Reconsidering animal models used to study autism spectrum disorder: Current state and optimizing future

Developmental pyrethroid exposure disrupts molecular pathways for MAP kinase and circadian rhythms in mouse brain

Neurodevelopmental disorders (NDDs) are a category of pervasive disorders of the developing nervous system with few or no recognized biomarkers. A significant portion of the risk for NDDs, including attention deficit hyperactivity disorder (ADHD), is contributed by the environment, and exposure to pyrethroid pesticides during pregnancy has been identified as a potential risk factor for NDD in the unborn child. We recently showed that low-dose developmental exposure to the pyrethroid pesticide deltamethrin in mice causes male-biased changes to ADHD- and NDD-relevant behaviors as well as the striatal dopamine system. Here, we used an integrated multiomics approach to determine the broadest possible set of biological changes in the mouse brain caused by developmental pyrethroid exposure (DPE). Using a litter-based, split-sample design, we exposed mouse dams during pregnancy and lactation to deltamethrin (3 mg/kg or vehicle every 3 days) at a concentration well below the EPA-determined benchmark dose used for regulatory guidance. We raised male offspring to adulthood, euthanized them, and pulverized and divided whole brain samples for split-sample transcriptomics, kinomics, and multiomics integration. Transcriptome analysis revealed alterations to multiple canonical clock genes, and kinome analysis revealed changes in the activity of multiple kinases involved in synaptic plasticity, including the mitogen-activated protein (MAP) kinase ERK. Multiomics integration revealed a dysregulated protein-protein interaction network containing primary clusters for MAP kinase cascades, regulation of apoptosis, and synaptic function. These results demonstrate that DPE causes a multimodal biophenotype in the brain relevant to ADHD and identifies new potential mechanisms of action.NEW & NOTEWORTHY Here, we provide the first evidence that low-dose developmental exposure to a pyrethroid pesticide, deltamethrin, results in molecular disruptions in the adult mouse brain in pathways regulating circadian rhythms and neuronal growth (MAP kinase). This same exposure causes a neurodevelopmental disorder (NDD)-relevant behavioral change in adult mice, making these findings relevant to the prevention of NDDs.

Effects of whole brain proton irradiation at conventional or ultra-high dose rate (FLASH), in adult male Sprague Dawley rats

Radiation is an effective treatment for many brain tumors, but often causes cognitive impairment. Ultra-high dose rate (FLASH) radiotherapy is less toxic to many normal tissues and may protect against adverse cognitive effects of cranial irradiation. Adult male Sprague Dawley rats received a single 18 Gy fraction of cranial irradiation with protons at 1 Gy/s (CV), 60 Gy/s (FLASH-60), 95 Gy/s (FLASH-95), or sham treatment (Control) (n ≥ 22/group). Rats were tested in open-field, acoustic (ASR) and tactile startle (TSR), novelty preference, radial water maze (RWM), Morris water maze (MWM), Cincinnati water maze configurations A and B (CWM-A CWM-B), and novelty tests. Locomotion was decreased and TSR increased in all irradiated rats and ASR increased in FLASH-95 rats compared with Controls. In MWM acquisition and reversal, the CV and FLASH-60 rats had reduced path efficiency but during shift and shift reversal all irradiated rats had increased latencies and reduced path efficiencies compared with Controls. In CWM-A all irradiated rats performed below Controls. There were no differences found in CWM-B, novelty tests, or RWM. In summary, FLASH treatment after 18 Gy cranial proton irradiation did not result in reduced cognitive toxicity.

Altered Neural Activity in the Mesoaccumbens Pathway Underlies Impaired Social Reward Processing in Shank3-Deficient Rats

Social behaviors are crucial for human connection and belonging, often impacted by conditions like Autism Spectrum Disorder (ASD). The mesoaccumbens pathway (ventral tegmental area (VTA) to the nucleus accumbense (NAc)) plays a pivotal role in social behavior and is implicated in ASD. However, the impact of ASD-related mutations on social reward processing remains insufficiently explored. This study focuses on the Shank3 mutation, associated with a rare genetic condition and linked to ASD, examining its influence on the mesoaccumbens pathway during behavior, using the Shank3-deficient rat model. Our findings indicate that Shank3-deficient rats exhibit atypical social interactions, associated with altered neuronal activity of VTA dopaminergic and GABAergic neurons and reduced dopamine release in the NAc. Moreover, they demonstrate that manipulating VTA neuronal activity can normalize this behavior, providing insights into the effects of Shank3 mutations on social reward processing  and identifying a potential neural pathway for intervention.

Carbamoylated Erythropoietin Rescues Autism-Relevant Social Deficits in BALB/cJ Mice

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects over 2% of the population worldwide and is characterized by repetitive behaviors, restricted areas of interest, deficits in social communication, and high levels of anxiety. Currently, there are no known effective treatments for the core features of ASD. The previous literature has established erythropoietin (EPO) as a promising antidepressant, working as a potent neurogenic and neurotrophic agent with hematopoietic side effects. Carbamoylated erythropoietin (CEPO), a chemically engineered non-hematopoietic derivative of EPO, appears to retain the neuroprotective factors of EPO without the hematologic properties. Recent evidence shows that CEPO corrects stress-related depressive behaviors in BALB/cJ (BALB) mice, which also have face validity as an ASD mouse model. We investigated whether CEPO can recover deficient social and anxiety-related behavioral deficits compared to C57BL/6J controls. After administering CEPO (40 μg/kg in phosphate-buffered saline) or vehicle over 21 days, we analyzed the mice's performance in the three-chamber social approach, the open field, the elevated plus maze, and the Porsolt's forced swim tasks. CEPO appeared to correct sociability in the three-chamber social approach task to C57 levels, increasing the amount of time the mice interacted with novel, social mice overall rather than altering the overall amount of exploratory activity in the maze. Consistent with this finding, there was no concomitant increase in the distance traveled in the open field, nor were there any alterations in the anxiety-related measures in the task. On the other hand, CEPO administration improved exploratory behavior in the elevated plus maze. This study marks the first demonstration of the benefits of a non-erythropoietic EPO derivative for social behavior in a mouse model of autism and merits further investigation into the mechanisms by which this action occurs.

Mapping the landscape of social behavior

Social interaction is integral to animal behavior. However, lacking tools to describe it in quantitative and rigorous ways has limited our understanding of its structure, underlying principles, and the neuropsychiatric disorders, like autism, that perturb it. Here, we present a technique for high-resolution 3D tracking of postural dynamics and social touch in freely interacting animals, solving the challenging subject occlusion and part-assignment problems using 3D geometric reasoning, graph neural networks, and semi-supervised learning. We collected over 110 million 3D pose samples in interacting rats and mice, including seven monogenic autism rat lines. Using a multi-scale embedding approach, we identified a rich landscape of stereotyped actions, interactions, synchrony, and body contacts. This high-resolution phenotyping revealed a spectrum of changes in autism models and in response to amphetamine not resolved by conventional measurements. Our framework and large library of interactions will facilitate studies of social behaviors and their neurobiological underpinnings.

A quantitative weight-of-evidence review of preclinical studies examining the potential developmental neurotoxicity of acetaminophen

Acetaminophen [paracetamol; N-acetyl-para-aminophenol (APAP)] is an antipyretic/analgesic commonly used in the treatment of fever and mild to moderate pain, headache, myalgia, and dysmenorrhea. Recent literature has questioned the safety of acetaminophen use during pregnancy, with an emphasis on whether exposure to the developing nervous system results in behavioral changes consistent with autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and/or other cognitive deficits in the offspring. No previous review has used a fully detailed, quantitative weight-of-evidence (QWoE) approach to critically examine the preclinical acetaminophen data with regards to potential developmental neurotoxicity (DNT). Following regulatory guidance, a QWoE framework using prespecified scoring criteria was developed consistent with previous approaches to characterize potential adverse DNT outcomes with considerations for biological relevance of the response to adverse outcomes (outcome score) and the strength of methods and study design (methods score). Considerations for the methods score included (1) experimental design, (2) details/reliability of measurement(s), (3) data transparency, and (4) translational/methodological relevance. Considerations for the outcome score included response-related (1) statistical significance, (2) dose-response, (3) relevance/reliability/magnitude, (4) plausibility, and (5) translational relevance, including consideration of systemic toxicity/hepatotoxicity and therapeutic and/or non-systemically toxic doses and durations of use. Application of this QWoE framework to the 34 in vivo studies identified that assess the potential DNT of acetaminophen resulted in 188 QWoE entries documented across 11 DNT endpoints: social behavior, stereotypic behavior, behavioral rigidity, attention/impulsivity, hyperactivity, anxiety-like behavior, sensorimotor function, spatial learning/memory, nonspatial learning/memory, neuroanatomy, and neurotransmission. For each endpoint, the mean outcome score and methods score were calculated for total entries and for entries segregated by sex to assist in determining data quality and potential adversity. Informed by all 188 entries, the QWoE analysis demonstrated data of moderate quality showing no consistent evidence of DNT in male and female rodents following exposure to acetaminophen at therapeutic and/or nonsystemically toxic doses. Although some of the DNT endpoints (behavioral rigidity, attention/impulsivity, spatial learning/memory, neuroanatomy, and neurotransmission) generally displayed a more limited dataset and/or relatively lower data quality, similar conclusions were drawn based on results indicating a lack of biological relevance and reliability of reported adverse effects. Overall, this QWoE analysis on the preclinical in vivo data demonstrates no consistent evidence of adverse effects following developmental exposure to acetaminophen at therapeutic and/or non-systemically toxic doses on the structure and function of the nervous system, including neuroanatomical, neurotransmission, and behavioral endpoints.

