Abnormalities of synaptic mitochondria in autism spectrum disorder and related neurodevelopmental disorders

NECAB family of neuronal calcium-binding proteins in health and disease

The N-terminal EF-hand calcium-binding proteins 1-3 (NECAB1-3) constitute a family of predominantly neuronal proteins characterized by the presence of at least one EF-hand calcium-binding domain and a functionally less well characterized C-terminal antibiotic biosynthesis monooxygenase domain. All three family members were initially discovered due to their interactions with other proteins. NECAB1 associates with synaptotagmin-1, a critical neuronal protein involved in membrane trafficking and synaptic vesicle exocytosis. NECAB2 interacts with predominantly striatal G-protein-coupled receptors, while NECAB3 partners with amyloid-β A4 precursor protein-binding family A members 2 and 3, key regulators of amyloid-β production. This demonstrates the capacity of the family for interactions with various classes of proteins. NECAB proteins exhibit distinct subcellular localizations: NECAB1 is found in the nucleus and cytosol, NECAB2 resides in endosomes and the plasma membrane, and NECAB3 is present in the endoplasmic reticulum and Golgi apparatus. The antibiotic biosynthesis monooxygenase domain, an evolutionarily ancient component, is akin to atypical heme oxygenases in prokaryotes but is not well-characterized in vertebrates. Prokaryotic antibiotic biosynthesis monooxygenase domains typically form dimers, suggesting that calcium-mediated conformational changes in NECAB proteins may induce antibiotic biosynthesis monooxygenase domain dimerization, potentially activating some enzymatic properties. However, the substrate for this enzymatic activity remains uncertain. Alternatively, calcium-mediated conformational changes might influence protein interactions or the subcellular localization of NECAB proteins by controlling the availability of protein-protein interaction domains situated between the EF hands and the antibiotic biosynthesis monooxygenase domain. This review summarizes what is known about genomic organization, tissue expression, intracellular localization, interaction partners, and the physiological and pathophysiological role of the NECAB family.

Mitochondrial regulation of adult hippocampal neurogenesis: Insights into neurological function and neurodevelopmental disorders

Mitochondria are essential regulators of cellular energy metabolism and play a crucial role in the maintenance and function of neuronal cells. Studies in the last decade have highlighted the importance of mitochondrial dynamics and bioenergetics in adult neurogenesis, a process that significantly influences cognitive function and brain plasticity. In this review, we examine the mechanisms by which mitochondria regulate adult neurogenesis, focusing on the impact of mitochondrial function on the behavior of neural stem/progenitor cells and the maturation and plasticity of newborn neurons in the adult mouse hippocampus. In addition, we explore the link between mitochondrial dysfunction, adult hippocampal neurogenesis and genes associated with cognitive deficits in neurodevelopmental disorders. In particular, we provide insights into how alterations in the transcriptional regulator NR2F1 affect mitochondrial dynamics and may contribute to the pathophysiology of the emerging neurodevelopmental disorder Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS). Understanding how genes involved in embryonic and adult neurogenesis affect mitochondrial function in neurological diseases might open new directions for therapeutic interventions aimed at boosting mitochondrial function during postnatal life.

Transcranial photobiomodulation for neurodevelopmental disorders: a narrative review

BACKGROUND

Neurodevelopmental disorders (NDDs) such as autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and Down syndrome (DS) significantly impact social, communicative, and behavioral functioning. Transcranial photobiomodulation (t-PBM) with near-infrared light is a promising non-invasive neurostimulation technique for neuropsychiatric disorders, including NDDs. This narrative review aimed to examine the preclinical and clinical evidence of photobiomodulation (PBM) in treating NDDs.

METHODS

A comprehensive search across six databases was conducted, using a combination of MeSH terms and title/abstract keywords: "photobiomodulation", "PBM", "neurodevelopmental disorders", "NDD", and others. Studies applying PBM to diagnosed NDD cases or animal models replicating NDDs were included. Protocols, reviews, studies published in languages other than English, and studies not evaluating clinical or cognitive outcomes were excluded.

