Biology subjects

Saito, T.

Publications and source records attributed to Saito, T..

107 records · Page 6Linked to original sources

bioRxiv2020

Increasing glucose uptake into neurons antagonizes brain aging and promotes health and life span under dietary restriction in Drosophila

Brain neurons play a central role in organismal aging, but there is conflicting evidence about the roles of neuronal glucose availability, glucose uptake and metabolism in aging and extended lifespan. Here, we analyzed metabolic changes in the brain neurons of Drosophila during aging. Using a genetically-encoded fluorescent ATP biosensor, we found decreased ATP concentration in the neuronal somata of aged flies, which was correlated with decreased glucose content, expression of glucose transporter and glycolytic enzymes and mitochondrial quality. The age-associated reduction in ATP concentration did not occur in brain neurons with suppressed glycolysis or enhanced glucose uptake, suggesting these pathways contribute to reductions in ATP. Despite age-associated mitochondrial damage, increasing glucose uptake maintained ATP levels, suppressed age-dependent locomotor deficits and extended the life span. Increasing neuronal glucose uptake during dietary restriction resulted in the longest lifespans, suggesting an additive effect of enhancing glucose availability during a bioenergetic challenge on aging.

neuroscience↗

bioRxiv2020

MARK4 with an Alzheimer's disease-related mutation promotes tau hyperphosphorylation directly and indirectly and exacerbates neurodegeneration

Accumulation of the microtubule-associated protein tau is associated with Alzheimers disease (AD). In AD brain, tau is abnormally phosphorylated at many sites, and phosphorylation at Ser262 and Ser356 play critical roles in tau accumulation and toxicity. Microtubule-affinity regulating kinase 4 (MARK4) phosphorylates tau at those sites, and a double de novo mutation in the linker region of MARK4, {Delta}G316E317InsD, is associated with an elevated risk of AD. However, it remains unclear how this mutation affects phosphorylation, aggregation, and accumulation of tau and tau-induced neurodegeneration. Here, we report that MARK4{Delta}G316E317D increases the abundance of highly phosphorylated, insoluble tau species and exacerbates neurodegeneration via Ser262/356-dependent and -independent mechanisms. Using transgenic Drosophila expressing human MARK4 (MARK4wt) or a mutant version of MARK4 (MARK4{Delta}G316E317D), we found that co-expression of MARK4wt and MARK4{Delta}G316E317D increased total tau levels and enhanced tau-induced neurodegeneration, and that MARK4{Delta}G316E317D had more potent effects than MARK4wt. Interestingly, the in vitro kinase activities of MARK4wt and MARK4{Delta}G316E317D were similar. Blocking tau phosphorylation at Ser262 and Ser356 by alanine substitutions protected tau from the effects of MARK4wt, but not from MARK4{Delta}G316E317D. While both MARK4wt and MARK4{Delta}G316E317D increased the levels of oligomeric forms of tau, MARK4{Delta}G316E317D further boosted the levels of tau phosphorylated at several sites other than Ser262/356 and increased the detergent insolubility of tau in vivo. Together, these findings suggest that MARK4{Delta}G316E317D increases tau levels and exacerbates tau toxicity via an additional gain-of-function mechanism, and that modification in this region of MARK4 may impact disease pathogenesis.

neuroscience↗

bioRxiv2020

Somatostatin receptor subtypes 1 and 4 redundantly regulate neprilysin, the major amyloid beta-degrading enzyme, in brain

Alzheimers disease (AD) brains are characterized by increased levels of the pathogenic amyloid beta (A{beta}) peptide, which accumulates into extracellular plaques. Finding a way to lower A{beta} levels is fundamental for the prevention and treatment of AD. Neprilysin is the major A{beta} degrading enzyme which is regulated by the neuropeptide somatostatin. Here we used a combination of in vitro and in vivo approaches to identify the subtype specificity of the five somatostatin receptors (SSTs) expressed in the brain, involved in the regulation of neprilysin. Using a battery of Sst double knockout (dKO) mice we show that neprilysin is regulated by SST1 and SST4 in a redundant manner. Sst1 and Sst4 dKO mice exhibit a specific decrease of presynaptic neprilysin in the Lacunosum molecular layer. Moreover, a genetic deficiency of Sst1 and Sst4 in amyloid beta precursor protein (App) knock-in mice, an AD mouse model, aggravates the A{beta} pathology in the hippocampus. As a first proof of concept towards an A{beta}-lowering strategy involving neprilysin, we demonstrate that treatment with an agonist selective for SST1 and SST4 ameliorates the A{beta} pathology and improves cognition in the App knock-in AD mouse model.