Prenatal gene editing for neurodevelopmental diseases: Ethical considerations

Neurodevelopmental diseases (NDDs) are notoriously difficult to treat because clinical symptoms stem from developmental processes that begin before birth. Prenatal gene editing could fill the treatment gap for NDDs by targeting and permanently correcting the genetic variants that underlie these pathogenic developmental processes. At the same time, there is a risk of unintended edits to the fetus or the pregnant person that could result in serious adverse consequences that are difficult, if not impossible, to undo. This raises ethical concerns that make the development of prenatal gene editing especially challenging. To date, there are no frameworks for considering the steps necessary for an ethical path forward for prenatal gene editing specifically. The 60-year history of in utero therapy has included the development of frameworks for other therapies that can provide starting points for addressing the unique issues of prenatal gene editing. We identified 12 themes from 17 ethical frameworks, literature, consensus statements, and government reports on prenatal interventions that could set precedents for prenatal gene editing interventions. In considering these alongside current criteria for postnatal gene therapies for NDDs, we discuss a path forward for prenatal gene editing interventions of NDDs.

Oxytocin in autism: Rethinking treatment and research through a neurodivergent perspective

This perspective piece addresses critical challenges in oxytocin-based interventions for autism, drawing on neurodivergent perspectives to highlight key issues in research relevance and inclusivity. Although oxytocin has been posited to modulate social and routinized behaviors in autistic individuals, empirical findings on its efficacy remain inconsistent. We argue that these behavioral targets may reflect neurotypical biases, often disregarding autistic individuals' perspectives, thereby limiting intervention acceptability and efficacy. Past research has frequently excluded marginalized autistic populations, including individuals with intellectual disabilities or gender-diverse identities, exacerbating generalizability issues. This piece advocates for a reorientation of research objectives in autism, proposing a shift from modifying core autistic behaviors towards enhancing quality of life through participatory research. By integrating autistic perspectives into study design and outcome selection, researchers move away from deficit-oriented frameworks and instead prioritize socially valid outcomes, such as reducing anxiety and improving adaptive functioning. Further, the perspective piece critiques the reliance on animal models, which often lack translational validity due to autism's complex social and communicative dimensions. In closing, we underscore the importance of inclusive, reproducible autism research practices that align with the lived experiences and priorities of autistic individuals. Embracing participatory research, alongside rigorous methodological adjustments, can foster advancements that effectively support the well-being of the autistic community.

Folate prevents the autism-related phenotype caused by developmental pyrethroid exposure in prairie voles

Neurodevelopmental disorders (NDDs) have dramatically increased in prevalence to an alarming one in six children, and yet both causes and preventions remain elusive. Recent human epidemiology and animal studies have implicated developmental exposure to pyrethroid pesticides, one of the most common classes of pesticides in the US, as an environmental risk factor for autism and neurodevelopmental disorders. Our previous research has shown that low-dose chronic developmental pyrethroid exposure (DPE) changes folate metabolites in the adult mouse brain. We hypothesize that DPE acts directly on molecular targets in the folate metabolism pathway, and that high-dose maternal folate supplementation can prevent or reduce the biobehavioral effects of DPE. We exposed pregnant prairie vole dams chronically to vehicle or low-dose deltamethrin (3 mg/kg/3 days) with or without high-dose folate supplementation (methylfolate, 5 mg/kg/3 days). The resulting DPE offspring showed broad deficits in five behavioral domains relevant to neurodevelopmental disorders (including the social domain); increased plasma folate concentrations; and increased neural expression of SHMT1, a folate cycle enzyme. Maternal folate supplementation prevented most of the behavioral phenotypes (except for repetitive behaviors) and caused potentially compensatory changes in neural expression of FOLR1 and MTHFR, two folate-related proteins. We conclude that DPE causes neurodevelopmental disorder-relevant behavioral deficits; DPE directly alters aspects of folate metabolism; and preventative interventions targeting folate metabolism are effective in reducing, but not eliminating, the behavioral effects of DPE.

Epigenetic underpinnings of the autistic mind: Histone modifications and prefrontal excitation/inhibition imbalance

Autism spectrum disorder (ASD) is complex neurobehavioral condition influenced by several cellular and molecular mechanisms that are often concerned with synaptogenesis and synaptic activity. Based on the excitation/inhibition (E/I) imbalance theory, ASD could be the result of disruption in excitatory and inhibitory synaptic transmission across the brain. The prefrontal cortex (PFC) is the chief regulator of executive function and can be affected by altered neuronal excitation and inhibition in the course of ASD. The molecular mechanisms involved in E/I imbalance are subject to epigenetic regulation. In ASD, altered enrichment and spreading of histone H3 and H4 modifications such as the activation-linked H3K4me2/3, H3K9ac, and H3K27ac, and repression-linked H3K9me2, H3K27me3, and H4K20me2 in the PFC result in dysregulation of molecules mediating synaptic excitation (ARC, EGR1, mGluR2, mGluR3, GluN2A, and GluN2B) and synaptic inhibition (BSN, EphA7, SLC6A1). Histone modifications are a dynamic component of the epigenetic regulatory elements with a pronounced effect on patterns of gene expression with regards to any biological process. The excitation/inhibition imbalance associated with ASD is based on the excitatory and inhibitory synaptic activity in different regions of the brain, including the PFC, the ultimate outcome of which is highly influenced by transcriptional activity of relevant genes.

Polygenicity in a box: Copy number variants, neural circuit development, and neurodevelopmental disorders

Clinically defined neurodevelopmental disorders (cd-NDDs), including Autistic Spectrum Disorder (ASD) and Schizophrenia (Scz), are primarily polygenic: Multiple risk genes distributed across the genome, in potentially infinite combinations, account for variable pathology. Polygenicity raises a fundamental question: Can "core" cd-NDD pathogenic mechanisms be identified given this genomic complexity? With the right models and analytic targets, a distinct class of polygenic mutations-Copy Number Variants (CNVs): contiguous gene deletions or duplications associated with cd-NDD risk-provide a singular opportunity to define cd-NDD pathology. CNVs orthologous to those that confer cd-NDD risk have been engineered in animals as well as human stem cells. Using these tools, one can determine how altered function of multiple genes cause serial stumbles over cell biological steps typically taken to build optimal "polygenic" neural circuits. Thus, cd-NDD pathology may be a consequence of polygenic deviations-stumbles-that exceed limits of adaptive variation for key developmental steps.

Development and evaluation of an autism pig model

Developing cost-effective and disease-relevant animal models is essential for advancing biomedical research into human disorders. Here we investigate the feasibility of a pig model for autism spectrum disorder (ASD) using embryonic exposure to valproic acid (VPA), an antiepileptic drug known to increase ASD risk. We established experimental paradigms to assess the behavioral characteristics of these pig models. Administration of VPA to Bama miniature pigs (Sus scrofa domestica) during critical embryonic stages resulted in abnormal gait, increased anxiety levels, reduced learning capabilities and altered social patterns, while largely preserving social preference of treated piglets. Notably, we detected significant neuroanatomical changes in cortical regions associated with ASD in the VPA-treated pigs, including cortical malformation, increased neuronal soma size, decreased dendritic complexity and reduced dendritic spine maturation. Transcriptome analysis of the prefrontal cortex of VPA-treated pigs further revealed substantial alterations in the expression of genes linked to ASD, especially genes of the dopamine signaling pathway, highlighting the model's relevance and potential for shedding light on ASD's underlying neuropathological and molecular mechanisms. These findings suggest that pig models could serve as a promising alternative to traditional rodent models and provide a more ethical substitute for the use of primates in translational research on neurodevelopmental disorders.