RESULTS

Nine studies were identified, including one preclinical and eight clinical studies (five on ASD, two on ADHD, and one on DS). The reviewed studies encompassed various t-PBM parameters (wavelengths: 635-905 nm) and targeted primarily frontal cortex areas. t-PBM showed efficacy in improving disruptive behavior, social communication, cognitive rigidity, sleep quality, and attention in ASD; in enhancing attention in ADHD; and in improving motor skills and verbal fluency in DS. Minimal adverse effects were reported. Proposed mechanisms involve enhanced mitochondrial function, modulated oxidative stress, and reduced neuroinflammation.

CONCLUSIONS

t-PBM emerges as a promising intervention for NDDs, with potential therapeutic effects across ASD, ADHD, and DS. These findings underscore the need for further research, including larger-scale, randomized sham-controlled clinical trials with comprehensive biomarker analyses, to optimize treatment parameters and understand the underlying mechanisms associated with the effects of t-PBM.

Citalopram exposure of hESCs during neuronal differentiation identifies dysregulated genes involved in neurodevelopment and depression

Selective serotonin reuptake inhibitors (SSRIs), including citalopram, are widely used antidepressants during pregnancy. However, the effects of prenatal exposure to citalopram on neurodevelopment remain poorly understood. We aimed to investigate the impact of citalopram exposure on early neuronal differentiation of human embryonic stem cells using a multi-omics approach. Citalopram induced time- and dose-dependent effects on gene expression and DNA methylation of genes involved in neurodevelopmental processes or linked to depression, such as BDNF, GDF11, CCL2, STC1, DDIT4 and GAD2. Single-cell RNA-sequencing analysis revealed distinct clusters of stem cells, neuronal progenitors and neuroblasts, where exposure to citalopram subtly influenced progenitor subtypes. Pseudotemporal analysis showed enhanced neuronal differentiation. Our findings suggest that citalopram exposure during early neuronal differentiation influences gene expression patterns associated with neurodevelopment and depression, providing insights into its potential neurodevelopmental impact and highlighting the importance of further research to understand the long-term consequences of prenatal SSRI exposure.

The research landscape concerning environmental factors in neurodevelopmental disorders: Endocrine disrupters and pesticides-A review

In recent years, environmental epidemiology and toxicology have seen a growing interest in the environmental factors that contribute to the increased prevalence of neurodevelopmental disorders, with the purpose of establishing appropriate prevention strategies. A literature review was performed, and 192 articles covering the topic of endocrine disruptors and neurodevelopmental disorders were found, focusing on polychlorinated biphenyls, polybrominated diphenyl ethers, bisphenol A, and pesticides. This study contributes to analyzing their effect on the molecular mechanism in maternal and infant thyroid function, essential for infant neurodevelopment, and whose alteration has been associated with various neurodevelopmental disorders. The results provide scientific evidence of the association that exists between the environmental neurotoxins and various neurodevelopmental disorders. In addition, other possible molecular mechanisms by which pesticides and endocrine disruptors may be associated with neurodevelopmental disorders are being discussed.

Synaptic and mitochondrial mechanisms behind alcohol-induced imbalance of excitatory/inhibitory synaptic activity and associated cognitive and behavioral abnormalities

Alcohol consumption during pregnancy can significantly impact the brain development of the fetus, leading to long-term cognitive and behavioral problems. However, the underlying mechanisms are not well understood. In this study, we investigated the acute and chronic effects of binge-like alcohol exposure during the third trimester equivalent in postnatal day 7 (P7) mice on brain cell viability, synapse activity, cognitive and behavioral performance, and gene expression profiles at P60. Our results showed that alcohol exposure caused neuroapoptosis in P7 mouse brains immediately after a 6-hour exposure. In addition, P60 mice exposed to alcohol during P7 displayed impaired learning and memory abilities and anxiety-like behaviors. Electrophysiological analysis of hippocampal neurons revealed an excitatory/inhibitory imbalance in alcohol-treated P60 mice compared to controls, with decreased excitation and increased inhibition. Furthermore, our bioinformatic analysis of 376 dysregulated genes in P60 mouse brains following alcohol exposure identified 50 synapse-related and 23 mitochondria-related genes. These genes encoded proteins located in various parts of the synapse, synaptic cleft, extra-synaptic space, synaptic membranes, or mitochondria, and were associated with different biological processes and functions, including the regulation of synaptic transmission, transport, synaptic vesicle cycle, metabolism, synaptogenesis, mitochondrial activity, cognition, and behavior. The dysregulated synapse and mitochondrial genes were predicted to interact in overlapping networks. Our findings suggest that altered synaptic activities and signaling networks may contribute to alcohol-induced long-term cognitive and behavioral impairments in mice, providing new insights into the underlying synaptic and mitochondrial molecular mechanisms and potential neuroprotective strategies.

