Characterizing autism spectrum disorders by key biochemical pathways

Aberrant Short Tandem Repeats: Pathogenicity, Mechanisms, Detection, and Roles in Neuropsychiatric Disorders

Short tandem repeat (STR) sequences are highly variable DNA segments that significantly contribute to human neurodegenerative disorders, highlighting their crucial role in neuropsychiatric conditions. This article examines the pathogenicity of abnormal STRs and classifies tandem repeat expansion disorders(TREDs), emphasizing their genetic characteristics, mechanisms of action, detection methods, and associated animal models. STR expansions exhibit complex genetic patterns that affect the age of onset and symptom severity. These expansions disrupt gene function through mechanisms such as gene silencing, toxic gain-of-function mutations leading to RNA and protein toxicity, and the generation of toxic peptides via repeat-associated non-AUG (RAN) translation. Advances in sequencing technologies-from traditional PCR and Southern blotting to next-generation and long-read sequencing-have enhanced the accuracy of STR variation detection. Research utilizing these technologies has linked STR expansions to a range of neuropsychiatric disorders, including autism spectrum disorders and schizophrenia, highlighting their contribution to disease risk and phenotypic expression through effects on genes involved in neurodevelopment, synaptic function, and neuronal signaling. Therefore, further investigation is essential to elucidate the intricate interplay between STRs and neuropsychiatric diseases, paving the way for improved diagnostic and therapeutic strategies.

The MNK-SYNGAP1 axis in specific learning disorder: gene expression pattern and new perspectives

Specific learning disorder (SLD) is a neurodevelopmental disorder that significantly affects children's academic performance. This study aimed to investigate the expression levels of the MAP Kinase Interacting Serine/Threonine Kinase 1-2 (MNK1, MNK2), Synaptic Ras GTPase Activating Protein 1 (SYNGAP1) genes, and the long non-coding RNA Synaptic Ras GTPase Activating Protein 1-Anti Sense1 (SYNGAP1-AS1), which are believed to play a key role in neurodevelopmental pathways, in children with SLD. Understanding the role of these genes in synaptic plasticity and cognitive function may provide insights into the molecular mechanisms underlying SLD. This study included 38 children diagnosed with SLD and 35 healthy controls aged 6 to 16. RNA was isolated from blood samples, and gene expression levels were measured using quantitative polymerase chain reaction (qPCR). The statistical analysis was conducted to compare the expression levels between the SLD and control groups and within SLD subgroups based on severity and sex. MNK1 and SYNGAP1 expression levels were significantly upregulated in the SLD group compared to the control group (8.33-fold and 16.52-fold increase, respectively; p < 0.001). lncSYNGAP1-AS1 showed a 26.58-fold increase, while MNK2 was downregulated by 2.2-fold, although these changes were not statistically significant. No significant differences were observed between sexes or between the severity subgroups of SLD.

CONCLUSION

he upregulation of MNK1 and SYNGAP1 in children with SLD suggests their involvement in the neurodevelopmental pathways associated with cognitive processes such as learning and memory. These findings provide a foundation for future research into the molecular basis and potential therapeutic targets of SLD.

WHAT IS KNOWN

• SYNGAP1 is a key regulator of synaptic plasticity and learning, primarily functioning through Ras signaling inhibition. Its deficiency impairs long-term potentiation (LTP) and is associated with neurodevelopmental disorders (NDDs) such as autism spectrum disorder (ASD) and intellectual disability. • The MAPK/ERK pathway plays a crucial role in learning and memory, and its dysregulation has been linked to several neurological conditions. MNK1/2 interacts with SYNGAP1 in synaptic signaling.

WHAT IS NEW

• This study is the first to demonstrate significant upregulation of SYNGAP1 and MKNK1 in children with SLD. • Understanding the role of the MKNK-SYNGAP1 axis may guide the development of targeted therapies aimed at enhancing synaptic plasticity to improve learning and memory outcomes in children with SLD.

Whole-genome sequencing analysis of Japanese autism spectrum disorder trios

AIM

Autism spectrum disorder (ASD) is a genetically and phenotypically heterogeneous neurodevelopmental disorder with a strong genetic basis. Conducting the first comprehensive whole-genome sequencing (WGS) analysis of Japanese ASD trios, this study aimed to elucidate the clinical significance of pathogenic variants and enhance the understanding of ASD pathogenesis.

METHODS

WGS was performed on 57 Japanese patients with ASD and their parents, investigating variants ranging from single-nucleotide variants to structural variants (SVs), short tandem repeats (STRs), mitochondrial variants, and polygenic risk score (PRS).

RESULTS

Potentially pathogenic variants that could explain observed phenotypes were identified in 18 patients (31.6%) overall and in 10 of 23 patients (43.5%) with comorbid intellectual developmental disorder (IDD). De novo variants in PTEN, CHD7, and HNRNPH2 were identified in patients referred for genetic counseling who exhibited previously reported phenotypes, including one patient with ASD who had profound IDD and macrocephaly with PTEN L320S. Analysis of the AlphaFold3 protein structure indicated potential inhibition of intramolecular interactions within PTEN. SV analysis identified deletions in ARHGAP11B and TMLHE. A pathogenic de novo mitochondrial variant was identified in a patient with ASD who had a history of encephalitis and cognitive decline. GO enrichment analysis of genes with nonsense variants and missense variants (Missense badness, PolyPhen-2, and Constraint >1) showed associations with regulation of growth and ATP-dependent chromatin remodeler activity. No reportable results were obtained in the analysis of STR and PRS.

CONCLUSION

Characterizing the comprehensive genetic architecture and phenotypes of ASD is a fundamental step towards unraveling its complex biology.

Nebulized vasopressin penetrates CSF and improves social cognition without inducing aggression in a rhesus monkey model of autism

Low cerebrospinal (CSF) arginine vasopressin (AVP) concentration is a biomarker of social impairment in low-social monkeys and children with autism, suggesting that AVP administration may improve primate social functioning. However, AVP administration also increases aggression, at least in "neurotypical" animals with intact AVP signaling. Here, we tested the effects of a voluntary drug administration method in low-social male rhesus monkeys with high autistic-like trait burden. Monkeys received nebulized AVP or placebo, using a within-subjects design. Study 1 (N = 8) investigated the effects of AVP administration on social cognition in two tests comparing responses to social versus nonsocial stimuli. Test 1: Placebo-administered monkeys lacked face recognition memory, whereas face recognition memory was "rescued" following AVP administration. In contrast, object recognition memory was intact and did not differ between administration conditions. Test 2: Placebo-administered monkeys did not respond to conspecific social communication cues, whereas following AVP administration, they reciprocated affiliative communication cues with species-typical affiliative responses. Importantly, AVP administration did not increase aggressive responses to conspecific aggressive or affiliative overtures. Study 2 (N = 4) evaluated the pharmacokinetics of this administration method. Following AVP nebulization, we observed a linear increase in cisternal CSF AVP levels, and a quadratic rise and fall in blood AVP levels. These findings indicate that nebulized AVP likely penetrates the central nervous system, selectively promotes species-typical responses to social information, and does not induce aggression in low-social individuals. Nebulized AVP therefore may hold promise for managing similar social symptoms in people with autism, particularly in very young or lower functioning individuals.

Polyphenols Targeting MAP Kinase Signaling Pathway in Neurological Diseases: Understanding Molecular Mechanisms and Therapeutic Targets

Polyphenols are a class of secondary metabolic products found in plants that have been extensively studied for how well they regulate biological processes, such as the proliferation of cells, autophagy, and apoptosis. The mitogen-activated protein kinase (MAPK)-mediated signaling cascade is currently identified as a crucial pro-inflammatory pathway that plays a significant role in the development of neuroinflammation. This process has been shown to contribute to the pathogenesis of several neurological conditions, such as Alzheimer's disease (AD), Parkinson's disease (PD), CNS damage, and cerebral ischemia. Getting enough polyphenols through eating habits has resulted in mitigating the effects of oxidative stress (OS) and lowering the susceptibility to associated neurodegenerative disorders, including but not limited to multiple sclerosis (MS), AD, stroke, and PD. Polyphenols possess significant promise in dealing with the root cause of neurological conditions by modulating multiple therapeutic targets simultaneously, thereby attenuating their complicated physiology. Several polyphenolic substances have demonstrated beneficial results in various studies and are presently undergoing clinical investigation to treat neurological diseases (NDs). The objective of this review is to provide a comprehensive summary of the different aspects of the MAPK pathway involved in neurological conditions, along with an appraisal of the progress made in using polyphenols to regulate the MAPK signaling system to facilitate the management of NDs.