neuroscience↗

bioRxiv2020

Promoter activity-based case-control association study on SLC6A4 highlighting hypermethylation and altered amygdala volume in male patients with schizophrenia

Associations between altered DNA methylation of the serotonin transporter (5-HTT)-encoding gene SLC6A4 and early life adversity, mood and anxiety disorders, and amygdala reactivity have been reported. However, few studies have examined epigenetic alterations of SLC6A4 in schizophrenia (SZ). We examined CpG sites of SLC6A4, whose DNA methylation levels have been reported to be altered in bipolar disorder, using three independent cohorts of patients with SZ and age-matched controls. We found significant hypermethylation of a CpG site in SLC6A4 in male patients with SZ in all three cohorts. We showed that chronic administration of risperidone did not affect the DNA methylation status at this CpG site using common marmosets, and that in vitro DNA methylation at this CpG site diminished the promoter activity of SLC6A4. We then genotyped the 5-HTT-linked polymorphic region (5-HTTLPR) and investigated the relationship among 5-HTTLPR, DNA methylation, and amygdala volume using brain imaging data. We found that patients harboring low-activity 5-HTTLPR alleles showed hypermethylation and they showed a negative correlation between DNA methylation levels and left amygdala volumes. These results suggest that hypermethylation of the CpG site in SLC6A4 is involved in the pathophysiology of SZ, especially in male patients harboring low-activity 5-HTTLPR alleles.

genetics↗

bioRxiv2020

Induction of Alzheimer's disease pathology by early-life stress

BackgroundAlzheimers disease (AD), a progressive neurodegenerative disorder, is a serious social problem. Recently, several early-life factors have been associated with an increased risk of a clinical diagnosis of AD. MethodsWe investigated the involvement of early-life stress in AD pathogenesis using heterozygous the amyloid precursor protein (APP) mutant mice (AppNL-G-F/wt) and wild-type (Appwt/wt) mice. Maternal separation was used as an animal paradigm for early-life stress. Object location and fear conditioning tests were performed to measure cognitive functions, in addition to biochemical tests. Immunohistochemical analyses were performed after the behavioral tests. ResultsWe found that maternal-separated Appwt/wt mice showed narrowing of vessels and decreased pericyte coverage of capillaries in prefrontal cortex, while maternal-separated AppNL-G-F/wt mice additionally showed impairment of cognitive function, and earlier formation of A{beta} plaques and disruption of the blood-brain barrier. Severe activation of microglia was detected in the maternal-separated AppNL-G-F/wt mice and maternal-separated Appwt/wt mice. At the early stage, morphological changes and inflammatory responses were observed in the microglia of the maternal-separated AppNL-G-F/wt mice and maternal-separated Appwt/wt mice, as well as morphological changes in the microglia of the non-maternal-separated AppNL-G-F/wt mice. ConclusionsMicroglia activation induced by maternal separation in combination with the APP mutation may impairs the vascular system, leading to AD progression. These findings therefore suggest that maternal separation causes early induction of AD pathology via angiopathy.

neuroscience↗

bioRxiv2020

Degradation modeling of water environmental DNA: Experiments on multiple DNA sources in pond and seawater

Environmental DNA (eDNA) methods have been developed to detect organism distribution and abundance/biomass in various environments. eDNA degradation is critical for eDNA evaluation. However, the dynamics and mechanisms of eDNA degradation are largely unknown, especially when considering different eDNA sources, e.g., cells and fragmental DNA. We experimentally evaluated the degradation rates of eDNA derived from multiple sources, including fragmental DNA, free cells, and inhabiting species. We conducted the experiment with pond and seawater to evaluate the differences between freshwater and marine habitats. We quantified the eDNA copies of free cells, fragmental DNA, and inhabiting species (Cyprinus carpio in the pond and Trachurus japonicus in the sea). Our results show that eDNA derived from both cells and fragmental DNA decreased exponentially in both the sea and pond samples. The degradation of eDNA from inhabiting species showed similar behavior to the cell-derived eDNA. We evaluated three degradation models with different assumptions and degradation steps and found that a simple exponential model is effective in most cases. Our findings on cell- and fragmental DNA-derived eDNA provide fundamental information about the eDNA degradation process and can be applied to elucidate eDNA behavior in natural environments.

