萩原 英雄

Abstract Proper maturation of neuronal and glial cells in the hippocampus is essential for emotional regulation and cognitive function. While pseudo-immaturity, defined as arrested or reversed development, has been extensively implicated in various neuropsychiatric conditions, the opposite phenomenon, hyper-maturity, remains underexplored. Here, we present transcriptomic evidence of hippocampal hyper-maturity across 17 datasets from 16 mouse models with genetic, pharmacological, or other experimental manipulations, identified through a comprehensive screening of over 260,000 omics datasets. These models were characterized by a pronounced overrepresentation of gene expression changes typically observed during postnatal development and included serotonin transporter knockout mice, glucocorticoid receptor overexpressing mice, and corticosterone-treated mice, models of depression and anxiety, Df(16)A ^+/− mice, a 22q11.2 deletion schizophrenia model, β-glucuronidase-deficient lysosomal storage disorder model mice, and senescence-prone SAMP8 mice. Meta-analysis of enriched pathways highlighted associations of synapse-related genes with the hyper-maturity signature. Behavioral annotations from public datasets further suggest that hippocampal hyper-maturity models predominantly exhibit increased anxiety-like behaviors, whereas immaturity models tend to display the opposite pattern. Notably, hippocampal hyper-maturity encompassed two transcriptional dimensions: enhanced postnatal development and accelerated aging. For example, SAMP8 mice aligned more with developmental enhancement, whereas corticosterone-treated and lysosomal storage disorder models reflected aging acceleration. Combined analysis with available single-cell RNA-sequencing data further delineated that microglia and granule cells may contribute to aging-associated transcriptional shifts. These findings suggest that hippocampal hyper-maturity and accelerated aging represent convergent molecular phenotypes associated with anxiety-like behavior. Bidirectional alterations in hippocampal maturity may serve as a transdiagnostic endophenotype and offer novel therapeutic or anti-aging targets for neuropsychiatric disorders.

Hyponatremia is the most common clinical electrolyte disorder. Once thought to be asymptomatic in response to adaptation by the brain, recent evidence suggests that chronic hyponatremia (CHN) may induce neurological manifestations, including psychological symptoms. However, the specific psychological symptoms induced by CHN, the mechanisms underlying these symptoms, and their potential reversibility remain unclear. Therefore, this study aimed to determine whether monoaminergic neurotransmission is associated with innate anxiety-like behaviors potentiated by CHN in a mouse model of CHN secondary to the syndrome of inappropriate antidiuresis. In the present study, using a mouse model of the syndrome of inappropriate antidiuresis presenting with CHN, we showed that the sustained reduction of serum sodium ion concentrations potentiated innate anxiety-like behaviors in the light/dark transition and open field tests. We also found that serotonin and dopamine levels in the amygdala were significantly lower in mice with CHN than in controls. Additionally, phosphorylation of extracellular signal-regulated kinase (ERK) in the amygdala was significantly reduced in mice with CHN. Notably, after correcting for CHN, the increased innate anxiety-like behaviors, decreased serotonin and dopamine levels, and reduced phosphorylation of ERK in the amygdala were normalized. These findings further underscore the importance of treating CHN and highlight potential therapeutic strategies for alleviating anxiety in patients with CHN, which will improve their quality of life.

BACKGROUND: The hippocampal dentate gyrus (DG) is a critical region that contributes to recent and remote memory. Granule cells within this region, in which adult neurogenesis occurs, undergo dynamic and reversible maturation via genetic and environmental factors during adulthood. A pseudo-immature state of DG granule cells, called immature DG (iDG), has been observed in the adult mice of certain mutant strains, which are considered animal models of neuropsychiatric and neurodegenerative disorders, such as intellectual disability, schizophrenia, autism, and Alzheimer's disease. However, the association between the iDG phenotype and recent and remote memories in the mouse models remains unclear. METHODS: We assessed spatial memory in the Barnes circular maze task in five mutant mouse models of the disorders with the iDG phenotype, including Camk2a heterozygous knockout (HET KO), forebrain-specific Calcineurin conditional KO (cKO), Neurogranin KO, and Hivep2 (Schnurri-2) KO, and hAPP-J20 transgenic mice. RESULTS: Camk2a HET KO mice and J20 mice spent less time around the target than their wild-type control mice in the memory retention tests one day and four weeks after the last training session. Calcineurin cKO, Neurogranin KO, and Schnurri-2 KO mice showed no significant differences in the time spent around the target from wild-type mice in the retention test 1 day after the training session, but those mutants spent less time around the target than their wild-type mice in the retest conducted four weeks later. CONCLUSIONS: These results indicated that mouse models of neuropsychiatric and neurodegenerative disorders exhibiting the iDG phenotype demonstrate a common behavioral characteristic of remote spatial memory deficits, suggesting the potential involvement of the pseudo-immature state of DG granule cells in remote memory dysfunction.