Growth-suppressor microRNAs mediate synaptic overgrowth and behavioral deficits in Fragile X mental retardation protein deficiency

Abnormal neuronal and synapse growth is a core pathology resulting from deficiency of the Fragile X mental retardation protein (FMRP), but molecular links underlying the excessive synthesis of key synaptic proteins remain incompletely defined. We find that basal brain levels of the growth suppressor let-7 microRNA (miRNA) family are selectively lowered in FMRP-deficient mice and activity-dependent let-7 downregulation is abrogated. Primary let-7 miRNA transcripts are not altered in FMRP-deficiency and posttranscriptional misregulation occurs downstream of MAPK pathway induction and elevation of Lin28a, a let-7 biogenesis inhibitor. Neonatal restoration of brain let-7 miRNAs corrects hallmarks of FMRP-deficiency, including dendritic spine overgrowth and social and cognitive behavioral deficits, in adult mice. Blockade of MAPK hyperactivation normalizes let-7 miRNA levels in both brain and peripheral blood plasma from Fmr1 KO mice. These results implicate dysregulated let-7 miRNA biogenesis in the pathogenesis of FMRP-deficiency, and highlight let-7 miRNA-based strategies for future biomarker and therapeutic development.

Three Decades of Valproate: A Current Model for Studying Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with increased prevalence and incidence in recent decades. Its etiology remains largely unclear, but it seems to involve a strong genetic component and environmental factors that, in turn, induce epigenetic changes during embryonic and postnatal brain development. In recent decades, clinical studies have shown that inutero exposure to valproic acid (VPA), a commonly prescribed antiepileptic drug, is an environmental factor associated with an increased risk of ASD. Subsequently, prenatal VPA exposure in rodents has been established as a reliable translational model to study the pathophysiology of ASD, which has helped demonstrate neurobiological changes in rodents, non-human primates, and brain organoids from human pluripotent stem cells. This evidence supports the notion that prenatal VPA exposure is a valid and current model to replicate an idiopathic ASD-like disorder in experimental animals. This review summarizes and describes the current features reported with this animal model of autism and the main neurobiological findings and correlates that help elucidate the pathophysiology of ASD. Finally, we discuss the general framework of the VPA model in comparison to other environmental and genetic ASD models.

Tales from the life and lab of a female social neuroscientist

This narrative review charts my unconventional path to becoming a social neuroscientist and describes my research findings - some baffling, some serendipitous, some pivotal - in the field of neuropeptide biology. I trace my childhood as a Bell Labs "brat" to my adolescence as a soccer-playing party girl, to my early days as a graduate student, when I first encountered oxytocin and vasopressin. These two molecules instantly captivated - and held - my attention and imagination. For more than 25 years, a core goal of my research program has been to better understand how these neuropeptides regulate social functioning across a range of species (e.g., meadow voles, mice, squirrel monkeys, rhesus monkeys, and humans), and to translate fundamental insights from this work to guide development of novel pharmacotherapies to treat social impairments in clinical populations. I also discuss my experience of being a woman and a mother in STEM, and identify the important people and events which helped shape my career and the scientist I am today.

APPlications of amyloid-β precursor protein metabolites in macrocephaly and autism spectrum disorder

Metabolites of the Amyloid-β precursor protein (APP) proteolysis may underlie brain overgrowth in Autism Spectrum Disorder (ASD). We have found elevated APP metabolites (total APP, secreted (s) APPα, and α-secretase adamalysins in the plasma and brain tissue of children with ASD). In this review, we highlight several lines of evidence supporting APP metabolites' potential contribution to macrocephaly in ASD. First, APP appears early in corticogenesis, placing APP in a prime position to accelerate growth in neurons and glia. APP metabolites are upregulated in neuroinflammation, another potential contributor to excessive brain growth in ASD. APP metabolites appear to directly affect translational signaling pathways, which have been linked to single gene forms of syndromic ASD (Fragile X Syndrome, PTEN, Tuberous Sclerosis Complex). Finally, APP metabolites, and microRNA, which regulates APP expression, may contribute to ASD brain overgrowth, particularly increased white matter, through ERK receptor activation on the PI3K/Akt/mTOR/Rho GTPase pathway, favoring myelination.

Recent advances to Neuroprotection: repurposing drugs against neuroinflammatory disorders

Cell death is a natural mechanism for biological clearance for the maintenance of homeostasis in a dynamic microenvironment of the central nervous system. Stress and various factors can lead to imbalance between cellular genesis and cell death leading to dysfunctionality and a number of neuropathological disorders. Drug repurposing can help bypass development time and cost. A complete understanding of drug actions and neuroinflammatory pathways can lead to effective control of neurodegenerative disorders. This review covers recent advances in various neuroinflammatory pathways understanding, biomarkers, and drug repurposing for neuroprotection.

Therapeutic modulation of JAK-STAT, mTOR, and PPAR-γ signaling in neurological dysfunctions

The cytokine-activated Janus kinase (JAK)-signal transducer and activator of transcription (STAT) cascade is a pleiotropic pathway that involves receptor subunit multimerization. The mammalian target of rapamycin (mTOR) is a ubiquitously expressed serine-threonine kinase that perceives and integrates a variety of intracellular and environmental stimuli to regulate essential activities such as cell development and metabolism. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a prototypical metabolic nuclear receptor involved in neural differentiation and axon polarity. The JAK-STAT, mTOR, and PPARγ signaling pathways serve as a highly conserved signaling hub that coordinates neuronal activity and brain development. Additionally, overactivation of JAK/STAT, mTOR, and inhibition of PPARγ signaling have been linked to various neurocomplications, including neuroinflammation, apoptosis, and oxidative stress. Emerging research suggests that even minor disruptions in these cellular and molecular processes can have significant consequences manifested as neurological and neuropsychiatric diseases. Of interest, target modulators have been proven to alleviate neuronal complications associated with acute and chronic neurological deficits. This research-based review explores the therapeutic role of JAK-STAT, mTOR, and PPARγ signaling modulators in preventing neuronal dysfunctions in preclinical and clinical investigations.

GABAergic synaptic transmission and cortical oscillation patterns in the primary somatosensory area of a valproic acid rat model of autism spectrum disorder

Autism spectrum disorder (ASD) is characterized by impaired social communication and interaction associated with repetitive or stereotyped behaviour. Prenatal valproic acid (VPA) exposure in rodents is a commonly used model of ASD. Resveratrol (RSV) has been shown to prevent interneuronal and behavioural impairments in the VPA model. We investigated the effects of prenatal VPA exposure and RSV on the GABAergic synaptic transmission, brain oscillations and on the genic expression of interneuron-associated transcription factor LHX6 in the primary somatosensory area (PSSA). Prenatal VPA exposure decreased the sIPSC and mIPSC frequencies and the sIPSC decay kinetics onto layers 4/5 pyramidal cells of PSSA. About 40% of VPA animals exhibited absence-like spike-wave discharge (SWD) events associated with behaviour arrest and increased power spectrum density of delta, beta and gamma cortical oscillations. VPA animals had reduced LHX6 expression in PSSA, but VPA animals treated with RSV had no changes on synaptic inhibition or LHX6 expression in the PSSA. SWD events associated with behaviour arrest and the abnormal increment of cortical oscillations were also absent in VPA animals treated with RSV. These findings provide new venues to investigate the role of both RSV and VPA in the pathophysiology of ASD and highlight the VPA animal model as an interesting tool to investigate pathways related to the aetiology and possible future therapies to this neuropsychiatric disorder.

Altered synaptic protein expression, aberrant spine morphology, and impaired spatial memory in Dlgap2 mutant mice, a genetic model of autism spectrum disorder

A microdeletion of approximately 2.4 Mb at the 8p23 terminal region has been identified in a Taiwanese autistic boy. Among the products transcribed/translated from genes mapped in this region, the reduction of DLGAP2, a postsynaptic scaffold protein, might be involved in the pathogenesis of autism spectrum disorder (ASD). DLGAP2 protein was detected in the hippocampus yet abolished in homozygous Dlgap2 knockout (Dlgap2 KO) mice. In this study, we characterized the hippocampal phenotypes in Dlgap2 mutant mice. Dlgap2 KO mice exhibited impaired spatial memory, indicating poor hippocampal function in the absence of DLGAP2. Aberrant expressions of postsynaptic proteins, including PSD95, SHANK3, HOMER1, GluN2A, GluR2, mGluR1, mGluR5, βCAMKII, ERK1/2, ARC, BDNF, were noticed in Dlgap2 mutant mice. Further, the spine density was increased in Dlgap2 KO mice, while the ratio of mushroom-type spines was decreased. We also observed a thinner postsynaptic density thickness in Dlgap2 KO mice at the ultrastructural level. These structural changes found in the hippocampus of Dlgap2 KO mice might be linked to impaired hippocampus-related cognitive functions such as spatial memory. Mice with Dlgap2 deficiency, showing signs of intellectual disability, a common co-occurring condition in patients with ASD, could be a promising animal model which may advance our understanding of ASD.