Trem2 expression in microglia is required to maintain normal neuronal bioenergetics during development

Triggering receptor expressed on myeloid cells 2 (Trem2) is a myeloid cell-specific gene expressed in brain microglia, with variants that are associated with neurodegenerative diseases, including Alzheimer's disease. Trem2 is essential for microglia-mediated synaptic refinement, but whether Trem2 contributes to shaping neuronal development remains unclear. Here, we demonstrate that Trem2 plays a key role in controlling the bioenergetic profile of pyramidal neurons during development. In the absence of Trem2, developing neurons in the hippocampal cornus ammonis (CA)1 but not in CA3 subfield displayed compromised energetic metabolism, accompanied by reduced mitochondrial mass and abnormal organelle ultrastructure. This was paralleled by the transcriptional rearrangement of hippocampal pyramidal neurons at birth, with a pervasive alteration of metabolic, oxidative phosphorylation, and mitochondrial gene signatures, accompanied by a delay in the maturation of CA1 neurons. Our results unveil a role of Trem2 in controlling neuronal development by regulating the metabolic fitness of neurons in a region-specific manner.

An Open-Label Case Series of Glutathione Use for Symptomatic Management in Children with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a type of neurodevelopmental disorder that has been diagnosed in an increasing number of children around the world. The existing data suggest that early diagnosis and intervention can improve ASD outcomes. The causes of ASD remain complex and unclear, and there are currently no clinical biomarkers for autism spectrum disorder. There is an increasing recognition that ASD might be associated with oxidative stress through several mechanisms including abnormal metabolism (lipid peroxidation) and the toxic buildup of reactive oxygen species (ROS). Glutathione acts as an antioxidant, a free radical scavenger and a detoxifying agent. This open-label pilot study investigates the tolerability and effectiveness of oral supplementation with OpitacTM gluthathione as a treatment for patients with ASD. The various aspects of glutathione OpitacTM glutathione bioavailability were examined when administered by oral routes. The absorption of glutathione from the gastrointestinal tract has been recently investigated. The results of this case series suggest that oral glutathione supplementation may improve oxidative markers, but this does not necessarily translate to the observed clinical improvement of subjects with ASD. The study reports a good safety profile of glutathione use, with stomach upset reported in four out of six subjects. This article discusses the role of the gut microbiome and redox balance in ASD and notes that a high baseline oxidative burden may make some patients poor responders to glutathione supplementation. In conclusion, an imbalance in redox reactions is only one of the many factors contributing to ASD, and further studies are necessary to investigate other factors, such as impaired neurotransmission, immune dysregulation in the brain, and mitochondrial dysfunction.

Identification of Neurotransmission and Synaptic Biological Processes Disrupted in Autism Spectrum Disorder Using Interaction Networks and Community Detection Analysis

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by communication deficits and repetitive behavioral patterns. Hundreds of candidate genes have been implicated in ASD, including neurotransmission and synaptic (NS) genes; however, the genetic architecture of this disease is far from clear. In this study, we seek to clarify the biological processes affected by NS gene variants identified in individuals with ASD and the global networks that link those processes together. For a curated list of 1216 NS candidate genes, identified in multiple databases and the literature, we searched for ultra-rare (UR) loss-of-function (LoF) variants in the whole-exome sequencing dataset from the Autism Sequencing Consortium (N = 3938 cases). Filtering for population frequency was carried out using gnomAD (N = 60,146 controls). NS genes with UR LoF variants were used to construct a network of protein-protein interactions, and the network's biological communities were identified by applying the Leiden algorithm. We further explored the expression enrichment of network genes in specific brain regions. We identified 356 variants in 208 genes, with a preponderance of UR LoF variants in the PDE11A and SYTL3 genes. Expression enrichment analysis highlighted several subcortical structures, particularly the basal ganglia. The interaction network defined seven network communities, clustering synaptic and neurotransmitter pathways with several ubiquitous processes that occur in multiple organs and systems. This approach also uncovered biological pathways that are not usually associated with ASD, such as brain cytochromes P450 and brain mitochondrial metabolism. Overall, the community analysis suggests that ASD involves the disruption of synaptic and neurotransmitter pathways but also ubiquitous, but less frequently implicated, biological processes.