Circuit mechanisms underlying sexually dimorphic outcomes of early life stress

Stress during early life influences brain development and can affect social, motor, and emotional processes. We describe a striking sex difference in the effects of early life stress (ELS), which produces anhedonia and anxiety-like behaviors in female adolescent mice, as reported previously, but repetitive behavioral pathology and social deficits in male adolescent mice. Notably, this parallels sex differences seen in the prevalence of psychiatric symptoms: depression and anxiety disorders are more common in girls and women, whereas neurodevelopmental disorders like autism spectrum disorder and Tourette syndrome are markedly more common in boys and men. We characterized the effects of ELS on the medial prefrontal cortex (mPFC) and on its projections to the dorsal striatum (dStr) and lateral septum (LS). ELS males, but not females, developed hyperactivity in the cortico-striatal circuit and hypoactivity in the cortico-septal circuit. Chemogenetic manipulation of cortico-striatal projection neurons modulates repetitive behavioral pathology and social behaviors in stressed males, and anhedonia in stressed females. Activation of cortico-septal projection neurons rescues social deficits in stressed males. We conclude that early life stress produces sexually dimorphic behavioral effects, with potential relevance to human psychiatric symptoms, through its differential effects on cortico-striatal and cortico-septal circuits.

Deriving comprehensive literature trends on multi-omics analysis studies in autism spectrum disorder using literature mining pipeline

Autism spectrum disorder (ASD) is characterized by highly heterogenous abnormalities in functional brain connectivity affecting social behavior. There is a significant progress in understanding the molecular and genetic basis of ASD in the last decade using multi-omics approach. Mining this large volume of biomedical literature for insights requires considerable amount of manual intervention for curation. Machine learning and artificial intelligence fields are advancing toward simplifying data mining from unstructured text data. Here, we demonstrate our literature mining pipeline to accelerate data to insights. Using topic modeling and generative AI techniques, we present a pipeline that can classify scientific literature into thematic clusters and can help in a wide array of applications such as knowledgebase creation, conversational virtual assistant, and summarization. Employing our pipeline, we explored the ASD literature, specifically around multi-omics studies to understand the molecular interplay underlying autism brain.

Hyperexcitability and translational phenotypes in a preclinical mouse model of SYNGAP1-related intellectual disability

Disruption of SYNGAP1 directly causes a genetically identifiable neurodevelopmental disorder (NDD) called SYNGAP1-related intellectual disability (SRID). Without functional SynGAP1 protein, individuals are developmentally delayed and have prominent features of intellectual disability (ID), motor impairments, and epilepsy. Over the past two decades, there have been numerous discoveries indicating the critical role of Syngap1. Several rodent models with a loss of Syngap1 have been engineered, identifying precise roles in neuronal structure and function, as well as key biochemical pathways key for synapse integrity. Homozygous loss of SYNGAP1/Syngap1 is lethal. Heterozygous mutations of Syngap1 result in a broad range of behavioral phenotypes. Our in vivo functional data, using the original mouse model from the Huganir laboratory, corroborated behaviors including robust hyperactivity and deficits in learning and memory in young adults. Furthermore, we described impairments in the domain of sleep, characterized using neurophysiological data that was collected with wireless, telemetric electroencephalography (EEG). Syngap1+/- mice exhibited elevated spiking events and spike trains, in addition to elevated power, most notably in the delta power frequency. For the first time, we illustrated that primary neurons from Syngap1+/- mice displayed: 1) increased network firing activity, 2) greater bursts, 3) and shorter inter-burst intervals between peaks, by utilizing high density microelectrode arrays (HD-MEA). Our work bridges in vitro electrophysiological neuronal activity and function with in vivo neurophysiological brain activity and function. These data elucidate quantitative, translational biomarkers in vivo and in vitro that can be utilized for the development and efficacy assessment of targeted treatments for SRID.

Mapping the landscape of social behavior

Social interaction is integral to animal behavior. However, we lack tools to describe it with quantitative rigor, limiting our understanding of its principles and neuropsychiatric disorders, like autism, that perturb it. Here, we present a technique for high-resolution 3D tracking of postural dynamics and social touch in freely interacting animals, solving the challenging subject occlusion and part assignment problems using 3D geometric reasoning, graph neural networks, and semi-supervised learning. We collected over 140 million 3D postures in interacting rodents, featuring new monogenic autism rat lines lacking reports of social behavioral phenotypes. Using a novel multi-scale embedding approach, we identified a rich landscape of stereotyped actions, interactions, synchrony, and body contact. This enhanced phenotyping revealed a spectrum of changes in autism models and in response to amphetamine that were inaccessible to conventional measurements. Our framework and large library of interactions will greatly facilitate studies of social behaviors and their neurobiological underpinnings.

Decoding the genetic landscape of autism: A comprehensive review

BACKGROUND

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by heterogeneous symptoms and genetic underpinnings. Recent advancements in genetic and epigenetic research have provided insights into the intricate mechanisms contributing to ASD, influencing both diagnosis and therapeutic strategies.

AIM

To explore the genetic architecture of ASD, elucidate mechanistic insights into genetic mutations, and examine gene-environment interactions.

METHODS

A comprehensive systematic review was conducted, integrating findings from studies on genetic variations, epigenetic mechanisms (such as DNA methylation and histone modifications), and emerging technologies [including Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas9 and single-cell RNA sequencing]. Relevant articles were identified through systematic searches of databases such as PubMed and Google Scholar.

RESULTS

Genetic studies have identified numerous risk genes and mutations associated with ASD, yet many cases remain unexplained by known factors, suggesting undiscovered genetic components. Mechanistic insights into how these genetic mutations impact neural development and brain connectivity are still evolving. Epigenetic modifications, particularly DNA methylation and non-coding RNAs, also play significant roles in ASD pathogenesis. Emerging technologies like CRISPR-Cas9 and advanced bioinformatics are advancing our understanding by enabling precise genetic editing and analysis of complex genomic data.

CONCLUSION

Continued research into the genetic and epigenetic underpinnings of ASD is crucial for developing personalized and effective treatments. Collaborative efforts integrating multidisciplinary expertise and international collaborations are essential to address the complexity of ASD and translate genetic discoveries into clinical practice. Addressing unresolved questions and ethical considerations surrounding genetic research will pave the way for improved diagnostic tools and targeted therapies, ultimately enhancing outcomes for individuals affected by ASD.

A critical review of the impact of candidate copy number variants on autism spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder (NDD) influenced by genetic, epigenetic, and environmental factors. Recent advancements in genomic analysis have shed light on numerous genes associated with ASD, highlighting the significant role of both common and rare genetic mutations, as well as copy number variations (CNVs), single nucleotide polymorphisms (SNPs) and unique de novo variants. These genetic variations disrupt neurodevelopmental pathways, contributing to the disorder's complexity. Notably, CNVs are present in 10 %-20 % of individuals with autism, with 3 %-7 % detectable through cytogenetic methods. While the role of submicroscopic CNVs in ASD has been recently studied, their association with genomic loci and genes has not been thoroughly explored. In this review, we focus on 47 CNV regions linked to ASD, encompassing 1632 genes, including protein-coding genes and long non-coding RNAs (lncRNAs), of which 659 show significant brain expression. Using a list of ASD-associated genes from SFARI, we detect 17 regions harboring at least one known ASD-related protein-coding gene. Of the remaining 30 regions, we identify 24 regions containing at least one protein-coding gene with brain-enriched expression and a nervous system phenotype in mouse mutants, and one lncRNA with both brain-enriched expression and upregulation in iPSC to neuron differentiation. This review not only expands our understanding of the genetic diversity associated with ASD but also underscores the potential of lncRNAs in contributing to its etiology. Additionally, the discovered CNVs will be a valuable resource for future diagnostic, therapeutic, and research endeavors aimed at prioritizing genetic variations in ASD.

Developmental pyrethroid exposure in mouse leads to disrupted brain metabolism in adulthood

Environmental and genetic risk factors, and their interactions, contribute significantly to the etiology of neurodevelopmental disorders (NDDs). Recent epidemiology studies have implicated pyrethroid pesticides as an environmental risk factor for autism and developmental delay. Our previous research showed that low-dose developmental exposure to the pyrethroid pesticide deltamethrin in mice caused male-biased changes in the brain and in NDD-relevant behaviors in adulthood. Here, we used a metabolomics approach to determine the broadest possible set of metabolic changes in the adult male mouse brain caused by low-dose pyrethroid exposure during development. Using a litter-based design, we exposed mouse dams during pregnancy and lactation to deltamethrin (3 mg/kg or vehicle every 3 days) at a concentration well below the EPA-determined benchmark dose used for regulatory guidance. We raised male offspring to adulthood and collected whole brain samples for untargeted high-resolution metabolomics analysis. Developmentally exposed mice had disruptions in 116 metabolites which clustered into pathways for folate biosynthesis, retinol metabolism, and tryptophan metabolism. As a cross-validation, we integrated metabolomics and transcriptomics data from the same samples, which confirmed previous findings of altered dopamine signaling. These results suggest that pyrethroid exposure during development leads to disruptions in metabolism in the adult brain, which may inform both prevention and therapeutic strategies.