PI3K/AKT/mTOR signalling inhibitor chrysophanol ameliorates neurobehavioural and neurochemical defects in propionic acid-induced experimental model of autism in adult rats

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder marked by social and communication deficits as well as repetitive behaviour. Several studies have found that overactivation of the PI3K/AKT/mTOR signalling pathways during brain development plays a significant role in autism pathogenesis. Overexpression of the PI3K/AKT/mTOR signalling pathway causes neurological disorders by increasing cell death, neuroinflammation, and oxidative stress. Chrysophanol, also known as chrysophanic acid, is a naturally occurring chemical obtained from the plant Rheum palmatum. This study aimed to examine the neuroprotective effect of CPH on neurobehavioral, molecular, neurochemical, and gross pathological alterations in ICV-PPA induced experimental model of autism in adult rats. The effects of ICV-PPA on PI3K/AKT/mTOR downregulation in the brain were studied in autism-like rats. Furthermore, we investigated how CPH affected myelin basic protein (MBP) levels in rat brain homogenate and apoptotic biomarkers such as caspase-3, Bax, and Bcl-2 levels in rat brain homogenate and blood plasma samples. Rats were tested for behavioural abnormalities such as neuromuscular dysfunction using an actophotometer, motor coordination using a beam crossing task (BCT), depressive behaviour using a forced swim test (FST), cognitive deficiency, and memory consolidation using a Morris water maze (MWM) task. In PPA-treated rats, prolonged oral CPH administration from day 12 to day 44 of the experimental schedule reduces autistic-like symptoms. Furthermore, in rat brain homogenates, blood plasma, and CSF samples, cellular, molecular, and cell death markers, neuroinflammatory cytokines, neurotransmitter levels, and oxidative stress indicators were investigated. The recent findings imply that CPH also restores abnormal neurochemical levels and may prevent autism-like gross pathological alterations, such as demyelination volume, in the rat brain.

Autism spectrum disorder in the fragile X premutation state: possible mechanisms and implications

There is increasing recognition of the heterogeneity of origin of cases of autism spectrum disorder (ASD) with multiple forms of ASD having been identified over the decades. Among these, a genetic etiology can be identified in 20-40% of cases when a full genetic work-up is completed. The Fragile X premutation state (characterized by the presence of 55-200 CGG repeats in the FMR1 gene) is a relatively newly identified disease state that has since been associated with several disorders including fragile X-associated tremor ataxia syndrome (FXTAS), fragile X-associated primary ovarian insufficiency (FXPOI) and most recently, fragile X-associated neurodevelopmental disorders (FXAND) which commonly includes anxiety and depression. In addition to these associated disorders, extant literature and clinical observations have suggested an association between the premutation state and ASD. In this paper, we review the literature pertinent to this and discuss possible molecular mechanisms that may explain this association. This includes lowered levels of the FMR1 Protein (FMRP), GABA deficits, mitochondrial dysfunction and secondary genetic abnormalities that is seen in premutation carriers as well as their increased vulnerability to environmental stressors. Understanding these mechanisms can facilitate development of targeted treatment for specific sub-groups of ASD and premutation disorders in future.

Leveraging a translational research approach to drive diagnostic and treatment advances for autism

Autism spectrum disorder (ASD) is a prevalent and poorly understood neurodevelopmental disorder. There are currently no laboratory-based diagnostic tests to detect ASD, nor are there any disease-modifying medications that effectively treat ASD's core behavioral symptoms. Scientific progress has been impeded, in part, by overreliance on model organisms that fundamentally lack the sophisticated social and cognitive abilities essential for modeling ASD. We therefore saw significant value in studying naturally low-social rhesus monkeys to model human social impairment, taking advantage of a large outdoor-housed colony for behavioral screening and biomarker identification. Careful development and validation of our animal model, combined with a strong commitment to evaluating the translational utility of our preclinical findings directly in patients with ASD, yielded a robust neurochemical marker (cerebrospinal fluid vasopressin concentration) of trans-primate social impairment and a first-in-class medication (intranasal vasopressin) shown in a small phase 2a pilot trial to improve social abilities in children with ASD. This translational research approach stands to advance our understanding of ASD in a manner not readily achievable with existing animal models, and can be adapted to investigate a variety of other human brain disorders which currently lack valid preclinical options, thereby streamlining translation and amplifying clinical impact more broadly.

Pten heterozygosity restores neuronal morphology in fragile X syndrome mice

Genetic studies of hippocampal granule neuron development have been used to elucidate cellular functions of Pten and Fmr1. While mutations in each gene cause neurodevelopmental disorders such as autism and fragile X syndrome, how Pten and Fmr1 function alone or together during normal development is not known. Moreover, Pten mRNA is bound by the fragile X mental retardation protein (FMRP) RNA binding protein, but how this physical interaction impinges on phosphatase and tensin homolog protein (PTEN) expression is not known. To understand the interaction of PTEN and FMRP, we investigated the dentate gyrus granule neuron development in Pten and Fmr1 knockout (KO) mice. Interestingly, heterozygosity of Pten restored Fmr1 KO cellular phenotypes, including dendritic arborization, and spine density, while PTEN protein expression was significantly increased in Fmr1 KO animals. However, complete deletion of both Pten and Fmr1 resulted in a dramatic increase in dendritic length, spine density, and spine length. In addition, overexpression of PTEN in Fmr1 KO Pten heterozygous background reduced dendritic length, arborization, spine density, and spine length including pS6 levels. Our findings suggest that PTEN levels are negatively regulated by FMRP, and some Fmr1 KO phenotypes are caused by dysregulation of PTEN protein. These observations provide evidence for the genetic interaction of PTEN and FMRP and a possible mechanistic basis for the pathogenesis of Fmr1-related fragile X neurodevelopmental disorders.

Translating the Role of mTOR- and RAS-Associated Signalopathies in Autism Spectrum Disorder: Models, Mechanisms and Treatment

Mutations affecting mTOR or RAS signaling underlie defined syndromes (the so-called mTORopathies and RASopathies) with high risk for Autism Spectrum Disorder (ASD). These syndromes show a broad variety of somatic phenotypes including cancers, skin abnormalities, heart disease and facial dysmorphisms. Less well studied are the neuropsychiatric symptoms such as ASD. Here, we assess the relevance of these signalopathies in ASD reviewing genetic, human cell model, rodent studies and clinical trials. We conclude that signalopathies have an increased liability for ASD and that, in particular, ASD individuals with dysmorphic features and intellectual disability (ID) have a higher chance for disruptive mutations in RAS- and mTOR-related genes. Studies on rodent and human cell models confirm aberrant neuronal development as the underlying pathology. Human studies further suggest that multiple hits are necessary to induce the respective phenotypes. Recent clinical trials do only report improvements for comorbid conditions such as epilepsy or cancer but not for behavioral aspects. Animal models show that treatment during early development can rescue behavioral phenotypes. Taken together, we suggest investigating the differential roles of mTOR and RAS signaling in both human and rodent models, and to test drug treatment both during and after neuronal development in the available model systems.

Randomized controlled trial of sulforaphane and metabolite discovery in children with Autism Spectrum Disorder

Background

Sulforaphane (SF), an isothiocyanate in broccoli, has potential benefits relevant to autism spectrum disorder (ASD) through its effects on several metabolic and immunologic pathways. Previous clinical trials of oral SF demonstrated positive clinical effects on behavior in young men and changes in urinary metabolomics in children with ASD.

Methods

We conducted a 15-week randomized parallel double-blind placebo-controlled clinical trial with 15-week open-label treatment and 6-week no-treatment extensions in 57 children, ages 3–12 years, with ASD over 36 weeks. Twenty-eight were assigned SF and 29 received placebo (PL). Clinical effects, safety and tolerability of SF were measured as were biomarkers to elucidate mechanisms of action of SF in ASD.

