Tau hyperphosphorylation is one hallmark of Alzheimer's disease (AD) pathology. Pharmaceutical companies have thus developed kinase inhibitors aiming to reduce tau hyperphosphorylation. One obstacle ...in screening for tau kinase inhibitors is the low phosphorylation levels of AD-related phospho-epitopes in normal adult mice and cultured cells. We have shown that hypothermia induces tau hyperphosphorylation in vitro and in vivo. Here, we hypothesized that hypothermia could be used to assess tau kinase inhibitors efficacy. Hypothermia applied to models of biological gradual complexity such as neuronal-like cells, ex vivo brain slices and adult non-transgenic mice leads to tau hyperphosphorylation at multiple AD-related phospho-epitopes. We show that Glycogen Synthase Kinase-3 inhibitors LiCl and AR-A014418, as well as roscovitine, a cyclin-dependent kinase 5 inhibitor, decrease hypothermia-induced tau hyperphosphorylation, leading to different tau phosphorylation profiles. Therefore, we propose hypothermia-induced hyperphosphorylation as a reliable, fast, convenient and inexpensive tool to screen for tau kinase inhibitors.
Evidence from clinical trials as well as from studies performed in animal models suggest that both amyloid and tau pathologies function in concert with other factors to cause the severe ...neurodegeneration and dementia in Alzheimer’s disease (AD) patients. Accumulating data in the literature suggest that microRNAs (miRNAs) could be such factors. These conserved, small nonprotein-coding RNAs are essential for neuronal function and survival and have been implicated in the regulation of key genes involved in genetic and sporadic AD. The study of miRNA changes in AD mouse models provides an appealing approach to address the cause-consequence relationship between miRNA dysfunction and AD pathology in humans. Mouse models also provide attractive tools to validate miRNA targets in vivo and provide unique platforms to study the role of specific miRNA-dependent gene pathways in disease. Finally, mouse models may be exploited for miRNA diagnostics in the fight against AD.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
The miR-15/107 group of microRNA (miRNA) gene is increasingly appreciated to serve key functions in humans. These miRNAs regulate gene expression involved in cell division, metabolism, stress ...response, and angiogenesis in vertebrate species. The miR-15/107 group has also been implicated in human cancers, cardiovascular disease and neurodegenerative disease, including Alzheimer's disease. Here we provide an overview of the following: (1) the evolution of miR-15/107 group member genes; (2) the expression levels of miRNAs in mammalian tissues; (3) evidence for overlapping gene-regulatory functions by different miRNAs; (4) the normal biochemical pathways regulated by miR-15/107 group miRNAs; and (5) the roles played by these miRNAs in human diseases. Membership in this group is defined based on sequence similarity near the mature miRNAs' 5′ end: all include the sequence AGCAGC. Phylogeny of this group of miRNAs is incomplete; thus, a definitive taxonomic classification (e.g., designation as a “superfamily”) is currently not possible. While all vertebrates studied to date express miR-15a, miR-15b, miR-16, miR-103, and miR-107, mammals alone are known to express miR-195, miR-424, miR-497, miR-503, and miR-646. Multiple different miRNAs in the miR-15/107 group are expressed at moderate to high levels in human tissues. We present data on the expression of all known miR-15/107 group members in human cerebral cortical gray matter and white matter using new miRNA profiling microarrays. There is extensive overlap in the mRNAs targeted by miR-15/107 group members. We show new data from cultured H4 cancer cells that demonstrate similarities in mRNAs targeted by miR-16 and miR-103 and also support the importance of the mature miRNAs' 5′ seed region in mRNA target recognition. In conclusion, the miR-15/107 group of miRNA genes is a fascinating topic of study for evolutionary biologists, miRNA biochemists, and clinically oriented translational researchers alike.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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.
Synaptic loss is an early pathological event in Alzheimer’s disease (AD), but its underlying molecular mechanisms remain largely unknown. Recently, microRNAs (miRNAs) have emerged as important ...modulators of synaptic function and memory.
We used miRNA array and quantitative polymerase chain reaction to examine the alteration of miRNAs in AD mice and patients as well as the Morris water maze to evaluate learning and memory in the mice. We also used adeno-associated virus or lentivirus to introduce tyrosine-protein phosphatase non-receptor type 1 (PTPN1) expression of silencing RNAs. Long-term potentiation and Golgi staining were used to evaluate the synaptic function and structure. We designed a peptide to interrupt miR-124/PTPN1 interaction.
Here we report that neuronal miR-124 is dramatically increased in the hippocampus of Tg2576 mice, a recognized AD mouse model. Similar changes were observed in specific brain regions of affected AD individuals. We further identified PTPN1 as a direct target of miR-124. Overexpression of miR-124 or knockdown of PTPN1 recapitulated AD-like phenotypes in mice, including deficits in synaptic transmission and plasticity as well as memory by impairing the glutamate receptor 2 membrane insertion. Most importantly, rebuilding the miR-124/PTPN1 pathway by suppression of miR-124, overexpression of PTPN1, or application of a peptide that disrupts the miR-124/PTPN1 interaction could restore synaptic failure and memory deficits.
