Resolving the Synaptic versus Developmental Dichotomy of Autism Risk Genes

Oxytocin treatment rescues irritability-like behavior in Cc2d1a conditional knockout mice

Irritability, a state of excessive reactivity to negative emotional stimuli, is common in individuals with autism spectrum disorder (ASD). Although it has a significant negative impact of patients' disease severity and quality of life, the neural mechanisms underlying irritability in ASD remain largely unclear. We have previously demonstrated that male mice lacking the Coiled-coil and C2 domain containing 1a (Cc2d1a) in forebrain excitatory neurons recapitulate numerous ASD-like behavioral phenotypes, including impaired social behaviors and pronounced repetitive behaviors. Here, using the bottle-brush test (BBT) to trigger and evaluate aggressive and defensive responses, we show that Cc2d1a deletion increases irritability-like behavior in male but not female mice, which is correlated with reduced number of oxytocin (OXT)-expressing neurons in the paraventricular nucleus (PVN) of the hypothalamus. Intranasal OXT administration or chemogenetic activation of OXT neurons in the PVN rescues irritability-like behavior in Cc2d1a conditional knockout (cKO) mice. Administration of a selective melanocortin receptor 4 agonist, RO27-3225, which potentiates endogenous OXT release, also alleviates irritability-like behavior in Cc2d1a cKO mice, an effect blocked by a specific OXT receptor antagonist, L-368,899. We additionally identify a projection connecting the posterior ventral segment of the medial amygdala (MeApv) and ventromedial nucleus of the ventromedial hypothalamus (VMHvl) for governing irritability-like behavior during the BBT. Chemogenetic suppression of the MeApv-VMHvl pathway alleviates irritability-like behavior in Cc2d1a cKO mice. Together, our study uncovers dysregulation of OXT system in irritability-like behavior in Cc2d1a cKO mice during the BBT and provide translatable insights into the development of OXT-based therapeutics for clinical interventions.

SRC family kinase inhibition rescues molecular and behavioral phenotypes, but not protein interaction network dynamics, in a mouse model of Fragile X syndrome

Glutamatergic synapses encode information from extracellular inputs using dynamic protein interaction networks (PINs) that undergo widespread reorganization following synaptic activity, allowing cells to distinguish between signaling inputs and generate coordinated cellular responses. Here, we investigate how Fragile X Messenger Ribonucleoprotein (FMRP) deficiency disrupts signal transduction through a glutamatergic synapse PIN downstream of NMDA receptor or metabotropic glutamate receptor (mGluR) stimulation. In cultured cortical neurons or acute cortical slices from P7, P17 and P60 FMR1-/y mice, the unstimulated protein interaction network state resembled that of wildtype littermates stimulated with mGluR agonists, demonstrating resting state pre-activation of mGluR signaling networks. In contrast, interactions downstream of NMDAR stimulation were similar to WT. We identified the Src family kinase (SFK) Fyn as a network hub, because many interactions involving Fyn were pre-activated in FMR1-/y animals. We tested whether targeting SFKs in FMR1-/y mice could modify disease phenotypes, and found that Saracatinib (SCB), an SFK inhibitor, normalized elevated basal protein synthesis, novel object recognition memory and social behavior in FMR1-/y mice. However, SCB treatment did not normalize the PIN to a wild-type-like state in vitro or in vivo, but rather induced extensive changes to protein complexes containing Shank3, NMDARs and Fyn. We conclude that targeting abnormal nodes of a PIN can identify potential disease-modifying drugs, but behavioral rescue does not correlate with PIN normalization.

Metabolic dynamics in astrocytes and microglia during post-natal development and their implications for autism spectrum disorders

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterized by elusive underlying mechanisms. Recent attention has focused on the involvement of astrocytes and microglia in ASD pathology. These glial cells play pivotal roles in maintaining neuronal homeostasis, including the regulation of metabolism. Emerging evidence suggests a potential association between ASD and inborn errors of metabolism. Therefore, gaining a comprehensive understanding of the functions of microglia and astrocytes in ASD is crucial for the development of effective therapeutic interventions. This review aims to provide a summary of the metabolism of astrocytes and microglia during post-natal development and the evidence of disrupted metabolic pathways in ASD, with particular emphasis on those potentially important for the regulation of neuronal post-natal maturation by astrocytes and microglia.