Results

Data from 22 children taking SF and 23 on PL were analyzed. Treatment effects on the primary outcome measure, the Ohio Autism Clinical Impressions Scale (OACIS), in the general level of autism were not significant between SF and PL groups at 7 and 15 weeks. The effect sizes on the OACIS were non-statistically significant but positive, suggesting a possible trend toward greater improvement in those on treatment with SF (Cohen’s d 0.21; 95% CI − 0.46, 0.88 and 0.10; 95% CI − 0.52, 0.72, respectively). Both groups improved in all subscales when on SF during the open-label phase. Caregiver ratings on secondary outcome measures improved significantly on the Aberrant Behavior Checklist (ABC) at 15 weeks (Cohen’s d − 0.96; 95% CI − 1.73, − 0.15), but not on the Social Responsiveness Scale-2 (SRS-2). Ratings on the ABC and SRS-2 improved with a non-randomized analysis of the length of exposure to SF, compared to the pre-treatment baseline (p < 0.001). There were significant changes with SF compared to PL in biomarkers of glutathione redox status, mitochondrial respiration, inflammatory markers and heat shock proteins. Clinical laboratory studies confirmed product safety. SF was very well tolerated and side effects of treatment, none serious, included rare insomnia, irritability and intolerance of the taste and smell.

Limitations

The sample size was limited to 45 children with ASD and we did not impute missing data. We were unable to document significant changes in clinical assessments during clinical visits in those taking SF compared to PL. The clinical results were confounded by placebo effects during the open-label phase.

Conclusions

SF led to small yet non-statistically significant changes in the total and all subscale scores of the primary outcome measure, while for secondary outcome measures, caregivers’ assessments of children taking SF showed statistically significant improvements compared to those taking PL on the ABC but not the SRS-2. Clinical effects of SF were less notable in children compared to our previous trial of a SF-rich preparation in young men with ASD. Several of the effects of SF on biomarkers correlated to clinical improvements. SF was very well tolerated and safe and effective based on our secondary clinical measures.

Trial registration: This study was prospectively registered at clinicaltrials.gov (NCT02561481) on September 28, 2015. Funding was provided by the U.S. Department of Defense.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13229-021-00447-5.

Targeting PI3K-AKT/mTOR signaling in the prevention of autism

PI3K-AKT/mTOR signaling pathway represents an essential signaling mechanism for mammalian enzyme-related receptors in transducing signals or biological processes such as cell development, differentiation, cell survival, protein synthesis, and metabolism. Upregulation of the PI3K-AKT/mTOR signaling pathway involves many human brain abnormalities, including autism and other neurological dysfunctions. Autism is a neurodevelopmental disorder associated with behavior and psychiatric illness. This research-based review discusses the functional relationship between the neuropathogenic factors associated with PI3K-AKT/mTOR signaling pathway. Ultimately causes autism-like conditions associated with genetic alterations, neuronal apoptosis, mitochondrial dysfunction, and neuroinflammation. Therefore, inhibition of the PI3K-AKT/mTOR signaling pathway may have an effective therapeutic value for autism treatment. The current review also summarizes the involvement of PI3K-AKT/mTOR signaling pathway inhibitors in the treatment of autism and other neurodegenerative disorders.

Autism Spectrum Disorder: Signaling Pathways and Prospective Therapeutic Targets

The Autism Spectrum Disorder (ASD) consists of a prevalent and heterogeneous group of neurodevelopmental diseases representing a severe burden to affected individuals and their caretakers. Despite substantial improvement towards understanding of ASD etiology and pathogenesis, as well as increased social awareness and more intensive research, no effective drugs have been successfully developed to resolve the main and most cumbersome ASD symptoms. Hence, finding better treatments, which may act as "disease-modifying" agents, and novel biomarkers for earlier ASD diagnosis and disease stage determination are needed. Diverse mutations of core components and consequent malfunctions of several cell signaling pathways have already been found in ASD by a series of experimental platforms, including genetic associations analyses and studies utilizing pre-clinical animal models and patient samples. These signaling cascades govern a broad range of neurological features such as neuronal development, neurotransmission, metabolism, and homeostasis, as well as immune regulation and inflammation. Here, we review the current knowledge on signaling pathways which are commonly disrupted in ASD and autism-related conditions. As such, we further propose ways to translate these findings into the development of genetic and biochemical clinical tests for early autism detection. Moreover, we highlight some putative druggable targets along these pathways, which, upon further research efforts, may evolve into novel therapeutic interventions for certain ASD conditions. Lastly, we also refer to the crosstalk among these major signaling cascades as well as their putative implications in therapeutics. Based on this collective information, we believe that a timely and accurate modulation of these prominent pathways may shape the neurodevelopment and neuro-immune regulation of homeostatic patterns and, hopefully, rescue some (if not all) ASD phenotypes.

Non-Syndromic Intellectual Disability and Its Pathways: A Long Noncoding RNA Perspective

Non-syndromic intellectual disability (NS-ID or idiopathic) is a complex neurodevelopmental disorder that represents a global health issue. Although many efforts have been made to characterize it and distinguish it from syndromic intellectual disability (S-ID), the highly heterogeneous aspect of this disorder makes it difficult to understand its etiology. Long noncoding RNAs (lncRNAs) comprise a large group of transcripts that can act through various mechanisms and be involved in important neurodevelopmental processes. In this sense, comprehending the roles they play in this intricate context is a valuable way of getting new insights about how NS-ID can arise and develop. In this review, we attempt to bring together knowledge available in the literature about lncRNAs involved with molecular and cellular pathways already described in intellectual disability and neural function, to better understand their relevance in NS-ID and the regulatory complexity of this disorder.

Involvements of Hyperhomocysteinemia in Neurological Disorders

Homocysteine (HCY), a physiological amino acid formed when proteins break down, leads to a pathological condition called hyperhomocysteinemia (HHCY), when it is over a definite limit. It is well known that an increase in HCY levels in blood, can contribute to arterial damage and several cardiovascular disease, but the knowledge about the relationship between HCY and brain disorders is very poor. Recent studies demonstrated that an alteration in HCY metabolism or a deficiency in folate or vitamin B12 can cause altered methylation and/or redox potentials, that leads to a modification on calcium influx in cells, or into an accumulation in amyloid and/or tau protein involving a cascade of events that culminate in apoptosis, and, in the worst conditions, neuronal death. The present review will thus summarize how much is known about the possible role of HHCY in neurodegenerative disease.

DNA Methylation of the Oxytocin Receptor Across Neurodevelopmental Disorders

Many neurodevelopmental disorders (NDDs) share common learning and behavioural impairments, as well as features such as dysregulation of the oxytocin hormone. Here, we examined DNA methylation (DNAm) in the 1st intron of the oxytocin receptor gene, OXTR, in patients with autism spectrum (ASD), attention deficit and hyperactivity (ADHD) and obsessive compulsive (OCD) disorders. DNAm of OXTR was assessed for cohorts of ASD (blood), ADHD (saliva), OCD (saliva), which uncovered sex-specific DNAm differences compared to neurotypical, tissue-matched controls. Individuals with ASD or ADHD exhibiting extreme DNAm values had lower IQ and more social problems, respectively, than those with DNAm within normative ranges. This suggests that OXTR DNAm patterns are altered across NDDs and may be correlated with common clinical outcomes.

FMRP and CYFIP1 at the Synapse and Their Role in Psychiatric Vulnerability

There is increasing awareness of the role genetic risk variants have in mediating vulnerability to psychiatric disorders such as schizophrenia and autism. Many of these risk variants encode synaptic proteins, influencing biological pathways of the postsynaptic density and, ultimately, synaptic plasticity. Fragile-X mental retardation 1 (FMR1) and cytoplasmic fragile-X mental retardation protein (FMRP)-interacting protein 1 (CYFIP1) contain 2 such examples of highly penetrant risk variants and encode synaptic proteins with shared functional significance. In this review, we discuss the biological actions of FMRP and CYFIP1, including their regulation of (i) protein synthesis and specifically FMRP targets, (ii) dendritic and spine morphology, and (iii) forms of synaptic plasticity such as long-term depression. We draw upon a range of preclinical studies that have used genetic dosage models of FMR1 and CYFIP1 to determine their biological function. In parallel, we discuss how clinical studies of fragile X syndrome or 15q11.2 deletion patients have informed our understanding of FMRP and CYFIP1, and highlight the latest psychiatric genomic findings that continue to implicate FMRP and CYFIP1. Lastly, we assess the current limitations in our understanding of FMRP and CYFIP1 biology and how they must be addressed before mechanism-led therapeutic strategies can be developed for psychiatric disorders.

