Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by impaired social communication and restricted repetitive behaviors, yet the contribution of trace elements remains poorly defined. We profiled 21 trace elements in individuals with ASD and identified significantly reduced copper levels, which negatively correlated with social symptom severity. Magnetic resonance imaging revealed decreased white matter volume in ASD, which also correlated with social impairment. To explore the mechanisms, we generated a copper-deficient mouse model that displayed ASD-like behaviors and impaired oligodendrocyte (OL) development. Copper deficiency disrupted hypoxia-inducible factor 1α (HIF1α)-dependent angiogenesis and metabolic regulation in the embryonic brain, leading to oxidative stress, mitochondrial dysfunction, and BCL2 interacting protein 3 (BNIP3)-mediated mitophagy in oligodendrocyte progenitor cells. These processes suppressed mechanistic target of rapamycin kinase (mTOR) signaling, reduced OL-lineage cells, and caused hypomyelination. Restoring mTOR activity rescued OL maturation and improved social behavior in copper-deficient mice. These findings identify a copper-HIF1α-BNIP3-mTOR signaling axis that links trace element imbalance to glial dysfunction and ASD-relevant behavioral phenotypes, providing mechanistic insight into neurodevelopment.

ABSTRACT Aim Given that alterations in oxytocinergic and immune systems have been implicated in the social and emotional difficulties of autism spectrum disorder (ASD), yet the associations between these biological factors and internal psychological constructs remain unclear, we examined the relationship between salivary oxytocin (OT) levels, inflammatory markers (interleukin‐1β [IL‐1β], IL‐6, IL‐8), self‐esteem, and perceived social support in children and adolescents with and without ASD. Methods 26 children and adolescents with ASD and 23 typically developing (TD) controls were included. Salivary OT and inflammatory cytokine levels were measured using enzyme‐linked immunosorbent and multiplex immunoassays. Results Salivary oxytocin levels were significantly lower in the ASD group than in the TD group after adjusting for age. In contrast, no significant group differences were observed in inflammatory markers (IL‐1β, IL‐6, or IL‐8). However, across participants, including those with ASD, higher OT levels were associated with greater self‐esteem and perceived social support. These findings suggest that oxytocin‐related socio‐emotional processes may be associated with socio‐emotional functioning across children and adolescents, including those with ASD. Participants with higher OT levels were associated with greater self‐esteem and perceived social support. Among the inflammatory markers, none of the cytokines (IL‐1β, IL‐6, or IL‐8) showed significant associations with the psychological measures, including AQ‐J total scores. Conclusion OT levels may be associated with socio‐emotional functioning and psychological well‐being across children and adolescents with and without ASD, regardless of diagnostic status. In contrast, no significant associations were observed between inflammatory markers and psychological measures in the present sample.

Background:Self-esteem is a critical factor in the psychological adjustment of children and adolescents, yet little is known about how autistic traits and parenting styles interact to relate self-worth in individuals with autism spectrum disorder (ASD). Understanding these relationships may provide important insights for family-based interventions. Methods:We conducted a cross-sectional study of 76 participants (ASD: n = 40; typically developing [TD]: n = 36). Autistic traits were assessed using the Japanese version of the Autism-Spectrum Quotient (AQ-J), parenting attitudes were evaluated with the Parental Nurturance and Parenting Scale (PNPS), and self-esteem was measured using the Rosenberg Self-Esteem Scale (RSES). In the ASD group, clinician-rated autism symptom severity was additionally assessed using the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2). Associations among autistic traits, parenting attitudes, and self-esteem were examined using multiple linear regression and partial correlation analyses. Results:Children and adolescents with ASD exhibited significantly lower self-esteem than their TD peers (RSES: ASD < TD, p < 0.01). In the combined sample, higher AQ-J scores were independently associated with lower self-esteem (β ≈ -0.48, p < 0.01). Within the ASD group, negative parenting attitudes were linked to lower self-esteem (β = -0.36, p = 0.02), whereas positive parenting attitudes showed a non-significant trend toward higher self-esteem (β = 0.20, p = 0.17). Conversely, clinician-rated autism symptom severity assessed by the ADOS-2 was not associated with self-esteem (β = 0.06, p = 0.72). Overall, parenting attitudes were more closely related to self-esteem than clinician-rated symptom severity in the ASD group. Conclusion:These findings underscore the relevance of parenting contexts in relation to self-esteem among youth with ASD. Although autistic traits were associated with greater vulnerability in self-esteem, supportive parenting attitudes were associated with more favorable self-esteem outcomes. Together, the results suggest that parenting-related factors may be important considerations when addressing psychological well-being in autistic children and adolescents.