AIMS: Alzheimer's disease (AD) is a leading cause of dementia, with increasing prevalence. Mutations in genes like MAPT, PSEN1, and PSEN2 are risk factors, leading to the development of several AD model mice. Recent hypotheses suggest AD brain pathology involves abnormal neurodevelopment, decreased pH, and neural hyperexcitation. However, it remains unclear to what extent these pathologies are reflected in the gene expression changes of AD models. This study aims to compare gene expression patterns in the brains of multiple AD model mice with those related to these three factors, evaluating the extent of overlap. METHODS: We conducted a comprehensive search of public databases, collecting 20 gene expression datasets from the hippocampus of AD model mice. These datasets were compared with gene sets related to hippocampal maturation, brain pH, and neural hyperexcitation to statistically assess overlap. Pathway enrichment analysis explored the biological relevance of these gene expression changes. RESULTS: The extent of overlap with maturity-, pH-, and hyperexcitation-associated genes varied across AD models, showing significant correlations between lower maturity, lower pH, and increased neural hyperexcitation. In MAPT mutant and APP+PSEN1 homozygous transgenic mice, these signatures became more pronounced with age. Pathway meta-analysis revealed that genes associated with maturity, pH, and hyperexcitation in AD models are involved in synaptic and channel functions, as well as inflammatory responses, consistent with previous studies. CONCLUSION: These findings suggest that pathophysiological changes related to maturity, pH, and neural hyperexcitation play varying roles across individual AD model mice. Our recent study found a negative correlation between disease progression and actual pH levels in human AD patients. Considering the results presented in this study, maturity and neural hyperexcitation, which are correlated with pH, may also be linked to disease progression. Thus, gene expression changes in these factors could be useful markers for assessing the pathology in AD models.

Abstract Introduction Major depressive disorder (MDD) is a prevalent and debilitating mental disorder that shares symptoms, genetics, and molecular changes in the brain with other psychiatric disorders, such as schizophrenia and bipolar disorder. Decreased brain pH, associated with increased lactate levels due to altered energy metabolism and neuronal hyperexcitation, has been consistently observed in schizophrenia and bipolar disorder. We recently demonstrated similar brain alterations in various animal models of neuropsychiatric disorders, including MDD. However, our understanding of brain pH alterations in human patients with MDD remains limited. Methods We conducted meta-analyses to assess postmortem brain pH in patients with MDD compared to control subjects, examining its relationships with recurrence of depressive episodes and illness duration, utilizing publicly available demographic data. Studies reporting individual raw pH data were identified through searches in the Stanley Medical Research Institute database, NCBI GEO database, PubMed, and Google Scholar. The data were analyzed using the random effects model, ANOVA, and ANCOVA. Results The random effects model, using 39 curated datasets (790 patients and 957 controls), indicated a significant decrease in brain pH in patients with MDD (Hedges’ g = −0.23, p = 0.0056). A two-way ANCOVA revealed that the effect of diagnosis on pH remained significant when considering covariates, including postmortem interval, age at death, and sex. Patients with recurrent episodes, but not a single episode, showed significantly lower pH than controls in both females and males (256 patients and 279 controls from seven datasets). Furthermore, a significant negative correlation was observed between brain pH and illness duration (115 patients from five datasets). Female preponderance of decreased pH was also found, possibly due to a longer illness duration and a higher tendency of recurrent episodes in females. Conclusion This study suggests a decrease in brain pH in patients with MDD, potentially associated with recurrent episodes and longer illness duration. As suggested from previous animal model studies, altered brain energy metabolism, leading to decreased pH, may serve as a potential transdiagnostic endophenotype for MDD and other neuropsychiatric disorders.

