-Seq and bioinformatics, we identified genes of the miR-132/212 network with documented roles in the regulation of Aβ metabolism, including Tau, Mapk, and Sirt1. Consistent with these findings, we show that the modulation of miR-132, or its target Sirt1, can directly regulate Aβ production in cells. Finally, both miR-132 and Sirt1 levels correlated with Aβ load in humans. Overall, our results support the hypothesis that the miR-132/212 network, including Sirt1 and likely other target genes, contributes to abnormal Aβ metabolism and senile plaque deposition in AD. This study strengthens the importance of miR-dependent networks in neurodegenerative disorders, and opens the door to multifactorial drug targets of AD by targeting Aβ and Tau.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Alzheimer's disease (AD) occurs as either an autosomal dominant inherited disease or sporadically. While familial mutant genes can be expressed in cells or in animal models to assess dysregulated ...functions, sporadic AD cannot be replicated in models given our lack of understanding of causality. Furthermore, the study of sporadic forms of AD is difficult given the inaccessibility of brain tissues in living individuals and the manifestation of symptoms years after the onset of disease. Here, the objective was to assess if induced pluripotent stem cell-derived neurons from well-ascertained sporadic AD individuals could represent potential cellular models to determine the underlying molecular mechanisms of disease. We used cryopreserved peripheral blood mononuclear cells from three well-ascertained sporadic AD and three non-cognitively impaired (NCI) individuals of the CIMA-Q cohort to obtain iPSC-derived neurons. Microtubule associated protein 2 was decreased in AD neurons, whereas expression of AD-associated amyloid precursor protein, tau, and amyloid-β peptide was similar in AD and NCI individuals. RNA sequencing identified several upregulated and downregulated mRNAs in AD relative to NCI neurons. Of these, complement Factor H (CFH), signal regulatory protein beta1 (SIRPB1), and insulin like growth factor binding protein 5 (IGFBP5) were previously associated with AD. In addition, several transcription factors not previously associated with AD, but involved in neuronal proliferation and differentiation were differentially expressed. The results identify novel avenues for the study of the underlying causes of sporadic AD and support the establishment of additional lines to identify mechanisms of disease in sporadic AD individuals.
Cortical spreading depression (CSD) is an evolutionarily conserved phenomenon that involves a slow and self-propagating depolarization wave associated with spontaneous depression of electrical ...neuronal activity. CSD plays a central role in the pathophysiology of several brain diseases and is considered to be able to promote “Preconditioning”. This phenomenon consists of the brain protecting itself against future injury by adaptation. Understanding of the molecular mechanisms underlying Preconditioning has significant clinical implications. We have already proposed that the long-lasting effects of CSD could be related to silencing of retrotransposon sequences by histone methylation. We analyzed DNA methylation of two retrotransposon sequences, LINE1 and L1, and their corresponding expression pattern after CSD induction. Based on immunoprecipitation assay of the methylated DNA (meDIP), we demonstrated hypermethylation of both sequences in preconditioned rat brain cortex compared with a control 24 h after CSD induction. Using quantitative PCR, we also showed that CSD induction caused a decrease of the transcript level of both retrotransposon sequences. Our data are consistent with the hypothesis of epigenetic modifications in Preconditioning-dependent neuroprotection by increasing genome stability via the silencing of retrotransposon sequences.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The abnormal regulation of amyloid-β (Aβ) metabolism (e.g., production, cleavage, clearance) plays a central role in Alzheimer's disease (AD). Among endogenous factors believed to participate in AD ...progression are the small regulatory non-coding microRNAs (miRs). In particular, the miR-132/212 cluster is severely reduced in the AD brain. In previous studies we have shown that miR-132/212 deficiency in mice leads to impaired memory and enhanced Tau pathology as seen in AD patients. Here we demonstrate that the genetic deletion of miR-132/212 promotes Aβ production and amyloid (senile) plaque formation in triple transgenic AD (3xTg-AD) mice. Using RNA-Seq and bioinformatics, we identified genes of the miR-132/212 network with documented roles in the regulation of Aβ metabolism, including Tau, Mapk, and Sirt1. Consistent with these findings, we show that the modulation of miR-132, or its target Sirt1, can directly regulate Aβ production in cells. Finally, both miR-132 and Sirt1 levels correlated with Aβ load in humans. Overall, our results support the hypothesis that the miR-132/212 network, including Sirt1 and likely other target genes, contributes to abnormal Aβ metabolism and senile plaque deposition in AD. This study strengthens the importance of miR-dependent networks in neurodegenerative disorders, and opens the door to multifactorial drug targets of AD by targeting Aβ and Tau.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