Altered socio-affective communication and amygdala development in mice with protocadherin10-deficient interneurons

Autism spectrum disorder (ASD) is a group of neurodevelopmental conditions associated with deficits in social interaction and communication, together with repetitive behaviours. The cell adhesion molecule protocadherin10 (PCDH10) is linked to ASD in humans. Pcdh10 is expressed in the nervous system during embryonic and early postnatal development and is important for neural circuit formation. In mice, strong expression of Pcdh10 in the ganglionic eminences and in the basolateral complex (BLC) of the amygdala was observed at mid and late embryonic stages, respectively. Both inhibitory and excitatory neurons expressed Pcdh10 in the BLC at perinatal stages and vocalization-related genes were enriched in Pcdh10-expressing neurons in adult mice. An epitope-tagged Pcdh10-HAV5 mouse line revealed endogenous interactions of PCDH10 with synaptic proteins in the young postnatal telencephalon. Nuanced socio-affective communication changes in call emission rates, acoustic features and call subtype clustering were primarily observed in heterozygous pups of a conditional knockout (cKO) with selective deletion of Pcdh10 in Gsh2-lineage interneurons. These changes were less prominent in heterozygous ubiquitous Pcdh10 KO pups, suggesting that altered anxiety levels associated with Gsh2-lineage interneuron functioning might drive the behavioural effects. Together, loss of Pcdh10 specifically in interneurons contributes to behavioural alterations in socio-affective communication with relevance to ASD.

Developmental pyrethroid exposure in mouse leads to disrupted brain metabolism in adulthood

Environmental and genetic risk factors, and their interactions, contribute significantly to the etiology of neurodevelopmental disorders (NDDs). Recent epidemiology studies have implicated pyrethroid pesticides as an environmental risk factor for autism and developmental delay. Our previous research showed that low-dose developmental exposure to the pyrethroid pesticide deltamethrin in mice caused male-biased changes in the brain and in NDD-relevant behaviors in adulthood. Here, we used a metabolomics approach to determine the broadest possible set of metabolic changes in the adult male mouse brain caused by low-dose pyrethroid exposure during development. Using a litter-based design, we exposed mouse dams during pregnancy and lactation to deltamethrin (3 mg/kg or vehicle every 3 days) at a concentration well below the EPA-determined benchmark dose used for regulatory guidance. We raised male offspring to adulthood and collected whole brain samples for untargeted high-resolution metabolomics analysis. Developmentally exposed mice had disruptions in 116 metabolites which clustered into pathways for folate biosynthesis, retinol metabolism, and tryptophan metabolism. As a cross-validation, we integrated metabolomics and transcriptomics data from the same samples, which confirmed previous findings of altered dopamine signaling. These results suggest that pyrethroid exposure during development leads to disruptions in metabolism in the adult brain, which may inform both prevention and therapeutic strategies.

Gestational hypothyroxinemia induces ASD-like phenotypes in behavior, proinflammatory markers, and glutamatergic protein expression in mouse offspring of both sexes

Background

The prevalence of autism spectrum disorder (ASD) has significantly risen in the past three decades, prompting researchers to explore the potential contributions of environmental factors during pregnancy to ASD development. One such factor of interest is gestational hypothyroxinemia (HTX), a frequent condition in pregnancy associated with cognitive impairments in the offspring. While retrospective human studies have linked gestational HTX to autistic traits, the cellular and molecular mechanisms underlying the development of ASD-like phenotypes remain poorly understood. This study used a mouse model of gestational HTX to evaluate ASD-like phenotypes in the offspring.

Methods

To induce gestational HTX, pregnant mice were treated with 2-mercapto-1-methylimidazole (MMI), a thyroid hormones synthesis inhibitor, in the tap-drinking water from embryonic days (E) 10 to E14. A separate group received MMI along with a daily subcutaneous injection of T4, while the control group received regular tap water during the entire pregnancy. Female and male offspring underwent assessments for repetitive, anxious, and social behaviors from postnatal day (P) 55 to P64. On P65, mice were euthanized for the evaluation of ASD-related inflammatory markers in blood, spleen, and specific brain regions. Additionally, the expression of glutamatergic proteins (NLGN3 and HOMER1) was analyzed in the prefrontal cortex and hippocampus.

Results

The HTX-offspring exhibited anxious-like behavior, a subordinate state, and impaired social interactions. Subsequently, both female and male HTX-offspring displayed elevated proinflammatory cytokines in blood, including IL-1β, IL-6, IL-17A, and TNF-α, while only males showed reduced levels of IL-10. The spleen of HTX-offspring of both sexes showed increased Th17/Treg ratio and M1-like macrophages. In the prefrontal cortex and hippocampus of male HTX-offspring, elevated levels of IL-17A and reduced IL-10 were observed, accompanied by increased expression of hippocampal NLGN3 and HOMER1. All these observations were compared to those observed in the Control-offspring. Notably, the supplementation with T4 during the MMI treatment prevents the development of the observed phenotypes. Correlation analysis revealed an association between maternal T4 levels and specific ASD-like outcomes.

Discussion

This study validates human observations, demonstrating for the first time that gestational HTX induces ASD-like phenotypes in the offspring, highlighting the need of monitoring thyroid function during pregnancy.

The role of prickle proteins in vertebrate development and pathology

Prickle is an evolutionarily conserved family of proteins exclusively associated with planar cell polarity (PCP) signalling. This signalling pathway provides directional and positional cues to eukaryotic cells along the plane of an epithelial sheet, orthogonal to both apicobasal and left-right axes. Through studies in the fruit fly Drosophila, we have learned that PCP signalling is manifested by the spatial segregation of two protein complexes, namely Prickle/Vangl and Frizzled/Dishevelled. While Vangl, Frizzled, and Dishevelled proteins have been extensively studied, Prickle has been largely neglected. This is likely because its role in vertebrate development and pathologies is still being explored and is not yet fully understood. The current review aims to address this gap by summarizing our current knowledge on vertebrate Prickle proteins and to cover their broad versatility. Accumulating evidence suggests that Prickle is involved in many developmental events, contributes to homeostasis, and can cause diseases when its expression and signalling properties are deregulated. This review highlights the importance of Prickle in vertebrate development, discusses the implications of Prickle-dependent signalling in pathology, and points out the blind spots or potential links regarding Prickle, which could be studied further.

Development of a New Scoring System in Higher Animals for Testing Cognitive Function in the Newborn Period: Effect of Prenatal Hypoxia-Ischemia

INTRODUCTION

Enhanced models for assessing cognitive function in the neonatal period are imperative in higher animals. Postnatal motor deficits, characteristic of cerebral palsy, emerge in newborn kits within our prenatal rabbit model of hypoxia-ischemia (HI). In humans, prenatal HI leads to intellectual disability and cerebral palsy. In a study examining cognitive function in newborn rabbits, we explored several questions. Is there a distinction between conditioned and unconditioned kits? Can the kits discern the human face or the laboratory coat? Do motorically normal kits, born after prenatal HI, exhibit cognitive deficits?

METHODS

The conditioning protocol was randomly assigned to kits from each litter. For conditioning, the same human, wearing a laboratory coat, fed the rabbit kits for 9 days before the cognitive test. The 6-arm radial maze was chosen for its simplicity and ease of use. Normally appearing kits, born after uterine ischemia at 79% or 92% term in New Zealand White rabbits, were compared to naïve kits. On postpartum day 22/23 or 29/30, the 6-arm maze helped determine if the kits recognized the original feeder from bystander (test 1) or the laboratory coat on bystander (test 2). The use of masks of feeder/bystander (test 3) assessed confounding cues. A weighted score was devised to address variability in entry to maze arms, time, and repeated-trial learning.

RESULTS

In conditioned kits, both naïve and HI kits exhibited a significant preference for the face of the feeder but not the laboratory coat. Cognitive deficits were minimal in normal-appearing HI kits.

CONCLUSION

The weighted score was amenable to statistical manipulation.

INTRODUCTION

Enhanced models for assessing cognitive function in the neonatal period are imperative in higher animals. Postnatal motor deficits, characteristic of cerebral palsy, emerge in newborn kits within our prenatal rabbit model of hypoxia-ischemia (HI). In humans, prenatal HI leads to intellectual disability and cerebral palsy. In a study examining cognitive function in newborn rabbits, we explored several questions. Is there a distinction between conditioned and unconditioned kits? Can the kits discern the human face or the laboratory coat? Do motorically normal kits, born after prenatal HI, exhibit cognitive deficits?