Abstract Background Altered brain energy metabolism is implicated in Alzheimer’s disease (AD). Limited and conflicting studies on brain pH changes, indicative of metabolic alterations associated with neural activity, warrant a comprehensive investigation into their relevance in this neurodegenerative condition. Furthermore, the relationship between these pH changes and established AD neuropathological evaluations, such as Braak staging, remains unexplored. Methods We conducted quantitative meta-analyses on postmortem brain and cerebrospinal fluid pH in patients with AD and non-AD controls, using publicly available demographic data. We collected raw pH data from studies in the NCBI GEO, PubMed, and Google Scholar databases. Results Our analysis of 20 datasets (723 patient samples and 524 control samples) using a random-effects model showed a significant decrease in brain and cerebrospinal fluid pH in patients compared to controls (Hedges’ g = -0.57, p < 0.0001). This decrease remained significant after considering postmortem interval, age at death, and sex. Notably, pH levels were negatively correlated with Braak stage, indicated by the random-effects model of correlation coefficients from 15 datasets (292 patient samples and 159 control samples) (adjusted r = -0.26, p < 0.0001). Furthermore, brain pH enhanced the discriminative power of the APOEε4 allele, the most prevalent risk gene for AD, in distinguishing patients from controls in a meta-analysis of four combined datasets (95 patient samples and 87 control samples). Conclusions The significant decrease in brain pH in AD underlines its potential role in disease progression and diagnosis. This decrease, potentially reflecting neural hyperexcitation, could enhance our understanding of neurodegenerative pathology and aid in developing diagnostic strategies.

Abstract Background Altered brain energy metabolism is implicated in Alzheimer’s disease (AD). Limited and conflicting studies on brain pH changes, indicative of metabolic alterations associated with neural activity, warrant a comprehensive investigation into their relevance in this neurodegenerative condition. Furthermore, the relationship between these pH changes and established AD neuropathological evaluations, such as Braak staging, remains unexplored. Methods We conducted quantitative meta-analyses on postmortem brain and cerebrospinal fluid pH in patients with AD and non-AD controls, using publicly available demographic data. We collected raw pH data from studies in the NCBI GEO, PubMed, and Google Scholar databases. Results Our analysis of 17 datasets (457 patients and 315 controls) using a random-effects model showed a significant decrease in brain and cerebrospinal fluid pH in patients compared to controls (Hedges’g= –0.54,p< 0.0001). This decrease remained significant after considering postmortem interval, age at death, and sex. Notably, pH levels were negatively correlated with Braak stage, indicated by the random-effects model of correlation coefficients from 15 datasets (292 patients and 159 controls) (adjustedr= –0.26,p< 0.0001). Furthermore, brain pH enhanced the discriminative power of theAPOEε4 allele, the most prevalent risk gene for AD, in distinguishing patients from controls in a meta-analysis of four combined datasets (95 patients and 87 controls). Conclusions The significant decrease in brain pH in AD underlines its potential role in disease progression and diagnosis. This decrease, potentially reflecting neural hyperexcitation, could enhance our understanding of neurodegenerative pathology and aid in developing diagnostic strategies.

Increased levels of lactate, an end-product of glycolysis, have been proposed as a potential surrogate marker for metabolic changes during neuronal excitation. These changes in lactate levels can result in decreased brain pH, which has been implicated in patients with various neuropsychiatric disorders. We previously demonstrated that such alterations are commonly observed in five mouse models of schizophrenia, bipolar disorder, and autism, suggesting a shared endophenotype among these disorders rather than mere artifacts due to medications or agonal state. However, there is still limited research on this phenomenon in animal models, leaving its generality across other disease animal models uncertain. Moreover, the association between changes in brain lactate levels and specific behavioral abnormalities remains unclear. To address these gaps, the International Brain pH Project Consortium investigated brain pH and lactate levels in 109 strains/conditions of 2294 animals with genetic and other experimental manipulations relevant to neuropsychiatric disorders. Systematic analysis revealed that decreased brain pH and increased lactate levels were common features observed in multiple models of depression, epilepsy, Alzheimer’s disease, and some additional schizophrenia models. While certain autism models also exhibited decreased pH and increased lactate levels, others showed the opposite pattern, potentially reflecting subpopulations within the autism spectrum. Furthermore, utilizing large-scale behavioral test battery, a multivariate cross-validated prediction analysis demonstrated that poor working memory performance was predominantly associated with increased brain lactate levels. Importantly, this association was confirmed in an independent cohort of animal models. Collectively, these findings suggest that altered brain pH and lactate levels, which could be attributed to dysregulated excitation/inhibition balance, may serve as transdiagnostic endophenotypes of debilitating neuropsychiatric disorders characterized by cognitive impairment, irrespective of their beneficial or detrimental nature.