BACKGROUND:Alzheimer's disease (AD) is associated with memory impairment and social cognitive dysfunction, including facial emotion recognition (FER) deficits. Our previous diffusion tensor imaging (DTI) study linked poor recognition of negative facial emotions in patients with AD to increased mean diffusivity (MD) in the left uncinate fasciculus (UF). Whether FER deficits in AD reflect microstructural alterations in related grey matter regions remains unclear. METHODS:In this cross-sectional study, 74 patients with AD and 28 cognitively normal (CN) subjects underwent behavioural assessments using the Facial Emotion Selection Test (FEST). A subset of 67 AD patients and 23 CN patients underwent magnetic resonance imaging. DTI was used to assess the fractional anisotropy (FA) and MD of the bilateral UF, and neurite orientation dispersion and density imaging (NODDI) was used to evaluate the neurite density index (NDI) and orientation dispersion index (ODI) of the insula, amygdala and temporal lobe. RESULTS:Patients with AD showed significantly lower FEST total, negative emotion, positive emotion and neutral expression scores. DTI revealed significantly lower FA and higher MD in the bilateral UF. In the AD group, higher bilateral UF MD was significantly associated with lower total FEST and negative emotional scores. NODDI analyses demonstrated significantly lower ODI in the insula, amygdala and temporal lobe in the AD group, whereas no significant between-group differences were observed in the NDI. In the uncorrected analyses, ODI showed trend-level positive associations with FEST performance; however, these associations did not remain significant after false discovery rate correction. Bilateral UF MD was negatively correlated with ODI in the insula and temporal lobes. CONCLUSIONS:FER is broadly impaired in AD and is associated with bilateral UF abnormalities and reduced ODI in the frontotemporal-limbic regions. These findings suggest that social cognitive dysfunction in AD involves broader frontotemporal-limbic network disruption than isolated white matter abnormalities.

IntroductionAssessment of autism spectrum disorder (ASD) relies on both parent-reported questionnaires and clinician-administered observational instruments. Although discrepancies between informants are common, their implications for autism severity evaluation remain unclear. This study examined informant discrepancies across parent-reported and clinician-rated measures, focusing on sex- and age-related effects.MethodsChildren and adolescents with ASD and typically developing (TD) controls were assessed using parent-reported measures, including the Social Responsiveness Scale, Second Edition (SRS-2), and the Japanese version of the Autism-Spectrum Quotient (AQ-J). Clinician-rated autism severity was assessed using the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2). Two-way analyses of variance were used to examine the diagnostic and sex-related effects. Hierarchical regression analyses were used to evaluate the associations between parent-reported subscales and ADOS-2 severity within the ASD group. Spearman's rank correlations were used to assess age-related changes in discrepancy scores separately by sex.ResultsParent-reported measures robustly differentiated the ASD and TD groups but showed few sex-related differences. In contrast, the ADOS-2 total score differed significantly by sex within the ASD group, with males exhibiting higher clinician-rated autism severity; however, most domain-level scores were not significant. Hierarchical regression analyses indicated limited associations between parent-reported subscales and clinician-rated severity. Sex remained a consistent predictor of ADOS-2 total scores. Age was negatively associated with SRS-2–ADOS-2 discrepancy scores among females, suggesting reduced parent–clinician discrepancy with increasing age in girls.ConclusionParent-reported and clinician-rated measures captured overlapping but distinct aspects of autism-related characteristics. The ADOS-2 total score identified a sex-related difference in clinician-rated severity that was not apparent in parent-reported measures; however, these findings should be interpreted cautiously, given documented limitations of the ADOS-2 in detecting some autistic female presentations. Overall, these findings highlight the complementary contributions of parent-reported and clinician-rated assessments and underscore the importance of considering informant perspectives when interpreting autism-related characteristics across contexts.