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.

High-Fat Diet Exacerbates Autistic-Like Restricted Repetitive Behaviors and Social Abnormalities in CC2D1A Conditional Knockout Mice

Autism spectrum disorder (ASD) represents a heterogeneous group of neurodevelopmental disorders characterized by deficits in social communication, social interaction, and the presence of restricted repetitive behaviors. The cause of ASD involves complex interactions between genetic and environmental factors. Haploinsufficiency of the Coiled-coil and C2 domain containing 1A (Cc2d1a) gene is causally linked to ASD, and obesity has been associated with worse outcomes for ASD. High-fat diet (HFD) feeding leads to the development of obesity and metabolic dysfunction; however, the effect of HFD on pre-existing autistic-like phenotypes remains to be clarified. Here, we report that male Cc2d1a conditional knockout (cKO) mice fed with HFD, from weaning onwards and throughout the experimental period, show a marked aggravation in autistic-like phenotypes, manifested in increased restricted repetitive behaviors and impaired performance in the preference for social novelty, but not in sociability and cognitive impairments assessed using the object location memory, novel object recognition, and Morris water maze tests. HFD feeding also results in increased numbers of reactive microglia and astrocytes, and exacerbates reductions in dendritic complexity and spine density of hippocampal CA1 pyramidal neurons. Furthermore, we demonstrate that chronic treatment with minocycline, a semisynthetic tetracycline-derived antibiotic, rescues the observed behavioral and morphological deficits in Cc2d1a cKO mice fed with HFD. Collectively, these findings highlight an aggravating role of HFD in pre-existing autistic-like phenotypes and suggest that minocycline treatment can alleviate abnormal neuronal morphology and behavioral symptoms associated with ASD resulted from the interplay between genetic and environmental risk factors.

Hippocampal Changes Elicited by Metabolic and Inflammatory Stressors following Prenatal Maternal Infection

The hippocampus participates in spatial navigation and behavioral processes, displays molecular plasticity in response to environmental challenges, and can play a role in neuropsychiatric diseases. The combined effects of inflammatory prenatal and postnatal challenges can disrupt the hippocampal gene networks and regulatory mechanisms. Using a proven pig model of viral maternal immune activation (MIA) matched to controls and an RNA-sequencing approach, the hippocampal transcriptome was profiled on two-month-old female and male offspring assigned to fasting, mimetic viral, or saline treatments. More than 2600 genes presented single or combined effects (FDR-adjusted p-value < 0.05) of MIA, postnatal stress, or sex. Biological processes and pathways encompassing messenger cyclic adenosine 3',5'-monophosphate (cAMP) signaling were enriched with genes including gastric inhibitory polypeptide receptor (GIPR) predominantly over-expressed in the MIA-exposed fasting males relative to groups that differed in sex, prenatal or postnatal challenge. While this pattern was amplified in fasting offspring, the postnatal inflammatory challenge appeared to cancel out the effects of the prenatal challenge. The transcription factors C-terminal binding protein 2 (CTBP2), RE1 silencing transcription factor (REST), signal transducer and activator of transcription 1 (STAT1), and SUZ12 polycomb repressive complex 2 subunit were over-represented among the genes impacted by the prenatal and postnatal factors studied. Our results indicate that one environmental challenge can influence the effect of another challenge on the hippocampal transcriptome. These findings can assist in the identification of molecular targets to ameliorate the effects of pre-and post-natal stressors on hippocampal-associated physiology and behavior.

CRISPR/Cas-Based Approaches to Study Schizophrenia and Other Neurodevelopmental Disorders

The study of diseases of the central nervous system (CNS) at the molecular level is challenging because of the complexity of neural circuits and the huge number of specialized cell types. Moreover, genomic association studies have revealed the complex genetic architecture of schizophrenia and other genetically determined mental disorders. Investigating such complex genetic architecture to decipher the molecular basis of CNS pathologies requires the use of high-throughput models such as cells and their derivatives. The time is coming for high-throughput genetic technologies based on CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat)/Cas systems to manipulate multiple genomic targets. CRISPR/Cas systems provide the desired complexity, versatility, and flexibility to create novel genetic tools capable of both altering the DNA sequence and affecting its function at higher levels of genetic information flow. CRISPR/Cas tools make it possible to find and investigate the intricate relationship between the genotype and phenotype of neuronal cells. The purpose of this review is to discuss innovative CRISPR-based approaches for studying the molecular mechanisms of CNS pathologies using cellular models.

