Loss of mTOR-dependent macroautophagy causes autistic-like synaptic pruning deficits

Biliverdin alleviates cerebral ischemia-reperfusion injury by regulating the P4hb/MAPK/mTOR pathway to inhibit autophagy

BACKGROUND

Biliverdin (BV) exhibits anti-inflammatory and antioxidative effects. Autophagy activation is crucial in the pathogenesis of cerebral ischemia-reperfusion injury (CIRI). This study aimed to investigate whether BV could ameliorate CIRI by regulating autophagy.

METHODS

A middle cerebral artery occlusion-reperfusion (MCAO/R) model in Sprague-Dawley (SD) rats and an oxygen-glucose deprivation/reoxygenation (OGD/R) model in PC12 cells were employed to explore the neuroprotective effects of BV and its underlying mechanisms. In these rats, once BV was administered post-MCAO/R, its treatment efficacy and underlying mechanisms were evaluated through behavioral, morphological, and molecular analyses. Alternatively, for PC12 cells, following successful OGD/R modeling, BV, autophagy activator rapamycin, prolyl 4-hydroxylase beta (P4hb) knockdown or overexpression, and the specific inhibitors of three classic autophagy pathways were applied. Cell viability (using CCK8 assay), Calcein/PI staining, autophagosome staining (using MDC assay), reverse transcription quantitative polymerase chain reaction, and western blot were subsequently carried out to investigate the mechanisms by which BV ameliorates CIRI.

RESULTS

BV alleviated CIRI by inhibiting autophagy. Further investigation suggested that BV downregulated P4hb expression. In vitro experiments showed that P4hb knockdown reduced autophagy in post-CIRI cells, while its overexpression reversed the effects of BV. Rescue experiments indicated that MAPK pathway inhibitors counteracted the effects of P4hb overexpression on autophagy post-CIRI.

CONCLUSION

BV improves CIRI by regulating the P4hb/MAPK/mTOR signaling pathway to inhibit autophagy, offering a novel therapeutic strategy for ischemic stroke.

The combined damage of bisphenol A and high fat diet to learning and memory in young male mice: the regulatory effect of BDNF/TrkB/PI3K/AKT pathway on autophagy

With the popularity of takeaway and processed food, combined exposure to Bisphenol A (BPA) and high fat diet (HFD) is becoming increasingly common. BPA or HFD intake in children could impair learning and memory ability, but the combined effect and mechanisms remain unclear. In this study, we fed young male mice with 0.1 μg/mL BPA (L-BPA), 0.2 μg/mL BPA (H-BPA), 60 %HFD (HFD), 0.1 BPA + HFD (L-BPA + HFD) and 0.2 BPA + HFD (H-BPA + HFD) for 8 weeks. The results showed that recognition memory and free exploration of mice were impaired in the BPA or HFD group, and the damage of exploration was more severe in the combined group. All treated groups showed morphological changes in hippocampal neurons. The levels of synaptic structural protein PSD-95 and SYN were reduced in BPA and HFD alone or in combination groups. BPA or HFD led to changes in autophagy levels in the hippocampus, manifested by decreased protein levels of mTOR and P62, increased level of LC3B, and more significant changes in the combined group. The BDNF/TrkB/PI3K/AKT pathway was inhibited in BPA or HFD groups, especially in the combined group. Our results suggested that combined BPA with HFD exposure could impair learning and memory ability, and the combined effect might be related to the BDNF/TrkB/PI3K/AKT pathway, which regulated mTOR mediated autophagy and finally caused hippocampal synaptic damage.

Mitigating effects of H3 receptor antagonism on cerebellar autophagic pathways and behavioral phenotypes in BTBR T+ tf/J mouse model of autism spectrum disorder

Accumulation of evidence suggested the involvement of autophagic pathways and their associated AktmTOR (mammalian target of rapamycin) signalling cascade in the pathogenesis of autism spectrum disorder (ASD). Histamine 3 receptors antagonism may be neuroprotective in ASD, as this antagonism modulates autophagy which is reported to be impaired in ASD. Therefore, the effects the novel H3 receptor antagonist E169 (2.5, 5, and 10 mg/kg, i.p.) on short-term memory (STM), long-term memory (LTM), and anxiety level in male Black and Tan BRachyury (BTBR) mice were evaluated using Novel object recognition test (NORT) and open field locomotor (OFT) tests respectively. In NORT, E169 (2.5 mg/kg, i.p.) significantly improved the memory of tested BTBR mice, and the effects of E169 were similar to those of the reference mTOR inhibitor rapamycin, and were reversed following co-administration with the centrally penetrant H3 receptor agonist (R)-α-methylhistamine (RAMH). Furthermore, E169 enhanced the BTBR memory by inhibiting H3 receptors and regulating the extent of disruption in the expression of cerebellar Akt, mTOR, and LC-3 proteins of treated mice. Moreover, E169 (2.5 mg/kg, i.p.) restored the disturbed anxiety levels and hyperactivity observed in OFT. In summary, the findings indicate that H3 receptor antagonists like E169 could play a role in simultaneously regulating disrupted brain neurotransmitters and the dysregulated cerebellar Akt-mTOR signaling pathway associated with autophagy in neurological diseases. Therefore, activation of cerebellar autophagy represented by H3 receptor antagonist E169 may serve as an effective pharmacological therapeutic target for the ASD-like behavioral phenotypes and may add new therapeutic management strategy for the multifactorial disorder ASD.

Synaptic disturbance in neurodevelopmental disorders: Perspectives from fragile X and Rett syndromes

Neurodevelopmental disorders (NDDs) are often referred to as "synaptopathies" because many of their behavioral symptoms arise from impaired synaptic development and function. However, the mechanisms that connect synaptic dysfunction to neurological symptoms remain unclear, mainly due to the wide variety of genetic and environmental factors involved in these disorders. Fragile X syndrome and Rett syndrome, two extensively studied monogenic NDDs, provide a unique opportunity to explore these mechanisms at molecular, cellular, and synaptic levels. This review summarizes the current understanding of how synaptic alterations contribute to the neurological symptoms observed in fragile X and Rett syndromes. A comparison of findings from mouse models indicates that an imbalance in local and distal connectivity may serve as a common feature of both disorders.

Auditory processing deficits in autism spectrum disorder: mechanisms, animal models, and therapeutic directions

Auditory processing abnormalities are a prominent feature of Autism Spectrum Disorder (ASD), significantly affecting sensory integration, communication, and social interaction. This review delves into the neurobiological mechanisms underlying these deficits, including structural and functional disruptions in the auditory cortex, imbalances in excitatory and inhibitory signaling, and synaptic dysfunction. Genetic contributions from mutations in CNTNAP2, SHANK3, FMR1, and FOXP2 are explored, highlighting their roles in auditory abnormalities. Animal models, such as BTBRT+tf/J mice (BTBR) and valproic acid (VPA)-exposed rodents, provide critical insights into the sensory abnormalities observed in ASD. In addition, the review discusses current pharmacological strategies and emerging interventions targeting neurotransmitter systems and synaptic plasticity. Notably, future directions are emphasized, highlighting the need for integrated pharmacological and auditory-specific therapies to enhance sensory processing and communication outcomes in ASD. Overall, this review aims to bridge the gap between basic neurobiological research and clinical application, guiding future studies and therapeutic developments in ASD-related auditory processing deficits.

Macroautophagy at the service of synapses

Post-mitotic and highly polarized neurons are dependent on the fitness of their synapses, which are often found a long distance away from the soma. How the synaptic proteome is maintained, dynamically reshaped, and continuously turned over is a topic of intense investigation. Autophagy, a highly conserved, lysosome-mediated degradation pathway has emerged as a vital component of long-term neuronal maintenance, and now more specifically of synaptic homeostasis. Here, we review the most recent findings on how autophagy undergoes both dynamic and local regulation at the synapse, and how it contributes to pre- and post-synaptic proteostasis and function. We also discuss the insights and open questions that this new evidence brings.