Sex differences in autism spectrum disorder (ASD) are increasingly recognized, not only in symptom presentation but also in underlying neurobiology and response to environmental factors. However, current diagnostic practices and animal models are male-centric, overlooking female-specific phenotypes and mechanisms. We conducted a multimodal, cross-species study to assess sex-dependent ASD phenotypes. In high-functioning adults with ASD and typically developing (TD) controls, we evaluated self-reported autistic traits, self-reported sensory sensitivity, and clinician-observed behaviors using standardized tools: Autism-Spectrum Quotient, Adolescent/Adult Sensory Profile, and Autism Diagnostic Observation Schedule, Second Edition (ADOS-2). In parallel, we assessed behavioral phenotypes in a paternal 15q11-q13 duplication mouse model (15q dup/+) using open-field, light-dark transition, and augmented reality-based behavioral assays. Among humans, individuals with ASD showed greater self-reported sensory sensitivity and autistic traits than TD individuals. Within the ASD group, female participants reported greater self-reported sensory sensitivity and exhibited lower clinician-rated impairments (ADOS-2) than male participants, despite comparable self-reported autistic traits. No sex differences were found among TD individuals. In contrast, female 15q dup/+ mice exhibited heightened light-related sensory reactivity and reduced exploratory behavior under bright light. These findings suggest that sex differences in light-related sensory reactivity may be more readily detected through behavioral measures in animal models. Our findings underscore the importance of considering sex as a biological and behavioral variable in ASD research. Cross-species, phenotype-oriented approaches that integrate human and animal data may uncover subtle phenotypic variations and enhance sex-informed diagnostics and interventions.

This study examined whether the timing of adverse childhood experiences (ACEs) is associated with differences in intellectual ability in adults with autism spectrum disorder (ASD) without intellectual disability. A total of 161 adults with ASD were categorized into three groups based on ACE onset: no ACEs (Group 0), early childhood ACEs (≤ 10 years; Group 1), and adolescent ACEs (11–18 years; Group 2). Intellectual ability was assessed using the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV). Findings revealed that Group 1 outperformed Group 2 on the picture completion and figure weights subtests, suggesting that early ACE exposure may be linked to distinct cognitive profiles in ASD. To account for the higher severity of post-traumatic stress disorder (PTSD) symptoms, including hypervigilance, in Group 1 compared to Group 2, we conducted multivariate analyses of covariance and logistic regression to control for potential confounders such as years of education and PTSD symptom severity, given that hypervigilance may influence cognitive task performance. However, the observed differences remained significant. These results suggest a potential association between the timing of ACE exposure and specific cognitive subdomains in adults with ASD. Furthermore, WAIS-IV subtests, particularly picture completion and figure weights, may serve as potential markers for identifying cognitive adaptations associated with early adversity in ASD individuals. Since this study was not a clinical trial, this section does not apply.

Oxytocin has been implicated in regulating social behaviour and emotional responses; however, the underlying neural circuits remain incompletely understood. Neurons expressing oxytocin receptors (OTRs) in the paraventricular thalamus (PVT) are emerging as a potential modulator of these processes. In this study, we investigated the specific role of OTR-expressing PVT neurons in sociability and fear-related behaviours. Using chemogenetic approaches, we found that bidirectional manipulation of these neurons significantly modulated social behaviour and fear extinction in mice. Inhibition of OTR-expressing PVT neurons impaired sociability and fear extinction, whereas activation selectively enhanced early extinction learning without affecting sociability. Electrophysiological analyses revealed that oxytocin increases tonic firing in PVT neurons, suggesting a mechanism for heightened excitability. In contrast, manipulation of OTR-expressing neurons in the medial prefrontal cortex had no effect on sociability. In a complementary human dataset, salivary oxytocin levels were modestly associated with thalamic microstructure and autism spectrum disorder trait severity. Although the experimental paradigms differed across species, these findings collectively suggest that OTR-expressing PVT neurons may contribute to social and emotional behaviours through circuit-specific mechanisms. These findings may have implications for psychiatric conditions such as autism spectrum disorder and anxiety. Future translational studies should explore the therapeutic potential of targeting oxytocin-related PVT function to treat social and fear-related deficits. Overall, these findings advance our understanding of the role of oxytocin in brain function and its relevance to mental health.