Changes of Cerebellar Cortex in a Valproic Acid-Induced Rat Model of Autism

In this study, 32 male Sprague-Dawley rats (8 for each group) were used in total to examine the effects of valproic acid on rat cerebellum. It was determined that the experimental group received valproic acid (600mg/kg) on embryonic day 15 and postnatal day 11, whereas the control group was treated with saline on the same days. Moreover, on the postnatal 30^th day, the cerebellums of all pups were removed and prepared for light and electron microscopy. The numerical density of granule cells in the cerebellum of experimental groups of rats increased whereas the numerical density of Purkinje cells decreased. Furthermore, the granule cells had a smaller mean nuclear diameter in one of the experimental groups while the Purkinje cells had in both experimental groups than those in the comparison group. Thus, the numerical density of synaptic discs and their mean diameter in the cerebellar granular layer of experimental groups were significantly decreased compared to the corresponding controls; also, the synapse-to-neurons ratio, a parameter indicating interneural connectivity, was the same. Consequently, it was seen that valproic acid administration to pups in prenatal or early postnatal days causes changes in number of neurons and synapses in the cerebellum of rats.

Exome sequencing analysis of Japanese autism spectrum disorder case-control sample supports an increased burden of synaptic function-related genes

Autism spectrum disorder (ASD) is a highly heritable, complex disorder in which rare variants contribute significantly to disease risk. Although many genes have been associated with ASD, there have been few genetic studies of ASD in the Japanese population. In whole exomes from a Japanese ASD sample of 309 cases and 299 controls, rare variants were associated with ASD within specific neurodevelopmental gene sets, including highly constrained genes, fragile X mental retardation protein target genes, and genes involved in synaptic function, with the strongest enrichment in trans-synaptic signaling (p = 4.4 × 10^-4, Q-value = 0.06). In particular, we strengthen the evidence regarding the role of ABCA13, a synaptic function-related gene, in Japanese ASD. The overall results of this case-control exome study showed that rare variants related to synaptic function are associated with ASD susceptibility in the Japanese population.

Mutations of the histone linker H1-4 in neurodevelopmental disorders and functional characterization of neurons expressing C-terminus frameshift mutant H1.4

Rahman syndrome (RMNS) is a rare genetic disorder characterized by mild to severe intellectual disability, hypotonia, anxiety, autism spectrum disorder, vision problems, bone abnormalities and dysmorphic facies. RMNS is caused by de novo heterozygous mutations in the histone linker gene H1-4; however, mechanisms underlying impaired neurodevelopment in RMNS are not understood. All reported mutations associated with RMNS in H1-4 are small insertions or deletions that create a shared frameshift, resulting in a H1.4 protein that is both truncated and possessing an abnormal C-terminus frameshifted tail (H1.4 CFT). To expand understanding of mutations and phenotypes associated with mutant H1-4, we identified new variants at both the C- and N-terminus of H1.4. The clinical features of mutations identified at the C-terminus are consistent with other reports and strengthen the support of pathogenicity of H1.4 CFT. To understand how H1.4 CFT may disrupt brain function, we exogenously expressed wild-type or H1.4 CFT protein in rat hippocampal neurons and assessed neuronal structure and function. Genome-wide transcriptome analysis revealed ~ 400 genes altered in the presence of H1.4 CFT. Neuronal genes downregulated by H1.4 CFT were enriched for functional categories involved in synaptic communication and neuropeptide signaling. Neurons expressing H1.4 CFT also showed reduced neuronal activity on multielectrode arrays. These data are the first to characterize the transcriptional and functional consequence of H1.4 CFT in neurons. Our data provide insight into causes of neurodevelopmental impairments associated with frameshift mutations in the C-terminus of H1.4 and highlight the need for future studies on the function of histone H1.4 in neurons.