The Potential of Salivary Lipid-Based Cannabis-Responsive Biomarkers to Evaluate Medical Cannabis Treatment in Children with Autism Spectrum Disorder

Introduction: Autism spectrum disorder (ASD) is a group of heterogeneous neurodevelopmental conditions affecting social communication and social interaction. Medical cannabis (MC) treatment shows promising results as an approach to reduce behavioral difficulties, as determined mainly by subjective observations. We have recently shown the potential of cannabis-responsive biomarkers detected in saliva of children with ASD to objectively quantify the impact of successful MC treatment using a metabolomics approach. Since the pathology of ASD is associated with abnormal lipid metabolism, we used lipidomics on the same samples to (1) expand the repertoire of cannabis-responsive biomarkers and (2) provide preliminary insight into the role of MC on lipid metabolism. Materials and Methods: Saliva samples collected from children with ASD (n=15) treated with MC (both before and at the time of maximal impact of treatment) and an age-matched group of typically developing (TD) children (n=9) were subjected to untargeted lipidomics. The study was observational. Each child from the ASD group was receiving a unique individualized MC treatment regimen using off-the-shelf products as permitted by California law under physician supervision for at least 1 year. Doses of tetrahydrocannabinol (THC) ranged from 0.05 to 50 mg and cannabidiol (CBD) from 7.5 to 200 mg per treatment. The ASD group was evaluated for signs of improvement using parental brief Likert scale surveys. Results: Twenty-two potential lipid-based cannabis-responsive biomarkers exhibiting a shift toward the TD physiological levels in children with ASD after MC treatment were identified. Members from all five lipid subclasses known to be present in saliva were characterized. Preliminary lipid association network analysis suggests involvement of two subnetworks previously linked to (1) inflammation and/or redox regulation and (2) oxidative stress. The significant changes in sphingomyelin in this study and in N-acetyl-aspartate (NAA) previously detected in the metabolomics analysis of the same saliva samples may indicate a role of MC in neuron function. Conclusions: Our findings suggest that lipid metabolites in saliva can potentially serve as cannabis-responsive biomarkers and objectively quantify the impact of MC treatment, and indicate a possible mechanism of action for MC. This preliminary study requires further investigation with a larger population and appropriate clinical trial monitoring.

[Recent research on neurodevelopmental disorders in children]

Neurodevelopmental disorders (NDDs) in children are a group of chronic developmental brain disorders caused by multiple genetic or acquired causes, including disorders of intellectual development, developmental speech or language disorders, autism spectrum disorders, developmental learning disorders, attention deficit hyperactivity disorder, tic disorders, and other neurodevelopmental disorders. With the improvement in the research level and the diagnosis and treatment techniques of NDDs, great progress has been made in the research on NDDs in children. This article reviews the research advances in NDDs, in order to further improve the breadth and depth of the understanding of NDDs in children among pediatricians.

Continuous high-frequency deep brain stimulation of the anterior insula modulates autism-like behavior in a valproic acid-induced rat model

BACKGROUND

Until now, the treatment of patients with autism spectrum disorder (ASD) remain a difficult problem. The insula is involved in empathy and sensorimotor integration, which are often impaired in individuals with ASD. Deep brain stimulation, modulating neuronal activity in specific brain circuits, has recently been considered as a promising intervention for neuropsychiatric disorders. Valproic acid (VPA) is a potential teratogenic agent, and prenatal exposure can cause autism-like symptoms including repetitive behaviors and defective sociability. Herein, we investigated the effects of continuous high-frequency deep brain stimulation in the anterior insula of rats exposed to VPA and explored cognitive functions, behavior, and molecular proteins connected to autism spectrum disorder.

METHODS

VPA-exposed offspring were bilaterally implanted with electrodes in the anterior insula (Day 0) with a recovery period of 1 week. (Day 0-7). High-frequency deep brain stimulation was applied from days 11 to 29. Three behavioral tests, including three-chamber social interaction test, were performed on days 7, 13, 18, 25 and 36, and several rats were used for analysis of immediate early genes and proteomic after deep brain stimulation intervention. Meanwhile, animals were subjected to a 20 day spatial learning and cognitive rigidity test using IntelliCage on day 11.

