Biology subjects

Saijo, K.

Publications and source records attributed to Saijo, K..

9 recordsLinked to original sources

bioRxiv2024

Tcf4 Deficiency Causes Recurrent Seizures in Mice

Transcription factor 4 (TCF4) is a transcription factor that is critical for the normal development and function of the central nervous system. Haploinsufficiency of TCF4 causes Pitt-Hopkins Syndrome (PTHS), a lifelong neurodevelopmental disorder characterized by seizures and intellectual disability. To expand our currently limited understanding of TCF4 function and PTHS pathophysiology, we created a mouse model of PTHS with largely astrocyte-specific heterozygous knockout of Tcf4. These mice developed severe recurrent seizures and had decreased lifespans. In addition, we found that these mice had astrogliosis as well as increased neuronal activity in the cortex, hippocampus, amygdala, and hypothalamus. Furthermore, single nucleus RNA sequencing analysis revealed global changes in the gene expression profiles of excitatory neurons, inhibitory neurons, astrocytes, and oligodendrocytes of PTHS compared to wild-type mice. Overall, this is the first report of a PTHS mouse model with seizures, providing the field with a tool to investigate the mechanisms of PTHS development and progression and develop therapeutics for PTHS and its associated epilepsy. HIGHLIGHTSO_LINovel PTHS mouse model that targets astrocytes develops epilepsy C_LIO_LIPTHS mice exhibit astrogliosis and increased neuron activity C_LIO_LIChanges in gene expression profile observed in PTHS mice across neurons and glial cells C_LI

neuroscience↗

bioRxiv2024

Role of copper during microglial inflammation

Copper plays crucial roles in various physiological functions of the nervous and immune systems. Dysregulation of copper homeostasis is linked to several diseases, including neurodegenerative diseases. Since dysfunctional microglial immunity can contribute to such diseases, we investigated the role of copper in microglial immunity. We found that both increased and decreased copper levels induced by chemical treatments suppresses lipopolysaccharide (LPS)-mediated inflammation in microglial cells, as determined by RT-qPCR analysis. RNA sequencing (RNA-seq) analysis confirmed that increased copper level reduces the inflammatory response to LPS; however, it also showed that decreased copper level affects genes involved in cell proliferation, transcription, and autophagosome regulation. These findings suggest that copper is vital for maintaining normal immune function in microglia, and both copper excess and deficiency can disrupt microglial immunity.

neuroscience↗

bioRxiv2023

Microglia Regulate Sleep via Calcium-Dependent Modulation of Norepinephrine Transmission

Sleep interacts reciprocally with immune system activity, but its specific relationship with microglia - the resident immune cells in the brain - remains poorly understood. Here we show that microglia can regulate sleep through a mechanism involving Gi-coupled GPCRs, intracellular Ca2+ signaling, and suppression of norepinephrine transmission. Chemogenetic activation of microglia Gi signaling strongly promoted sleep, whereas pharmacological blockade of Gi-coupled P2Y12 receptors decreased sleep. Two-photon imaging showed that P2Y12/Gi activation elevated microglia intracellular Ca2+, and blockade of this Ca2+ elevation largely abolished the Gi-induced sleep increase. Microglia Ca2+ level also increased at natural wake-to-sleep transitions, caused partly by reduced norepinephrine. Furthermore, imaging of norepinephrine activity with its biosensor showed that microglia P2Y12/Gi activation significantly reduced norepinephrine, partly by increasing the adenosine concentration. Thus, microglia can regulate sleep through reciprocal interactions with norepinephrine transmission.

neuroscience↗

bioRxiv2022

Coenzyme Q regulates UCP1 expression and thermogenesis through the integrated stress responses

Coenzyme Q (CoQ) is an essential component of mitochondrial respiration1 and required for thermogenic activity in brown adipose tissues2 (BAT). CoQ deficiency leads to a wide range of pathological manifestations3 but mechanistic consequences of CoQ deficiency in specific tissues such as BAT remain poorly understood. Here we show that pharmacological or genetic CoQ deficiency (50-75% reduction) in BAT leads to accumulation of cytosolic mitochondrial RNAs (mtRNAs) and activation of the eIF2 kinase PKR resulting in the induction of the integrated stress response (ISR) and suppression of UCP1 expression in an ATF4-dependent fashion. Surprisingly, despite diminished UCP1 levels, BAT CoQ deficiency increases whole-body metabolic rates at room temperature and thermoneutrality resulting in decreased weight gain on high fat diets (HFD). This mitohormesis like effect of BAT CoQ insufficiency is dependent on the ATF4-FGF21 axis in BAT revealing an unexpected role for CoQ in the modulation of whole-body energy expenditure with wide-ranging implications for primary and secondary CoQ deficiencies.

cell biology↗

bioRxiv2020

Mitohormesis reprograms macrophage metabolism to enforce tolerance

Macrophages generate mitochondrial reactive oxygen and electrophilic species (mtROS, mtRES) as antimicrobials during Toll-like receptor (TLR)-dependent inflammatory responses. Whether mitochondrial stress caused by these molecules impacts macrophage function is unknown. Here we demonstrate that both pharmacologically- and lipopolysaccharide (LPS)-driven mitochondrial stress in macrophages triggers a stress response called mitohormesis. LPS-driven mitohormetic stress adaptations occur as macrophages transition from an LPS-responsive to LPS-tolerant state where stimulus-induced proinflammatory gene transcription is impaired, suggesting tolerance is a product of mitohormesis. Indeed, like LPS, pharmacologically-triggered mitohormesis suppresses mitochondrial oxidative metabolism and acetyl-CoA production needed for histone acetylation and proinflammatory gene transcription, and is sufficient to enforce an LPS-tolerant state. Thus, mtROS and mtRES are TLR-dependent signaling molecules that trigger mitohormesis as a negative feedback mechanism to restrain inflammation via tolerance. Moreover, bypassing TLR signaling and pharmacologically triggering mitohormesis represents a novel anti-inflammatory strategy that co-opts this stress response to impair epigenetic support of proinflammatory gene transcription by mitochondria. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/347443v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@c5c03org.highwire.dtl.DTLVardef@16cd130org.highwire.dtl.DTLVardef@119b461org.highwire.dtl.DTLVardef@914ee4_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2020