Exploring Dapagliflozin's Influence on Autophagic Flux in Mania-like Behaviour: Insights from the LKB1/AMPK/LC3 Pathway in a Mouse Model

Mania-like episodes are neuropsychiatric disturbances associated with bipolar disorder (BD). Autophagic flux disturbance evolved as one of the molecular mechanisms implicated in mania. Recently, Dapagliflozin (DAPA) has corrected autophagic signaling in several neurological disorders. Yet, no endeavours examined the autophagic impact of DAPA in mania-like behaviours. This study aimed to investigate the effect of DAPA on disrupted autophagic pathways in a mouse model of mania-like behaviour. Mania-like behaviour was induced through paradoxical sleep deprivation (PSD) using the multiple-platform method for a duration of 36 h. Mice were divided into three groups, with DAPA (1 mg/kg/day, orally) administered for one week. Behavioural assessments were conducted on the 7th day. DAPA mitigated anxiety-like behaviour in the open field test and improved motor coordination and muscle tone in the rotarod test. Mechanistically, DAPA activated hippocampal autophagy-related markers; liver kinase B1/AMP-activated protein kinase (LKB1/AMPK) pathway, autophagy related gene 7 (ATG7), and microtubule-associated protein light chain 3II (LC3II). This was associated with reduced levels of the autophagosome receptor p62 protein, which subsequently enhanced GABAA receptor-associated protein (GABARAP), facilitating the surface presentation of GABAA receptors. Additionally, DAPA upregulated the GABAB receptor R2 subunit through trophic factors such as brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). Furthermore, DAPA mitigated elevated serum stress hormones and restored the balance between proinflammatory and anti-inflammatory cytokines in both cortical and hippocampal tissues. These findings highlight the role of autophagic flux modulation by DAPA and its therapeutic potential in mitigating mania-like behaviours.

Genotype-phenotype correlation for skin and neuropsychiatric features in tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by pathogenic variants in TSC1 and TSC2. The condition manifests as diverse symptoms across multiple organ systems and is frequently associated with neuropsychiatric symptoms. However, the relationship between the severity of these manifestations remains poorly understood. This study aimed to elucidate correlations between the severity of various skin and neuropsychiatric symptoms and the underlying TSC1/TSC2 pathology.

PRRG4 Brain-Specific Conditional Knockout Mice Display Autism Spectrum Disorder-Like Behaviors

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized primarily by social deficits and repetitive behaviors. The mechanisms of ASD are complex and are not yet fully understood, although many ASD risk genes and mouse models have been reported. It has been suggested that deletion of PRRG4 (proline-rich and Gla domain 4) deletion may contribute to autism symptoms in patients with WAGR (Wilms' tumor, aniridia, gonadoblastoma, mental retardation) syndrome. The mouse model with PRRG4 gene deletion has not been reported so far. This study investigated whether brain-specific conditional knockout of PRRG4 induces ASD-like symptoms in mice by crossing the PRRG4fl/fl mice with Emx1-Cre mice, which express Cre in the cerebral cortex and hippocampus.

RESULTS

The PRRG4 brain-specific knockout (PRRG4fl/fl-Cre+, PRRG4-CKO) mice exhibited social deficits, repetitive behaviors, and anxiety-like symptoms compared to PRRG4fl/fl control mice according to the results of various behavioral tests. PRRG4 knockout led to the increase in total dendritic length, branching, and dendritic spine density in the pyramidal neurons of the cerebral cortex and hippocampus, as well as enhanced levels of synaptic proteins including SYP and PSD95. Immunoprecipitation experiment with PRRG4 antibodies showed dramatic decreased interaction of PRRG4 and MAGI2 proteins in brain tissues from PRRG4-CKO mice compared to PRRG4fl/fl control mice. GST-RBD pull-down assay showed a significant decrease in RhoA-GTP levels in the cerebral cortex and hippocampus of PRRG4-CKO mice.

CONCLUSIONS

Brain-specific conditional knockout of the PRRG4 in mice leads to ASD-like symptoms. PRRG4 protein may regulate dendritic and synaptic development in mice by activating RhoA through interaction with MAGI2. These findings provide evidence for a comprehensive understanding of PRRG4 function in vivo and support the association between PRRG4 loss and ASD phenotypes observed in WAGR syndrome.

The Notch Signaling Pathway: A Potential Target for Mental Disorders

The highly conserved Notch signaling pathway plays a critical role in cell fate determination during metazoan development through cell-to-cell communication. The classical pathway consists of Notch receptors, ligands, intracellular effectors, DNA-binding proteins, and other regulatory molecules. Recent research has highlighted its involvement in the pathogenesis of several diseases. In autism, bipolar disorder, and schizophrenia, the Notch signaling pathway is implicated in key processes such as neuronal development and synaptic plasticity. Furthermore, it has been shown to play significant roles in other mental health conditions, including anxiety, depression, post-traumatic stress disorder, and neurocognitive disorders. However, the precise mechanisms underlying the contribution of Notch to these conditions remain poorly understood. This review examines the current understanding of the Notch signaling pathway in mental disorders, highlighting its role in their pathophysiology and summarizing therapeutic strategies aimed at modulating this pathway to improve mental health outcomes.

Abnormalities of brain dynamics based on large-scale cortical network modeling in autism spectrum disorder

Synaptic increase is a common phenomenon in the brain of autism spectrum disorder (ASD). However, the impact of increased synapses on the neurophysiological activity of ASD remains unclear. To address this, we propose a large-scale cortical network model based on empirical structural connectivity data using the Wendling model, which successfully simulates both pathological and physiological electroencephalography (EEG) signals. Building on this, the EEG functional network is constructed using the phase lag index, effectively characterizing the functional connectivity. Our modeling results indicate that EEG activity and functional network properties undergo significant changes by globally increasing synaptic coupling strength. Specifically, it leads to abnormal neural oscillations clinically reported in ASD, including the decreased dominant frequency, the decreased relative power in the α band and the increased relative power in the δ+θ band, particularly in the frontal lobe. At the same time, the clustering coefficient and global efficiency of the functional network decrease, while the characteristic path length increases, suggesting that the functional network of ASD is inefficient and poorly integrated. Additionally, we find insufficient functional connectivity across multiple brain regions in ASD, along with decreased wavelet coherence in the α band within the frontal lobe and between the frontal and temporal lobes. Considering that most of the synaptic increases in ASD are limited, brain regions are further randomly selected to increase the local synaptic coupling strength. The results show that disturbances in local brain regions can also facilitate the development of ASD. This study reveals the intrinsic link between synapse increase and abnormal brain activity in ASD, and inspires treatments related to synapse pruning.

Stress dynamically modulates neuronal autophagy to gate depression onset

Chronic stress remodels brain homeostasis, in which persistent change leads to depressive disorders1. As a key modulator of brain homeostasis2, it remains elusive whether and how brain autophagy is engaged in stress dynamics. Here we discover that acute stress activates, whereas chronic stress suppresses, autophagy mainly in the lateral habenula (LHb). Systemic administration of distinct antidepressant drugs similarly restores autophagy function in the LHb, suggesting LHb autophagy as a common antidepressant target. Genetic ablation of LHb neuronal autophagy promotes stress susceptibility, whereas enhancing LHb autophagy exerts rapid antidepressant-like effects. LHb autophagy controls neuronal excitability, synaptic transmission and plasticity by means of on-demand degradation of glutamate receptors. Collectively, this study shows a causal role of LHb autophagy in maintaining emotional homeostasis against stress. Disrupted LHb autophagy is implicated in the maladaptation to chronic stress, and its reversal by autophagy enhancers provides a new antidepressant strategy.

Severity of autism-related symptoms in treatment-resistant schizophrenia: associations with cognitive performance, psychosocial functioning, and neurological soft signs - Clinical evidence and ROC analysis

Treatment-resistant schizophrenia (TRS) occurs when symptoms persist despite adequate antipsychotic treatment in terms of both timing and dosage. This severe condition is often overlooked, despite the existence of guidelines, with an average delay of 4-9 years before the introduction of clozapine, the gold standard treatment. We hypothesized that schizophrenia patients with severe autistic symptoms are more prone to develop TRS. To test this, we administered the Positive and Negative Syndrome Scale for Schizophrenia Autism Severity Scale (PAUSS) to 117 patients diagnosed with schizophrenia. Our results revealed that both TRS and clozapine non-responder (CLZ-nR) groups had higher rates of autistic symptoms than non-TRS patients. A machine learning model was developed to examine the relationship between PAUSS scores and TRS, obtaining an accuracy of 0.65 and an AUC of 0.67. Specifically, PAUSS items N6 ("lack of spontaneity and flow of conversation") and N7 ("stereotypical thinking") emerged as the most significant factors in the model. In addition, PAUSS was correlated with cognitive and social functions, as well as soft neurological signs, in TRS patients. Autism-related symptoms were found to predict significant variance in motor coordination, verbal fluency, functional ability and soft neurological signs. These results suggest that autism-related symptoms in schizophrenia may define a distinct subgroup with unique neurobiological characteristics.

Neural cell competition sculpting brain from cradle to grave

Darwinian selection, operating within the cellular ecosystem of multicellular organisms, drives a pervasive surveillance mechanism of cell-cell competition that shapes tissue architecture and function. While cell competition eliminates suboptimal cells to ensure tissue integrity across various tissues, neuronal competition specifically sculpts neural networks to establish precise circuits for sensory, motor and cognitive functions. However, our understanding of cell competition across diverse neural cell types in both developmental and pathological contexts remains limited. Here, we review recent advances on the phenomenon, and mechanisms and potential functions of neural cell competition (NCC), ranging from neural progenitors, neurons, astrocytes and oligodendrocytes to microglia. Physiological NCC governs cellular survival, proliferation, arborization, organization, function and territorial colonization, whereas dysregulated NCC may cause neurodevelopmental disorders, accelerate aging, exacerbate neurodegenerative diseases and drive brain tumor progression. Future work that leverages cell competition mechanisms may help to improve cognition and curb diseases.