RESULTS

Deep brain stimulation improved the sociability and social novelty preference at day 18 prior to those at day 13, and the improvement has reached the upper limit compared to day 25. As for repetitive/stereotypic-like behavior, self- grooming time were reduced at day 18 and reached the upper limit, and the numbers of burried marbles were reduced at day 13 prior to those at day 18 and day 25. The improvements of sociability and social novelty preference were persistent after the stimulation had ceased. Spatial learning ability and cognitive rigidity were unaffected. We identified 35 proteins in the anterior insula, some of which were intimately linked to autism, and their expression levels were reversed upon administration of deep brain stimulation.

CONCLUSIONS

Autism-like behavior was ameliorated and autism-related proteins were reversed in the insula by deep brain stimulation intervention, these findings reveal that the insula may be a potential target for DBS in the treatment of autism, which provide a theoretical basis for its clinical application., although future studies are still warranted.

Age, brain region, and gene dosage-differential transcriptomic changes in Shank3-mutant mice

Shank3 is an abundant excitatory postsynaptic scaffolding protein implicated in various neurodevelopmental disorders, including autism spectrum disorder (ASD), Phelan-McDermid syndrome, intellectual disability, and schizophrenia. Shank3-mutant mice show various molecular, synaptic, and behavioral deficits, but little is known about how transcriptomic phenotypes vary across different ages, brain regions, and gene dosages. Here, we report transcriptomic patterns in the forebrains of juvenile and adult homozygous Shank3-mutant mice that lack exons 14–16 and also the prefrontal, hippocampal, and striatal transcriptomes in adult heterozygous and homozygous Shank3-mutant mice. The juvenile and adult mutant transcriptomes show patterns opposite from and similar to those observed in ASD (termed reverse-ASD and ASD-like patterns), respectively. The juvenile transcriptomic changes accompany synaptic upregulations and ribosomal and mitochondrial downregulations, whereas the adult transcriptome show opposite changes. The prefrontal, hippocampal, and striatal transcriptomes show differential changes in ASD-related gene expressions and biological functions associated with synapse, ribosome, mitochondria, and spliceosome. These patterns also differ across heterozygous and homozygous Shank3-mutant mice. These results suggest age, brain region, and gene dosage-differential transcriptomic changes in Shank3-mutant mice.

Slc6a20a Heterozygous and Homozygous Mutant Mice Display Differential Behavioral and Transcriptomic Changes

SLC6A20A is a proline and glycine transporter known to regulate glycine homeostasis and NMDA receptor (NMDAR) function in the brain. A previous study found increases in ambient glycine levels and NMDA receptor-mediated synaptic transmission in the brains of Slc6a20a-haploinsufficient mice, but it remained unknown whether Slc6a20a deficiency leads to disease-related behavioral deficits in mice. Here, we report that Slc6a20a heterozygous and homozygous mutant mice display differential behavioral phenotypes in locomotor, repetitive behavioral, and spatial and fear memory domains. In addition, these mice show differential transcriptomic changes in synapse, ribosome, mitochondria, autism, epilepsy, and neuron-related genes. These results suggest that heterozygous and homozygous Slc6a20a deletions in mice lead to differential changes in behaviors and transcriptomes.

iTRAQ-Based Proteomics Analysis of Rat Cerebral Cortex Exposed to Valproic Acid before Delivery

Autism spectrum disorder (ASD) is a neurological and developmental disorder characterized by social and communication difficulties. Valproic acid (VPA) injection during pregnancy elicits autism-like behavior in the offspring, making it a classic animal model of ASD. However, the mechanisms involved have not yet been determined. In this study, we used iTRAQ (isobaric tags for relative and absolute quantification) proteomics analysis of the cerebral cortex of a VPA rat model (VPA group) and controls (CON group). The results showed that 79 differentially expressed proteins (DEPs) were identified between the VPA group and the CON group. Based on bioinformatics analysis, the DEPs were mainly enriched at synapses, especially glutamatergic synapses and GABAergic synapses. Some DEPs were involved in energy metabolism, thyroid hormone synthesis pathway, and Na⁺-K⁺-ATPase. Cytoskeleton and endoplasmic reticulum (ER) stress-related proteins were also involved. Some DEPs matched either the ASD gene database or previous reports on cerebral cortical transcriptome studies in VPA rat models. Dysregulation of these DEPs in the cerebral cortex of VPA rats may be responsible for autism-like behavior in rats. We also found that some DEPs were associated with neuropsychiatric disorders, implying that these diseases share common signaling pathways and mechanisms. Moreover, increased expression of DEPs was associated with energy metabolism in the cerebral cortex of VPA rats, implying that ASD may be a distinct type of mitochondrial dysfunction that requires further investigation.