Pursuing genetic testing for children with autism spectrum disorders: What do parents think?

The American Academy of Pediatrics, the American College of Medical Genetics and Genomics, and the American Academy of Neurology recommend genetic testing, as a genetic evaluation tool, for children diagnosed with autism spectrum disorders (ASD). Despite the potential benefits, the utilization of genetic testing is low. We proposed an integrated theoretical framework to examine parents' intention and associated psychosocial factors in pursuing genetic testing for their children with ASD. Recruiting primarily from the Interactive Autism Network, a nationwide sample of 411 parents of children with ASD who had never pursued genetic testing for their children completed our theory-based online survey. Data were analyzed using structural equation modeling. About half of the parents were willing to pursue genetic testing for their children with ASD. Findings of the structural equation modeling suggested a good model fit between our integrated theoretical framework and survey data. Parents' intention was significantly and positively associated with their attitudes toward genetic testing, subjective norm, and self-efficacy in having their children tested. This study serves as an initial window to understand parental intention to pursue genetic testing for their children with ASD. Our findings can help physicians and genetic counselors understand, educate, counsel, and support parents' decision-making about having their children with ASD genetically tested. Furthermore, our study can also assist physicians and genetic counselors in developing theory- and evidence-based patient education materials to enhance genetic testing knowledge among parents of children with ASD.

From Rare Copy Number Variants to Biological Processes in ADHD

OBJECTIVE

Attention deficit hyperactivity disorder (ADHD) is a highly heritable psychiatric disorder. The objective of this study was to define ADHD-associated candidate genes and their associated molecular modules and biological themes, based on the analysis of rare genetic variants.

METHODS

The authors combined data from 11 published copy number variation studies in 6,176 individuals with ADHD and 25,026 control subjects and prioritized genes by applying an integrative strategy based on criteria including recurrence in individuals with ADHD, absence in control subjects, complete coverage in copy number gains, and presence in the minimal region common to overlapping copy number variants (CNVs), as well as on protein-protein interactions and information from cross-species genotype-phenotype annotation.

RESULTS

The authors localized 2,241 eligible genes in the 1,532 reported CNVs, of which they classified 432 as high-priority ADHD candidate genes. The high-priority ADHD candidate genes were significantly coexpressed in the brain. A network of 66 genes was supported by ADHD-relevant phenotypes in the cross-species database. Four significantly interconnected protein modules were found among the high-priority ADHD genes. A total of 26 genes were observed across all applied bioinformatic methods. Lookup in the latest genome-wide association study for ADHD showed that among those 26 genes, POLR3C and RBFOX1 were also supported by common genetic variants.

CONCLUSIONS

Integration of a stringent filtering procedure in CNV studies with suitable bioinformatics approaches can identify ADHD candidate genes at increased levels of credibility. The authors' analytic pipeline provides additional insight into the molecular mechanisms underlying ADHD and allows prioritization of genes for functional validation in validated model organisms.

Sodium hydrogen exchanger 9 NHE9 (SLC9A9) and its emerging roles in neuropsychiatric comorbidity

Variations in SLC9A9 gene expression and protein function are associated with multiple human diseases, which range from Attention-deficit/hyperactivity disorder (ADHD) to glioblastoma multiforme. In an effort to determine the full spectrum of human disease associations with SLC9A9, we performed a systematic review of the literature. We also review SLC9A9's biochemistry, protein structure, and function, as well as its interacting partners with the goal of identifying mechanisms of disease and druggable targets. We report gaps in the literature regarding the genes function along with consistent trends in disease associations that can be used to further research into treating the respective diseases. We report that SLC9A9 has strong associations with neuropsychiatric diseases and various cancers. Interestingly, we find strong overlap in SLC9A9 disease associations and propose a novel role for SLC9A9 in neuropsychiatric comorbidity. In conclusion, SLC9A9 is a multifunctional protein that, through both its endosome regulatory function and its protein-protein interaction network, has the ability to modulate signaling axes, such as the PI3K pathway, among others.

MAP/ERK Signaling in Developing Cognitive and Emotional Function and Its Effect on Pathological and Neurodegenerative Processes

The signaling pathway of the microtubule-associated protein kinase or extracellular regulated kinase (MAPK/ERK) is a common mechanism of extracellular information transduction from extracellular stimuli to the intracellular space. The transduction of information leads to changes in the ongoing metabolic pathways and the modification of gene expression patterns. In the central nervous system, ERK is expressed ubiquitously, both temporally and spatially. As for the temporal ubiquity, this signaling system participates in three key moments: (i) Embryonic development; (ii) the early postnatal period; and iii) adulthood. During embryonic development, the system is partly responsible for the patterning of segmentation in the encephalic vesicle through the FGF8-ERK pathway. In addition, during this period, ERK directs neurogenesis migration and the final fate of neural progenitors. During the early postnatal period, ERK participates in the maturation process of dendritic trees and synaptogenesis. During adulthood, ERK participates in social and emotional behavior and memory processes, including long-term potentiation. Alterations in mechanisms related to ERK are associated with different pathological outcomes. Genetic alterations in any component of the ERK pathway result in pathologies associated with neural crest derivatives and mental dysfunctions associated with autism spectrum disorders. The MAP-ERK pathway is a key element of the neuroinflammatory pathway triggered by glial cells during the development of neurodegenerative diseases, such as Parkinson's and Alzheimer's disease, Huntington's disease, and amyotrophic lateral sclerosis, as well as prionic diseases. The process triggered by MAPK/ERK activation depends on the stage of development (mature or senescence), the type of cellular element in which the pathway is activated, and the anatomic neural structure. However, extensive gaps exist with regards to the targets of the phosphorylated ERK in many of these processes.

Genetic landscape of autism spectrum disorder in Vietnamese children

Autism spectrum disorder (ASD) is a complex disorder with an unclear aetiology and an estimated global prevalence of 1%. However, studies of ASD in the Vietnamese population are limited. Here, we first conducted whole exome sequencing (WES) of 100 children with ASD and their unaffected parents. Our stringent analysis pipeline was able to detect 18 unique variants (8 de novo and 10 ×-linked, all validated), including 12 newly discovered variants. Interestingly, a notable number of X-linked variants were detected (56%), and all of them were found in affected males but not in affected females. We uncovered 17 genes from our ASD cohort in which CHD8, DYRK1A, GRIN2B, SCN2A, OFD1 and MDB5 have been previously identified as ASD risk genes, suggesting the universal aetiology of ASD for these genes. In addition, we identified six genes that have not been previously reported in any autism database: CHM, ENPP1, IGF1, LAS1L, SYP and TBX22. Gene ontology and phenotype-genotype analysis suggested that variants in IGF1, SYP and LAS1L could plausibly confer risk for ASD. Taken together, this study adds to the genetic heterogeneity of ASD and is the first report elucidating the genetic landscape of ASD in Vietnamese children.

mTOR signalling pathway - A root cause for idiopathic autism?

Autism spectrum disorder (ASD) is a complex neurodevelopmental monogenic disorder with a strong genetic influence. Idiopathic autism could be defined as a type of autism that does not have a specific causative agent. Among signalling cascades, mTOR signalling pathway plays a pivotal role not only in cell cycle, but also in protein synthesis and regulation of brain homeostasis in ASD patients. The present review highlights, underlying mechanism of mTOR and its role in altered signalling cascades as a triggering factor in the onset of idiopathic autism. Further, this review discusses how distorted mTOR signalling pathway stimulates truncated translation in neuronal cells and leads to downregulation of protein synthesis at dendritic spines of the brain. This review concludes by suggesting downstream regulators such as p70S6K, eIF4B, eIF4E of mTOR signalling pathway as promising therapeutic targets for idiopathic autistic individuals. [BMB Reports 2019; 52(7): 424-433].

Emerging connections between cerebellar development, behaviour and complex brain disorders

The human cerebellum has a protracted developmental timeline compared with the neocortex, expanding the window of vulnerability to neurological disorders. As the cerebellum is critical for motor behaviour, it is not surprising that most neurodevelopmental disorders share motor deficits as a common sequela. However, evidence gathered since the late 1980s suggests that the cerebellum is involved in motor and non-motor function, including cognition and emotion. More recently, evidence indicates that major neurodevelopmental disorders such as intellectual disability, autism spectrum disorder, attention-deficit hyperactivity disorder and Down syndrome have potential links to abnormal cerebellar development. Out of recent findings from clinical and preclinical studies, the concept of the 'cerebellar connectome' has emerged that can be used as a framework to link the role of cerebellar development to human behaviour, disease states and the design of better therapeutic strategies.