Paeoniflorin modulates AGEs/RAGE/P38MAPK/ERK/mTOR autophagy pathway to improve cognitive dysfunction in MRL/lpr mice

OBJECTIVE

The objective of this study was to investigate the therapeutic effects of paeoniflorin (PA) on cognitive impairment and to elucidate its potential mechanisms in MRL/lpr mice, a model of systemic lupus erythematosus-associated cognitive dysfunction.

METHOD

Cognitive performance and behavioral responses were assessed using a comprehensive battery of tests, including the Morris water maze, the Novel object recognition test, and the Y maze. Neuropathological changes in the hippocampal regions were visualized through Nissl, HE and Immunohistochemistry staining. Protein expression levels of receptor for advanced glycation end-products (RAGE) and LC3B were quantified by immunofluorescence, while the ultrastructure of autophagic organelles was examined using transmission electron microscopy (TEM). Inflammatory cytokines, namely tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6) were quantified in both serum and hippocampal homogenates by enzyme-linked immunosorbent assay (ELISA). The hippocampal expression of advanced glycation end-products (AGEs), RAGE, p62, Beclin-1, and key proteins involved in the mitogen-activated protein kinase (MAPK) pathways, including p38MAPK, ERK, and mTOR were analyzed by Western blotting.

RESULT

Paeoniflorin ameliorates cognitive dysfunction, neuronal damage, pro-inflammatory cytokine production in MRL/lpr mice. Paeoniflorin suppresses RAGE and autophagy levels and P38 MAPK/ERK/mTOR signaling pathway activation in the hippocampus of MRL/lpr mice.

CONCLUSION

Paeoniflorin may exert its neuroprotective effects by modulating the AGEs/RAGE/P38MAPK/ERK/mTOR autophagy signaling pathway.

Activation of Hippocampal Neuronal NADPH Oxidase NOX2 Promotes Depressive-Like Behaviour and Cognition Deficits in Chronic Restraint Stress Mouse Model

BACKGROUND

Nicotinamide adenosine dinucleotide phosphate oxidases (NOX) play important roles in mediating stress-induced depression. Three NOX isotypes are expressed mainly in the brain: NOX2, NOX3 and NOX4. In this study, the expression and cellular sources of these NOX isoforms was investigated in the context of stress-induced depression.

METHODS

Chronic restraint stress (CRS)-induced depressive-like behaviour and cognitive deficits were evaluated by tail suspension tests, forced swimming tests and the Morris water maze test. Hippocampal NOX expression was determined by immunofluorescence staining and western blotting. The hippocampal levels of the brain-derived neurotrophic factor (BDNF) mRNA were determined via quantitative real-time -polymerase chain reaction. Glucocorticoid levels in the hippocampus were measured using ELISA kits.

RESULTS

In the mouse CRS model, a significant increase in NOX2 expression was observed in the hippocampus, whereas no significant changes in NOX3 and NOX4 expression were detected. Next, NOX2 expression was primarily localised to neurons (NeuN+) but not microglia (Iba-1+) or astrocytes (GFAP+). Treatment with gp91ds-tat, a specific NOX2 inhibitor, effectively mitigated the behavioural deficits induced by CRS. The decreased expression of the BDNF mRNA in the hippocampus of CRS mice was restored upon gp91ds-tat treatment. A positive correlation was identified between neuronal NOX2 expression and serum glucocorticoid levels.

CONCLUSIONS

Our study indicated that neuronal NOX2 may be a critical mediator of depression-like behaviours and spatial cognitive deficits in mice subjected to CRS. Blockade of NOX2 signalling may be a promising therapeutic strategy for depression.

Developmental neurotoxicity of bisphenol F and bisphenol S in animal model systems: A literature review

Neurodevelopmental disorders have complex etiologies, stemming both from genetic and environmental risk factors, including gestational exposure to bisphenol A (BPA). BPA is an endocrine-disrupting chemical widely used in the synthesis of plastics and epoxy-resins. In 2012, the Food and Drug Administration issued a ban on the use of BPA in certain baby and childhood products, which contributed to the proliferation of BPA-free products. To make products without BPA, plastic and epoxy manufacturers often use chemical analogs, including bisphenol F (BPF) and bisphenol S (BPS). However, the structural and biochemical similarities BPF and BPS share with BPA suggest they may have similar molecular and cellular impacts on the developing nervous system, despite consumers generally regarding BPA-free products as safer alternatives. In this review, we synthesized all available peer-reviewed primary literature to date reporting on the neurodevelopmental impacts of BPF and/or BPS in animal models. In total, 61 papers were identified as relevant to the topic, including evaluation of BPF- and BPS-associated neurodevelopmental phenotypes such as changes in neurodevelopmental gene expression, the proliferation and differentiation of neural stem cells, synaptogenesis, central nervous system morphology, neuronal cell death, and behavior. Though less extensively studied than BPA, the collective works described here indicate that BPF and BPS can act as developmental neurotoxicants in animal models, urging further mechanistic and epidemiological analyses of these bisphenol analogs, as well as a reconsideration by regulatory agencies of policies surrounding their usage.

Distinct features of EEG microstates in autism spectrum disorder revealed by meta-analysis: the contribution of individual age to heterogeneity across studies

Background and purpose

Electroencephalographic (EEG) microstates, as quasi-stable scalp EEG spatial patterns, are characterized by their high temporal resolution, making them a potentially powerful approach for studying the function of large-scale brain networks. A substantial body of research has demonstrated that abnormalities in the function or structure of large-scale brain networks are closely related to many characteristics of autism spectrum disorder (ASD). Investigating the EEG microstate features of individuals with autism can help reveal the nature of autism. To date, numerous studies have observed unique resting-state microstate patterns in individuals with autism. However, the results of these studies have not been consistent. Therefore, the present study aims to assess the differences in microstate parameters between ASD and non-autistic groups through meta-analysis and to explore the sources of research heterogeneity.

Method

This meta-analysis was preregistered with PROSPERO (CRD42024599897) and followed PRISMA guidelines. Studies in English comparing EEG microstate patterns between ASD and Non-autistic groups were retrieved by database search to October 20, 2024. The meta-analysis was then conducted using RevMan5.2. Pooled results are expressed as standardized mean difference (SMD). Heterogeneity (I²) and publication bias were assessed using Stata15.0.

Result

Seven studies enrolling 194 ASD individuals were included, four deemed high quality and three moderate quality according to bias risk assessment. Microstate B duration and coverage were significantly greater in the pooled ASD group (duration SMD=0.83, 95%CI: 0.17-1.5; coverage SMD=0.54, 95%CI: 0.18-0.90), but heterogeneity could not be excluded. Microstate C occurrence frequency was also in the ASD group (SMD= -0.61, 95%CI: -1.08 to -0.15), and heterogeneity was significant. Sensitivity analysis revealed that only the group difference in microstate B coverage was robust. Subgroup analysis suggested that age was the main source of heterogeneity in microstate B and C coverage. Results were not affected by publication bias according to Egger's test.

Conclusion

Future studies on the EEG microstate characteristics of ASD must control for age as an important cofounding variable.

Systematic Review Registration

PROSPERO, identifier CRD42024599897.

PDZD8 promotes autophagy at ER-lysosome membrane contact sites to regulate activity-dependent synaptic growth

Building synaptic connections requires coordinating a host of cellular activities from cell signaling to protein turnover, placing a high demand on intracellular communication. Membrane contact sites (MCSs) formed between organelles have emerged as key signaling hubs for coordinating diverse cellular activities, yet their roles in the developing nervous system remain obscure. We investigate the in vivo function of the endoplasmic reticulum (ER) MCS tethering and lipid-transfer protein PDZD8, which was recently linked to intellectual disability, in the nervous system. We find that PDZD8 is required for activity-dependent synaptic bouton formation in multiple paradigms. PDZD8 is sufficient to drive excess synaptic bouton formation through an autophagy-dependent mechanism and required for synapse development when autophagy is limited. PDZD8 accelerates autophagic flux by promoting lysosome maturation at ER-late endosome/lysosome MCSs. We propose that PDZD8 functions in the nervous system to increase autophagy during periods of high demand, including activity-dependent synaptic growth.