ecology↗

bioRxiv2019

Fibrillar Aβ triggers microglial proteome alterations and dysfunction in Alzheimer mouse models

Microglial dysfunction is a key pathological feature of Alzheime[r]s disease (AD), but little is known about proteome-wide changes in microglia during the course of AD pathogenesis and their functional consequences. Here, we performed an in-depth and time-resolved proteomic characterization of microglia in two mouse models of amyloid {beta} (A{beta}) pathology, the overexpression APPPS1 and the knock-in APP-NL-G-F (APP-KI) model. We identified a large panel of Microglial A{beta} Response Proteins (MARPs) that reflect a heterogeneity of microglial alterations during early, middle and advanced stages of A{beta} deposition. Although both mouse models display severe microglial alterations at late stages of amyloid pathology, MARP signatures occur earlier in the APPPS1 mice. Strikingly, the kinetic differences in proteomic profiles correlated with the presence of fibrillar A{beta}, rather than dystrophic neurites, suggesting that fibrillar A{beta} aggregates are the main drivers of the AD-associated microglial phenotype and the observed functional decline. The identified microglial proteomic fingerprints of AD provide a valuable resource for functional studies of novel molecular targets and potential biomarkers for monitoring AD progression or therapeutic efficacy.

neuroscience↗

bioRxiv2019

Annexin A2 depletion exacerbates the intracerebral microhemorrhage induced by acute rickettsia and Ebola virus infections

Intracerebral microhemorrhages (CMHs) are small foci of hemorrhages in the cerebrum. Acute infections induced by some intracellular pathogens, including rickettsia, can result in CMHs. Annexin a2 (ANXA2) has been documented to play a functional role during intracellular bacterial adhesion. Here we report that ANXA2-knockout (KO) mice are more susceptible to CMHs in response to rickettsia and Ebola virus infections, suggesting an essential role of ANXA2 in protecting vascular integrity during these intracellular pathogen infections. Proteomic analysis via mass spectrometry of whole brain lysates and brain-derived endosomes from ANXA2-KO and wild-type (WT) mice post-infection with R. australis revealed that a variety of significant proteins were differentially expressed, and the follow-up function enrichment analysis had identified several relevant cell-cell junction functions. Immunohistology study confirmed that both infected WT and infected ANXA2-KO mice were subjected to adherens junctional protein (VE-cadherin) damages. However, key blood-brain barrier (BBB) components, tight junctional proteins ZO-1 and occludin, were disorganized in the brains from R. australis-infected ANXA2-KO mice, but not those of infected WT mice. Similar ANXA2-KO dependent CMHs and fragments of ZO-1 and occludin were also observed in Ebola virus-infected ANXA2-KO mice, but not found in infected WT mice. Overall, our study revealed a novel role of ANXA2 in the formation of CMHs during R. australis and Ebola virus infections; and the underlying mechanism is relevant to the role of ANXA2-regulated tight junctions and its role in stabilizing the BBB in these deadly infections. Author SummaryTraditionally, spontaneous intracerebral microhemorrhages (CMHs) were defined as small foci of intracerebral hemorrhages. Such atraumatic CMHs are due to the rupture of a weak blood vessel wall. Infections complicating cerebrovascular accidents have been extensively investigated. However, the role of CMHs complicating infections, in particularly acute systemic infections, has been poorly explored. Population-based retrospective cohort studies suggest there are potentially more undiscovered cases of CMHs accompanying acute systemic infections. Given both the lack of an animal model and cellular/molecular pathophysiology of CMHs following acute systemic infections, there is an urgent need to increase our comprehensive understanding of acute infection-induced CMHs. Overall, our study revealed a novel role of annexin a2 (ANXA2) in the formation of CMHs during R. australis and Ebola virus infections; and the underlying mechanism is relevant to the role of ANXA2-regulated endothelial tight junctions and its role in stabilizing the blood-brain barrier in these deadly infections.