Association of genes with phenotype in autism spectrum disorder

Autism spectrum disorder (ASD) is a genetic heterogeneous neurodevelopmental disorder that is characterized by impairments in social interaction and speech development and is accompanied by stereotypical behaviors such as body rocking, hand flapping, spinning objects, sniffing and restricted behaviors. The considerable significance of the genetics associated with autism has led to the identification of many risk genes for ASD used for the probing of ASD specificity and shared cognitive features over the past few decades. Identification of ASD risk genes helps to unravel various genetic variants and signaling pathways which are involved in ASD. This review highlights the role of ASD risk genes in gene transcription and translation regulation processes, as well as neuronal activity modulation, synaptic plasticity, disrupted key biological signaling pathways, and the novel candidate genes that play a significant role in the pathophysiology of ASD. The current emphasis on autism spectrum disorders has generated new opportunities in the field of neuroscience, and further advancements in the identification of different biomarkers, risk genes, and genetic pathways can help in the early diagnosis and development of new clinical and pharmacological treatments for ASD.

Corticostriatal Transmission Is Selectively Enhanced in Striatonigral Neurons with Postnatal Loss of Tsc1

mTORC1 is a central signaling hub that integrates intra- and extracellular signals to regulate a variety of cellular metabolic processes. Mutations in regulators of mTORC1 lead to neurodevelopmental disorders associated with autism, which is characterized by repetitive, inflexible behaviors. These behaviors may result from alterations in striatal circuits that control motor learning and habit formation. However, the consequences of mTORC1 dysregulation on striatal neuron function are largely unknown. To investigate this, we deleted the mTORC1 negative regulator Tsc1 from identified striatonigral and striatopallidal neurons and examined how cell-autonomous upregulation of mTORC1 activity affects their morphology and physiology. We find that loss of Tsc1 increases the excitability of striatonigral, but not striatopallidal, neurons and selectively enhances corticostriatal synaptic transmission. These findings highlight the critical role of mTORC1 in regulating striatal activity in a cell type- and input-specific manner, with implications for striatonigral pathway dysfunction in neuropsychiatric disease.

Arginine vasopressin in cerebrospinal fluid is a marker of sociality in nonhuman primates

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by core social impairments. ASD remains poorly understood because of the difficulty in studying disease biology directly in patients and the reliance on mouse models that lack clinically relevant, complex social cognition abilities. We use ethological observations in rhesus macaques to identify male monkeys with naturally occurring low sociality. These monkeys showed differences in specific neuropeptide and kinase signaling pathways compared to socially competent male monkeys. Using a discovery and replication design, we identified arginine vasopressin (AVP) in cerebrospinal fluid (CSF) as a key marker of group differences in monkey sociality; we replicated these findings in an independent monkey cohort. We also confirmed in an additional monkey cohort that AVP concentration in CSF is a stable trait-like measure. Next, we showed in a small pediatric cohort that CSF AVP concentrations were lower in male children with ASD compared to age-matched male children without ASD (but with other medical conditions). We demonstrated that CSF AVP concentration was sufficient to accurately distinguish ASD cases from medical controls. These data suggest that AVP and its signaling pathway warrant consideration in future research studies investigating new targets for diagnostics and drug development in ASD.

NEGR1 and FGFR2 cooperatively regulate cortical development and core behaviours related to autism disorders in mice

Autism spectrum disorders are neurodevelopmental conditions with diverse aetiologies, all characterized by common core symptoms such as impaired social skills and communication, as well as repetitive behaviour. Cell adhesion molecules, receptor tyrosine kinases and associated downstream signalling have been strongly implicated in both neurodevelopment and autism spectrum disorders. We found that downregulation of the cell adhesion molecule NEGR1 or the receptor tyrosine kinase fibroblast growth factor receptor 2 (FGFR2) similarly affects neuronal migration and spine density during mouse cortical development in vivo and results in impaired core behaviours related to autism spectrum disorders. Mechanistically, NEGR1 physically interacts with FGFR2 and modulates FGFR2-dependent extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) signalling by decreasing FGFR2 degradation from the plasma membrane. Accordingly, FGFR2 overexpression rescues all defects due to Negr1 knockdown in vivo. Negr1 knockout mice present phenotypes similar to Negr1-downregulated animals. These data indicate that NEGR1 and FGFR2 cooperatively regulate cortical development and suggest a role for defective NEGR1-FGFR2 complex and convergent downstream ERK and AKT signalling in autism spectrum disorders.

Novel Contribution of Secreted Amyloid-β Precursor Protein to White Matter Brain Enlargement in Autism Spectrum Disorder

The most replicated neuroanatomical finding in autism is the tendency toward brain overgrowth, especially in younger children. Research shows that both gray and white matter are enlarged. Proposed mechanisms underlying brain enlargement include abnormal inflammatory and neurotrophic signals that lead to excessive, aberrant dendritic connectivity via disrupted pruning and cell adhesion, and enlargement of white matter due to excessive gliogenesis and increased myelination. Amyloid-β protein precursor (βAPP) and its metabolites, more commonly associated with Alzheimer's disease (AD), are also dysregulated in autism plasma and brain tissue samples. This review highlights findings that demonstrate how one βAPP metabolite, secreted APPα, and the ADAM family α-secretases, may lead to increased brain matter, with emphasis on increased white matter as seen in autism. sAPPα and the ADAM family α-secretases contribute to the anabolic, non-amyloidogenic pathway, which is in contrast to the amyloid (catabolic) pathway known to contribute to Alzheimer disease. The non-amyloidogenic pathway could produce brain enlargement via genetic mechanisms affecting mRNA translation and polygenic factors that converge on molecular pathways (mitogen-activated protein kinase/MAPK and mechanistic target of rapamycin/mTOR), promoting neuroinflammation. A novel mechanism linking the non-amyloidogenic pathway to white matter enlargement is proposed: α-secretase and/or sAPPα, activated by ERK receptor signaling activates P13K/AKt/mTOR and then Rho GTPases favoring myelination via oligodendrocyte progenitor cell (OPC) activation of cofilin. Applying known pathways in AD to autism should allow further understanding and provide options for new drug targets.

A Synaptic Perspective of Fragile X Syndrome and Autism Spectrum Disorders

Altered synaptic structure and function is a major hallmark of fragile X syndrome (FXS), autism spectrum disorders (ASDs), and other intellectual disabilities (IDs), which are therefore classified as synaptopathies. FXS and ASDs, while clinically and genetically distinct, share significant comorbidity, suggesting that there may be a common molecular and/or cellular basis, presumably at the synapse. In this article, we review brain architecture and synaptic pathways that are dysregulated in FXS and ASDs, including spine architecture, signaling in synaptic plasticity, local protein synthesis, (m)RNA modifications, and degradation. mRNA repression is a powerful mechanism for the regulation of synaptic structure and efficacy. We infer that there is no single pathway that explains most of the etiology and discuss new findings and the implications for future work directed at improving our understanding of the pathogenesis of FXS and related ASDs and the design of therapeutic strategies to ameliorate these disorders.

Possible Metabolic Alterations among Autistic Male Children: Clinical and Biochemical Approaches

The present cross-sectional, hospital-based study was carried out on 146 Egyptian male children, 73 males with autism who were comparable with another 73 healthy age- and sex-matched children, recruited from the outpatients' psychiatric clinics of the Neuropsychiatric and Pediatric Departments of South Valley and Assiut University Hospitals, Egypt. Neuropsychological assessments of autistic males were done using CARS, short sensory profile and intelligent quotients. Serum markers of mitochondrial dysfunction (lactate, pyruvate, and lactate to pyruvate ratio, creatine kinase (CK), L-carnitine, ammonia, lactate dehydrogenase, pyruvate kinase, alanine transaminase and aspartate transaminase), oxidative stress and blood levels of heavy metals (mercury, lead and aluminium) were measured. Serum cholesterol, cortisol, free testosterone, estradiol, dehydroepiandrostenedione, adenosine deaminase and Helicobacter pylori antigen in stool were also performed. There was evidence of mitochondrial dysfunction among autistic children. Additionally, there were significantly lower serum total cholesterol, cortisol and estradiol as well as significantly higher dehydroepiandrostenedione (DHEA) and free testosterone (p < 0.05 for all markers). Twenty-eight (38%) cases were positive for H. pylori antigen in their stool with significant higher serum ammonia and lower adenosine deaminase than in H. pylori-negative autistic children. Mitochondrial dysfunction, H. pylori infection and low cholesterol were prevalent among autistic male children, which should be targeted during autism management.