Conserved components of the macroautophagy machinery in Caenorhabditis elegans

Macroautophagy involves the sequestration of cytoplasmic contents in a double-membrane autophagosome and its subsequent delivery to lysosomes for degradation and recycling. In Caenorhabditis elegans, autophagy participates in diverse processes such as stress resistance, cell fate specification, tissue remodeling, aging, and adaptive immunity. Genetic screens in C. elegans have identified a set of metazoan-specific autophagy genes that form the basis for our molecular understanding of steps unique to the autophagy pathway in multicellular organisms. Suppressor screens have uncovered multiple mechanisms that modulate autophagy activity under physiological conditions. C. elegans also provides a model to investigate how autophagy activity is coordinately controlled at an organismal level. In this chapter, we will discuss the molecular machinery, regulation, and physiological functions of autophagy, and also methods utilized for monitoring autophagy during C. elegans development.

Animal studies reveal downregulation of the Beclin-1 autophagy pathway as shared mechanism in Autism Spectrum Disorder: a systematic review and meta-analysis

BACKGROUND

Autism Spectrum Disorder (ASD) is a heterogeneous neurodevelopmental condition with complex etiology, involving genetic and environmental influences on brain development and behavior. Dysregulation of mammalian target of rapamycin (mTOR) signaling alters neuronal growth and synaptic plasticity, and has emerged as a potential underlying pathway in ASD.

GOAL AND METHODS

To investigate mTOR dysregulation as a common mechanism in ASD, we performed a systematic review, and a meta-analysis of 192 studies examining mTOR signaling in diverse genetic and environmental animal models.

RESULTS

Our random-effects model identified significant alterations in mTOR pathway-related proteins. For several proteins (p-AKT, PTEN, p-mTOR, p-EIF4e, LC3-II, p-S6K and p-S6), subgroup analyses revealed clear species-, sex-, age-, or brain region-specific effects. Interestingly, Beclin-1 was consistently downregulated across all subgroups.

CONCLUSION

Our findings support mTOR-pathway dysregulation in ASD. The observed consistent downregulation of Beclin-1 highlights autophagy as a common mechanism, and provides new leads for novel ASD biomarker and treatment development.

Prenatal Exposure To Valproic Acid Induces Increased Autism-Like Behaviors and Impairment of Learning and Memory Functions in Rat Offspring by Upregulating ADAM10 Expression

Autism spectrum disorder (ASD) involves a complex neurodevelopmental pathogenesis. A disintegrin and metalloproteinase 10 (ADAM10) plays a crucial role in embryonic brain development and neural network stability. This study aimed to investigate the influence of ADAM10 on excitation/inhibition (E/I) balance, autism-like behaviors, and learning and memory dysfunction in rats prenatally exposed to valproic acid (VPA) and determine potential intervention strategies. The VPA-exposed group exhibited increased levels of ADAM10 and secreted amyloid precursor protein-α (sAPPα). Moreover, overexpression of glutamate decarboxylase 1 and N-methyl-D-aspartate receptors was observed. High-performance liquid chromatography-mass spectrometry revealed elevated levels of glutamate, glutamine, and γ-aminobutyric acid, as well as an E/I imbalance in the VPA group. Additionally, narrower synaptic clefts as well as increased postsynaptic density and synaptic vesicles were observed. Remarkably, intraperitoneal administration of ADAM10 inhibitor during the critical period of synaptic development significantly improved ASD-like behavior and learning and memory function in VPA-exposed rats. This intervention effectively reduced abnormally high sAPPα levels in the prefrontal cortex and corrected abnormal E/I balance. Thus, inhibiting ADAM10 overexpression may improve the E/I imbalance, alleviate core symptoms of ASD, and improve learning and memory dysfunction. The use of ADAM10 inhibitor represents a potential therapeutic strategy for treating ASD patients with intellectual disabilities.

CRISPRi-based screen of autism spectrum disorder risk genes in microglia uncovers roles of ADNP in microglia endocytosis and synaptic pruning

Autism Spectrum Disorders (ASD) are a set of neurodevelopmental disorders with complex biology. The identification of ASD risk genes from exome-wide association studies and de novo variation analyses has enabled mechanistic investigations into how ASD-risk genes alter development. Most functional genomics studies have focused on the role of these genes in neurons and neural progenitor cells. However, roles for ASD risk genes in other cell types are largely uncharacterized. There is evidence from postmortem tissue that microglia, the resident immune cells of the brain, appear activated in ASD. Here, we used CRISPRi-based functional genomics to systematically assess the impact of ASD risk gene knockdown on microglia activation and phagocytosis. We developed an iPSC-derived microglia-neuron coculture system and high-throughput flow cytometry readout for synaptic pruning to enable parallel CRISPRi-based screening of phagocytosis of beads, synaptosomes, and synaptic pruning. Our screen identified ADNP, a high-confidence ASD risk genes, as a modifier of microglial synaptic pruning. We found that microglia with ADNP loss have altered endocytic trafficking, remodeled proteomes, and increased motility in coculture.

Neuronal autophagy in the control of synapse function

Neurons are long-lived postmitotic cells that capitalize on autophagy to remove toxic or defective proteins and organelles to maintain neurotransmission and the integrity of their functional proteome. Mutations in autophagy genes cause congenital diseases, sharing prominent brain dysfunctions including epilepsy, intellectual disability, and neurodegeneration. Ablation of core autophagy genes in neurons or glia disrupts normal behavior, leading to motor deficits, memory impairment, altered sociability, and epilepsy, which are associated with defects in synapse maturation, plasticity, and neurotransmitter release. In spite of the importance of autophagy for brain physiology, the substrates of neuronal autophagy and the mechanisms by which defects in autophagy affect synaptic function in health and disease remain controversial. Here, we summarize the current state of knowledge on neuronal autophagy, address the existing controversies and inconsistencies in the field, and provide a roadmap for future research on the role of autophagy in the control of synaptic function.

11C-UCB-J PET imaging is consistent with lower synaptic density in autistic adults

The neural bases of autism are poorly understood at the molecular level, but evidence from animal models, genetics, post-mortem studies, and single-gene disorders implicate synaptopathology. Here, we use positron emission tomography (PET) to assess the density of synapses with synaptic vesicle glycoprotein 2A (SV2A) in autistic adults using 11C-UCB-J. Twelve autistic (mean (SD) age 25 (4) years; six males), and twenty demographically matched non-autistic individuals (26 (3) years; eleven males) participated in a 11C-UCB-J PET scan. Binding potential, BPND, was the primary outcome measure and computed with the centrum semiovale as the reference region. Partial volume correction with Iterative Yang was applied to control for possible volumetric differences. Mixed-model statistics were calculated for between-group differences. Relationships to clinical characteristics were evaluated based on clinician ratings of autistic features. Whole cortex synaptic density was 17% lower in the autism group (p = 0.01). All brain regions in autism had lower 11C-UCB-J BPND compared to non-autistic participants. This effect was evident in all brain regions implicated in autism. Significant differences were observed across multiple individual regions, including the prefrontal cortex (-15%, p = 0.02), with differences most pronounced in gray matter (p < 0.0001). Synaptic density was significantly associated with clinical measures across the whole cortex (r = 0.67, p = 0.02) and multiple regions (rs = -0.58 to -0.82, ps = 0.05 to <0.01). The first in vivo investigation of synaptic density in autism with PET reveals pervasive and large-scale lower density in the cortex and across multiple brain areas. Synaptic density also correlated with clinical features, such that a greater number of autistic features were associated with lower synaptic density. These results indicate that brain-wide synaptic density may represent an as-yet-undiscovered molecular basis for the clinical phenotype of autism and associated pervasive alterations across a diversity of neural processes.

Multi-omics study reveals differential expression and phosphorylation of autophagy-related proteins in autism spectrum disorder

Our multi-omics study investigated the molecular mechanisms underlying autism spectrum disorder (ASD) using Shank3Δ4-22 and Cntnap2-/- mouse models. Through global- and phospho- proteomics of the mouse cortex, we focused on shared molecular changes and found that autophagy was particularly affected in both models. Global proteomics identified a small number of differentially expressed proteins that significantly impact postsynaptic components and synaptic function, including key pathways such as mTOR signaling. Phosphoproteomics revealed unique phosphorylation sites in autophagy-related proteins such as ULK2, RB1CC1, ATG16L1, and ATG9, suggesting that altered phosphorylation patterns contribute to impaired autophagic flux in ASD. SH-SY5Y cells with SHANK3 gene deletion showed elevated LC3-II and p62 levels, indicating autophagosome accumulation and autophagy initiation, while the reduced level of the lysosomal activity marker LAMP1 suggested impaired autophagosome-lysosome fusion. The study highlights the involvement of reactive nitrogen species and nitric oxide (NO) on autophagy disruption. Importantly, inhibition of neuronal NO synthase (nNOS) by 7-NI normalized autophagy markers levels in the SH-SY5Y cells and primary cultured neurons. We have previously shown that nNOS inhibition improved synaptic and behavioral phenotypes in Shank3Δ4-22 and Cntnap2-/- mouse models. Our multi-omics study reveals differential expression and phosphorylation of autophagy-related proteins in ASD but further investigation is needed to prove the full involvement of autophagy in ASD. Our study underscores the need for further examination into the functional consequences of the identified phosphorylation sites, which may offer potential novel therapeutic autophagy-related targets for ASD treatment.