METHODS

The conditioning protocol was randomly assigned to kits from each litter. For conditioning, the same human, wearing a laboratory coat, fed the rabbit kits for 9 days before the cognitive test. The 6-arm radial maze was chosen for its simplicity and ease of use. Normally appearing kits, born after uterine ischemia at 79% or 92% term in New Zealand White rabbits, were compared to naïve kits. On postpartum day 22/23 or 29/30, the 6-arm maze helped determine if the kits recognized the original feeder from bystander (test 1) or the laboratory coat on bystander (test 2). The use of masks of feeder/bystander (test 3) assessed confounding cues. A weighted score was devised to address variability in entry to maze arms, time, and repeated-trial learning.

RESULTS

In conditioned kits, both naïve and HI kits exhibited a significant preference for the face of the feeder but not the laboratory coat. Cognitive deficits were minimal in normal-appearing HI kits.

CONCLUSION

The weighted score was amenable to statistical manipulation.

Modulation of gut microbiota with probiotics as a strategy to counteract endogenous and exogenous neurotoxicity

The existing data demonstrate that probiotic supplementation affords protective effects against neurotoxicity of exogenous (e.g., metals, ethanol, propionic acid, aflatoxin B1, organic pollutants) and endogenous (e.g., LPS, glucose, Aβ, phospho-tau, α-synuclein) agents. Although the protective mechanisms of probiotic treatments differ between various neurotoxic agents, several key mechanisms at both the intestinal and brain levels seem inherent to all of them. Specifically, probiotic-induced improvement in gut microbiota diversity and taxonomic characteristics results in modulation of gut-derived metabolite production with increased secretion of SFCA. Moreover, modulation of gut microbiota results in inhibition of intestinal absorption of neurotoxic agents and their deposition in brain. Probiotics also maintain gut wall integrity and inhibit intestinal inflammation, thus reducing systemic levels of LPS. Centrally, probiotics ameliorate neurotoxin-induced neuroinflammation by decreasing LPS-induced TLR4/MyD88/NF-κB signaling and prevention of microglia activation. Neuroprotective mechanisms of probiotics also include inhibition of apoptosis and oxidative stress, at least partially by up-regulation of SIRT1 signaling. Moreover, probiotics reduce inhibitory effect of neurotoxic agents on BDNF expression, on neurogenesis, and on synaptic function. They can also reverse altered neurotransmitter metabolism and exert an antiamyloidogenic effect. The latter may be due to up-regulation of ADAM10 activity and down-regulation of presenilin 1 expression. Therefore, in view of the multiple mechanisms invoked for the neuroprotective effect of probiotics, as well as their high tolerance and safety, the use of probiotics should be considered as a therapeutic strategy for ameliorating adverse brain effects of various endogenous and exogenous agents.

Hyperexcitability and translational phenotypes in a preclinical mouse model of SYNGAP1-Related Intellectual Disability

Disruption of SYNGAP1 directly causes a genetically identifiable neurodevelopmental disorder (NDD) called SYNGAP1-related intellectual disability (SRID). Without functional SynGAP1 protein, individuals are developmentally delayed and have prominent features of intellectual disability, motor impairments, and epilepsy. Over the past two decades, there have been numerous discoveries indicting the critical role of Syngap1. Several rodent models with a loss of Syngap1 have been engineered identifying precise roles in neuronal structure and function, as well as key biochemical pathways key for synapse integrity. Homozygous loss of SYNGAP1/Syngap1 is lethal. Heterozygous mutations of Syngap1 result in a broad range of behavioral phenotypes. Our in vivo functional data, using the original mouse model from the Huganir laboratory, corroborated behaviors including robust hyperactivity and deficits in learning and memory in young adults. Furthermore, we described impairments in the domain of sleep, characterized using neurophysiological data collected with wireless, telemetric electroencephalography (EEG). Syngap1+/- mice exhibited elevated spiking events and spike trains, in addition to elevated power, most notably in the delta power frequency. For the first time, we illustrated primary neurons from Syngap1+/- mice displayed increased network firing activity, greater bursts, and shorter inter-burst intervals between peaks by employing high density microelectrode arrays (HD-MEA). Our work bridges in-vitro electrophysiological neuronal activity and function with in vivo neurophysiological brain activity and function. These data elucidate quantitative, translational biomarkers in vivo and in vitro that can be utilized for the development and efficacy assessment of targeted treatments for SRID.

Developmental pyrethroid exposure disrupts molecular pathways for MAP kinase and circadian rhythms in mouse brain

Neurodevelopmental disorders (NDDs) are a category of pervasive disorders of the developing nervous system with few or no recognized biomarkers. A significant portion of the risk for NDDs, including attention deficit hyperactivity disorder (ADHD), is contributed by the environment, and exposure to pyrethroid pesticides during pregnancy has been identified as a potential risk factor for NDD in the unborn child. We recently showed that low-dose developmental exposure to the pyrethroid pesticide deltamethrin in mice causes male-biased changes to ADHD- and NDD-relevant behaviors as well as the striatal dopamine system. Here, we used an integrated multiomics approach to determine the broadest possible set of biological changes in the mouse brain caused by developmental pyrethroid exposure (DPE). Using a litter-based, split-sample design, we exposed mouse dams during pregnancy and lactation to deltamethrin (3 mg/kg or vehicle every 3 days) at a concentration well below the EPA-determined benchmark dose used for regulatory guidance. We raised male offspring to adulthood, euthanized them, and pulverized and divided whole brain samples for split-sample transcriptomics, kinomics and multiomics integration. Transcriptome analysis revealed alterations to multiple canonical clock genes, and kinome analysis revealed changes in the activity of multiple kinases involved in synaptic plasticity, including the mitogen-activated protein (MAP) kinase ERK. Multiomics integration revealed a dysregulated protein-protein interaction network containing primary clusters for MAP kinase cascades, regulation of apoptosis, and synaptic function. These results demonstrate that DPE causes a multi-modal biophenotype in the brain relevant to ADHD and identifies new potential mechanisms of action.

Recent applications of positron emission tomographic (PET) imaging in psychiatric drug discovery

INTRODUCTION

Psychiatry is one of the medical disciplines that suffers most from a lack of innovation in its therapeutic arsenal. Many failures in drug candidate trials can be explained by pharmacological properties that have been poorly assessed upstream, in terms of brain passage, brain target binding and clinical outcomes. Positron emission tomography can provide pharmacokinetic and pharmacodynamic data to help select candidate-molecules for further clinical trials.

AREAS COVERED

This review aims to explain and discuss the various methods using positron-emitting radiolabeled molecules to trace the cerebral distribution of the drug-candidate or indirectly measure binding to its therapeutic target. More than an exhaustive review of PET studies in psychopharmacology, this article highlights the contributions this technology can make in drug discovery applied to psychiatry.

EXPERT OPINION

PET neuroimaging is the only technological approach that can, in vivo in humans, measure cerebral delivery of a drug candidate, percentage and duration of target binding, and even the pharmacological effects. PET studies in a small number of subjects in the early stages of the development of a psychotropic drug can therefore provide the pharmacokinetic/pharmacodynamic data required for subsequent clinical evaluation. While PET technology is demanding in terms of radiochemical, radiopharmacological and nuclear medicine expertise, its integration into the development process of new drugs for psychiatry has great added value.

Genetically modified animals as models of neurodevelopmental conditions: A review of systematic review reporting quality

Using genetically modified animals to model neurodevelopmental conditions helps better our understanding of biology underlying these conditions. Animal research has unique characteristics not shared with clinical research, meaning systematic review methods must be adapted to this context. We aim to evaluate the quantity, characteristics, and reporting quality of systematic reviews which synthesise research using genetically modified animals to model neurodevelopmental conditions. On 23 January 2023, we searched PubMed, Embase, and the Web of Science Core Collection to identify systematic reviews of genetic neurodevelopmental condition animal research where the modified gene was one in a list of 102 genes associated with neurodevelopmental conditions identified through large-scale exome sequencing or Fmr1, Mecp2, or Ube3a. Two independent reviewers screened studies based on full text and assessed the reporting quality of relevant reviews using an adapted version of the PRISMA checklist (PRISMA-Pre). Twelve review publications met our criteria. We found mixed levels of reporting: items such as identifying the publication as a systematic review in the title, search strategies, and funding sources being well reported, and others such as protocol registration and data sharing less well reported. We also identified 19 review registrations via PROSPERO, most of which remain unpublished after their anticipated end dates. Systematic reviews are limited by lack of reporting. Increased awareness of reporting guidelines may help authors increase the transparency and reproducibility, and therefore the reliability, of their systematic reviews.

Assessing motor development and function in mouse models of neurodevelopmental disorders

Alterations in motor development often accompany neurodevelopmental disorders (NDD) and can have an impact on social interaction and communication. Studying motor development and function in mouse models of NDDs can offer a window to identify underlying biological mechanisms and establish preclinical outcome measures for testing therapeutics. This chapter describes tests to measure motor developmental milestones early postnatally and adult motor functions in mouse models of NDDs.