Taken together, these results identified the miR-124/PTPN1 pathway as a critical mediator of synaptic dysfunction and memory loss in AD, and the miR-124/PTPN1 pathway could be considered as a promising novel therapeutic target for AD patients.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In preclinical research on Alzheimer's disease and related tauopathies, tau phosphorylation analysis is routinely employed in both cellular and animal models. However, recognizing the sensitivity of ...tau phosphorylation to various extrinsic factors, notably temperature, is vital for experimental accuracy. Hypothermia can trigger tau hyperphosphorylation, while hyperthermia leads to its dephosphorylation. Nevertheless, the rapidity of tau phosphorylation in response to unintentional temperature variations remains unknown. In cell cultures, the most significant temperature change occurs when the cells are removed from the incubator before harvesting, and in animal models, during anesthesia prior to euthanasia. In this study, we investigate the kinetics of tau phosphorylation in N2a and SH-SY5Y neuronal cell lines, as well as in mice exposed to anesthesia. We observed changes in tau phosphorylation within the few seconds upon transferring cell cultures from their 37°C incubator to room temperature conditions. However, cells placed directly on ice post-incubation exhibited negligible phosphorylation changes. In vivo, isoflurane anesthesia rapidly resulted in tau hyperphosphorylation within the few seconds needed to lose the pedal withdrawal reflex in mice. These findings emphasize the critical importance of preventing temperature variation in researches focused on tau. To ensure accurate results, we recommend avoiding anesthesia before euthanasia and promptly placing cells on ice after removal from the incubator. By controlling temperature fluctuations, the reliability and validity of tau phosphorylation studies can be significantly enhanced.
Aβ-related cerebral amyloid angiopathy (CAA) is a major cause of primary non-traumatic brain hemorrhage. In families with an early onset of the disease, CAA can be due to amyloid precursor protein ...(APP) pathogenic variants or duplications. APP duplications lead to a ~1.5-fold increased APP expression, resulting in Aβ overproduction and deposition in the walls of leptomeningeal vessels. We hypothesized that rare variants in the 3'untranslated region (UTR) of APP might lead to APP overexpression in patients with CAA and no APP pathogenic variant or duplication. We performed direct sequencing of the whole APP 3'UTR in 90 patients with CAA and explored the functional consequences of one previously unreported variant. We identified three sequence variants in four patients, of which a two-base pair deletion (c.*331_*332del) was previously unannotated and absent from 175 controls of same ethnicity. This latter variant was associated with increased APP expression in vivo and in vitro. Bioinformatics and functional assays showed that the APP c.*331_*332del variant affected APP messenger RNA (mRNA) structure and binding of two microRNAs (miR-582-3p and miR-892b), providing a mechanism for the observed effects on APP expression. These results identify APP 3'UTR sequence variants as genetic determinants of Aβ-CAA.
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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 midbrain dopamine (DA) cell death underlying Parkinson's disease (PD) is associated with upregulation of pre‐enkephalin (pENK) in striatopallidal neurons. Our previous results obtained with ...1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) parkinsonian monkeys suggest that increased striatal expression of pENK mRNA is a compensatory mechanism to alleviate PD‐related motor symptoms. In this study, we tested the hypothesis that increased pENK expression in the striatum protects against the neurotoxic insults of MPTP in mice. To this end, recombinant adeno‐associated virus serotype 2 also containing green fluorescent protein was used to overexpress pENK prior to DA depletion. Our results showed that overexpression of pENK in the striatum of MPTP mice induced: (i) increased levels of the opioid peptide enkephalin (ENK) in the striatum; (ii) higher densities of ENK‐positive fibers in both the globus pallidus (GP) and the substantia nigra; (iii) higher locomotor activity; and (iv) a higher density of striatal tyrosine hydroxylase‐positive fibers in the striatum. In addition, striatal overexpression of pENK in MPTP ‐treated mice led to 52 and 43% higher DA concentrations and DA turnover, respectively, in the GP compared to sham‐treated MPTP mice. These observations are in agreement with the idea that increased expression of pENK at an early stage of disease can improve PD symptoms.
We provide evidence that in MPTP mouse model of Parkinson's disease, viral vector‐mediated striatal overexpression of pENK before dopamine depletion reduced degeneration of nigrostriatal dopaminergic terminals, and increased dopamine concentration and dopamine turnover in the globus pallidus. Therefore, increased expression of ENK in the basal ganglia could have protective effects against MPTP insult.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract Gene dosage effects of Amyloid precursor protein ( APP ) can cause familial AD. Recent evidence suggest that microRNA (miRNA) pathways, implicated in gene transcriptional control, could be ...involved in the development of sporadic Alzheimer's disease (AD). We therefore investigated whether miRNAs could participate in the regulation of APP gene expression. We show that miRNAs belonging to the miR-20a family (that is, miR-20a, miR-17-5p and miR-106b) could regulate APP expression in vitro and at the endogenous level in neuronal cell lines. A tight correlation between these miRNAs and APP was found during brain development and in differentiating neurons. We thus identify miRNAs as novel endogenous regulators of APP expression, suggesting that variations in miRNA expression could contribute to changes in APP expression in the brain during development and disease. This possibility is further corroborated by the observation that a statistically significant decrease in miR-106b expression was found in sporadic AD patients.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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