Major depressive disorder (depression) is a leading cause of disability. The severity of depression is affected by many factors, one of which being comorbidity with diabetes mellitus (DM). The comorbidity of depression with DM is a major public health concern due to the high incidence of both conditions and their mutually exacerbating pathophysiology. However, the mechanisms by which DM exacerbates depression remain largely unknown, and elucidating these regulatory mechanisms would contribute to a significant unmet clinical need. We generated a comorbid mouse model of depression and DM (comorbid model), which was extensively compared with depression and DM models. Depressive and anhedonic phenotypes were more severe in the comorbid model. We thus concluded that the comorbid model recapitulated exacerbated depression-related behaviors comorbid with DM in clinic. RNA sequencing analysis of prefrontal cortex tissue revealed that the brain pH homeostasis gene set was one of the most affected in the comorbid model. Furthermore, brain pH negatively correlated with anhedonia-related behaviors in the depression and comorbid models. By contrast, these correlations were not detected in DM or control group, neither of which had been exposed to chronic stress. This suggested that the addition of reduced brain pH to stress-exposed conditions had synergistic and aversive effects on anhedonic phenotypes. Because brain pH was strongly correlated with brain lactate level, which correlated with blood glucose levels, these findings highlight the therapeutic importance of glycemic control not only for DM, but also for psychiatric problems in patients with depression comorbid with DM.

Increased levels of lactate, an end-product of glycolysis, have been proposed as a potential surrogate marker for metabolic changes during neuronal excitation. These changes in lactate levels can result in decreased brain pH, which has been implicated in patients with various neuropsychiatric disorders. We previously demonstrated that such alterations are commonly observed in five mouse models of schizophrenia, bipolar disorder, and autism, suggesting a shared endophenotype among these disorders rather than mere artifacts due to medications or agonal state. However, there is still limited research on this phenomenon in animal models, leaving its generality across other disease animal models uncertain. Moreover, the association between changes in brain lactate levels and specific behavioral abnormalities remains unclear. To address these gaps, the International Brain pH Project Consortium investigated brain pH and lactate levels in 109 strains/conditions of 2,294 animals with genetic and other experimental manipulations relevant to neuropsychiatric disorders. Systematic analysis revealed that decreased brain pH and increased lactate levels were common features observed in multiple models of depression, epilepsy, Alzheimer’s disease, and some additional schizophrenia models. While certain autism models also exhibited decreased pH and increased lactate levels, others showed the opposite pattern, potentially reflecting subpopulations within the autism spectrum. Furthermore, utilizing large-scale behavioral test battery, a multivariate cross-validated prediction analysis demonstrated that poor working memory performance was predominantly associated with increased brain lactate levels. Importantly, this association was confirmed in an independent cohort of animal models. Collectively, these findings suggest that altered brain pH and lactate levels, which could be attributed to dysregulated excitation/inhibition balance, may serve as transdiagnostic endophenotypes of debilitating neuropsychiatric disorders characterized by cognitive impairment, irrespective of their beneficial or detrimental nature.

Disordered sleep is a global social problem and an established significant risk factor for psychological and metabolic diseases. We profiled non-targeted metabolites in saliva from mouse models of chronic sleep disorder (CSD). We identified 288 and 55 metabolites using CE-FTMS and LC-TOFMS, respectively, among which concentrations of 58 (CE-FTMS) and three (LC-TOFMS) were significantly changed by CSD. Pathway analysis revealed that CSD significantly suppressed glycine, serine and threonine metabolism. Arginine and proline metabolic pathways were among those that were both upregulated and downregulated. Pathways of alanine, aspartate and glutamate metabolism, genetic information processing, and the TCA cycle tended to be downregulated, whereas histidine metabolism tended to be upregulated in mice with CSD. Pyruvate, lactate, malate, succinate and the glycemic amino acids alanine, glycine, methionine, proline, and threonine were significantly decreased, whereas 3-hydroxybutyric and 2-hydroxybutyric acids associated with ketosis were significantly increased, suggesting abnormal glucose metabolism in mice with CSD. Increases in the metabolites histamine and kynurenic acid that are associated with the central nervous system- and decreased glycine, might be associated with sleep dysregulation and impaired cognitive dysfunction in mice with CSD. Our findings suggested that profiling salivary metabolites could be a useful strategy for diagnosing CSD.