Day-to-day spontaneous social behaviours is quantitatively and qualitatively affected in a 16p11.2 deletion mouse model

Background

Autism spectrum disorders affect more than 1% of the population, impairing social communication and increasing stereotyped behaviours. A micro-deletion of the 16p11.2 BP4-BP5 chromosomic region has been identified in 1% of patients also displaying intellectual disabilities. In mouse models generated to understand the mechanisms of this deletion, learning and memory deficits were pervasive in most genetic backgrounds, while social communication deficits were only detected in some models.

Methods

To complement previous studies, we itemized the social deficits in the mouse model of 16p11.2 deletion on a hybrid C57BL/6N × C3H.Pde6b+ genetic background. We examined whether behavioural deficits were visible over long-term observation periods lasting several days and nights, to parallel everyday-life assessment of patients. We recorded the individual and social behaviours of mice carrying a heterozygous deletion of the homologous 16p11.2 chromosomic region (hereafter Del/+) and their wild-type littermates from both sexes over two or three consecutive nights during social interactions of familiar mixed-genotype quartets of males and of females, and of same-genotype unfamiliar female pairs.

Results

We observed that Del/+ mice of both sexes increased significantly their locomotor activity compared to wild-type littermates. In the social domain, Del/+ mice of both sexes displayed widespread deficits, even more so in males than in females in quartets of familiar individuals. In pairs, significant perturbations of the organisation of the social communication and behaviours appeared in Del/+ females.

Discussion

Altogether, this suggests that, over long recording periods, the phenotype of the 16p11.2 Del/+ mice was differently affected in the locomotor activity and the social domains and between the two sexes. These findings confirm the importance of testing models in long-term conditions to provide a comprehensive view of their phenotype that will refine the study of cellular and molecular mechanisms and complement pre-clinical targeted therapeutic trials.

Altered neural activity in the mesoaccumbens pathway underlies impaired social reward processing in Shank3-deficient rats

Social behaviors are crucial for human connection and belonging, often impacted in conditions like Autism Spectrum Disorder (ASD). The mesoaccumbens pathway (VTA and NAc) plays a pivotal role in social behavior and is implicated in ASD. However, the impact of ASD-related mutations on social reward processing remains insufficiently explored. This study focuses on the Shank3 mutation, associated with a rare genetic condition and linked to ASD, examining its influence on the mesoaccumbens pathway during behavior, using the Shank3-deficient rat model. Our findings indicate that Shank3-deficient rats exhibit atypical social interactions and have difficulty adjusting behavior based on reward values, associated with modified neuronal activity of VTA dopaminergic and GABAergic neurons and reduced dopamine release in the NAc. Moreover, we demonstrate that manipulating VTA neuronal activity can normalize this behavior, providing insights into the effects of Shank3 mutations on social reward and behavior, and identify a potential neural pathway for intervention.

Dynamic Foraging Behavior Performance Is Not Affected by Scn2a Haploinsufficiency

Dysfunction in the gene SCN2A, which encodes the voltage-gated sodium channel Nav1.2, is strongly associated with neurodevelopmental disorders including autism spectrum disorder and intellectual disability (ASD/ID). This dysfunction typically manifests in these disorders as a haploinsufficiency, where loss of one copy of a gene cannot be compensated for by the other allele. Scn2a haploinsufficiency affects a range of cells and circuits across the brain, including associative neocortical circuits that are important for cognitive flexibility and decision-making behaviors. Here, we tested whether Scn2a haploinsufficiency has any effect on a dynamic foraging task that engages such circuits. Scn2a +/- mice and wild-type (WT) littermates were trained on a choice behavior where the probability of reward between two options varied dynamically across trials and where the location of the high reward underwent uncued reversals. Despite impairments in Scn2a-related neuronal excitability, we found that both male and female Scn2a +/- mice performed these tasks as well as wild-type littermates, with no behavioral difference across genotypes in learning or performance parameters. Varying the number of trials between reversals or probabilities of receiving reward did not result in an observable behavioral difference, either. These data suggest that, despite heterozygous loss of Scn2a, mice can perform relatively complex foraging tasks that make use of higher-order neuronal circuits.

Altered Developmental Trajectory in Male and Female Rats in a Prenatal Valproic Acid Exposure Model of Autism Spectrum Disorder

Early motor and sensory developmental delays precede Autism Spectrum Disorder (ASD) diagnosis and may serve as early indicators of ASD. The literature on sensorimotor development in animal models is sparse, male centered, and has mixed findings. We characterized early development in a prenatal valproic acid (VPA) model of ASD and found sex-specific developmental delays in VPA rats. We created a developmental composite score combining 15 test readouts, yielding a reliable gestalt measure spanning physical, sensory, and motor development, that effectively discriminated between VPA and control groups. Considering the heterogeneity in ASD phenotype, the developmental composite offers a robust metric that can enable comparison across different animal models of ASD and can serve as an outcome measure for early intervention studies.

Characterizing the personality and gray matter volume of chimpanzees that exhibit autism-related socio-communicative phenotypes

Autism spectrum disorder (ASD) is a developmental disorder characterized by stereotypies or repetitive behaviors and impairments in social behavior and socio-communicative skills. One hallmark phenotype of ASD is poor joint attention skills compared to neurotypical controls. In addition, individuals with ASD have lower scores on several of the Big 5 personality dimensions, including Extraversion. Here, we examine these traits in a nonhuman primate model (chimpanzees; Pan troglodytes) to further understand the relationship between personality and joint attention skills, as well as the genetic and neural systems that contribute to these phenotypes. We used archival data including receptive joint attention (RJA) performance, personality based on caretaker ratings, and magnetic resonance images from 189 chimpanzees. We found that, like humans, chimpanzees who performed worse on the RJA task had lower Extraversion scores. We also found that joint attention skills and several personality dimensions, including Extraversion, were significantly heritable. There was also a borderline significant genetic correlation between RJA and Extraversion. A conjunction analysis examining gray matter volume showed that there were five main brain regions associated with both higher levels of Extraversion and social cognition. These regions included the right posterior middle and superior temporal gyrus, bilateral inferior frontal gyrus, left inferior frontal sulcus, and left superior frontal sulcus, all regions within the social brain network. Altogether, these findings provide further evidence that chimpanzees serve as an excellent model for understanding the mechanisms underlying social impairment related to ASD. Future research should further examine the relationship between social cognition, personality, genetics, and neuroanatomy and function in nonhuman primate models.

In depth characterization of midbrain organoids derived from wild type iPSC lines

The ability to model human neurological tissues in vitro has been a major hurdle to effective drug development for neurological disorders. iPSC-derived brain organoids have emerged as a compelling solution to this problem as they have the potential to relevantly model the protein expression pattern and physiology of specific brain regions. Although many protocols now exist for the production of brain organoids, few attempts have been made to do an in-depth kinetic evaluation of expression of mature regiospecific markers of brain organoids. To address this, we differentiated midbrain-specific brain organoids from iPSC-lines derived from three apparently healthy individuals using a matrix-free, bioreactor method. We monitored the expression of midbrain-specific neuronal markers from 7 to 90-days using immunofluorescence and immunohistology. The organoids were further characterized using electron microscopy and RNA-seq. In addition to serving as a potential benchmark for the future evaluation of other differentiation protocols, the markers observed in this study can be useful as control parameters to identify and evaluate the disease phenotypes in midbrain organoid derived from patient iPSC-lines with genetic neurological disorders.

Mechanisms of copy number variants in neuropsychiatric disorders: From genes to therapeutics

Copy number variants (CNVs) are genomic imbalances strongly linked to the aetiology of neuropsychiatric disorders such as schizophrenia and autism. By virtue of their large size, CNVs often contain many genes, providing a multi-genic view of disease processes that can be dissected in model systems. Thus, CNV research provides an important stepping stone towards understanding polygenic disease mechanisms, positioned between monogenic and polygenic risk models. In this review, we will outline hypothetical models for gene interactions occurring within CNVs and discuss different approaches used to study rodent and stem cell disease models. We highlight recent work showing that genetic and pharmacological strategies can be used to rescue important aspects of CNV-mediated pathophysiology, which often converges onto synaptic pathways. We propose that using a rescue approach in complete CNV models provides a new path forward for precise mechanistic understanding of complex disorders and a tangible route towards therapeutic development.