Non-ionotropic signaling through the NMDA receptor GluN2B carboxy-terminal domain drives dendritic spine plasticity and reverses fragile X phenotypes

N-methyl-D-aspartate (NMDA)-induced spine shrinkage proceeds independently of ion flux and requires the initiation of de novo protein synthesis. Using subtype-selective pharmacological and genetic tools, we find that structural plasticity is dependent on ligand binding to GluN2B-containing NMDA receptors (NMDARs) and signaling via the GluN2B carboxy-terminal domain (CTD). Disruption of non-ionotropic signaling by replacing the GluN2B CTD with the GluN2A CTD leads to an increase in spine density, dysregulated basal protein synthesis, exaggerated long-term depression mediated by G-protein-coupled metabotropic glutamate receptors (mGluR-LTD), and epileptiform activity reminiscent of phenotypes observed in the Fmr1 knockout (KO) model of fragile X syndrome. By crossing the Fmr1 KO mice with animals in which the GluN2A CTD has been replaced with the GluN2B CTD, we observe a correction of these core fragile X phenotypes. These findings suggest that non-ionotropic NMDAR signaling through GluN2B may represent a novel therapeutic target for the treatment of fragile X and related causes of intellectual disability and autism.

Chemogenetic induction of CA1 hyperexcitability triggers indistinguishable autistic traits in asymptomatic mice differing in Ambra1 expression and sex

Among the genomic alterations identified as risk factors in mice models of autism spectrum disorders (ASD), heterozygous deletion of Ambra1 (Activating Molecule in Beclin1-Regulated Autophagy) triggers an ASD phenotype associated with hippocampal hyperexcitability exclusively in the female sex although Ambra1 protein is comparably expressed in the hippocampus of symptomatic females and asymptomatic males. Given the intricate relationship between Ambra1 deficiency and sex in the etiology of ASD, we took advantage of asymptomatic mice including Ambra1+/- males and wild-type (Wt) mice of both sexes to investigate whether their non-pathogenic variations in Ambra1 levels could underlie a differential susceptibility to exhibit ASD-like traits in response to experimental elevation of hippocampal excitability. Here we report that selective activation of inhibitory DREADD in CA1 parvalbumin-positive interneurons (PV-IN) reduces GABAergic currents onto pyramidal neurons (PN), causes social and attentional deficits, and augments the proportion of immature/thin spines in CA1 PN dendrites to the same extent in Ambra1+/- males and Wt mice of both sexes. Our findings show that the substantial hippocampal variations in pro-autophagic Ambra1 gene product shown by asymptomatic mice differing in mutation and/or sex do not underlie a differential reactivity to chemogenetic induction of idiopathic ASD.

Novel 5-HT6R modulators as mTOR-dependent neuronal autophagy inductors

Autophagy is a natural process in which the cell degrades substances through the lysosomal pathway. One of the most studied mechanisms for regulating autophagy is the mTOR signaling pathway. Recent research has shown that the 5-HT6 receptor is linked to the mTOR pathway and can affect cognition in various neurodevelopmental models. Therefore, developing 5-HT6 receptor antagonists could improve cognition by inducing autophagy through the inhibition of the mTOR pathway. Our study reports two in-house-designed 5-HT6R antagonists, PUC-10 and its indazole analogue PUC-55, that induce mTOR-dependent autophagy. PUC-10, an indole-based 5-HT6 receptor antagonist with high binding affinity (Ki = 14.6 nM) and antagonist potency (IC50 = 32 nM), demonstrated more than 90% at 25 µM cellular viability and a high capacity to induce autophagy in the neuroblastoma SH-SY5Y cell line. Similarly, its indazole analogue, PUC-55 (Ki = 37.5 nM), exhibited high cellular viability and potent autophagy-inducing activity. Both compounds induced overexpression of the 5-HT6 receptor after 24 h of stimulation, contrasting with the effects observed with Rapamycin (100 nM), a well-known mTOR inhibitor. Additionally, the signaling pathway was characterized, showing that both PUC-10 and PUC-55 induce autophagy by inhibiting the mTOR pathway, suggesting their potential therapeutic applications for neurological disorders.

Transcallosal white matter and cortical gray matter variations in autistic adults aged 30-73 years

BACKGROUND

Autism spectrum disorder (ASD) is a lifelong condition that profoundly impacts health, independence, and quality of life. However, research on brain aging in autistic adults is limited, and microstructural variations in white and gray matter remain poorly understood. To address this critical gap, we assessed novel diffusion MRI (dMRI) biomarkers, free water, and free water corrected fractional anisotropy (fwcFA), and mean diffusivity (fwcMD) across 32 transcallosal tracts and their corresponding homotopic grey matter origin/endpoint regions of interest (ROIs) in middle and old aged autistic adults.

METHODS

Forty-three autistic adults aged 30-73 and 43 age-, sex-, and IQ-matched neurotypical controls underwent dMRI scans. We examined free water, fwcFA, fwcMD differences between the two groups and age-related pattern of each dMRI metric across the whole brain for each group. The relationships between clinical measures of ASD and free water in regions that significantly differentiated autistic adults from neurotypical controls were also explored. In supplementary analyses, we also assessed free water uncorrected FA and MD using conventional single tensor modeling.

RESULTS

Autistic adults exhibited significantly elevated free water in seven frontal transcallosal tracts compared to controls. In controls, age-related increases in free water and decreases in fwcFA were observed across most transcallosal tracts. However, these age-associated patterns were entirely absent in autistic adults. In gray matter, autistic adults showed elevated free water in the calcarine cortices and lower fwcMD in the dorsal premotor cortices compared to controls. Lastly, age-related increases in free water were found across all white matter and gray matter ROIs in neurotypical controls, whereas no age-related associations were detected in any dMRI metrics for autistic adults.

LIMITATIONS

We only recruited cognitively capable autistic adults, which limits the generalizability of our findings across the full autism spectrum. The cross-sectional design precludes inferences about microstructural changes over time in middle and old aged autistic adults.

CONCLUSIONS

Our findings revealed increased free water load in frontal white matter in autistic adults and identified distinct age-associated microstructural variations between the two groups. These findings highlight more heterogeneous brain aging profiles in autistic adults. Our study also demonstrated the importance of quantifying free water in dMRI studies of ASD.

Biological subtyping of autism via cross-species fMRI

It is frequently assumed that the phenotypic heterogeneity in autism spectrum disorder reflects underlying pathobiological variation. However, direct evidence in support of this hypothesis is lacking. Here, we leverage cross-species functional neuroimaging to examine whether variability in brain functional connectivity reflects distinct biological mechanisms. We find that fMRI connectivity alterations in 20 distinct mouse models of autism (n=549 individual mice) can be clustered into two prominent hypo- and hyperconnectivity subtypes. We show that these connectivity profiles are linked to distinct signaling pathways, with hypoconnectivity being associated with synaptic dysfunction, and hyperconnectivity reflecting transcriptional and immune-related alterations. Extending these findings to humans, we identify analogous hypo- and hyperconnectivity subtypes in a large, multicenter resting state fMRI dataset of n=940 autistic and n=1036 neurotypical individuals. Remarkably, hypo- and hyperconnectivity autism subtypes are replicable across independent cohorts (accounting for 25.1% of all autism data), exhibit distinct functional network architecture, are behaviorally dissociable, and recapitulate synaptic and immune mechanisms identified in corresponding mouse subtypes. Our cross-species investigation, thus, decodes the heterogeneity of fMRI connectivity in autism into distinct pathway-specific etiologies, offering a new empirical framework for targeted subtyping of autism.

A cellular and molecular basis of leptin resistance

Similar to most humans with obesity, diet-induced obese (DIO) mice have high leptin levels and fail to respond to the exogenous hormone, suggesting that their obesity is caused by leptin resistance, the pathogenesis of which is unknown. We found that leptin treatment reduced plasma levels of leucine and methionine, mTOR-activating ligands, leading us to hypothesize that chronic mTOR activation might reduce leptin signaling. Rapamycin, an mTOR inhibitor, reduced fat mass and increased leptin sensitivity in DIO mice but not in mice with defects in leptin signaling. Rapamycin restored leptin's actions on POMC neurons and failed to reduce the weight of mice with defects in melanocortin signaling. mTOR activation in POMC neurons caused leptin resistance, whereas POMC-specific mutations in mTOR activators decreased weight gain of DIO mice. Thus, increased mTOR activity in POMC neurons is necessary and sufficient for the development of leptin resistance in DIO mice, establishing a key pathogenic mechanism leading to obesity.