Calcineurin (Cn), a phosphatase important for synaptic plasticity and neuronal development, has been implicated in the etiology and pathophysiology of neuropsychiatric disorders, including schizophrenia, intellectual disability, autism spectrum disorders, epilepsy, and Alzheimer's disease. Forebrain-specific conditional Cn knockout mice have been known to exhibit multiple behavioral phenotypes related to these disorders. In this study, we investigated whether Cn mutant mice show pseudo-immaturity of the dentate gyrus (iDG) in the hippocampus, which we have proposed as an endophenotype shared by these disorders. Expression of calbindin and GluA1, typical markers for mature DG granule cells (GCs), was decreased and that of doublecortin, calretinin, phospho-CREB, and dopamine D1 receptor (Drd1), markers for immature GC, was increased in Cn mutants. Phosphorylation of cAMP-dependent protein kinase (PKA) substrates (GluA1, ERK2, DARPP-32, PDE4) was increased and showed higher sensitivity to SKF81297, a Drd1-like agonist, in Cn mutants than in controls. While cAMP/PKA signaling is increased in the iDG of Cn mutants, chronic treatment with rolipram, a selective PDE4 inhibitor that increases intracellular cAMP, ameliorated the iDG phenotype significantly and nesting behavior deficits with nominal significance. Chronic rolipram administration also decreased the phosphorylation of CREB, but not the other four PKA substrates examined, in Cn mutants. These results suggest that Cn deficiency induces pseudo-immaturity of GCs and that cAMP signaling increases to compensate for this maturation abnormality. This study further supports the idea that iDG is an endophenotype shared by certain neuropsychiatric disorders.

Abstract CHAMP1 is a gene associated with intellectual disability, which was originally identified as being involved in the maintenance of kinetochore–microtubule attachment. To explore the neuronal defects caused by CHAMP1 deficiency, we established mice that lack CHAMP1. Mice that are homozygous knockout for CHAMP1 were slightly smaller than wild type mice and died soon after birth on pure C57BL/6J background. Although gross anatomical defects were not found in CHAMP1-/- mouse brains, mitotic cells were increased in the cerebral cortex. Neuronal differentiation was delayed in CHAMP1-/- neural stem cells in vitro, which was also suggested in vivo by CHAMP1 knockdown. In a behavioral test battery, adult CHAMP1 heterozygous-knockout mice showed mild memory defects, altered social interaction, and depression-like behaviors. In transcriptomic analysis, genes related to neurotransmitter transport and neurodevelopmental disorder were downregulated in embryonic CHAMP1-/- brains. These results suggest that CHAMP1 plays a role in neuronal development, and CHAMP1-deficient mice resemble some aspects of individuals with CHAMP1 mutations.

The human vesicular monoamine transporter 1 (VMAT1) harbors unique substitutions (Asn136Thr/Ile) that affect monoamine uptake into synaptic vesicles. These substitutions are absent in all known mammals, suggesting their contributions to distinct aspects of human behavior modulated by monoaminergic transmissions, such as emotion and cognition. To directly test the impact of these human-specific mutations, we introduced the humanized residues into mouse Vmat1 via CRISPR/Cas9-mediated genome editing and examined changes at the behavioral, neurophysiological, and molecular levels. Behavioral tests revealed reduced anxiety-related traits of Vmat1 Ile mice, consistent with human studies, and electrophysiological recordings showed altered oscillatory activity in the amygdala under anxiogenic conditions. Transcriptome analyses further identified changes in gene expressions in the amygdala involved in neurodevelopment and emotional regulation, which may corroborate the observed phenotypes. This knock-in mouse model hence provides compelling evidence that the mutations affecting monoaminergic signaling and amygdala circuits have contributed to the evolution of human socio-emotional behaviors.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is characterized by impairments in social interaction and restricted/repetitive behaviors. The neurotransmitter γ<italic>-</italic>aminobutyric acid (GABA) through GABA_A receptor signaling in the immature brain plays a key role in the development of neuronal circuits. Excitatory/inhibitory imbalance in the mature brain has been investigated as a pathophysiological mechanism of ASD. However, whether and how disturbances of GABA signaling in embryos that are caused by GABA_A receptor inhibitors cause ASD-like pathophysiology are poorly understood. The present study examined whether exposure to the GABA_A receptor antagonist picrotoxin causes ASD-like pathophysiology in offspring by conducting behavioral tests from the juvenile period to adulthood and performing gene expression analyses in mature mouse brains. Here, we found that male mice that were prenatally exposed to picrotoxin exhibited a reduction of active interaction time in the social interaction test in both adolescence and adulthood. The gene expression analyses showed that picrotoxin-exposed male mice exhibited a significant increase in the gene expression of odorant receptors. Weighted gene co-expression network analysis showed a strong correlation between social interaction and enrichment of the “odorant binding” pathway gene module. Our findings suggest that exposure to a GABA_A receptor inhibitor during the embryonic period induces ASD-like behavior, and impairments in odorant function may contribute to social deficits in offspring.