pathology↗

bioRxiv2019

Disrupted remapping of place cells and grid cells in knock-in model of Alzheimer’s disease

Patients with Alzheimers disease (AD) frequently suffer from spatial memory impairment and wandering behavior, but brain circuits causing such symptoms remain largely unclear. In healthy brains, spatially-tuned hippocampal place cells and entorhinal grid cells represent distinct spike patterns in different environments, a circuit function called "remapping" that underlies pattern separation of spatial memory. We investigated whether knock-in expression of mutated amyloid precursor protein deteriorates the remapping of place cells and grid cells. We found that the remapping of CA1 place cells was disrupted although their spatial tuning was only mildly diminished. Grid cells in the medial entorhinal cortex (MEC) were impaired, sending severely disrupted remapping signals to the hippocampus. Furthermore, fast gamma oscillations were disrupted in both CA1 and MEC, resulting in impaired fast gamma coupling in the MEC[->]CA1 circuit. These results point to the link between grid cell impairment and remapping disruption as a circuit mechanism causing spatial memory impairment in AD.

pathology↗

bioRxiv2019

Epigenetics biomarkers of delirium: immune response, inflammatory response and cholinergic synaptic involvement evidenced by genome-wide DNA methylation analysis of delirious inpatients

BackgroundThe authors previously hypothesized the role of epigenetics in pathophysiology of delirium, and tested DNA methylation (DNAm) change among pro-inflammatory cytokines along with aging in blood, glia and neuron. The authors reported that DNAm level of the TNF-alpha decreases along with aging in blood and glia, but not in neuron; however, DNAm differences between delirium cases and non-delirium controls have not been investigated directly. Therefore, in the present study, DNAm differences in blood between delirium patients and controls without delirium were examined.\n\nMethodsA case-control study with 92 subjects was conducted. Whole blood samples were collected and genome-wide DNAm was measured by the Infinium HumanMethylationEPIC BeadChip arrays. The correlation between DNAm levels in the TNF-alpha and age, network analysis, and the correlation between age and DNAm age were tested.\n\nResultsOnly delirium cases showed 3 CpGs sites in the TNF-alpha significantly correlated to age after multiple corrections. A genome-wide significant CpG site near the gene of LDLRAD4 was identified. In addition, network analysis showed several significant pathways with false discovery rate adjusted p-value < 0.05. The top pathway with GO was immune response, and the second top pathway with KEGG was cholinergic synapse. Although there was no statistically significant difference, DNAm age among non-delirium controls showed \"slower aging\" compared to delirium cases.\n\nConclusionsDNAm differences were shown both at gene and network levels between delirium cases and non-delirium controls. This finding indicates that DNAm status in blood has a potential to be used as epigenetic biomarkers for delirium.

neuroscience↗

bioRxiv2019

DNA methylation change in neurotrophic genes with aging and delirium evidenced from three independent cohorts

INTRODUCTIONWe previously reported the association between DNA methylation (DNAm) of pro-inflammatory cytokine genes and aging. Neurotrophic factors are also known to be associated with aging and neurocognitive disorders. Thus, we hypothesized that DNAm of neurotrophic genes change with aging, especially in delirium patients.\n\nMETHODSDNAm were analyzed using HumanMethylationEPIC BeadChip Kit in 3 independent cohorts; blood from 383 Grady Trauma Project subjects, brain from 21 neurosurgery patients, and blood from 87 inpatients with and without delirium.\n\nRESULTSBoth blood and brain samples showed that most of the DNAm of neurotrophic genes were positively correlated with aging. Furthermore, DNAm of neurotrophic genes were positively correlated with aging in delirium cases than in non-delirium controls.\n\nDISCUSSIONThese findings support our hypothesis that the neurotrophic genes may be epigenetically modulated with aging, and this process may be contributing to the pathophysiology of delirium.