Overview of genetic models of autism spectrum disorders

Autism spectrum disorders (ASDs) are a group of neurodevelopment disorders that are characterized by heterogenous cognitive deficits and genetic factors. As more ASD risk genes are identified, genetic animal models have been developed to parse out the underlying neurobiological mechanisms of ASD. In this review, we discuss a subset of genetic models of ASD, focusing on those that have been widely studied and strongly linked to ASD. We focus our discussion of these models in the context of the theories and potential mechanisms of ASD, including disruptions in cell growth and proliferation, spine dynamics, synaptic transmission, excitation/inhibition balance, intracellular signaling, neuroinflammation, and behavior. In addition to ASD pathophysiology, we examine the limitations and challenges that genetic models pose for the study of ASD biology. We end with a review of innovative techniques and concepts of ASD pathology that can be further applied to and studied using genetic ASD models.

Loss of the Chr16p11.2 ASD candidate gene QPRT leads to aberrant neuronal differentiation in the SH-SY5Y neuronal cell model

Background

Altered neuronal development is discussed as the underlying pathogenic mechanism of autism spectrum disorders (ASD). Copy number variations of 16p11.2 have recurrently been identified in individuals with ASD. Of the 29 genes within this region, quinolinate phosphoribosyltransferase (QPRT) showed the strongest regulation during neuronal differentiation of SH-SY5Y neuroblastoma cells. We hypothesized a causal relation between this tryptophan metabolism-related enzyme and neuronal differentiation. We thus analyzed the effect of QPRT on the differentiation of SH-SY5Y and specifically focused on neuronal morphology, metabolites of the tryptophan pathway, and the neurodevelopmental transcriptome.

Methods

The gene dosage-dependent change of QPRT expression following Chr16p11.2 deletion was investigated in a lymphoblastoid cell line (LCL) of a deletion carrier and compared to his non-carrier parents. Expression of QPRT was tested for correlation with neuromorphology in SH-SY5Y cells. QPRT function was inhibited in SH-SY5Y neuroblastoma cells using (i) siRNA knockdown (KD), (ii) chemical mimicking of loss of QPRT, and (iii) complete CRISPR/Cas9-mediated knock out (KO). QPRT-KD cells underwent morphological analysis. Chemically inhibited and QPRT-KO cells were characterized using viability assays. Additionally, QPRT-KO cells underwent metabolite and whole transcriptome analyses. Genes differentially expressed upon KO of QPRT were tested for enrichment in biological processes and co-regulated gene-networks of the human brain.

Results

QPRT expression was reduced in the LCL of the deletion carrier and significantly correlated with the neuritic complexity of SH-SY5Y. The reduction of QPRT altered neuronal morphology of differentiated SH-SY5Y cells. Chemical inhibition as well as complete KO of the gene were lethal upon induction of neuronal differentiation, but not proliferation. The QPRT-associated tryptophan pathway was not affected by KO. At the transcriptome level, genes linked to neurodevelopmental processes and synaptic structures were affected. Differentially regulated genes were enriched for ASD candidates, and co-regulated gene networks were implicated in the development of the dorsolateral prefrontal cortex, the hippocampus, and the amygdala.

Conclusions

In this study, QPRT was causally related to in vitro neuronal differentiation of SH-SY5Y cells and affected the regulation of genes and gene networks previously implicated in ASD. Thus, our data suggest that QPRT may play an important role in the pathogenesis of ASD in Chr16p11.2 deletion carriers.

Activation of ERK/CREB/BDNF pathway involved in abnormal behavior of neonatally Borna virus-infected rats

BACKGROUND

Neuropsychiatric disorders are devastating illnesses worldwide; however, the potential involvement of viruses in the pathophysiological mechanisms of psychiatric diseases have not been clearly elucidated. Borna disease virus (BDV) is a neurotropic, noncytopathic RNA virus.

MATERIALS AND METHODS

In this study, we infected neonatal rats intracranially with BDV Hu-H1 and Strain V within 24 hours of birth. Psychological phenotypes were assessed using sucrose preference test, open field test, elevated plus maze test, and forced swim test. The protein expression of ERK/CREB/BDNF pathway was assessed by Western blotting of in vitro and in vivo samples.

RESULTS

Hu-H1-infected rats showed anxiety-like behavior 8 weeks postinfection while Strain V-infected rats demonstrated a certain abnormal behavior. Phosphorylated ERK1/2 was significantly upregulated in the hippocampi of Strain V- and Hu-H1-infected rats compared with control rats, indicating that Raf/MEK/ERK signaling was activated.

CONCLUSION

The data suggested that infection of neonatal rats with BDV Hu-H1 and Strain V caused behavioral abnormalities that shared common molecular pathways, providing preliminary evidences to investigate the underlying mechanisms of psychiatric disorders caused by BDV.

Recurrent de novo mutations in neurodevelopmental disorders: properties and clinical implications

Next-generation sequencing (NGS) is now more accessible to clinicians and researchers. As a result, our understanding of the genetics of neurodevelopmental disorders (NDDs) has rapidly advanced over the past few years. NGS has led to the discovery of new NDD genes with an excess of recurrent de novo mutations (DNMs) when compared to controls. Development of large-scale databases of normal and disease variation has given rise to metrics exploring the relative tolerance of individual genes to human mutation. Genetic etiology and diagnosis rates have improved, which have led to the discovery of new pathways and tissue types relevant to NDDs. In this review, we highlight several key findings based on the discovery of recurrent DNMs ranging from copy number variants to point mutations. We explore biases and patterns of DNM enrichment and the role of mosaicism and secondary mutations in variable expressivity. We discuss the benefit of whole-genome sequencing (WGS) over whole-exome sequencing (WES) to understand more complex, multifactorial cases of NDD and explain how this improved understanding aids diagnosis and management of these disorders. Comprehensive assessment of the DNM landscape across the genome using WGS and other technologies will lead to the development of novel functional and bioinformatics approaches to interpret DNMs and drive new insights into NDD biology.

Autism-like behavior caused by deletion of vaccinia-related kinase 3 is improved by TrkB stimulation

Kang et al. showed that reduced vaccinia-related kinase 3 (VRK3) expression affects synaptic structure and function and results in cognitive dysfunction and autism-like behaviors in mice. TrkB stimulation reverses the altered synaptic properties and restores autism-like behaviors in VRK3-deficient mice.

Vaccinia-related kinases (VRKs) are multifaceted serine/threonine kinases that play essential roles in various aspects of cell signaling, cell cycle progression, apoptosis, and neuronal development and differentiation. However, the neuronal function of VRK3 is still unknown despite its etiological potential in human autism spectrum disorder (ASD). Here, we report that VRK3-deficient mice exhibit typical symptoms of autism-like behavior, including hyperactivity, stereotyped behaviors, reduced social interaction, and impaired context-dependent spatial memory. A significant decrease in dendritic spine number and arborization were identified in the hippocampus CA1 of VRK3-deficient mice. These mice also exhibited a reduced rectification of AMPA receptor–mediated current and changes in expression of synaptic and signaling proteins, including tyrosine receptor kinase B (TrkB), Arc, and CaMKIIα. Notably, TrkB stimulation with 7,8-dihydroxyflavone reversed the altered synaptic structure and function and successfully restored autism-like behavior in VRK3-deficient mice. These results reveal that VRK3 plays a critical role in neurodevelopmental disorders and suggest a potential therapeutic strategy for ASD.

Bidirectional manipulation of mTOR signaling disrupts socially mediated vocal learning in juvenile songbirds

Early life experiences can have long-lasting behavioral consequences because they are encoded when the brain is most malleable. The mechanistic target of rapamycin (mTOR) signaling cascade modulates experience-dependent synaptic plasticity, among other processes. mTOR has been almost exclusively examined in adult rodent learning models, but may be especially important in organizing neural circuits required for developmental acquisition of meaningful complex behaviors. It is among the most commonly implicated factors in neurodevelopmental autism spectrum disorders (ASD), characterized, in part, by distinct social and communication phenotypes. Here, we investigated mTOR in juvenile zebra finch songbirds. Much as children learn language, young male zebra finches need to interact socially with an adult tutor to learn a meaningful song. The memory of the tutor's song structure guides the juvenile's own song, which it uses to communicate for the rest of its life. We hypothesized that mTOR is required for juveniles to learn song. To this end, we first discovered that hearing song activates mTOR signaling in a brain area required for tutor song memorization in males old enough to copy song but not in younger males or females, who cannot sing. We then showed that both inhibition and constitutive activation of mTOR during tutor experiences significantly diminished tutor song copying. Finally, we found that constitutive mTOR activation lowered a behavioral measure of the juvenile's social engagement during tutor experiences, mirroring the relationship in humans. These studies therefore advance understanding about the effects of experience in the context of neurodevelopmental disorders and typical neural development.