IntroductionAtypical auditory processing is a core characteristic of autism spectrum disorder (ASD), potentially stemming from disrupted thalamocortical circuits and frontal modulation. This study investigated whether individual differences in cortical microstructure, as measured by neurite orientation dispersion and density imaging, are associated with auditory brainstem responses (ABR) and whether these ABR measures are associated with autism traits and atypical sensory processing.MethodsWe recruited 15 adults with ASD (9 males, 6 females; mean age 26.9 ± 6.7 years) and 12 typically developing controls (12 males; mean age 37.1 ± 8.0 years) and assessed microstructural properties in the thalamus, temporal cortex, and orbitofrontal cortex (OFC). Auditory processing was evaluated via ABR recorded under forward-masking conditions.ResultsIn this preliminary, exploratory analysis, mediation models suggested that the amplitude of wave PVII mediated the association between the orientation dispersion index in the temporal cortex and autism traits, as measured by the Autism-Spectrum Quotient. Similarly, the ΔVI amplitude (peak-to-peak potential between NVI and PVI) mediated the relationship between the neurite density index in the OFC and atypical sensory behaviors, assessed using the Adolescent/Adult Sensory Profile. In the ASD group, reduced PVII amplitude was linked to difficulties in attention switching and imagination, while increased ΔVI amplitude was associated with sensory avoidance.Discussion/conclusionOur preliminary and exploratory findings tentatively suggest that microstructural variability in the temporal cortex and OFC may relate to auditory neural responses and to sensory and cognitive features of ASD. However, given the small and demographically imbalanced sample, these results should be regarded as hypothesis-generating rather than confirmatory. These candidate brain–behavior pathways should be tested in larger, demographically matched cohorts before any mechanistic interpretation regarding sensory dysfunction in autism can be drawn.

AIM:This study aimed to explore the relationship between self-esteem and tumor necrotic factor-alpha (TNF-α) expression in individuals with autism spectrum disorder (ASD). Self-esteem was assessed using the Contingencies of Self-Worth (CSW) scale, with a focus on external and internal contingencies, and TNF-α expression was measured, given its association with both ASD pathophysiology and self-esteem in prior studies. METHODS:We enrolled 51 high-functioning individuals with ASD and 34 typically developed (TD) individuals. Self-esteem was assessed using the Japanese version of the CSW scale, which evaluates seven domains, and the Personal Sense of Power. TNF-α expression in plasma was quantified via ELISA. Correlations of CSW scores and the Personal Sense of Power with TNF-α levels were analyzed using multiple regression models adjusted for confounding factors such as age, sex, education level, and autistic symptoms. RESULTS:In ASD individuals, TNF-α expression was significantly negatively correlated with the external CSW domain of others' approval and showed a trend toward negative correlations with appearance and relationship harmony. These correlations were not observed in the TD individuals. Likewise, the Personal Sense of Power within family settings showed a trend toward positive correlations with TNF-α expression in ASD individuals, but not in TD individuals. DISCUSSION:This study highlights the implication of TNF-α levels in the self-esteem of ASD individuals, particularly in interpersonal relationships. Lower TNF-α expression was associated with higher self-esteem in social contexts, independent of the severity of autistic symptoms. These findings suggest a biological link between inflammatory pathways and self-esteem in ASD, contributing to a deeper understanding of the interplay between immune function and psychological well-being in this population.

Sensory issues are common in autism spectrum disorders (ASD) and can significantly affect daily living. The phenomena of gating and habituation of event-related potentials (ERPs) to repetitive stimuli have been suggested as potential biomarkers reflecting atypical sensory processing in ASD. Sensory hypersensitivity and anxiety are closely related in ASD, and habituation to emotionally evocative stimuli may serve as a more sensitive biomarker for sensory hypersensitivity symptoms. However, previous studies have primarily used tonal stimuli, and there has been little investigation into whether habituation to emotionally evocative sounds is impaired in ASD patients. In this study, we compared the degree of habituation of the P1-N1 peak-to-peak amplitude in response to repeated tones and fearful vocalizations between control and ASD groups. Contrary to expectations, no significant difference was observed for fearful vocalizations between the groups, while ASD patients showed significantly reduced habituation to tonal sounds in the left parieto-occipital region. Furthermore, we found a significant correlation between the degree of habituation to tonal sounds in the left parieto-occipital region and sensory hypersensitivity symptoms in ASD patients, and similar abnormalities in BTBR mice, an animal model of ASD. These results suggest that habituation to tonal sounds, rather than emotionally evocative stimuli, may serve as a translational biomarker reflecting sensory hypersensitivity symptoms.