AIM: Experimental animals, such as non-human primates (NHPs), mice, Zebrafish, and Drosophila, are frequently employed as models to gain insights into human physiology and pathology. In developmental neuroscience and related research fields, information about the similarities of developmental gene expression patterns between animal models and humans is vital to choose what animal models to employ. Here, we aimed to statistically compare the similarities of developmental changes of gene expression patterns in the brains of humans with those of animal models frequently used in the neuroscience field. METHODS: The developmental gene expression datasets that we analyzed consist of the fold-changes and P values of gene expression in the brains of animals of various ages compared with those of the youngest postnatal animals available in the dataset. By employing the running Fisher algorithm in a bioinformatics platform, BaseSpace, we assessed similarities between the developmental changes of gene expression patterns in the human (Homo sapiens) hippocampus with those in the dentate gyrus (DG) of the rhesus monkey (Macaca mulatta), the DG of the mouse (Mus musculus), the whole brain of Zebrafish (Danio rerio), and the whole brain of Drosophila (D. melanogaster). RESULTS: Among all possible comparisons of different ages and animals in developmental changes in gene expression patterns within the datasets, those between rhesus monkeys and mice were highly similar to those of humans with significant overlap P-value as assessed by the running Fisher algorithm. There was the highest degree of gene expression similarity between 40-59-year-old humans and 6-12-year-old rhesus monkeys (overlap P-value = 2.1 × 10- 72). The gene expression similarity between 20-39-year-old humans and 29-day-old mice was also significant (overlap P = 1.1 × 10- 44). Moreover, there was a similarity in developmental changes of gene expression patterns between 1-2-year-old Zebrafish and 40-59-year-old humans (Overlap P-value = 1.4 × 10- 6). The overlap P-value of developmental gene expression patterns between Drosophila and humans failed to reach significance (30 days Drosophila and 6-11-year-old humans; overlap P-value = 0.0614). CONCLUSIONS: These results indicate that the developmental gene expression changes in the brains of the rhesus monkey, mouse, and Zebrafish recapitulate, to a certain degree, those in humans. Our findings support the idea that these animal models are a valid tool for investigating the development of the brain in neurophysiological and neuropsychiatric studies.

<title>Abstract</title>The human vesicular monoamine transporter 1 (<italic>VMAT1</italic>) harbors unique substitutions (Asn136Thr/Ile) that affect monoamine uptake into synaptic vesicles. These substitutions are absent in all known mammals, suggesting their contributions to distinct aspects of human behavior modulated by monoaminergic transmission, such as emotion and cognition. To directly test the impact of these human-specific mutations, we introduced the humanized residues into mouse <italic>Vmat1</italic> via CRISPR/Cas9-mediated genome editing and examined changes at the behavioral, neurophysiological and molecular levels. Behavioral tests revealed reduced anxiety-related traits of <italic>Vmat1</italic>^Ile mice, consistent with human studies, and electrophysiological recordings showed altered oscillatory activity in the amygdala under anxiogenic conditions. Transcriptome analyses further identified amygdala-specific changes in the expression of genes involved in neurodevelopment and emotional regulation, which may corroborate the observed phenotypes. This knock-in mouse model hence provides compelling evidence that the mutations affecting monoaminergic signaling and amygdala circuits have contributed to the evolution of human socio-emotional behaviors.

Mouse models of various neuropsychiatric disorders, such as schizophrenia, often display an immature dentate gyrus, characterized by increased numbers of immature neurons and neuronal progenitors and a dearth of mature neurons. We previously demonstrated that the CRMP5-associated GTPase (CRAG), a short splice variant of Centaurin-γ3/AGAP3, is highly expressed in the dentate gyrus. CRAG promotes cell survival and antioxidant defense by inducing the activation of serum response factors at promyelocytic leukemia protein bodies, which are nuclear stress-responsive domains, during neuronal development. However, the physiological role of CRAG in neuronal development remains unknown. Here, we analyzed the role of CRAG using dorsal forebrain-specific CRAG/Centaurin-γ3 knockout mice. The mice revealed maturational abnormality of the hippocampal granule cells, including increased doublecortin-positive immature neurons and decreased calbindin-positive mature neurons, a typical phenotype of immature dentate gyri. Furthermore, the mice displayed hyperactivity in the open-field test, a common measure of exploratory behavior, suggesting that these mice may serve as a novel model for neuropsychiatric disorder associated with hyperactivity. Thus, we conclude that CRAG is required for the maturation of neurons in the dentate gyrus, raising the possibility that its deficiency might promote the development of psychiatric disorders in humans.