Reorganization of postmitotic neuronal chromatin accessibility for maturation of serotonergic identity

Assembly of transcriptomes encoding unique neuronal identities requires selective accessibility of transcription factors to cis-regulatory sequences in nucleosome-embedded postmitotic chromatin. Yet, the mechanisms controlling postmitotic neuronal chromatin accessibility are poorly understood. Here, we show that unique distal enhancers define the Pet1 neuron lineage that generates serotonin (5-HT) neurons in mice. Heterogeneous single-cell chromatin landscapes are established early in postmitotic Pet1 neurons and reveal the putative regulatory programs driving Pet1 neuron subtype identities. Distal enhancer accessibility is highly dynamic as Pet1 neurons mature, suggesting the existence of regulatory factors that reorganize postmitotic neuronal chromatin. We find that Pet1 and Lmx1b control chromatin accessibility to select Pet1-lineage-specific enhancers for 5-HT neurotransmission. Additionally, these factors are required to maintain chromatin accessibility during early maturation suggesting that postmitotic neuronal open chromatin is unstable and requires continuous regulatory input. Together, our findings reveal postmitotic transcription factors that reorganize accessible chromatin for neuron specialization.

Synaptic protein interaction networks encode experience by assuming stimulus-specific and brain-region-specific states

A core network of widely expressed proteins within the glutamatergic post-synapse mediates activity-dependent synaptic plasticity throughout the brain, but the specific proteomic composition of synapses differs between brain regions. Here, we address the question, how does proteomic composition affect activity-dependent protein-protein interaction networks (PINs) downstream of synaptic activity? Using quantitative multiplex co-immunoprecipitation, we compare the PIN response of in vivo or ex vivo neurons derived from different brain regions to activation by different agonists or different forms of eyeblink conditioning. We report that PINs discriminate between incoming stimuli using differential kinetics of overlapping and non-overlapping PIN parameters. Further, these "molecular logic rules" differ by brain region. We conclude that although the PIN of the glutamatergic post-synapse is expressed widely throughout the brain, its activity-dependent dynamics show remarkable stimulus-specific and brain-region-specific diversity. This diversity may help explain the challenges in developing molecule-specific drug therapies for neurological disorders.

Postsynaptic autism spectrum disorder genes and synaptic dysfunction

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

Shank3 Deficiency is Associated With Altered Profile of Neurotransmission Markers in Pups and Adult Mice

Alterations in the balance between excitation and inhibition, especially in the brain's critical developmental periods, are considered an integral part of the pathophysiology of autism. However, the precise mechanisms have not yet been established. SH3 and multiple Ankyrin repeat domains 3 (Shank3) deficient mice represent a well-established transgenic model of a neurodevelopmental disorder with autistic symptomatology. In this study, we characterize the consequences of Shank3 deficiency according to (1) expression of specific markers of different neuronal populations in pups and adult mice and (2) social behaviour and anxiety in adult mice. Our research found enhanced expression of serotonin transporter and choline acetyltransferase in the hippocampus and hypothalamus in Shank3-deficient pups. We demonstrated marked brain region differences in expression of excitatory glutamatergic markers in pups and adult Shank3 deficient mice. We also observed reduced expression of inhibitory GABAergic markers and GABA receptor subunits in several brain areas in both pups and adult Shank3 deficient mice. Further analysis of dopaminergic brain areas (nucleus accumbens, ventral tegmental area) revealed lower expression levels of GABAergic markers in adult Shank3 deficient mice. Adult Shank3^- deficient mice exhibited excessive repetitive behaviour, a higher level of anxiety, and lower locomotor activity. Our data support the theory of an imbalance between excitatory and inhibitory neurotransmission in conditions of abnormal SHANK3 protein. We therefore suggest that autism-like conditions are accompanied by reduced expression of GABAergic markers in the brain during early development as well as in the adult age, which could be associated with long-lasting behavioural abnormalities.

Autistic-like traits in laboratory rodents exposed to phthalic acid esters during early development - an animal model of autism?