Neuropsychiatric disorders pose profound challenges to both research and treatment, largely due to their clinical heterogeneity and the limited understanding of their underlying biological mechanisms. While bulk RNA sequencing (bulk RNA-seq) has been widely used to study gene expression, it cannot resolve cell-type-specific signals or detect rare cellular subpopulations. In contrast, single-cell RNA sequencing (scRNA-seq) and single-nucleus RNA sequencing (snRNA-seq) have emerged as transformative technologies, enabling transcriptomic profiling at single-cell resolution. These approaches have revealed immunological alterations across a wide range of disorders. This review introduces recent findings from sc/snRNA-seq studies of immune-related mechanisms in psychiatric disorders-including schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorder, and attention-deficit/hyperactivity disorder-as well as in neurological conditions such as Alzheimer's disease, Parkinson's disease, dementia with Lewy bodies, multiple sclerosis, and anti-NMDA receptor encephalitis. While sc/snRNA-seq overcome averaging effects of bulk RNA-seq by resolving cell types, these methods still face challenges. We outline a roadmap that integrates bulk RNA-seq and sc/snRNA-seq to mitigate the remaining gaps.

Dendritic spine abnormalities are believed to be one of the critical etiologies of autism spectrum disorder (ASD). Over the past decade, the importance of microglia in brain development, particularly in synaptic elimination, has become evident. Thus, microglial abnormalities may lead to synaptic dysfunction, which may underlie the pathogenesis of ASD. Several human studies have demonstrated aberrant microglial activation in the brains of individuals with ASD, and studies in animal models of ASD have also shown a relationship between microglial dysfunction and synaptic abnormalities. However, there are very few methods available to directly assess whether phagocytosis by human microglia is abnormal. Microglia are tissue-resident macrophages with phenotypic similarities to monocyte-derived macrophages, both of which consistently exhibit pathological phenotypes in individuals with ASD. Therefore, in this study, we examined the phagocytosis capacity of human macrophages derived from peripheral blood monocytes. These macrophages were polarized into two types: those induced by granulocyte-macrophage colony-stimulating factor (GM-CSF MΦ, traditionally referred to as “M1 MΦ”) and those induced by macrophage colony-stimulating factor (M-CSF MΦ, traditionally referred to as “M2 MΦ”). Synaptosomes purified from human induced pluripotent stem cell-derived neuron were used to assess phagocytosis capacity. Our results revealed that M-CSF MΦ exhibited higher phagocytosis capacity compared to GM-CSF MΦ, whereas ASD-M-CSF MΦ showed a marked impairment in phagocytosis. Additionally, we found a positive correlation between phagocytosis capacity and cluster of differentiation 209 expression. This research contributes to a deeper understanding of the pathobiology of ASD and offers new insights into potential therapeutic targets for the disorder.

AimAdverse childhood experiences are potentially traumatic events with long‐lasting effects on the health and well‐being of patients with autism spectrum disorder (ASD). It is important to clarify which types of long‐lasting autism‐related symptoms are influenced by childhood experiences to design future intervention studies. However, few studies have examined the association between childhood experiences and autistic symptoms in large samples of adults with ASD and individuals with typical development (TD). In this study, we evaluate the effects of adverse childhood experiences on multiple ASD phenotypes among both individuals with ASD and those with TD.MethodWe combined questionnaire evaluations; Childhood Abuse and Trauma Scale, the Japanese version of the Autism‐Spectrum Quotient, Conners' Adult ADHD Rating Scale, the Japanese version of the Impact of Event Scale‐Revised, and the Japanese version of the Adolescent/Adult Sensory Profile.ResultsIndividuals with ASD and those with TD (n = 205 and 104, respectively) were included. There were significant correlations between the extent of adverse childhood experiences and severity of attention‐deficit/hyperactivity disorder symptoms, posttraumatic stress disorder symptoms, and hypersensitivity in both participants with ASD and those with TD. By contrast, ASD core symptoms showed no significant correlation with adverse childhood experiences in either group. These results remained consistent after adjusting for age, sex, and the estimated intelligence quotient.ConclusionThese findings suggest the need for a detailed disentanglement of ASD‐related core and peripheral symptoms of adverse childhood experiences, which may help to appropriately set outcomes for future early interventions for the childhood experiences of individuals with ASD.