<title>Abstract</title>Altered brain energy metabolism associated with increase in lactate levels and the resultant decrease in pH have been increasingly implicated in multiple neuropsychiatric disorders, such as schizophrenia, bipolar disorder, autism spectrum disorder and neurodegenerative disorders. Although it is controversial, change of pH/ lactate level as a primary feature of these diseases, rather than a result of confounding factors such as medication and agonal state, has been evidenced. Animal models that can be studied without such confounding factors inherent to humans are a suitable alternative to understand the controversy. However, the knowledge in animal models regarding brain pH and lactate and their relation to behavioral outcomes is limited in the context of neuropsychiatric disease conditions. In this study, we investigated the common occurrence of changes in the pH and lactate levels in the brain in animal models by analyzing 65 animal models related to neuropsychiatric and neurodegenerative diseases with 1,239 animals. Additionally, we evaluated the behavioral phenotypes relative to the chemical changes in the brain. Among the models, 27 and 24 had significant changes in brain pH and lactate levels, respectively, including Shank2 KO mice, Clock mutant mice, serotonin transporter KO mice, mice with a paternal duplication of human chromosome 15q11-13, Fmr1 KO mice, BTBR mice, APP-J20 Tg mice, social defeat stress-exposed mice, corticosterone-treated mice, and streptozotocin-induced diabetic mice. Meta-analysis of the data revealed a highly significant negative correlation between brain pH and lactate levels, suggestive of increased lactate levels causing decreased brain pH. Statistical learning algorithm based on the comprehensive data has revealed that the increased brain lactate levels can be predominantly predicted by the indices for the percentage of correct response in working memory test, with a significant simple, negative correlation. Our results suggest that brain energy metabolism is commonly altered in many animal models of neuropsychiatric and neurodegenerative diseases, which may be associated with working memory performance. We consider our study to be an essential step suggesting that the brain endophenotypes serve as a basis for the transdiagnostic characterization of the biologically heterogeneous and debilitating cognitive illnesses. Based on these results, we are openly accepting collaborations to extend these findings and to test the hypotheses generated in this study using more animal models. We welcome any mice/rat models of diseases with or without any behavioral phenotypes.

Bipolar disorder is a major mental illness characterized by severe swings in mood and activity levels which occur with variable amplitude and frequency. Attempts have been made to identify mood states and biological features associated with mood changes to compensate for current clinical diagnosis, which is mainly based on patients' subjective reports. Here, we used infradian (a cycle > 24 h) cyclic locomotor activity in a mouse model useful for the study of bipolar disorder as a proxy for mood changes. We show that metabolome patterns in peripheral blood could retrospectively predict the locomotor activity levels. We longitudinally monitored locomotor activity in the home cage, and subsequently collected peripheral blood and performed metabolomic analyses. We then constructed cross-validated linear regression models based on blood metabolome patterns to predict locomotor activity levels of individual mice. Our analysis revealed a significant correlation between actual and predicted activity levels, indicative of successful predictions. Pathway analysis of metabolites used for successful predictions showed enrichment in mitochondria metabolism-related terms, such as "Warburg effect" and "citric acid cycle." In addition, we found that peripheral blood metabolome patterns predicted expression levels of genes implicated in bipolar disorder in the hippocampus, a brain region responsible for mood regulation, suggesting that the brain-periphery axis is related to mood-change-associated behaviors. Our results may serve as a basis for predicting individual mood states through blood metabolomics in bipolar disorder and other mood disorders and may provide potential insight into systemic metabolic activity in relation to mood changes.

It is agreed upon that adult hippocampal neurogenesis (AHN) occurs in the dentate gyrus (DG) in rodents. However, the existence of AHN in humans, particularly in elderly individuals, remains to be determined. Recently, several studies reported that neural progenitor cells, neuroblasts, and immature neurons were detected in the hippocampus of elderly humans, based on the expressions of putative markers for these cells, claiming that this provides evidence of the persistence of AHN in humans. Herein, we briefly overview the phenomenon that we call "dematuration," in which mature neurons dedifferentiate to a pseudo-immature status and re-express the molecular markers of neural progenitor cells and immature neurons. Various conditions can easily induce dematuration, such as inflammation and hyper-excitation of neurons, and therefore, the markers for neural progenitor cells and immature neurons may not necessarily serve as markers for AHN. Thus, the aforementioned studies have not presented definitive evidence for the persistence of hippocampal neurogenesis throughout adult life in humans, and we would like to emphasize that those markers should be used cautiously when presented as evidence for AHN. Increasing AHN has been considered as a therapeutic target for Alzheimer's disease (AD); however, given that immature neuronal markers can be re-expressed in mature adult neurons, independent of AHN, in various disease conditions including AD, strategies to increase the expression of these markers in the DG may be ineffective or may worsen the symptoms of such diseases.