Brain MR Imaging Findings and Associated Outcomes in Carriers of the Reciprocal Copy Number Variation at 16p11.2

Purpose To identify developmental neuroradiologic findings in a large cohort of carriers who have deletion and duplication at 16p11.2 (one of the most common genetic causes of autism spectrum disorder [ASD]) and assess how these features are associated with behavioral and cognitive outcomes. Materials and Methods Seventy-nine carriers of a deletion at 16p11.2 (referred to as deletion carriers; age range, 1-48 years; mean age, 12.3 years; 42 male patients), 79 carriers of a duplication at 16p11.2 (referred to as duplication carriers; age range, 1-63 years; mean age, 24.8 years; 43 male patients), 64 unaffected family members (referred to as familial noncarriers; age range, 1-46 years; mean age, 11.7 years; 31 male participants), and 109 population control participants (age range, 6-64 years; mean age, 25.5 years; 64 male participants) were enrolled in this cross-sectional study. Participants underwent structural magnetic resonance (MR) imaging and completed cognitive and behavioral tests. MR images were reviewed for development-related abnormalities by neuroradiologists. Differences in frequency were assessed with a Fisher exact test corrected for multiple comparisons. Unsupervised machine learning was used to cluster radiologic features and an association between clusters and cognitive and behavioral scores from IQ testing, and parental measures of development were tested by using analysis of covariance. Volumetric analysis with automated segmentation was used to confirm radiologic interpretation. Results For deletion carriers, the most prominent features were dysmorphic and thicker corpora callosa compared with familial noncarriers and population control participants (16%; P < .001 and P < .001, respectively) and a greater likelihood of cerebellar tonsillar ectopia (30.7%; P < .002 and P < .001, respectively) and Chiari I malformations (9.3%; P < .299 and P < .002, respectively). For duplication carriers, the most salient findings compared with familial noncarriers and population control participants were reciprocally thinner corpora callosa (18.6%; P < .003 and P < .001, respectively), decreased white matter volume (22.9%; P < .001, and P < .001, respectively), and increased ventricular volume (24.3%; P < .001 and P < .001, respectively). By comparing cognitive assessments to imaging findings, the presence of any imaging feature associated with deletion carriers indicated worse daily living, communication, and social skills compared with deletion carriers without any radiologic abnormalities (P < .005, P < .002, and P < .004, respectively). For the duplication carriers, presence of decreased white matter, callosal volume, and/or increased ventricle size was associated with decreased full-scale and verbal IQ scores compared with duplication carriers without these findings (P < .007 and P < .004, respectively). Conclusion In two genetically related cohorts at high risk for ASD, reciprocal neuroanatomic abnormalities were found and determined to be associated with cognitive and behavioral impairments. ^© RSNA, 2017 Online supplemental material is available for this article.

Platelets as a surrogate disease model of neurodevelopmental disorders: Insights from Fragile X Syndrome

Fragile X Syndrome (FXS) is the most common inherited form of intellectual disability and the leading monogenic cause of autism spectrum disorders (ASD). Despite a large number of therapeutics developed in past years, there is currently no targeted treatment approved for FXS. In fact, translation of the positive and very promising preclinical findings from animal models to human subjects has so far fallen short owing in part to the low predictive validity of the Fmr1 ko mouse, an overly simplistic model of the complex human disease. This issue stresses the critical need to identify new surrogate human peripheral cell models of FXS, which may in fact allow for the identification of novel and more efficient therapies. Of all described models, blood platelets appear to be one of the most promising and appropriate disease models of FXS, in part owing to their close biochemical similarities with neurons. Noteworthy, they also recapitulate some of FXS neuron's core molecular dysregulations, such as hyperactivity of the MAPK/ERK and PI3K/Akt/mTOR pathways, elevated enzymatic activity of MMP9 and decreased production of cAMP. Platelets might therefore help furthering our understanding of FXS pathophysiology and might also lead to the identification of disease-specific biomarkers, as was shown in several psychiatric disorders such as schizophrenia and Alzheimer's disease. Moreover, there is additional evidence suggesting that platelet signaling may assist with prediction of cognitive phenotype and could represent a potent readout of drug efficacy in clinical trials. Globally, given the neurobiological overlap between different forms of intellectual disability, platelets may be a valuable window to access the molecular underpinnings of ASD and other neurodevelopmental disorders (NDD) sharing similar synaptic plasticity defects with FXS. Platelets are indeed an attractive model for unraveling pathophysiological mechanisms involved in NDD as well as to search for diagnostic and therapeutic biomarkers.

Metabolic Dysfunction Underlying Autism Spectrum Disorder and Potential Treatment Approaches

Autism spectrum disorder (ASD) is characterized by deficits in sociability and communication, and increased repetitive and/or restrictive behaviors. While the etio-pathogenesis of ASD is unknown, clinical manifestations are diverse and many possible genetic and environmental factors have been implicated. As such, it has been a great challenge to identify key neurobiological mechanisms and to develop effective treatments. Current therapies focus on co-morbid conditions (such as epileptic seizures and sleep disturbances) and there is no cure for the core symptoms. Recent studies have increasingly implicated mitochondrial dysfunction in ASD. The fact that mitochondria are an integral part of diverse cellular functions and are susceptible to many insults could explain how a wide range of factors can contribute to a consistent behavioral phenotype in ASD. Meanwhile, the high-fat, low-carbohydrate ketogenic diet (KD), used for nearly a century to treat medically intractable epilepsy, has been shown to enhance mitochondrial function through a multiplicity of mechanisms and affect additional molecular targets that may address symptoms and comorbidities of ASD. Here, we review the evidence for the use of metabolism-based therapies such as the KD in the treatment of ASD as well as emerging co-morbid models of epilepsy and autism. Future research directions aimed at validating such therapeutic approaches and identifying additional and novel mechanistic targets are also discussed.

Identification of Biomarkers of Impaired Sensory Profiles among Autistic Patients

BACKGROUND

Autism is a neurodevelopmental disorder that displays significant heterogeneity. Comparison of subgroups within autism, and analyses of selected biomarkers as measure of the variation of the severity of autistic features such as cognitive dysfunction, social interaction impairment, and sensory abnormalities might help in understanding the pathophysiology of autism.

METHODS AND PARTICIPANTS

In this study, two sets of biomarkers were selected. The first included 7, while the second included 6 biomarkers. For set 1, data were collected from 35 autistic and 38 healthy control participants, while for set 2, data were collected from 29 out of the same 35 autistic and 16 additional healthy subjects. These markers were subjected to a principal components analysis using either covariance or correlation matrices. Moreover, libraries composed of participants categorized into units were constructed. The biomarkers used include, PE (phosphatidyl ethanolamine), PS (phosphatidyl serine), PC (phosphatidyl choline), MAP2K1 (Dual specificity mitogen-activated protein kinase kinase 1), IL-10 (interleukin-10), IL-12, NFκB (nuclear factor-κappa B); PGE2 (prostaglandin E2), PGE2-EP2, mPGES-1 (microsomal prostaglandin synthase E-1), cPLA2 (cytosolic phospholipase A2), 8-isoprostane, and COX-2 (cyclo-oxygenase-2).

RESULTS

While none of the studied markers correlated with CARS and SRS as measure of cognitive and social impairments, six markers significantly correlated with sensory profiles of autistic patients. Multiple regression analysis identifies a combination of PGES, mPGES-1, and PE as best predictors of the degree of sensory profile impairment. Library identification resulted in 100% correct assignments of both autistic and control participants based on either set 1 or 2 biomarkers together with a satisfactory rate of assignments in case of sensory profile impairment using different sets of biomarkers.

CONCLUSION

The two selected sets of biomarkers were effective to separate autistic from healthy control subjects, demonstarting the possibility to accurately predict the severity of autism using the selected biomarkers. The effectiveness of the identified libraries lied in the fact that they were helpful in correctly assigning the study population as control or autistic patients and in classifying autistic patients with different degree of sensory profile impairment.