Bassoon, Presynaptic Scaffolding Protein: Narrative Review in Health and Disease

The release of synaptic vesicles (SVs) at the synaptic junction is a complex process involving various specialized proteins that work in unison. Among these, Bassoon has emerged as a significant protein, particularly noted for its association with various neurological and aging-related diseases. Due to its structural and functional roles, Bassoon has become a focus of recent research, especially in understanding its implications in neurodegenerative and psychiatric disorders. In this narrative review, we explore Bassoon's structure, function, and its role across a spectrum of neurological disorders. Neurotransmission is a tightly regulated process that relies on specialized structures within the presynaptic terminal, such as the presynaptic active zone (AZ), to precisely control SV release in response to incoming signals. The AZ comprises a complex network of large, multidomain proteins, with Bassoon playing a crucial role in this arrangement. Bassoon facilitates the tethering and reloading of SVs, ensuring responsiveness to high-frequency signals, while also maintaining proteostasis at the presynapse. This involves orchestrating the localization of proteins essential for neuronal development and plasticity. Bassoon's large size and unique structural features enable it to interact with and regulate the function of multiple proteins, making it integral to presynaptic functioning. Variants in the Bassoon gene have been linked to a variety of neurodegenerative and psychiatric conditions, including Progressive Supranuclear Palsy, multiple system atrophy (MSA), epilepsy, schizophrenia, bipolar disorder, and Parkinson's disease. This review delves into Bassoon's pivotal role in preserving presynaptic integrity and how disruptions in its functions may contribute to these disorders.

Sex Differences in the Relationship Between Cortical Thickness and Sensory Motor Symptoms in Adults on the Autism Spectrum

Background: Autism spectrum disorder (ASD) involves alterations in both cortical morphology and sensory processing. These structural and perceptual changes may lie on a continuum with typically developing (TD) individuals. However, investigations on possible links between these two factors are lacking, and it remains to be seen if their relationship differs by sex. We hypothesized that cortical thickness in the postcentral gyrus (a somatosensory processing hub) would correlate with sensory processing symptoms in a combined cohort of autistic and TD individuals. We also hypothesized that these correlations would differ based on sex. Methods: We studied 23 autistic adults and 27 TD adults using magnetic resonance imaging to measure the cortical thickness of the postcentral gyrus and the Ritvo Autism Asperger Diagnostic Scale-Revised (RAADS-R) to measure autism characteristics, with a particular focus on the sensory motor subscale. Results: The left postcentral gyrus (PCG) was found to be thicker in the autism group than in the TD group (d = 0.946, p = 0.003), particularly in autistic males compared to TD males and TD females. The RAADS-R sensory motor subscale and bilateral PCG cortical thickness were positively correlated across both autistic and TD males (Spearman's rho = 0.481, p = 0.008) but not females. These correlations were specific to the sensory motor subscale, as no correlations were found for RAADS-R total score or any of the other subscales. Conclusions: These results demonstrate sex-specific differences in the relationship between cortical thickness at the PCG and sensory processing in autistic individuals and that these differences exist along a continuum that extends into the TD population. Our findings contribute to furthering our understanding of sex-specific neuroanatomical differences in people on the autism spectrum. The left PCG thickness could be a potential sex-specific biomarker for sensorimotor function that is generally applicable in both neurotypical and autism populations. With further validations, this biomarker could be used to track responses to interventions targeting sensorimotor challenges in people on the autism spectrum.

Retinoic Acid Promotes Neuronal Differentiation While Increasing Proteins and Organelles Related to Autophagy

Retinoic acid (RA) is commonly used to differentiate SH-SY5Y neuroblastoma cells. This effect is sustained by a specific modulation of gene transcription, leading to marked changes in cellular proteins. In this scenario, autophagy may be pivotal in balancing protein synthesis and degradation. The present study analyzes whether some autophagy-related proteins and organelles are modified during RA-induced differentiation of SH-SY5Y cells. RA-induced effects were compared to those induced by starvation. SH-SY5Y cells were treated with a single dose of 10 µM RA or grown in starvation, for 3 days or 7 days. After treatments, cells were analyzed at light microscopy and transmission electron microscopy to assess cell morphology and immunostaining for specific markers (nestin, βIII-tubulin, NeuN) and some autophagy-related proteins (Beclin 1, LC3). We found that both RA and starvation differentiate SH-SY5Y cells. Specifically, cell differentiation was concomitant with an increase in autophagy proteins and autophagy-related organelles. However, the effects of a single dose of 10 μM RA persist for at least 7 days, while prolonged starvation produces cell degeneration and cell loss. Remarkably, the effects of RA are modulated in the presence of autophagy inhibitors or stimulators. The present data indicate that RA-induced differentiation is concomitant with an increased autophagy.

Turning garbage into gold: Autophagy in synaptic function

Trillions of synapses in the human brain enable thought and behavior. Synaptic connections must be established and maintained, while retaining dynamic flexibility to respond to experiences. These processes require active remodeling of the synapse to control the composition and integrity of proteins and organelles. Macroautophagy (hereafter, autophagy) provides a mechanism to edit and prune the synaptic proteome. Canonically, autophagy has been viewed as a homeostatic process, which eliminates aged and damaged proteins to maintain neuronal survival. However, accumulating evidence suggests that autophagy also degrades specific cargoes in response to neuronal activity to impact neuronal transmission, excitability, and synaptic plasticity. Here, we will discuss the diverse roles, regulation, and mechanisms of neuronal autophagy in synaptic function and contributions from glial autophagy in these processes.

The multifaceted role of mitochondria in autism spectrum disorder

Normal brain functioning relies on high aerobic energy production provided by mitochondria. Failure to supply a sufficient amount of energy, seen in different brain disorders, including autism spectrum disorder (ASD), may have a significant negative impact on brain development and support of different brain functions. Mitochondrial dysfunction, manifested in the abnormal activities of the electron transport chain and impaired energy metabolism, greatly contributes to ASD. The aberrant functioning of this organelle is of such high importance that ASD has been proposed as a mitochondrial disease. It should be noted that aerobic energy production is not the only function of the mitochondria. In particular, these organelles are involved in the regulation of Ca2+ homeostasis, different mechanisms of programmed cell death, autophagy, and reactive oxygen and nitrogen species (ROS and RNS) production. Several syndromes originated from mitochondria-related mutations display ASD phenotype. Abnormalities in Ca2+ handling and ATP production in the brain mitochondria affect synaptic transmission, plasticity, and synaptic development, contributing to ASD. ROS and Ca2+ regulate the activity of the mitochondrial permeability transition pore (mPTP). The prolonged opening of this pore affects the redox state of the mitochondria, impairs oxidative phosphorylation, and activates apoptosis, ultimately leading to cell death. A dysregulation between the enhanced mitochondria-related processes of apoptosis and the inhibited autophagy leads to the accumulation of toxic products in the brains of individuals with ASD. Although many mitochondria-related mechanisms still have to be investigated, and whether they are the cause or consequence of this disorder is still unknown, the accumulating data show that the breakdown of any of the mitochondrial functions may contribute to abnormal brain development leading to ASD. In this review, we discuss the multifaceted role of mitochondria in ASD from the various aspects of neuroscience.

Impaired macroautophagy confers substantial risk for intellectual disability in children with autism spectrum disorders

Autism spectrum disorder (ASD) represents a complex of neurological and developmental disabilities characterized by clinical and genetic heterogeneity. While the causes of ASD are still unknown, many ASD risk factors are found to converge on intracellular quality control mechanisms that are essential for cellular homeostasis, including the autophagy-lysosomal degradation pathway. Studies have reported impaired autophagy in ASD human brain and ASD-like synapse pathology and behaviors in mouse models of brain autophagy deficiency, highlighting an essential role for defective autophagy in ASD pathogenesis. To determine whether altered autophagy in the brain may also occur in peripheral cells that might provide useful biomarkers, we assessed activities of autophagy in lympoblasts from ASD and control subjects. We find that lymphoblast autophagy is compromised in a subset of ASD participants due to impaired autophagy induction. Similar changes in autophagy are detected in postmortem human brains from ASD individuals and in brain and peripheral blood mononuclear cells from syndromic ASD mouse models. Remarkably, we find a strong correlation between impaired autophagy and intellectual disability in ASD participants. By depleting the key autophagy gene Atg7 from different brain cells, we provide further evidence that autophagy deficiency causes cognitive impairment in mice. Together, our findings suggest autophagy dysfunction as a convergent mechanism that can be detected in peripheral blood cells from a subset of autistic individuals, and that lymphoblast autophagy may serve as a biomarker to stratify ASD patients for the development of targeted interventions.