Phthalates are chemical substances that are widely used to provide flexibility and durability to plastic materials. They leach from products in which they are mixed and reach living organisms. Results from experimental studies suggest that exposure to phthalates can have a negative impact on an individual's neuronal system and behavior. In this regard, exposure during early ontogenesis seems to be particularly dangerous due to the extensive growth and development of body structures and functions. Disruption during this critical time can result in alterations of behavior and the emergence of neurodevelopmental disorders, such as autism spectrum disorder (ASD). Various animal models have been used to elucidate the pathogenesis of this disease. They are fundamental for research, and although the translation of results to humans is difficult, new animal models are being developed. The aim of this review is to summarize laboratory rodent studies in which early developmental phthalate exposure resulted in brain alterations and autistic-like behavioral traits. We also discuss the possibility of using early developmental phthalate exposure in rodents to create a new animal model of autism.

Remodeling of the Homer-Shank interactome mediates homeostatic plasticity

Neurons maintain stable levels of excitability using homeostatic synaptic scaling, which adjusts the strength of a neuron's postsynaptic inputs to compensate for extended changes in overall activity. Here, we investigated whether prolonged changes in activity affect network-level protein interactions at the synapse. We assessed a glutamatergic synapse protein interaction network (PIN) composed of 380 binary associations among 21 protein members in mouse neurons. Manipulating the activation of cultured mouse cortical neurons induced widespread bidirectional PIN alterations that reflected rapid rearrangements of glutamate receptor associations involving synaptic scaffold remodeling. Sensory deprivation of the barrel cortex in live mice (by whisker trimming) caused specific PIN rearrangements, including changes in the association between the glutamate receptor mGluR5 and the kinase Fyn. These observations are consistent with emerging models of experience-dependent plasticity involving multiple types of homeostatic responses. However, mice lacking Homer1 or Shank3B did not undergo normal PIN rearrangements, suggesting that the proteins encoded by these autism spectrum disorder-linked genes serve as structural hubs for synaptic homeostasis. Our approach demonstrates how changes in the protein content of synapses during homeostatic plasticity translate into functional PIN alterations that mediate changes in neuron excitability.

The Emergence of Network Activity Patterns in the Somatosensory Cortex - An Early Window to Autism Spectrum Disorders

Across mammalian species, patterned activity in neural populations is a prominent feature of developing sensory cortices. Numerous studies have long appreciated the diversity of these patterns, characterizing their differences in spatial and temporal dynamics. In the murine somatosensory cortex, neuronal co-activation is thought to guide the formation of sensory maps and prepare the cortex for sensory processing after birth. While pioneering studies deftly utilized slice electrophysiology and unit recordings to characterize correlated activity, a detailed understanding of the underlying circuits remains poorly understood. More recently, advances in in vivo calcium imaging in awake mouse pups and increasing genetic tractability of neuronal types have allowed unprecedented manipulation of circuit components at select developmental timepoints. These novel approaches have proven fundamental in uncovering the identity of neurons engaged in correlated activity during development. In particular, recent studies have highlighted interneurons as key in refining the spatial extent and temporal progression of patterned activity. Here, we discuss how emergent synchronous activity across the first postnatal weeks is shaped by underlying gamma aminobutyric acid (GABA)ergic contributors in the somatosensory cortex. Further, the importance of participation in specific activity patterns per se for neuronal maturation and perdurance will be of particular highlight in this survey of recent literature. Finally, we underscore how aberrant neuronal synchrony and disrupted inhibitory interneuron activity underlie sensory perturbations in neurodevelopmental disorders, particularly Autism Spectrum Disorders (ASDs), emphasizing the importance of future investigative approaches that incorporate the spatiotemporal features of patterned activity alongside the cellular components to probe disordered circuit assembly.

Gene Module Analysis Reveals Cell-Type Specificity and Potential Target Genes in Autism's Pathogenesis