Individuals with autism spectrum disorder (ASD) are more likely to experience adverse childhood experiences (ACEs) compared with typically developing (TD) individuals, which predisposes them to an elevated risk of mental health issues. This review elucidates the profound impact of ACEs on individuals with ASD by synthesizing findings from a plethora of epidemiologic and biological studies, encompassing genetics, epigenetics, and neuroimaging. Despite the limited number of studies explicitly focusing on this intersection, the extant literature consistently demonstrates that ASD individuals are disproportionately affected by ACEs, leading to significant deterioration in mental health and brain function. Furthermore, the nature and extent of the effects of ACEs appear to diverge between ASD and TD populations, underscoring the necessity for tailored clinical and research approaches. Understanding these complex and intertwined interactions is imperative for advancing both clinical practice and research, with the goal of mitigating the adverse outcomes associated with ACEs in ASD individuals.

BackgroundSocial isolation during critical periods of development is associated with alterations in behavior and neuronal circuitry. This study aimed to investigate the immediate and developmental effects of social isolation on firing properties, neuronal activity-regulated pentraxin (NARP) and parvalbumin (PV) expression in the prefrontal cortex (PFC), social behavior in juvenile socially isolated mice, and the biological relevance of NARP expression in autism spectrum disorder (ASD).MethodsMice were subjected to social isolation during postnatal days 21–35 (P21–P35) and were compared with group-housed control mice. Firing properties in the PFC pyramidal neurons were altered in P35 socially isolated mice, which might be associated with alterations in NARP and PV expression.ResultsIn adulthood, mice that underwent juvenile social isolation exhibited difficulty distinguishing between novel and familiar mice during a social memory task, while maintaining similar levels of social interaction as the control mice. Furthermore, a marked decrease in NARP expression in lymphoblastoid cell lines derived from adolescent humans with ASD as compared to typically developing (TD) humans was found.ConclusionOur study highlights the role of electrophysiological properties, as well as NARP and PV expression in the PFC in mediating the developmental consequences of social isolation on behavior.

Abstract Background A growing body of evidence suggests that immune dysfunction and inflammation in the peripheral tissues as well as the central nervous system are associated with the neurodevelopmental deficits observed in autism spectrum disorder (ASD). Elevated expression of pro-inflammatory cytokines in the plasma, serum, and peripheral blood mononuclear cells of ASD has been reported. These cytokine expression levels are associated with the severity of behavioral impairments and symptoms in ASD. In a prior study, our group reported that tumor necrosis factor-α (TNF-α) expression in granulocyte–macrophage colony-stimulating factor-induced macrophages (GM-CSF MΦ) and the TNF-α expression ratio in GM-CSF MΦ/M-CSF MΦ (macrophage colony-stimulating factor-induced macrophages) was markedly higher in individuals with ASD than in typically developed (TD) individuals. However, the mechanisms of how the macrophages and the highly expressed cytokines affect neurons remain to be addressed. Methods To elucidate the effect of macrophages on human neurons, we used a co-culture system of control human-induced pluripotent stem cell-derived neurons and differentiated macrophages obtained from the peripheral blood mononuclear cells of five TD individuals and five individuals with ASD. All participants were male and ethnically Japanese. Results Our results of co-culture experiments showed that GM-CSF MΦ affect the dendritic outgrowth of neurons through the secretion of pro-inflammatory cytokines, interleukin-1α and TNF-α. Macrophages derived from individuals with ASD exerted more severe effects than those derived from TD individuals. Limitations The main limitations of our study were the small sample size with a gender bias toward males, the use of artificially polarized macrophages, and the inability to directly observe the interaction between neurons and macrophages from the same individuals. Conclusions Our co-culture system revealed the non-cell autonomous adverse effects of GM-CSF MΦ in individuals with ASD on neurons, mediated by interleukin-1α and TNF-α. These results may support the immune dysfunction hypothesis of ASD, providing new insights into its pathology.