Neurons Specialize in Presynaptic Autophagy: A Perspective to Ameliorate Neurodegeneration

The efficient and prolonged neurotransmission is reliant on the coordinated action of numerous synaptic proteins in the presynaptic compartment that remodels synaptic vesicles for neurotransmitter packaging and facilitates their exocytosis. Once a cycle of neurotransmission is completed, membranes and associated proteins are endocytosed into the cytoplasm for recycling or degradation. Both exocytosis and endocytosis are closely regulated in a timely and spatially constrained manner. Recent research demonstrated the impact of dysfunctional synaptic vesicle retrieval in causing retrograde degeneration of midbrain neurons and has highlighted the importance of such endocytic proteins, including auxilin, synaptojanin1 (SJ1), and endophilin A (EndoA) in neurodegenerative diseases. Additionally, the role of other associated proteins, including leucine-rich repeat kinase 2 (LRRK2), adaptor proteins, and retromer proteins, is being investigated for their roles in regulating synaptic vesicle recycling. Research suggests that the degradation of defective vesicles via presynaptic autophagy, followed by their recycling, not only revitalizes them in the active zone but also contributes to strengthening synaptic plasticity. The presynaptic autophagy rejuvenating terminals and maintaining neuroplasticity is unique in autophagosome formation. It involves several synaptic proteins to support autophagosome construction in tiny compartments and their retrograde trafficking toward the cell bodies. Despite having a comprehensive understanding of ATG proteins in autophagy, we still lack a framework to explain how autophagy is triggered and potentiated in compact presynaptic compartments. Here, we reviewed synaptic proteins' involvement in forming presynaptic autophagosomes and in retrograde trafficking of terminal cargos. The review also discusses the status of endocytic proteins and endocytosis-regulating proteins in neurodegenerative diseases and strategies to combat neurodegeneration.

Glial-derived TNF/Eiger signaling promotes somatosensory neurite sculpting

The selective elimination of inappropriate projections is essential for sculpting neural circuits during development. The class IV dendritic arborization (C4da) sensory neurons of Drosophila remodel the dendritic branches during metamorphosis. Glial cells in the central nervous system (CNS), are required for programmed axonal pruning of mushroom body (MB) γ neurons during metamorphosis in Drosophila. However, it is entirely unknown whether the glial cells are involved in controlling the neurite pruning of C4da sensory neurons. Here, we show that glial deletion of Eiger (Egr), orthologous to mammalian tumor necrosis factor TNF superfamily ligand, results in dendrite remodeling deficiency of Drosophila C4da sensory neurons. Moreover, the attenuation of neuronal Wengen (Wgn) and Grindelwald (Grnd), the receptors for TNF ligands, is also examined for defects in dendrite remodeling. We further discover that Wgn and Grnd facilitate dendrite elimination through the JNK Signaling. Overall, our findings demonstrate that glial-derived Egr signal links to the neuronal receptor Wgn/Grnd, activating the JNK signaling pathway and promoting developmental neuronal remodeling. Remarkably, our findings reveal a crucial role of peripheral glia in dendritic pruning of C4da neurons.

Neonatal infection with Bordetella pertussis promotes autism-like phenotypes in mice

Autism spectrum disorder (ASD) has been linked with infections early in life. Here we demonstrate that the infection of neonatal mice with the respiratory pathogen Bordetella pertussis leads to neuroinflammation, neurodevelopmental defects, and ASD-like behaviors. Following the respiratory challenge of neonatal mice with B. pertussis, multiple atypical CNS findings were observed, including blood-brain barrier disruption, dissemination of live B. pertussis bacteria to the brain with the concomitant infiltration of inflammatory monocytes, neutrophils, and activated IL-17A- and IFN-γ-producing CD4 T cells. Microglia from infected mice were activated, with impaired phagocytic function, resulting in defective synaptic pruning and disrupted neuronal circuit formation. Impaired neurodevelopment in B. pertussis-infected post-natal mice was associated with ASD-like behavioral abnormalities in young adulthood. Our data indicate that infection with virulent B. pertussis during infancy increases the risk of autism-like behavior in young adult mice. A study into the potential role of B. pertussis in human ASD is warranted.

Interplay of epilepsy and long-term potentiation: implications for memory

The interplay between long-term potentiation (LTP) and epilepsy represents a crucial facet in understanding synaptic plasticity and memory within neuroscience. LTP, a phenomenon characterized by a sustained increase in synaptic strength, is pivotal in learning and memory processes, particularly in the hippocampus. This review delves into the intricate relationship between LTP and epilepsy, exploring how alterations in synaptic plasticity mechanisms akin to those seen in LTP contribute to the hyperexcitable state of epilepsy. This state is conceptualized as a dysregulation between LTP and LTD (Long-term depression), leading to pathologically enhanced synaptic efficacy. Additionally, the role of neuroinflammation in both LTP and epilepsy is examined, highlighting how inflammatory mediators can influence synaptic plasticity. The dual role of neuroinflammatory pathways, enhancing or inhibiting LTP, is a focal area of ongoing research. The significance of various signaling pathways, including the MAPK, mTOR, and WNT/β-catenin pathways, in the modulation of synaptic plasticity and their relevance in both LTP and epilepsy. These pathways are instrumental in memory formation, consolidation, and epileptogenesis, illustrating a complex interaction between cellular mechanisms in the nervous system. Lastly, the role of calcium signaling in the relationship between LTP and epilepsy is scrutinized. Aberrant calcium signaling in epilepsy leads to an enhanced, yet pathologically altered, LTP. This dysregulation disrupts normal neural pathways, potentially leading to cognitive dysfunction, particularly in memory encoding and retrieval. The review emphasizes the need for targeted interventions in epilepsy that address cognitive functions alongside seizure control.

Soluble epoxide hydrolase deletion rescues behavioral and synaptic deficits by AMPK-mTOR pathway in autism animals

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social defects often accompanied with emotional comorbidities. Aberrations in synaptic function and plasticity are the core feature in the pathophysiology of ASD. Targeting soluble epoxide hydrolase (sEH) has been found to exert protection in a wide-range of pathological conditions. However, the regulation of sEH deficiency on the synaptic deficits of ASD and the underlying mechanisms remain unclear. The valproate (VPA)-treated ASD animal model with genetic sEH knockout was applied in the present study. The results showed that the sEH expression was significantly increased in the prefrontal cortex of VPA-treated animals. Although no effect was found on tail malformation and body weight loss, genetic sEH deletion alleviated social deficits, and fear learning and memory extinction in the VPA-treated mice. After a series of electrophysiological assessments, we found that the beneficial effects of sEH deletion focused on the long-term synaptic plasticity, rather than presynaptic efficiency, in the VPA-treated mice. Furthermore, we observed that the dysregulated AMPK-mTOR pathway was restored under genetic sEH deletion in VPA-treated mice. Taken together, these findings uncovered an important role of sEH deficiency in the synaptic dysfunctions of ASD mediated by AMPK-mTOR pathway, providing a novel therapeutic target for ASD.

Sigma-1 receptor modulation by fluvoxamine ameliorates valproic acid-induced autistic behavior in rats: Involvement of chronic ER stress modulation, enhanced autophagy and M1/M2 microglia polarization

Autism spectrum disorder (ASD) is a neurodevelopmental disorder. While, fluvoxamine (FVX) is an antidepressant and widely prescribed to ASD patients, clinical results are inconclusive and the mechanism of FVX in the management of ASD is unclear. This study determined the potential therapeutic impact of FVX, a sigma-1 receptor (S1R) agonist, against the valproic acid (VPA)-induced model of autism. On gestational day 12.5, Wistar pregnant rats were given a single intraperitoneal (i.p.) injection of either VPA (600 mg/kg) or normal saline (10 mL/kg, vehicle-control). Starting on postnatal day (PND) 21 to PND 50, FVX (30 mg/kg, P·O. daily) and NE-100, (S1R) antagonist, (1 mg/kg, i.p. daily) were given to male pups. Behavior tests and histopathological changes were identified at the end of the experiment. In addition, the cerebellum biomarkers of endoplasmic reticulum (ER) stress and autophagy were assessed. Microglial cell polarization to M1 and M2 phenotypes was also assessed. FVX effectively mitigated the histopathological alterations in the cerebellum caused by VPA. FVX enhanced sociability and stereotypic behaviors in addition to its noteworthy impact on autophagy enhancement, ER stress deterioration, and controlling microglial cell polarization. The current investigation confirmed that the S1R agonist, FVX, can lessen behavioral and neurochemical alterations in the VPA-induced rat model of autism.