Hyperexcitability and translational phenotypes in a preclinical model of SYNGAP1 mutations

SYNGAP1 is a critical gene for neuronal development, synaptic structure, and function. Although rare, the disruption of SYNGAP1 directly causes a genetically identifiable neurodevelopmental disorder (NDD) called SYNGAP1 -related intellectual disability. Without functional SynGAP1 protein, patients present with intellectual disability, motor impairments, and epilepsy. Previous work using mouse models with a variety of germline and conditional mutations has helped delineate SynGAP1's critical roles in neuronal structure and function, as well as key biochemical signaling pathways essential to synapse integrity. Homozygous loss of SYNGAP1 is embryonically lethal. Heterozygous mutations of SynGAP1 result in a broad range of phenotypes including increased locomotor activity, impaired working spatial memory, impaired cued fear memory, and increased stereotypic behavior. Our in vivo functional data, using the original germline mutation mouse line from the Huganir laboratory, corroborated robust hyperactivity and learning and memory deficits. Here, we describe impairments in the translational biomarker domain of sleep, characterized using neurophysiological data collected with wireless telemetric electroencephalography (EEG). We discovered Syngap1+/- mice exhibited elevated spike trains in both number and duration, in addition to elevated power, most notably in the delta power band. Primary neurons from Syngap1+/- mice displayed increased network firing activity, greater spikes per burst, and shorter inter-burst intervals between peaks using high density micro-electrode arrays (HD-MEA). This work is translational, innovative, and highly significant as it outlines functional impairments in Syngap1 mutant mice. Simultaneously, the work utilized untethered, wireless neurophysiology that can discover potential biomarkers of Syngap1 RI-D, for clinical trials, as it has done with other NDDs. Our work is substantial forward progress toward translational work for SynGAP1R-ID as it bridges in-vitro electrophysiological neuronal activity and function with in vivo neurophysiological brain activity and function. These data elucidate multiple quantitative, translational biomarkers in vivo and in vitro for the development of treatments for SYNGAP1-related intellectual disability.

Bridge-building between communities: Imagining the future of biomedical autism research

A paradigm shift in research culture is required to ease perceived tensions between autistic people and the biomedical research community. As a group of autistic and non-autistic scientists and stakeholders, we contend that through participatory research, we can reject a deficit-based conceptualization of autism while building a shared vision for a neurodiversity-affirmative biomedical research paradigm.

Early postnatal development of the MDGA2+/- mouse model of synaptic dysfunction

Synaptic dysfunction underlies many neurodevelopmental disorders (NDDs). The membrane-associated mucin domain-containing glycosylphosphatidylinositol anchor proteins (MDGAs) regulate synaptic development by modulating neurexin-neuroligin complex formation. Since understanding the neurodevelopmental profile and the sex-based differences in the manifestation of the symptoms of NDDs is important for their early diagnosis, we tested a mouse model haploinsufficient for MDGA2 (MDGA2+/-) on a neurodevelopmental test battery, containing sensory, motor, and cognitive measures, as well as ultrasonic vocalizations. When male and female MDGA2+/- and wildtype (WT) C57BL/6 J mice were examined from 2 to 23 days of age using this test battery, genotype and sex differences in body weight, sensory-motor processes, and ultrasonic vocalizations were observed. The auditory startle reflex appeared earlier in the MDGA2+/- than in WT mice and the MDGA2+/- mice produced fewer ultrasonic vocalizations. The MDGA2+/- mice showed reduced locomotion and rearing than WT mice in the open field after 17 days of age and spent less time investigating a novel object than WT mice at 21 days of age. Female MDGA2+/- mice weighed less than WT females and showed lower grip strength, indicating a delay in sensory-motor development in MDGA2+/- mice, which appears to be more pronounced in females than males. The behavioural phenotypes resulting from MDGA2 haploinsufficiency suggests that it shows delayed development of motor behaviour, grip strength and exploratory behaviour, non-social phenotypes of NDDs.

Hyperexcitability and translational phenotypes in a preclinical model of SYNGAP1 mutations

SYNGAP1 is a critical gene for neuronal development, synaptic structure, and function. Although rare, the disruption of SYNGAP1 directly causes a genetically identifiable neurodevelopmental disorder (NDD) called SYNGAP1-related intellectual disability. Without functional SynGAP1 protein, patients present with intellectual disability, motor impairments, and epilepsy. Previous work using mouse models with a variety of germline and conditional mutations has helped delineate SynGAP1's critical roles in neuronal structure and function, as well as key biochemical signaling pathways essential to synapse integrity. Homozygous loss of SYNGAP1 is embryonically lethal. Heterozygous mutations of SynGAP1 result in a broad range of phenotypes including increased locomotor activity, impaired working spatial memory, impaired cued fear memory, and increased stereotypic behavior. Our in vivo functional data, using the original germline mutation mouse line from the Huganir laboratory, corroborated robust hyperactivity and learning and memory deficits. Here, we describe impairments in the translational biomarker domain of sleep, characterized using neurophysiological data collected with wireless telemetric electroencephalography (EEG). We discovered Syngap1 +/- mice exhibited elevated spike trains in both number and duration, in addition to elevated power, most notably in the delta power band. Primary neurons from Syngap1 +/- mice displayed increased network firing activity, greater spikes per burst, and shorter inter-burst intervals between peaks using high density micro-electrode arrays (HD-MEA). This work is translational, innovative, and highly significant as it outlines functional impairments in Syngap1 mutant mice. Simultaneously, the work utilized untethered, wireless neurophysiology that can discover potential biomarkers of Syngap1R-ID, for clinical trials, as it has done with other NDDs. Our work is substantial forward progress toward translational work for SynGAP1R-ID as it bridges in-vitro electrophysiological neuronal activity and function with in vivo neurophysiological brain activity and function. These data elucidate multiple quantitative, translational biomarkers in vivo and in vitro for the development of treatments for SYNGAP1-related intellectual disability.

Autism-associated gene shank3 is necessary for social contagion in zebrafish

BACKGROUND

Animal models enable targeting autism-associated genes, such as the shank3 gene, to assess their impact on behavioural phenotypes. However, this is often limited to simple behaviours relevant for social interaction. Social contagion is a complex phenotype forming the basis of human empathic behaviour and involves attention to the behaviour of others for recognizing and sharing their emotional or affective state. Thus, it is a form of social communication, which constitutes the most common developmental impairment across autism spectrum disorders (ASD).

METHODS

Here we describe the development of a zebrafish model that identifies the neurocognitive mechanisms by which shank3 mutation drives deficits in social contagion. We used a CRISPR-Cas9 technique to generate mutations to the shank3a gene, a zebrafish paralogue found to present greater orthology and functional conservation relative to the human gene. Mutants were first compared to wild types during a two-phase protocol that involves the observation of two conflicting states, distress and neutral, and the later recall and discrimination of others when no longer presenting such differences. Then, the whole-brain expression of different neuroplasticity markers was compared between genotypes and their contribution to cluster-specific phenotypic variation was assessed.

RESULTS

The shank3 mutation markedly reduced social contagion via deficits in attention contributing to difficulties in recognising affective states. Also, the mutation changed the expression of neuronal plasticity genes. However, only downregulated neuroligins clustered with shank3a expression under a combined synaptogenesis component that contributed specifically to variation in attention.

LIMITATIONS

While zebrafish are extremely useful in identifying the role of shank3 mutations to composite social behaviour, they are unlikely to represent the full complexity of socio-cognitive and communication deficits presented by human ASD pathology. Moreover, zebrafish cannot represent the scaling up of these deficits to higher-order empathic and prosocial phenotypes seen in humans.

CONCLUSIONS

We demonstrate a causal link between the zebrafish orthologue of an ASD-associated gene and the attentional control of affect recognition and consequent social contagion. This models autistic affect-communication pathology in zebrafish and reveals a genetic attention-deficit mechanism, addressing the ongoing debate for such mechanisms accounting for emotion recognition difficulties in autistic individuals.

The Emerging Role of Flavonoids in Autism Spectrum Disorder: A Systematic Review

Although autism spectrum disorder (ASD) is a multifaceted neurodevelopmental syndrome, accumulating evidence indicates that oxidative stress and inflammation are common features of ASD. Flavonoids, one of the largest and best-investigated classes of plant-derived compounds, are known to exert antioxidant, anti-inflammatory, and neuroprotective effects. This review used a systematic search process to assess the available evidence on the effect of flavonoids on ASD. A comprehensive literature search was carried out in PubMed, Scopus, and Web of Science databases following the PRISMA guidelines. A total of 17 preclinical studies and 4 clinical investigations met our inclusion criteria and were included in the final review. Most findings from animal studies suggest that treatment with flavonoids improves oxidative stress parameters, reduces inflammatory mediators, and promotes pro-neurogenic effects. These studies also showed that flavonoids ameliorate the core symptoms of ASD, such as social deficits, repetitive behavior, learning and memory impairments, and motor coordination. However, there are no randomized placebo-controlled trials that support the clinical efficacy of flavonoids in ASD. We only found open-label studies and case reports/series, using only two flavonoids such as luteolin and quercetin. These preliminary clinical studies indicate that flavonoid administration may improve specific behavioral symptoms of ASD. Overall, this review is the first one to systematically report evidence for the putative beneficial effects of flavonoids on features of ASD. These promising preliminary results may provide the rationale for future randomized controlled trials aimed at confirming these outcomes.