Increased expression of SLC25A1/CIC causes an autistic-like phenotype with altered neuron morphology

N ε-lysine acetylation within the lumen of the endoplasmic reticulum is a recently characterized protein quality control system that positively selects properly folded glycoproteins in the early secretory pathway. Overexpression of the endoplasmic reticulum acetyl-CoA transporter AT-1 in mouse forebrain neurons results in increased dendritic branching, spine formation and an autistic-like phenotype that is attributed to altered glycoprotein flux through the secretory pathway. AT-1 overexpressing neurons maintain the cytosolic pool of acetyl-CoA by upregulation of SLC25A1, the mitochondrial citrate/malate antiporter and ATP citrate lyase, which converts cytosolic citrate into acetyl-CoA. All three genes have been associated with autism spectrum disorder, suggesting that aberrant cytosolic-to-endoplasmic reticulum flux of acetyl-CoA can be a mechanistic driver for the development of autism spectrum disorder. We therefore generated a SLC25A1 neuron transgenic mouse with overexpression specifically in the forebrain neurons. The mice displayed autistic-like behaviours with a jumping stereotypy. They exhibited increased steady-state levels of citrate and acetyl-CoA, disrupted white matter integrity with activated microglia and altered synaptic plasticity and morphology. Finally, quantitative proteomic and acetyl-proteomic analyses revealed differential adaptations in the hippocampus and cortex. Overall, our study reinforces the connection between aberrant cytosolic-to-endoplasmic reticulum acetyl-CoA flux and the development of an autistic-like phenotype.

C1q/TNF-related protein-1: Potential biomarker for early diagnosis of autism spectrum disorder

INTRODUCTION

Autism spectrum disorders (ASDs) are neurodevelopmental diseases characterized by communication inabilities, social interaction impairment, repetitive behavior, as well as learning problems. Although the exact mechanism underlying this disease is still obscure, researchers believe that several factors play a significant role in its development and pathogenesis. Some authors have reported an association between adipokines family and autism. C1q/TNF-related protein-1 (CTRP1) is a member of the adipokines family, and we hypothesized that this adipokine might have an influential role in the pathogenesis of ASDs. Since there is no specific marker for screening the disease, we evaluated CTRP1 as a potential marker for achieving this purpose.

METHODS

Blood samples were collected from 82 (41 ASDs boys, 41 healthy boys as controls) children aged 5-7 years old. CTRP1 gene expression and CTRP1 serum level were measured by quantitative realtime-PCR and enzyme-linked immunosorbent assay methods, respectively.

RESULTS

It was found that CTRP1 is significantly elevated in autistic children in comparison to healthy controls, both at the gene expression level, as well as at the serum level; demonstrating a good diagnostic value with a good range of sensitivity and specificity for detecting ASDs.

CONCLUSION

CTRP1 expression is elevated in ASDs boys aged 5-7 years old, suggesting a role for this adipokine in ASDs pathophysiology. Also, receiver operating characteristic curve analyses revealed that this adipokine could be utilized as a diagnostic biomarker for differentiating ASDs patients from healthy individuals along with other recently proposed biomarkers.

Postsynaptic autism spectrum disorder genes and synaptic dysfunction

This review provides an overview of the synaptic dysfunction of neuronal circuits and the ensuing behavioral alterations caused by mutations in autism spectrum disorder (ASD)-linked genes directly or indirectly affecting the postsynaptic neuronal compartment. There are plenty of ASD risk genes, that may be broadly grouped into those involved in gene expression regulation (epigenetic regulation and transcription) and genes regulating synaptic activity (neural communication and neurotransmission). Notably, the effects mediated by ASD-associated genes can vary extensively depending on the developmental time and/or subcellular site of expression. Therefore, in order to gain a better understanding of the mechanisms of disruptions in postsynaptic function, an effort to better model ASD in experimental animals is required to improve standardization and increase reproducibility within and among studies. Such an effort holds promise to provide deeper insight into the development of these disorders and to improve the translational value of preclinical studies.