Multiple genetic factors contribute to the pathogenesis of autism spectrum disorder (ASD), a kind of neurodevelopmental disorder. Genes were usually studied separately for their associations with ASD. However, genes associated with ASD do not act alone but interact with each other in a network module. The identification of these modules is the basis for the systematic understanding of the pathogenesis of ASD. Moreover, ASD is characterized by highly pathogenic heterogeneity, and gene modules associated with ASD are cell-type-specific. In this study, based on the single-nucleus RNA sequencing data of 41 post-mortem tissue samples from the prefrontal cortex and anterior cingulate cortex of 19 ASD patients and 16 control individuals, we applied sparse module activity factorization, a matrix decomposition method consistent with the multi-factor and heterogeneous characteristics of ASD pathogenesis, to identify cell-type-specific gene modules. Then, statistical procedures were performed to detect highly reproducible cell-type-specific ASD-associated gene modules. Through the enrichment analysis of cell markers, 31 cell-type-specific gene modules related to ASD were further screened out. These 31 gene modules are all enriched with curated ASD risk genes. Finally, we utilized the expression patterns of these cell-type-specific ASD-associated gene modules to build predictive models for ASD. The excellent predictive performance also proved the associations between these gene modules and ASD. Our study confirmed the multifactorial and cell-type-specific characteristics of ASD pathogeneses. The results showed that excitatory neurons such as L2/3, L4, and L5/6-CC play essential roles in ASD's pathogenic processes. We identified the potential ASD target genes that act together in cell-type-specific modules, such as NRG3, KCNIP4, BAI3, PTPRD, LRRTM4, and LINGO2 in the L2/3 gene modules. Our study offers new potential genomic targets for ASD and provides a novel method to study gene modules involved in the pathogenesis of ASD.

Postnatal therapeutic approaches in genetic neurodevelopmental disorders

Genetic neurodevelopmental disorders are characterized by abnormal neurophysiological and behavioral phenotypes, affecting individuals worldwide. While the subject has been heavily researched, current treatment options relate mostly to alleviating symptoms, rather than targeting the altered genome itself. In this review, we address the neurogenetic basis of neurodevelopmental disorders, genetic tools that are enabling precision research of these disorders in animal models, and postnatal gene-therapy approaches for neurodevelopmental disorders derived from preclinical studies in the laboratory.

Core transcriptional networks in Williams syndrome: IGF1-PI3K-AKT-mTOR, MAPK and actin signaling at the synapse echo autism

Gene networks for disorders of social behavior provide the mechanisms critical for identifying therapeutic targets and biomarkers. Large behavioral phenotypic effects of small human deletions make the positive sociality of Williams syndrome (WS) ideal for determining transcriptional networks for social dysfunction currently based on DNA variations for disorders such as autistic spectrum disorder (ASD) and schizophrenia (SCHZ). Consensus on WS networks has been elusive due to the need for larger cohort size, sensitive genome-wide detection and analytic tools. We report a core set of WS network perturbations in a cohort of 58 individuals (34 with typical, 6 atypical deletions and 18 controls). Genome-wide exon-level expression arrays robustly detected changes in differentially expressed gene (DEG) transcripts from WS deleted genes that ranked in the top 11 of 12 122 transcripts, validated by quantitative reverse transcription PCR, RNASeq and western blots. WS DEG's were strictly dosed in the full but not the atypical deletions that revealed a breakpoint position effect on non-deleted CLIP2, a caveat for current phenotypic mapping based on copy number variants. Network analyses tested the top WS DEG's role in the dendritic spine, employing GeneMANIA to harmonize WS DEGs with comparable query gene-sets. The results indicate perturbed actin cytoskeletal signaling analogous to the excitatory dendritic spines. Independent protein-protein interaction analyses of top WS DEGs generated a 100-node graph annotated topologically revealing three interacting pathways, MAPK, IGF1-PI3K-AKT-mTOR/insulin and actin signaling at the synapse. The results indicate striking similarity of WS transcriptional networks to genome-wide association study-based ASD and SCHZ risk suggesting common network dysfunction for these disorders of divergent sociality.

Conditional knockout of MET receptor tyrosine kinase in cortical excitatory neurons leads to enhanced learning and memory in young adult mice but early cognitive decline in older adult mice