La maladie d'Alzheimer (MA) est la forme de démence la plus fréquente dans le monde. Au niveau microscopique, le cerveau des patients atteints par la MA présente deux principales caractéristiques ...pathologiques : les plaques amyloïdes, constituées d'agrégats du peptide Aβ (Amyloïde Bêta), et les dégénérescences neurofibrillaires, formées par des agrégats de la protéine Tau anormalement hyperphosphorylée. Parmi les facteurs endogènes qui pourraient participer à la progression de la MA, il y a les microARNs (miRs). Les miRs sont des petits ARNs non codants qui régulent l’expression de gènes cibles au niveau post-transcriptionnel. En particulier, la famille miR-132/212 est fortement régulée à la baisse dans le cerveau des patients atteints de la MA. Des études précédentes ont démontré que, chez la souris 3xTg-AD, un modèle de la MA, la délétion génétique de la famille miR-132/212 conduit à une augmentation de la phosphorylation et de l’agrégation de la protéine Tau, les deux mécanismes présumés à la base de la formation des dégénérescences neurofibrillaires. En dehors de son rôle dans la MA, la famille miR-132/212 est également impliquée dans plusieurs troubles neurologiques. Notamment, son niveau d’expression est dérégulé dans d’autres pathologies neurodégénératives, telles que la démence fronto-temporale et la maladie de Parkinson. Il est donc possible que la famille miR-132/212 contribue au processus neurodégénératif de ces pathologies. Dans ce contexte, les travaux présentés visent à étudier le rôle de la famille miR132/212 dans la MA et, plus généralement, dans le cerveau. Tout d’abord, puisque la famille miR-132/212 a déjà un rôle connu dans la formation des dégénérescences neurofibrillaires, nous avons évalué son implication dans la formation des plaques amyloïdes, deuxième caractéristique pathologique de la MA. Nous avons ainsi démontré que la délétion génétique de la famille miR-132/212 favorise la production du peptide Aβ et la formation de plaques amyloïdes chez le modèle murin 3xTg-AD. En utilisant une approche d’ARN-Seq et de bio-informatique, nous avons identifié des gènes faisant partie du réseau de la famille miR-132/212 qui ont des rôles dans la régulation du métabolisme de l'Aβ, y compris Tau, Mapk et Sirt1. En accord avec ces résultats, nous avons montré que la modulation du miR-132, ou de sa cible Sirt1, peut réguler directement la production d’Aβ dans les cellules. Finalement, nous avons démontré que les niveaux de la famille miR-132/212 corrèlent avec la quantité des plaques amyloïdes chez l'Homme. Ensuite, afin d’élucider le rôle de la famille miR-132/212 dans le cerveau, nous nous sommes concentrés sur l’identification de cibles régulées par cette dernière. Dans un premier temps, cette analyse a été conduite dans plusieurs modèles cellulaires in vitro, dans lesquels le rôle du miR-132, un des deux composants de la famille, a été spécifiquement étudié. Dans ce contexte, nous avons démontré que les cibles régulées par le miR-132 sont peu nombreuses et spécifiques au type cellulaire considéré. Dans un deuxième temps, l’analyse d’identification des cibles a été conduite dans un modèle de souris de délétion conditionnelle pour la famille miR-132/212 que nous avons spécifiquement généré. Nous avons ainsi caractérisé des cibles et des réseaux moléculaires modulés par la famille miR-132/212 dans ce modèle. Pris ensemble, ces résultats suggèrent que i) Le réseau de la famille miR-132/212, dont Sirt1 et probablement d'autres gènes cibles, participe à la production du peptide Aβ et la formation de plaques amyloïdes dans la MA ; ii) Même si le miR-132 peut potentiellement cibler un grand nombre de gènes simultanément, son ciblage est sélectif et spécifique au contexte cellulaire étudié. Enfin, les résultats obtenus mettent en évidence un ensemble de nouvelles cibles et de voies de signalisation régulées par la famille miR-132/212. En conclusion, ces travaux contribuent à l'avancement des connaissances du rôle physiologique et pathologique de la famille miR-132/212 dans le cerveau.