neuroscience↗

bioRxiv2019

Developmental Characterization of Zswim5 Expression in the Progenitor Domains and Tangential Migration Pathways of Cortical Interneurons in the Mouse Forebrain

GABAergic interneurons play an essential role in modulating cortical networks. The progenitor domains of cortical interneurons are localized in developing ventral forebrain, including the medial ganglionic eminence (MGE), caudal ganglionic eminence (CGE), preoptic area (POA) and preoptic hypothalamic border domain (POH). Here, we characterized the expression pattern of Zswim5, an MGE-enriched gene in the mouse forebrain. At E11.5 to E13.5, prominent Zswim5 expression was detected in the subventricular zone (SVZ) of MGE, CGE, POA and POH of ventral telencephalon in which progenitors of cortical interneurons resided. At E15.5 and E17.5, Zswim5 remained detectable in the SVZ of pallidal primordium (MGE). Zswim5 mRNA was markedly decreased after birth and was absent in the adult forebrain. Interestingly, Zswim5 expression pattern resembled the tangential migration pathways of cortical interneurons. Zswim5-positive cells in the MGE appeared to migrate from the MGE through the SVZ of LGE to overlying neocortex. Indeed, Zswim5 was co-localized with Nkx2.1 and Lhx6, markers of progenitos and migratory cortical interneurons. Double labeling showed that Mash1/Ascl1-positive cells did not express Zswim5. Zswim5 expressing cells showed none or at most low levels of Ki67 but co-expressed Tuj1 in the SVZ of MGE. These results suggest that Zswim5 is immediately upregulated as progenitors exiting cell cycle to become postmitotic. Given that recent studies have elucidated that the cell fate of cortical interneurons is determined shortly after postmitotic, the timing of Zswim5 expression in early postmitotic cortical interneurons suggests a potential role of Zswim5 in regulation of neurogenesis and tangential migration of cortical interneurons.

neuroscience↗

bioRxiv2019

Autophagy controls lipid droplet formation by fine-tuning NCoR1 levels

Lipid droplets (LDs) are dynamic organelles that store neutral lipids during times of energy excess, such as following a meal. LDs serve as an energy reservoir during fasting and have a buffering capacity that prevents lipotoxicity. Autophagy and the autophagic machinery have been proposed to play a role in LD biogenesis but the underlying molecular mechanism remains unclear. Here, we show that when nuclear receptor co-repressor 1 (NCoR1), which inhibits the transactivation of nuclear receptors, accumulates due to autophagy suppression, LD biogenesis is blocked. Ablation of ATG7, a gene essential for autophagy, suppressed the expression of gene targets of liver X receptor (LXR), a nuclear receptor responsible for fatty acid and triglyceride synthesis in an NCoR1-dependent manner. LD biogenesis in response to fasting and after hepatectomy was hampered by the suppression of autophagy. These results indicate that autophagy controls physiological hepatosteatosis by fine-tuning NCoR1 protein levels.

cell biology↗

bioRxiv2019

Spontaneous activity generated within the olfactory bulb establishes the discrete wiring of mitral cell dendrites

In developing brains, activity-dependent remodeling facilitates the formation of precise neuronal connectivity. Synaptic competition is known to facilitate synapse elimination; however, it has remained unknown how different synapses compete to each other within a postsynaptic cell. Here we investigate how a mitral cell in the olfactory bulb prunes all but one primary dendrite during the developmental remodeling process. We find that spontaneous activity generated within the olfactory bulb is essential. We show that strong glutamatergic inputs to one dendrite trigger branch-specific changes in RhoA activity to facilitate the pruning of the remaining dendrites: NMDAR-dependent local signals suppress RhoA to protect it from pruning; however, the subsequent neuronal depolarization induces neuron-wide activation of RhoA to prune non-protected dendrites. NMDAR-RhoA signals are also essential for the synaptic competition in the barrel cortex. Our results demonstrate a general principle whereby activity-dependent lateral inhibition across synapses establishes a discrete receptive field of a neuron.

neuroscience↗

bioRxiv2019

Cell type-specific genetic regulation of expression in the granule cell layer of the human dentate gyrus