Microglia and brain-derived neurotrophic factor (BDNF) are essential for the neuroplasticity that characterizes critical developmental periods. The experience-dependent development of social behaviors-associated with the medial prefrontal cortex (mPFC)-has a critical period during the juvenile period in mice. However, whether microglia and BDNF affect social development remains unclear. Herein, we aimed to elucidate the effects of microglia-derived BDNF on social behaviors and mPFC development. Mice that underwent social isolation during p21-p35 had increased Bdnf in the microglia accompanied by reduced adulthood sociability. Additionally, transgenic mice overexpressing microglial Bdnf-regulated using doxycycline at different time points-underwent behavioral, electrophysiological, and gene expression analyses. In these mice, long-term overexpression of microglial BDNF impaired sociability and excessive mPFC inhibitory neuronal circuit activity. However, administering doxycycline to normalize BDNF from p21 normalized sociability and electrophysiological function in the mPFC, whereas normalizing BDNF from later ages (p45-p50) did not normalize electrophysiological abnormalities in the mPFC, despite the improved sociability. To evaluate the possible role of BDNF in human sociability, we analyzed the relationship between adverse childhood experiences and BDNF expression in human macrophages, a possible proxy for microglia. Results show that adverse childhood experiences positively correlated with BDNF expression in M2 but not M1 macrophages. In summary, our study demonstrated the influence of microglial BDNF on the development of experience-dependent social behaviors in mice, emphasizing its specific impact on the maturation of mPFC function, particularly during the juvenile period. Furthermore, our results propose a translational implication by suggesting a potential link between BDNF secretion from macrophages and childhood experiences in humans.

Autism spectrum disorder (ASD) is a heterogeneous disorder characterized by impaired social communication and restricted repetitive behaviors, however the biological mechanisms remain unclear. Although trace elements play essential roles in the living body, it is unclear how alterations of trace elements in ASD are involved in pathogenesis. Here we analyzed the plasma metallome and identified the alterations of 11 elements in individuals with ASD. The copper decrease was negatively correlated with ASD symptom scores. A copper-deficient mouse model reflecting the condition showed ASD-like behaviors and impaired oligodendrocyte development. In copper-deficient mice, mechanistic target of rapamycin (mTOR) signaling was reduced, and its activation by agonist improved social impairment and oligodendrocyte developmental defects. Supporting these results, white matter volumes were negatively correlated with social symptoms in individuals with ASD. Our results demonstrate that copper-deficiency contributes to ASD by causing oligodendrocytes impairment via mTOR signaling. Our findings indicate that the effects of copper-deficiency and mTOR imbalance are relevant to the pathogenesis of ASD and are potential therapeutic targets. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was founded by The Japan Agency for Medical Research and Development (AMED) Translational Research Grant Seeds A140 (NU, SS), AMED-CREST 22gm1510009h0001 (MM), AMED-PRIM 21wm04250XXs0101 (MM), AMED 21uk1024002s0201 (MM), 20gm6310015h0001 (MM), The Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (B) 23H02837 (NU), 19H03581 (HM), 20H03604 (MM), JSPS Grant-in-Aid for Scientific Research (C) 20K06872 (NU), JSPS Grant-in-Aid for Early-Career Scientists 23K14443 (MD), JSPS Grant-in-Aid for Challenging Research (Exploratory) 19K21754 (HM), Uehara Memorial Foundation (NU), Takeda Science Foundation (NU), Naito Foundation (NU) Mochida Memorial Foundation for Medical and Pharmaceutical Research (NU), Inamori Foundation (NU), SENSHIN Medical Research Foundation (NU), Osaka Medical Research Foundation for Intractable Diseases (NU, MD), MEI Grant supported by Osaka University (NU), and Osaka University Medical Doctor Scientist Training Program (NN). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All procedures were approved by the Ethics Committee of Osaka University (#19394), University of Fukui (#20200112), and Nara Medical University (#1319), and were conducted in accordance with the Ethical Guidelines for Medical and Health Research Involving Human Subjects of the Ministry of Health, Labour and Welfare of Japan. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The data supporting the findings of this study are available from the corresponding author upon reasonable request.