Significance of GABAA Receptor for Cognitive Function and Hippocampal Pathology

The hippocampus is a primary area for contextual memory, known to process spatiotemporal information within a specific episode. Long-term strengthening of glutamatergic transmission is a mechanism of contextual learning in the dorsal cornu ammonis 1 (CA1) area of the hippocampus. CA1-specific immobilization or blockade of α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor delivery can impair learning performance, indicating a causal relationship between learning and receptor delivery into the synapse. Moreover, contextual learning also strengthens GABA_A (gamma-aminobutyric acid) receptor-mediated inhibitory synapses onto CA1 neurons. Recently we revealed that strengthening of GABA_A receptor-mediated inhibitory synapses preceded excitatory synaptic plasticity after contextual learning, resulting in a reduced synaptic excitatory/inhibitory (E/I) input balance that returned to pretraining levels within 10 min. The faster plasticity at inhibitory synapses may allow encoding a contextual memory and prevent cognitive dysfunction in various hippocampal pathologies. In this review, we focus on the dynamic changes of GABA_A receptor mediated-synaptic currents after contextual learning and the intracellular mechanism underlying rapid inhibitory synaptic plasticity. In addition, we discuss that several pathologies, such as Alzheimer’s disease, autism spectrum disorders and epilepsy are characterized by alterations in GABA_A receptor trafficking, synaptic E/I imbalance and neuronal excitability.

Molecular Changes in Prader-Willi Syndrome Neurons Reveals Clues About Increased Autism Susceptibility

Background: Prader-Willi syndrome (PWS) is a neurodevelopmental disorder characterized by hormonal dysregulation, obesity, intellectual disability, and behavioral problems. Most PWS cases are caused by paternal interstitial deletions of 15q11.2-q13.1, while a smaller number of cases are caused by chromosome 15 maternal uniparental disomy (PW-UPD). Children with PW-UPD are at higher risk for developing autism spectrum disorder (ASD) than the neurotypical population. In this study, we used expression analysis of PW-UPD neurons to try to identify the molecular cause for increased autism risk.

Methods: Dental pulp stem cells (DPSC) from neurotypical control and PWS subjects were differentiated to neurons for mRNA sequencing. Significantly differentially expressed transcripts among all groups were identified. Downstream protein analysis including immunocytochemistry and immunoblots were performed to confirm the transcript level data and pathway enrichment findings.

Results: We identified 9 transcripts outside of the PWS critical region (15q11.2-q13.1) that may contribute to core PWS phenotypes. Moreover, we discovered a global reduction in mitochondrial transcripts in the PW-UPD + ASD group. We also found decreased mitochondrial abundance along with mitochondrial aggregates in the cell body and neural projections of +ASD neurons.

Conclusion: The 9 transcripts we identified common to all PWS subtypes may reveal PWS specific defects during neurodevelopment. Importantly, we found a global reduction in mitochondrial transcripts in PW-UPD + ASD neurons versus control and other PWS subtypes. We then confirmed mitochondrial defects in neurons from individuals with PWS at the cellular level. Quantification of this phenotype supports our hypothesis that the increased incidence of ASD in PW-UPD subjects may arise from mitochondrial defects in developing neurons.

Intracellular oxygen metabolism during bovine oocyte and preimplantation embryo development

We report a novel method to profile intrcellular oxygen concentration (icO2) during in vitro mammalian oocyte and preimplantation embryo development using a commercially available multimodal phosphorescent nanosensor (MM2). Abattoir-derived bovine oocytes and embryos were incubated with MM2 in vitro. A series of inhibitors were applied during live-cell multiphoton imaging to record changes in icO2 associated with mitochondrial processes. The uncoupler carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) uncouples mitochondrial oxygen consumption to its maximum, while antimycin inhibits complex III to ablate mitochondrial oxygen consumption. Increasing oxygen consumption was expected to reduce icO2 and decreasing oxygen consumption to increase icO2. Use of these inhibitors quantifies how much oxygen is consumed at basal in comparison to the upper and lower limits of mitochondrial function. icO2 measurements were compared to mitochondrial DNA copy number analysed by qPCR. Antimycin treatment increased icO2 for all stages tested, suggesting significant mitochondrial oxygen consumption at basal. icO2 of oocytes and preimplantation embryos were unaffected by FCCP treatment. Inner cell mass icO2 was lower than trophectoderm, perhaps reflecting limitations of diffusion. Mitochondrial DNA copy numbers were similar between stages in the range 0.9-4 × 106 copies and did not correlate with icO2. These results validate the MM2 probe as a sensitive, non-toxic probe of intracellular oxygen concentration in mammalian oocytes and preimplantation embryos.