Alzheimer's disease (AD) is the most common form of dementia in the world. At the microscopic level, two main pathological features characterize the brain of AD patients: amyloid plaques, consisting of aggregates of the Aβ (Amyloid Beta) peptide, and neurofibrillary tangles, formed by aggregates of abnormally hyperphosphorylated Tau protein. Endogenous factors that may be involved in the progression of AD include microRNAs (miRs). MiRs are small non-coding RNAs that regulate the expression of target genes at the post-transcriptional level. In particular, the miR-132/212 family is strongly downregulated in the brain of AD patients. Previous studies have shown that in the 3xTg-AD mouse model of AD, the genetic deletion of the miR-132/212 family leads to an increase in phosphorylation and aggregation of Tau protein, two mechanisms leading to the formation of neurofibrillary tangles. Apart from its role in AD, the miR-132/212 family is also involved in several neurological disorders. In particular, its level of expression is deregulated in other neurodegenerative pathologies, such as frontotemporal dementia and Parkinson's disease. It is therefore possible that the miR-132/212 family contributes to the neurodegenerative process of these pathologies. In this context, the work presented aims to study the role of the miR-132/212 family in AD and, more generally, in the brain. First of all, since the miR-132/212 family already has a known role in the formation of neurofibrillary tangles, we wanted to evaluate its involvement in the formation of the other major pathological feature of AD: the amyloid plaques. We have demonstrated that the genetic deletion of the miR-132/212 family promotes Aβ production and amyloid plaque formation in the 3xTg-AD mice. Using RNA-Seq and bioinformatics, we identified genes of the miR-132/212 network with documented roles in the regulation of Aβ metabolism, including Tau, mapk, and sirt1. Consistent with these findings, we show that the modulation of miR-132, or its target sirt1, can directly regulate Aβ production in cells. Finally, we have shown that miR-132/212 levels correlate with the amount of amyloid plaques in humans. Then, in order to elucidate the role of the miR-132/212 family in the brain, we focused on identifying targets regulated by the miR-132/212 family. In a first step, this analysis was conducted in several in vitro cell models, in which the role of miR-132, one of two components of the family, was specifically studied. In this context, we have demonstrated that the targets regulated by miR-132 are few and specific to the cell type considered. In a second step, the target identification analysis was conducted in a conditional knockout mouse model for the miR-132/212 family that we specifically generated. We have therefore characterized the molecular targets and networks modulated by the miR-132/212 family in this model. Taken together, these results suggest that i) miR-132/212 network, including Sirt1 and likely other target genes, contributes to abnormal Aβ metabolism and senile plaque deposition in AD; ii) Although miR-132 can potentially target a large number of genes simultaneously, its targeting is selective and specific to the cellular context studied. Finally, the results obtained highlight a set of new targets and signalling pathways regulated by the miR-132/212 family. In conclusion, this work contributes to the advancement of the knowledge of the physiological and pathological role of the miR-132/212 family in the brain.
This review highlights the importance and the complexity of tumour biology and microenvironment in the progression and therapy resistance of glioma. Specific gene mutations, the possible functions of ...several non-coding microRNAs and the intra-tumour and inter-tumour heterogeneity of cell types contribute to limit the efficacy of the actual therapeutic options. In this scenario, identification of molecular biomarkers of response and the use of multimodal in vivo imaging and in particular the Positron Emission Tomography (PET) based molecular approach, can help identifying glioma features and the modifications occurring during therapy at a regional level. Indeed, a better understanding of tumor heterogeneity and the development of diagnostic procedures can favor the identification of a cluster of patients for personalized medicine in order to improve the survival and their quality of life.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The human epidermal growth factor receptor 2 (HER2) is normally associated with a highly aggressive and infiltrating phenotype in breast cancer lesions with propensity to spread into metastases. In ...clinic, the detection of HER2 in primary tumors and in their metastases is currently based on invasive methods. Recently, nuclear molecular imaging techniques, including positron emission tomography and single photon emission computed tomography (SPECT), allowed the detection of HER2 lesions in vivo. We have developed a 99mTc-radiolabeled nanosilica system, functionalized with a trastuzumab half-chain, able to act as drug carrier and SPECT radiotracer for the identification of HER2-positive breast cancer cells. To this aim, nanoparticles functionalized or not with trastuzumab half-chain, were radiolabeled using the 99mTc-tricarbonyl approach and evaluated in HER2 positive and negative breast cancer models. Cell uptake experiments, combined with flow cytometry and fluorescence imaging, suggested that active targeting provides higher efficiency and selectivity in tumor detection compared to passive diffusion, indicating that our radiolabeling strategy did not affect the nanoconjugate binding efficiency. Ex vivo biodistribution of 99mTc-nanosilica in a SK-BR-3 (HER2+) tumor xenograft at 4 h postinjection was higher in targeted compared to nontargeted nanosilica, confirming the in vitro data. In addition, viability and toxicity tests provided evidence on nanoparticle safety in cell cultures. Our results encourage further assessment of silica 99mTc-nanoconjugates to validate a safe and versatile nanoreporter system for both diagnosis and treatment of aggressive breast cancer.
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