Bi-allelic NRXN1α deletion in microglia derived from iPSC of an autistic patient increases interleukin-6 production and impairs supporting function on neuronal networking

Autism spectrum disorder (ASD) is a set of heterogeneous neurodevelopmental conditions, with a highly diverse genetic hereditary component, including altered neuronal circuits, that has an impact on communication skills and behaviours of the affected individuals. Beside the recognised role of neuronal alterations, perturbations of microglia and the associated neuroinflammatory processes have emerged as credible contributors to aetiology and physiopathology of ASD. Mutations in NRXN1, a member of the neurexin family of cell-surface receptors that bind neuroligin, have been associated to ASD. NRXN1 is known to be expressed by neurons where it facilitates synaptic contacts, but it has also been identified in glial cells including microglia. Asserting the impact of ASD-related genes on neuronal versus microglia functions has been challenging. Here, we present an ASD subject-derived induced pluripotent stem cells (iPSC)-based in vitro system to characterise the effects of the ASD-associated NRXN1 gene deletion on neurons and microglia, as well as on the ability of microglia to support neuronal circuit formation and function. Using this approach, we demonstrated that NRXN1 deletion, impacting on the expression of the alpha isoform (NRXN1α), in microglia leads to microglial alterations and release of IL6, a pro-inflammatory interleukin associated with ASD. Moreover, microglia bearing the NRXN1α-deletion, lost the ability to support the formation of functional neuronal networks. The use of recombinant IL6 protein on control microglia-neuron co-cultures or neutralizing antibody to IL6 on their NRXN1α-deficient counterparts, supported a direct contribution of IL6 to the observed neuronal phenotype. Altogether, our data suggest that, in addition to neurons, microglia are also negatively affected by NRXN1α-deletion, and this significantly contributes to the observed neuronal circuit aberrations.

Exploring Synaptic Pathways in Traumatic Brain Injury: A Cross-Phenotype Genomics Approach

Traumatic brain injury (TBI), a global leading cause of mortality and disability, lacks effective treatments to enhance recovery. Synaptic remodeling has been postulated as one mechanism that influences outcomes after TBI. We sought to investigate whether common mechanisms affecting synapse maintenance are shared between TBI and other neuropsychiatric conditions using pathway enrichment tools and genome-wide genotype data, with the goal of highlighting novel treatment targets. We leveraged an integrative approach, combining data from genome-wide association studies with pathway and gene-set enrichment analyses. Literature review-based and Reactome database-driven approaches were combined to identify synapse-related pathways of interest in TBI outcome and to assess for shared associations with conditions in which synapse-related pathobiological mechanisms have been implicated, including Alzheimer's disease, schizophrenia (SCZ), major depressive disorder, post-traumatic stress disorder, attention-deficit hyperactivity disorder, and autism spectrum disorder. Gene and pathway-level enrichment analyses were conducted using MAGMA and its extensions, e- and H-MAGMA, followed by Mendelian randomization to investigate potential causal associations. Of the 98 pathways tested, 32 were significantly enriched in the included conditions. In TBI outcome, we identified significant enrichment in five pathways: "Serotonin clearance from the synaptic cleft" (p = 0.0001), "Presynaptic nicotinic acetylcholine receptors" (p = 0.0003), "Postsynaptic nicotinic acetylcholine receptors" (p = 0.0003), "Highly sodium permeable postsynaptic acetylcholine nicotinic receptors" (p = 0.0001), and "Acetylcholine binding and downstream events" pathways (p = 0.0003). These associations highlight potential involvement of the cholinergic and serotonergic systems in post-TBI recovery. Three of those pathways were shared between TBI and SCZ, suggesting possible pathophysiologic commonalities. In this study, we utilize comparative and integrative genomic approaches across brain conditions that share synaptic mechanisms to explore the pathophysiology of TBI outcomes. Our results implicate associations between TBI outcome and synaptic pathways as well as pathobiological overlap with other neuropsychiatric diseases.

Supplementing with Vitamin D during Pregnancy Reduces Inflammation and Prevents Autism-Related Behaviors in Offspring Caused by Maternal Immune Activation

Autism spectrum disorder (ASD), a neurodevelopmental disorder of unknown etiology with limited treatment options, has emerged as a significant public health concern. Studies have demonstrated that prenatal vitamin D deficiency is a risk factor for ASD development in offspring; however, the underlying mechanism remains unclear. In this project, vitamin D was administered orally to pregnant mice with/without the subsequent administration of polyriboinosinic polyribocytidylic acid (Poly(I:C)), which induced the maternal immune activation (MIA). Our results showed that vitamin D supplementation during pregnancy alleviated MIA-induced ASD-like behaviors in offspring. Moreover, vitamin D supplementation reduced the MIA-induced elevation of interleukin-6 (IL-6) and IL-17a levels in both the maternal ileum and fetal brains. It also suppressed signal transducer and activator of transcription 3 (Stat3) activation and the elevated expression of serum amyloid A1 and A2 (SAA1/2) in the ileum of MIA-affected pregnant mice. This study revealed that vitamin D may reduce the expression of IL-17a by inhibiting the IL-6/Stat3/SAA signaling pathway, thereby improving ASD-like behavior in offspring mice, and provide a new theoretical support for the prevention and treatment of ASD by scientific dietary interventions and nutritional supplement during pregnancy.

Neuroglia in autism spectrum disorders

Autism spectrum disorder (ASD) is characterized by difficulties in social interaction, communication, and repetitive behavior, typically diagnosed during early childhood and attributed to altered neuronal network connectivity. Several genetic and environmental risk factors contribute to ASD, including pre- or early life immune activation, which can trigger microglial and astroglial reactivity, impacting early neurodevelopment. In ASD, astrocytes show altered glutamate metabolism, directly influencing neuronal network activity, while microglia display impaired synaptic pruning, an essential developmental process for the refinement of neuronal connections. Additionally, reduced myelination in specific cortical and subcortical regions may affect brain connectivity in ASD, with white matter integrity correlating with the severity of the disorder, suggesting an important role for oligodendrocytes and myelin in ASD. This chapter provides an overview of current literature on the role of neuroglia cells in ASD, with a focus on immune activation, glutamate signaling, synaptic pruning, and myelination.

Transcriptomic Evidence Reveals the Dysfunctional Mechanism of Synaptic Plasticity Control in ASD

BACKGROUND/OBJECTIVES

A prominent endophenotype in Autism Spectrum Disorder (ASD) is the synaptic plasticity dysfunction, yet the molecular mechanism remains elusive. As a prototype, we investigate the postsynaptic signal transduction network in glutamatergic neurons and integrate single-cell nucleus transcriptomics data from the Prefrontal Cortex (PFC) to unveil the malfunction of translation control.

METHODS

We devise an innovative and highly dependable pipeline to transform our acquired signal transduction network into an mRNA Signaling-Regulatory Network (mSiReN) and analyze it at the RNA level. We employ Cell-Specific Network Inference via Integer Value Programming and Causal Reasoning (CS-NIVaCaR) to identify core modules and Cell-Specific Probabilistic Contextualization for mRNA Regulatory Networks (CS-ProComReN) to quantitatively reveal activated sub-pathways involving MAPK1, MKNK1, RPS6KA5, and MTOR across different cell types in ASD.

RESULTS

The results indicate that specific pivotal molecules, such as EIF4EBP1 and EIF4E, lacking Differential Expression (DE) characteristics and responsible for protein translation with long-term potentiation (LTP) or long-term depression (LTD), are dysregulated. We further uncover distinct activation patterns causally linked to the EIF4EBP1-EIF4E module in excitatory and inhibitory neurons.

CONCLUSIONS

Importantly, our work introduces a methodology for leveraging extensive transcriptomics data to parse the signal transduction network, transforming it into mSiReN, and mapping it back to the protein level. These algorithms can serve as potent tools in systems biology to analyze other omics and regulatory networks. Furthermore, the biomarkers within the activated sub-pathways, revealed by identifying convergent dysregulation, illuminate potential diagnostic and prognostic factors in ASD.

Dysregulated acetylcholine-mediated dopamine neurotransmission in the eIF4E Tg mouse model of autism spectrum disorders

Autism spectrum disorder (ASD) consists of diverse neurodevelopmental conditions where core behavioral symptoms are critical for diagnosis. Altered dopamine (DA) neurotransmission in the striatum has been suggested to contribute to the behavioral features of ASD. Here, we examine DA neurotransmission in a mouse model of ASD characterized by elevated expression of eukaryotic initiation factor 4E (eIF4E), a key regulator of cap-dependent translation, using a comprehensive approach that encompasses genetics, behavior, synaptic physiology, and imaging. The results indicate that increased eIF4E expression leads to behavioral inflexibility and impaired striatal DA release. The loss of normal DA neurotransmission is due to a defect in nicotinic receptor signaling that regulates calcium dynamics in dopaminergic axons. These findings provide a mechanistic understanding of ASD symptoms and offer a foundation for targeted therapeutic interventions by revealing the intricate interplay between eIF4E, DA neurotransmission, and behavioral flexibility.