The selective serotonin reuptake inhibitor fluoxetine (FLX) is widely used to treat depression and anxiety disorders. Chronic FLX treatment reportedly induces cellular responses in the brain, including increased adult hippocampal and cortical neurogenesis and reversal of neuron maturation in the hippocampus, amygdala, and cortex. However, because most previous studies have used rodent models, it remains unclear whether these FLX-induced changes occur in the primate brain. To evaluate the effects of FLX in the primate brain, we used immunohistological methods to assess neurogenesis and the expression of neuronal maturity markers following chronic FLX treatment (3 mg/kg/day for 4 weeks) in adult marmosets (n = 3 per group). We found increased expression of doublecortin and calretinin, markers of immature neurons, in the hippocampal dentate gyrus of FLX-treated marmosets. Further, FLX treatment reduced parvalbumin expression and the number of neurons with perineuronal nets, which indicate mature fast-spiking interneurons, in the hippocampus, but not in the amygdala or cerebral cortex. We also found that FLX treatment increased the generation of cortical interneurons; however, significant up-regulation of adult hippocampal neurogenesis was not observed in FLX-treated marmosets. These results suggest that dematuration of hippocampal neurons and increased cortical neurogenesis may play roles in FLX-induced effects and/or side effects. Our results are consistent with those of previous studies showing hippocampal dematuration and increased cortical neurogenesis in FLX-treated rodents. In contrast, FLX did not affect hippocampal neurogenesis or dematuration of interneurons in the amygdala and cerebral cortex.

<p>統合失調症や双極性障害は，人種や地域に関わらずその生涯有病率は約1％と言われ，十分な治療法が確立されていない深刻な精神疾患である．しかし，発症要因はもちろん，脳内でどのような異常が生じているのかについては未だによくわかっていない．我々の研究室では，これまでに180種類以上の遺伝子改変マウスや薬物投与マウスの行動を解析した結果，統合失調症や双極性障害などの精神疾患患者の症状に類似した行動異常のパターンを示すマウス系統を多数見出してきた．その中でも特に顕著な行動異常を示す複数系統のマウスの脳を調べたところ，成体の脳であるにも関わらず海馬歯状回の神経細胞のほとんどが擬似的に未成熟な状態にあるという現象（「未成熟歯状回」）を発見した．また，正常なマウスでも抗うつ薬やてんかん症状を誘発するピロカルピンの投与によって未成熟歯状回に酷似した現象を誘導できることもわかってきた．さらに，この未成熟歯状回に類似した現象は，統合失調症患者や双極性障害患者の死後脳でも生じていることが確認された．一方，他の複数の研究室からも，統合失調症患者の皮質や扁桃体などに擬似的に未成熟な細胞があるという報告がなされるようになってきた．我々は，成人であっても歯状回や皮質を含む脳領域の一部の細胞が擬似的に未成熟な状態であることが，精神疾患の中間表現型の一つではないかと考えている．今後，この脳の細胞の成熟度変化について発生メカニズムを解明し，成熟度の制御法を確立することによって，新しい精神疾患の診断法や治療法の開発が進むことが期待される．</p>

Adequate maturation of neurons and their integration into the hippocampal circuit is crucial for normal cognitive function and emotional behavior, and disruption of this process could cause disturbances in mental health. Previous reports have shown that mice heterozygous for a null mutation in α -CaMKII, which encodes a key synaptic plasticity molecule, display abnormal behaviors related to schizophrenia and other psychiatric disorders. In these mutants, almost all neurons in the dentate gyrus are arrested at a pseudoimmature state at the molecular and electrophysiological levels, a phenomenon defined as "immature dentate gyrus (iDG)." To date, the iDG phenotype and shared behavioral abnormalities (including working memory deficit and hyperlocomotor activity) have been discovered in Schnurri-2 knockout, mutant SNAP-25 knock-in, and forebrain-specific calcineurin knockout mice. In addition, both chronic fluoxetine treatment and pilocarpine-induced seizures reverse the neuronal maturation, resulting in the iDG phenotype in wild-type mice. Importantly, an iDG-like phenomenon was observed in post-mortem analysis of brains from patients with schizophrenia/bipolar disorder. Based on these observations, we proposed that the iDG is a potential endophenotype shared by certain types of neuropsychiatric disorders. This review summarizes recent data describing this phenotype and discusses the data's potential implication in elucidating the pathophysiology of neuropsychiatric disorders.