Early Chronic Memantine Treatment-Induced Transcriptomic Changes in Wild-Type and Shank2-Mutant Mice

Shank2 is an excitatory postsynaptic scaffolding protein strongly implicated in autism spectrum disorders (ASDs). Shank2-mutant mice with a homozygous deletion of exons 6 and 7 (Shank2-KO mice) show decreased NMDA receptor (NMDAR) function and autistic-like behaviors at juvenile [∼postnatal day (P21)] and adult (>P56) stages that are rescued by NMDAR activation. However, at ∼P14, these mice show the opposite change – increased NMDAR function; moreover, suppression of NMDAR activity with early, chronic memantine treatment during P7–21 prevents NMDAR hypofunction and autistic-like behaviors at later (∼P21 and >P56) stages. To better understand the mechanisms underlying this rescue, we performed RNA-Seq gene-set enrichment analysis of forebrain transcriptomes from wild-type (WT) and Shank2-KO juvenile (P25) mice treated early and chronically (P7–21) with vehicle or memantine. Vehicle-treated Shank2-KO mice showed upregulation of synapse-related genes and downregulation of ribosome- and mitochondria-related genes compared with vehicle-treated WT mice. They also showed a transcriptomic pattern largely opposite that observed in ASD (reverse-ASD pattern), based on ASD-related/risk genes and cell-type–specific genes. In memantine-treated Shank2-KO mice, chromatin-related genes were upregulated; mitochondria, extracellular matrix (ECM), and actin-related genes were downregulated; and the reverse-ASD pattern was weakened compared with that in vehicle-treated Shank2-KO mice. In WT mice, memantine treatment, which does not alter NMDAR function, upregulated synaptic genes and downregulated ECM genes; memantine-treated WT mice also exhibited a reverse-ASD pattern. Therefore, early chronic treatment of Shank2-KO mice with memantine alters expression of chromatin, mitochondria, ECM, actin, and ASD-related genes.

Camk2a-Cre and Tshz3 Expression in Mouse Striatal Cholinergic Interneurons: Implications for Autism Spectrum Disorder

Camk2a-Cre mice have been widely used to study the postnatal function of several genes in forebrain projection neurons, including cortical projection neurons (CPNs) and striatal medium-sized spiny neurons (MSNs). We linked heterozygous deletion of TSHZ3/Tshz3 gene to autism spectrum disorder (ASD) and used Camk2a-Cre mice to investigate the postnatal function of Tshz3, which is expressed by CPNs but not MSNs. Recently, single-cell transcriptomics of the adult mouse striatum revealed the expression of Camk2a in interneurons and showed Tshz3 expression in striatal cholinergic interneurons (SCINs), which are attracting increasing interest in the field of ASD. These data and the phenotypic similarity between the mice with Tshz3 haploinsufficiency and Camk2a-Cre-dependent conditional deletion of Tshz3 (Camk2a-cKO) prompted us to better characterize the expression of Tshz3 and the activity of Camk2a-Cre transgene in the striatum. Here, we show that the great majority of Tshz3-expressing cells are SCINs and that all SCINs express Tshz3. Using lineage tracing, we demonstrate that the Camk2a-Cre transgene is expressed in the SCIN lineage where it can efficiently elicit the deletion of the Tshz3-floxed allele. Moreover, transcriptomic and bioinformatic analysis in Camk2a-cKO mice showed dysregulated striatal expression of a number of genes, including genes whose human orthologues are associated with ASD and synaptic signaling. These findings identifying the expression of the Camk2a-Cre transgene in SCINs lineage lead to a reappraisal of the interpretation of experiments using Camk2a-Cre-dependent gene manipulations. They are also useful to decipher the cellular and molecular substrates of the ASD-related behavioral abnormalities observed in Tshz3 mouse models.