Fetal innate immunity contributes to the induction of atypical behaviors in a mouse model of maternal immune activation

Maternal immune activation (MIA) increases likelihood of altered neurodevelopmental outcomes. Maternal cytokines are proposed to affect fetal brain development in mice; however, the contribution of fetal immunity to neurodevelopmental disorders is largely unexplored. Here, we show that MIA mediated by Toll-like receptor 3 (TLR3), but not other TLRs, induces a specific set of behavioral phenotypes including decreased sociability and increased restricted repetitive behavior in offspring. Accordingly, these behavioral phenotypes were absent when offspring were deficient for Trif, the downstream adapter molecule of TLR3. Using single-cell RNA sequencing, we identified clusters of border-associated macrophages that were significantly enriched in the fetal brain following TLR3-MIA, and these clusters were diminished in Trif-/- fetal brains.Moreover, we found that triggering TLR3-TRIF in offspring can occur through transplacental viral infection, resulting in altered behavioral phenotypes. Collectively, our data indicate that fetal innate immunity contributes to MIA-induced atypical behaviors in mice.

neuroscience↗

bioRxiv2020

Cytoskeletal tension forces mitohormesis

Mitochondria control eukaryotic cell fate by producing the energy needed to support life and the signals required to execute programmed cell death. The biochemical milieu is known to affect mitochondrial function and contribute to the dysfunctional mitochondrial phenotypes implicated in cancer and the morbidities of ageing. However, the physical characteristics of the extracellular matrix are also altered in cancer and in aging tissues. We demonstrate that cells sense the physical properties of the extracellular matrix and activate a mitochondrial stress response that adaptively tunes mitochondrial function via SLC9A1-dependent ion exchange and HSF1-dependent transcription. Overall, our data indicate that adhesion-mediated mechanosignaling may play an unappreciated role in the altered mitochondrial functions observed in aging and cancer. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=154 SRC="FIGDIR/small/979583v3_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1ecdaceorg.highwire.dtl.DTLVardef@1112c32org.highwire.dtl.DTLVardef@6c99a1org.highwire.dtl.DTLVardef@1da1e5f_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2019

Phf15, a novel transcriptional repressor regulating inflammation in mouse microglia

AimExcessive microglial inflammation has emerged as a key player in mediating the effects of aging and neurodegeneration on brain dysfunction. Thus, there is great interest in discovering transcriptional repressors that can control this process. We aimed to examine whether Phf15--one of the top differentially expressed genes in microglia during aging in humans--could regulate transcription of pro-inflammatory mediators in microglia. MethodsRT-qPCR was used to assess Phf15 mRNA expression in mouse brain during aging. Loss-of-function (shRNA-mediated knockdown (KD) and CRISPR/Cas9-mediated knockout (KO) of Phf15) and gain-of-function (retroviral overexpression (OE) of murine Phf15 cDNA) studies in a murine microglial cell line (SIM-A9) followed by immune activation with lipopolysaccharide (LPS) were used to determine the effect of Phf15 on pro-inflammatory factor (Tnf, Il-1{beta}, Nos2) mRNA expression. RNA-sequencing was used to determine global transcriptional changes after Phf15 knockout under basal conditions and after LPS stimulation. ResultsPhf15 expression increases in mouse brain during aging, similar to humans. KD, KO and OE studies determined that Phf15 represses mRNA expression levels of pro-inflammatory mediators such as Tnf, Il-1{beta} and Nos2. Global transcriptional changes after Phf15 KO showed that Phf15 specifically represses genes related to the antiviral (type I interferon) response and cytokine production in microglia. ConclusionWe provide the first evidence that Phf15 is an important transcriptional repressor of microglial inflammation, regulating the antiviral response and pro-inflammatory cytokine production. Importantly, Phf15 regulates both basal and signal-dependent activation and controls the magnitude and duration of the microglial inflammatory response.

neuroscience↗

bioRxiv2019

Defective cell death of distinct microglial subsets contributes to ADHD-like behavior in mice

Microglia are resident immune cells in the central nervous system that play essential roles to maintain homeostasis and neuronal function. Microglia are heterogeneous cells but the mechanisms by which they contribute to normal brain development remain unclear. Here,we show that microglia in the developing striatum and thalamus undergo pyroptosis,a type of lytic cell death that occurs as a result of Caspase-1 (CASP1) activation downstream of inflammasomes. We observe that pyroptosis occurs in a spatiotemporally regulated and Casp1-dependent manner during fetal brain development. Mice lacking Casp1 or the inflammasome regulating molecules, NLRP3, IL-1R, and Gasdermin D exhibit behavior changes characterized by hyperactivity, inattention, and impulsivity that are similar to attention-deficit/hyperactivity disorder (ADHD). Furthermore, re-expression of Casp1 in Cx3cr1+ cells including microglia restores normal behavior and cell death. We demonstrate that injection of an NLRP3 inhibitor into pregnant wild-type mice is sufficient to induce ADHD-like behaviors in offspring. These data suggest that microglial inflammasome activation and pyroptosis are essential for normal brain development and that genetic and pharmacological disruptions in this pathway may represent new ADHD risk factors.

neuroscience↗