Altered behavior, brain structure, and neurometabolites in a rat model of autism-specific maternal autoantibody exposure

Maternal immune dysregulation is a prenatal risk factor for autism spectrum disorder (ASD). Importantly, a clinically relevant connection exists between inflammation and metabolic stress that can result in aberrant cytokine signaling and autoimmunity. In this study we examined the potential for maternal autoantibodies (aAbs) to disrupt metabolic signaling and induce neuroanatomical changes in the brains of exposed offspring. To accomplish this, we developed a model of maternal aAb exposure in rats based on the clinical phenomenon of maternal autoantibody-related ASD (MAR-ASD). Following confirmation of aAb production in rat dams and antigen-specific immunoglobulin G (IgG) transfer to offspring, we assessed offspring behavior and brain structure longitudinally. MAR-ASD rat offspring displayed a reduction in pup ultrasonic vocalizations and a pronounced deficit in social play behavior when allowed to freely interact with a novel partner. Additionally, longitudinal in vivo structural magnetic resonance imaging (sMRI) at postnatal day 30 (PND30) and PND70, conducted in a separate cohort of animals, revealed sex-specific differences in total and regional brain volume. Treatment-specific effects by region appeared to converge on midbrain and cerebellar structures in MAR-ASD offspring. Simultaneously, in vivo 1H magnetic resonance spectroscopy (1H-MRS) data were collected to examine brain metabolite levels in the medial prefrontal cortex. Results showed that MAR-ASD offspring displayed decreased levels of choline-containing compounds and glutathione, accompanied by increased taurine compared to control animals. Overall, we found that rats exposed to MAR-ASD aAbs present with alterations in behavior, brain structure, and neurometabolites; reminiscent of findings observed in clinical ASD.

Opioids and autism spectrum disorder: liaisons dangereuses?

A recent laboratory study in the Journal examined the effects of repeated exposures of neonatal mice to fentanyl on autism-like behaviour via opioid receptor-mediated DNA hypermethylation of the Grin2B gene, which encodes the GluN2B subunit of the NMDA receptor. These experiments provide mechanisms and biological plausibility but do not directly demonstrate that opioid exposure in early life induces autism spectrum disorder in humans. Experimental modelling of human neuropsychiatric disorders is extremely challenging since most subjective psychiatric symptoms used to establish diagnosis in humans cannot be convincingly ascertained in laboratory rodents. While some human epidemiological data show associations between repeated exposures to opioids during early life, it remains undetermined whether opioid exposure is an independent risk factor for developing autism spectrum disorder in the young.

Developmental pyrethroid exposure causes a neurodevelopmental disorder phenotype in mice

Neurodevelopmental disorders (NDDs) are a widespread and growing public health challenge, affecting as many as 17% of children in the United States. Recent epidemiological studies have implicated ambient exposure to pyrethroid pesticides during pregnancy in the risk for NDDs in the unborn child. Using a litter-based, independent discovery-replication cohort design, we exposed mouse dams orally during pregnancy and lactation to the Environmental Protection Agency's reference pyrethroid, deltamethrin, at 3 mg/kg, a concentration well below the benchmark dose used for regulatory guidance. The resulting offspring were tested using behavioral and molecular methods targeting behavioral phenotypes relevant to autism and NDD, as well as changes to the striatal dopamine system. Low-dose developmental exposure to the pyrethroid deltamethrin (DPE) decreased pup vocalizations, increased repetitive behaviors, and impaired both fear conditioning and operant conditioning. Compared with control mice, DPE mice had greater total striatal dopamine, dopamine metabolites, and stimulated dopamine release, but no difference in vesicular dopamine capacity or protein markers of dopamine vesicles. Dopamine transporter protein levels were increased in DPE mice, but not temporal dopamine reuptake. Striatal medium spiny neurons showed changes in electrophysiological properties consistent with a compensatory decrease in neuronal excitability. Combined with previous findings, these results implicate DPE as a direct cause of an NDD-relevant behavioral phenotype and striatal dopamine dysfunction in mice and implicate the cytosolic compartment as the location of excess striatal dopamine.

Ameliorating age-dependent effects of resveratrol on VPA-induced social impairments and anxiety-like behaviors in a rat model of Neurodevelopmental Disorder

Although anxiety disorders, as well as difficulties in social interaction, are documented in children with autism spectrum disorder (ASD) as a neurodevelopmental disorder, the effectiveness of potential therapeutic procedures considering age and sex differences is under serious discussion. The present study aimed to investigate the effect of resveratrol (RSV) on anxiety-like behaviors and social interaction in juvenile and adult rats of both sex in a valproic acid (VPA)-induced autistic-like model. Prenatal exposure to VPA was associated with increased anxiety, also causing a significant reduction in social interaction in juvenile male subjects. Further administration of RSV attenuated VPA-induced anxiety symptoms in both sexes of adult animals and significantly increased the sociability index in male and female juvenile rats. Taken together, it can be concluded that treatment with RSV can attenuate some of the harsh effects of VPA. This treatment was especially effective on anxiety-like traits in adult subjects of both sexes regarding their performance in open field and EPM. We encourage future research to consider the sex and age-specific mechanisms behind the RSV treatment in the prenatal VPA model of autism.

Maternal immune activation affects socio-communicative behavior in adult rats

A wide body of evidence suggests a relationship between maternal immune activation (MIA) and neurodevelopmental disorders such as autism spectrum disorder (ASD). Since social and communicative deficits are included in the first diagnostic criterion of ASD, we aimed to characterize socio-communicative behaviors in the MIA model based on prenatal exposure to poly(I:C). Our previous studies demonstrated impaired socio-communicative functioning in poly(I:C)-exposed adolescent rats. Therefore, the current study sought to clarify whether these changes would persist beyond adolescence. For this purpose, we analyzed behavior during the social interaction test and recorded ultrasonic vocalizations (USVs) accompanying interactions between adult poly(I:C) rats. The results demonstrated that the altered pattern of social behavior in poly(I:C) males was accompanied by the changes in acoustic parameters of emitted USVs. Poly(I:C) males also demonstrated an impaired olfactory preference for social stimuli. While poly(I:C) females did not differ from controls in socio-positive behaviors, they displayed aggression during the social encounter and were more reactive to somatosensory stimulation. Furthermore, the locomotor pattern of poly(I:C) animals were characterized by repetitive behaviors. Finally, poly(I:C) reduced parvalbumin and GAD67 expression in the cerebellum. The results showed that prenatal poly(I:C) exposure altered the pattern of socio-communicative behaviors of adult rats in a sex-specific manner.

The impact of maternal immune activation on embryonic brain development

The adult brain is a complex structure with distinct functional sub-regions, which are generated from an initial pool of neural epithelial cells within the embryo. This transition requires a number of highly coordinated processes, including neurogenesis, i.e., the generation of neurons, and neuronal migration. These take place during a critical period of development, during which the brain is particularly susceptible to environmental insults. Neurogenesis defects have been associated with the pathogenesis of neurodevelopmental disorders (NDDs), such as autism spectrum disorder and schizophrenia. However, these disorders have highly complex multifactorial etiologies, and hence the underlying mechanisms leading to aberrant neurogenesis continue to be the focus of a significant research effort and have yet to be established. Evidence from epidemiological studies suggests that exposure to maternal infection in utero is a critical risk factor for NDDs. To establish the biological mechanisms linking maternal immune activation (MIA) and altered neurodevelopment, animal models have been developed that allow experimental manipulation and investigation of different developmental stages of brain development following exposure to MIA. Here, we review the changes to embryonic brain development focusing on neurogenesis, neuronal migration and cortical lamination, following MIA. Across published studies, we found evidence for an acute proliferation defect in the embryonic MIA brain, which, in most cases, is linked to an acceleration in neurogenesis, demonstrated by an increased proportion of neurogenic to proliferative divisions. This is accompanied by disrupted cortical lamination, particularly in the density of deep layer neurons, which may be a consequence of the premature neurogenic shift. Although many aspects of the underlying pathways remain unclear, an altered epigenome and mitochondrial dysfunction are likely mechanisms underpinning disrupted neurogenesis in the MIA model. Further research is necessary to delineate the causative pathways responsible for the variation in neurogenesis phenotype following MIA, which are likely due to differences in timing of MIA induction as well as sex-dependent variation. This will help to better understand the underlying pathogenesis of NDDs, and establish therapeutic targets.