Human genetic studies established MET gene as a risk factor for autism spectrum disorders. We have previously shown that signaling mediated by MET receptor tyrosine kinase, expressed in early postnatal developing forebrain circuits, controls glutamatergic neuron morphological development, synapse maturation, and cortical critical period plasticity. Here we investigated how MET signaling affects synaptic plasticity, learning and memory behavior, and whether these effects are age-dependent. We found that in young adult (postnatal 2-3 months) Met conditional knockout (Met^fx/fx:emx1^cre, cKO) mice, the hippocampus exhibits elevated plasticity, measured by increased magnitude of long-term potentiation (LTP) and depression (LTD) in hippocampal slices. Surprisingly, in older adult cKO mice (10-12 months), LTP and LTD magnitudes were diminished. We further conducted a battery of behavioral tests to assess learning and memory function in cKO mice and littermate controls. Consistent with age-dependent LTP/LTD findings, we observed enhanced spatial memory learning in 2-3 months old young adult mice, assessed by hippocampus-dependent Morris water maze test, but impaired spatial learning in 10-12 months mice. Contextual and cued learning were further assessed using a Pavlovian fear conditioning test, which also revealed enhanced associative fear acquisition and extinction in young adult mice, but impaired fear learning in older adult mice. Lastly, young cKO mice also exhibited enhanced motor learning. Our results suggest that a shift in the window of synaptic plasticity and an age-dependent early cognitive decline may be novel circuit pathophysiology for a well-established autism genetic risk factor.

DNA methylation and psychotherapy response in trauma-exposed men with appetitive aggression

Exposure to violence can lead to appetitive aggression (AA), the positive feeling and fascination associated with violence, and posttraumatic stress disorder (PTSD), characterised by hyperarousal, reexperience and feelings of ongoing threat. Psychotherapeutic interventions may act via DNA methylation, an environmentally sensitive epigenetic mechanism that can influence gene expression. We investigated epigenetic signatures of psychotherapy for PTSD and AA symptoms in South African men with chronic trauma exposure. Participants were assigned to one of three groups: narrative exposure therapy for forensic offender rehabilitation (FORNET), cognitive behavioural therapy or waiting list control (n = 9-10/group). Participants provided saliva and completed the Appetitive Aggression Scale and PTSD Symptom Severity Index at baseline, 8-month and 16-month follow-up. The relationship, over time, between methylation in 22 gene promoter region sites, symptom scores, and treatment was assessed using linear mixed models. Compared to baseline, PTSD and AA symptom severity were significantly reduced at 8 and 16 months, respectively, in the FORNET group. Increased methylation of genes implicated in dopaminergic neurotransmission (NR4A2) and synaptic plasticity (AUTS2) was associated with reduced PTSD symptom severity in participants receiving FORNET. Analyses across participants revealed a proportional relationship between AA and methylation of TFAM, a gene involved in mitochondrial biosynthesis.

VLDL-specific increases of fatty acids in autism spectrum disorder correlate with social interaction

BACKGROUND

Abnormalities of lipid metabolism contributing to the autism spectrum disorder (ASD) pathogenesis have been suggested, but the mechanisms are not fully understood. We aimed to characterize the lipid metabolism in ASD and to explore a biomarker for clinical evaluation.

METHODS

An age-matched case-control study was designed. Lipidomics was conducted using the plasma samples from 30 children with ASD compared to 30 typical developmental control (TD) children. Large-scale lipoprotein analyses were also conducted using the serum samples from 152 children with ASD compared to 122 TD children. Data comparing ASD to TD subjects were evaluated using univariate (Mann-Whitney test) and multivariate analyses (conditional logistic regression analysis) for main analyses using cofounders (diagnosis, sex, age, height, weight, and BMI), Spearman rank correlation coefficient, and discriminant analyses.

FINDINGS

Forty-eight significant metabolites involved in lipid biosynthesis and metabolism, oxidative stress, and synaptic function were identified in the plasma of ASD children by lipidomics. Among these, increased fatty acids (FAs), such as omega-3 (n-3) and omega-6 (n-6), showed correlations with clinical social interaction score and ASD diagnosis. Specific reductions of very-low-density lipoprotein (VLDL) and apoprotein B (APOB) in serum of ASD children also were found by large-scale lipoprotein analysis. VLDL-specific reduction in ASD was correlated with APOB, indicating VLDL-specific dyslipidaemia associated with APOB in ASD children.

INTERPRETATION

Our results demonstrated that the increases in FAs correlated positively with social interaction are due to VLDL-specific degradation, providing novel insights into the lipid metabolism underlying ASD pathophysiology.

FUNDING

This study was supported mainly by MEXT, Japan.