Laser capture microdissection followed by RNA-seq (LCM-seq) was used to profile the transcriptional landscape of the granule cell layer of the dentate gyrus (DG-GCL) in human hippocampus, and contrasted to homogenate tissue. We identified widespread cell type-specific aging and genetic effects in the DG-GCL that were either missing or directionally discordant in corresponding bulk hippocampus RNA-seq data from largely the same subjects. Of the [~]9 million eQTLs in the DG-GCL, 15% were not in bulk hippocampus, including 15 schizophrenia genome-wide association study (GWAS) risk variants. We then created custom transcriptome-wide association study (TWAS) genetic weights from the DG-GCL which identified many novel schizophrenia-associated genetic signals not found in TWAS from bulk hippocampus, including GRM3 and CACNA1C. These results highlight the biological resolution of cell type-specific expression profiling using targeted sampling strategies like LCM, and complement homogenate and single nuclei approaches in human brain.

neuroscience↗

bioRxiv2018

Insoluble Aβ overexpression in an App knock-in mouse model alters microstructure and gamma oscillations in the prefrontal cortex, and social and anxiety-related behaviours

We studied two new App knock-in mice models of Alzheimers disease (AppNL-F and AppNL-G-F), which generate elevated levels of A{beta}40 and A{beta}42 without the confounds associated with APP overexpression. This enabled us to assess changes in anxiety-related and social behaviours, and neural alterations potentially underlying such changes, driven specifically by A{beta} accumulation. AppNL-G-F knock-in mice exhibited subtle deficits in tasks assessing social memory, but not in social motivation tasks. In anxiety-assessing tasks, AppNL-G-F knock-in mice exhibited: 1) increased thigmotaxis in the Open Field (OF), yet; 2) reduced closed-arm, and increased open-arm, time in the Elevated Plus Maze (EPM). Their ostensibly-anxiogenic OF profile, yet ostensibly-anxiolytic EPM profile, could hint at altered cortical mechanisms affecting decision-making (e.g. disinhibition), rather than simple core deficits in emotional motivation. Consistent with this possibility, alterations in microstructure, glutamatergic-dependent gamma oscillations, and glutamatergic gene expression were all observed in the prefrontal cortex, but not the amygdala, of AppNL-G-F knock-in mice. Thus, insoluble A{beta} overexpression drives prefrontal cortical alterations, potentially underlying changes in social and anxiety-related behavioural tasks.\n\nHighlightsO_LIAppNL-G-F KI mice displayed differing anxiety behaviours in two tests of anxiety.\nC_LIO_LIPrefrontal gamma was no longer NMDA-receptor dependent in AppNL-G-F KI mice.\nC_LIO_LIPrefrontal expression of Grin2b was reduced in AppNL-G-F KI mice.\nC_LIO_LIDTI found structural alterations in the hippocampus and prefrontal cortex in AppNL-G-F KI mice.\nC_LI

neuroscience↗

bioRxiv2017

A variant of the Morris water task for assessing learning and memory processes in mice

The Morris water task (MWT) is commonly used to assess rodent spatial learning and memory. Our goal was to develop a 3-phase variant of the hidden goal water task to assess old and new spatial memories acquired in the same context using various measures of spatial learning in C57BL/6 mice. In the first phase, mice were pre-trained to an initially hidden location. The second phase consisted of a massed training session to a new location in the same apparatus and context. The final phase consisted of a competition test between the original and new platform locations. AppNL-G-F/NL-G-F mice, a novel transgenic mouse model for Alzheimers disease (AD), were also used as an independent variable to validate this 3-phase variant of MWT. The results of the present study showed that C57 mice acquired and retained both the old and new location representations; however, AppNL-G-F/NL-G-F mice retained a recently acquired spatial memory but did not remember the old location acquired in the same apparatus and context. The results showed that C57 mice can show precise place learning and memory with the right amount of training and acquire and retain multiple spatial memory locations in the same environment whereas this ability was impaired in AppNL-G-F/NL-G-F mice. In the visible platform test, however, all groups of mice showed normal sensorimotor ability and motivation. These findings indicate that this new version of the MWT provides a robust way for assessment of old and new memories in mice. This paradigm could also be exploited to assess manipulations of neural circuits implicated in learning and memory processes as well as for research investigating human brain diseases.

neuroscience↗