Behavioral Phenotyping for Autism Spectrum Disorders in Mice

Gut microbiota transfer from the preclinical maternal immune activation model of autism is sufficient to induce sex-specific alterations in immune response and behavioural outcomes

The gut microbiome plays a vital role in health and disease, including neurodevelopmental disorders like autism spectrum disorder (ASD). ASD affects 4:1 males-to-females, and sex differences are apparent in gut microbiota composition among ASD individuals and in animal models of this condition, such as the maternal immune activation (MIA) mouse model. However, few studies have included sex as a biological variable when assessing the role of gut microbiota in mediating ASD symptoms. Using the MIA model of ASD, we assessed whether gut microbiota contributes to the sex differences in the presentation of ASD-like behaviors. Gut microbiota transplantation from MIA or vehicle/control male and female mice into healthy, otherwise unmanipulated, 4-week-old C57Bl/6 mice was performed for 6 treatments over 12 days. Colonization with male, but not female, MIA microbiota was sufficient to reduce sociability, decrease microbiota diversity and increase neuroinflammation with more pronounced deficits in male recipients. Colonization with both male and female donor microbiota altered juvenile ultrasonic vocalizations and anxiety-like behavior in recipients of both sexes, and there was an accompanied change in the gut microbiota and serum cytokine IL-4 and IL-7 levels of all recipients of MIA gut microbiota. In addition to the increases in gut microbes associated with pathological states, the female donor microbiota profile also had increases in gut microbes with known neural protective effects (e.g., Lactobacillus and Rikenella). These results suggest that gut reactivity to environmental insults, such as in the MIA model, may play a role in shaping the sex disparity in ASD development.

Automated Video Tracking of Autistic Children's Movement During Caregiver-Child Interaction: An Exploratory Study

Objective, quantitative measures of caregiver-child interaction during play are needed to complement caregiver or examiner ratings for clinical assessment and tracking intervention responses. In this exploratory study, we examined the feasibility of using automated video tracking, Noldus EthoVision XT, to measure 159 2-to-7-year-old autistic children's patterns of movement during play-based, caregiver-child interactions and examined their associations with standard clinical measures and human observational coding of caregiver-child joint engagement. Results revealed that autistic children who exhibited higher durations and velocity of movement were, on average, younger, had lower cognitive abilities, greater autism-related features, spent less time attending to the caregiver, and showed lower levels of joint engagement. After adjusting for age and nonverbal cognitive abilities, we found that children who remained in close proximity to their caregiver were more likely to engage in joint engagement that required support from the caregiver. These findings suggest that video tracking offers promise as a scalable, quantitative, and relevant measure of autism-related behaviors.

Animal Models of Autistic-like Behavior in Rodents: A Scoping Review and Call for a Comprehensive Scoring System

Appropriate animal models of human diseases are a cornerstone in the advancement of science and medicine. To create animal models of neuropsychiatric and neurobehavioral diseases such as autism spectrum disorder (ASD) necessitates the development of sufficient neurobehavioral measuring tools to translate human behavior to expected measurable behavioral features in animals. If possible, the severity of the symptoms should also be assessed. Indeed, at least in rodents, adequate neurobehavioral and neurological tests have been developed. Since ASD is characterized by a number of specific behavioral trends with significant severity, animal models of autistic-like behavior have to demonstrate the specific characteristic features, namely impaired social interactions, communication deficits, and restricted, repetitive behavioral patterns, with association to several additional impairments such as somatosensory, motor, and memory impairments. Thus, an appropriate model must show behavioral impairment of a minimal number of neurobehavioral characteristics using an adequate number of behavioral tests. The proper animal models enable the study of ASD-like-behavior from the etiologic, pathogenetic, and therapeutic aspects. From the etiologic aspects, models have been developed by the use of immunogenic substances like polyinosinic-polycytidylic acid (PolyIC), lipopolysaccharide (LPS), and propionic acid, or other well-documented immunogens or pathogens, like Mycobacterium tuberculosis. Another approach is the use of chemicals like valproic acid, polychlorinated biphenyls (PCBs), organophosphate pesticides like chlorpyrifos (CPF), and others. These substances were administered either prenatally, generally after the period of major organogenesis, or, especially in rodents, during early postnatal life. In addition, using modern genetic manipulation methods, genetic models have been created of almost all human genetic diseases that are manifested by autistic-like behavior (i.e., fragile X, Rett syndrome, SHANK gene mutation, neuroligin genes, and others). Ideally, we should not only evaluate the different behavioral modes affected by the ASD-like behavior, but also assess the severity of the behavioral deviations by an appropriate scoring system, as applied to humans. We therefore propose a scoring system for improved assessment of ASD-like behavior in animal models.

Zika virus infection impairs synaptogenesis, induces neuroinflammation, and could be an environmental risk factor for autism spectrum disorder outcome

Zika virus (ZIKV) infection was first associated with Central Nervous System (CNS) infections in Brazil in 2015, correlated with an increased number of newborns with microcephaly, which ended up characterizing the Congenital Zika Syndrome (CZS). Here, we investigated the impact of ZIKV infection on the functionality of iPSC-derived astrocytes. Besides, we extrapolated our findings to a Brazilian cohort of 136 CZS children and validated our results using a mouse model. Interestingly, ZIKV infection in neuroprogenitor cells compromises cell migration and causes apoptosis but does not interfere in astrocyte generation. Moreover, infected astrocytes lost their ability to uptake glutamate while expressing more glutamate transporters and secreted higher levels of IL-6. Besides, infected astrocytes secreted factors that impaired neuronal synaptogenesis. Since these biological endophenotypes were already related to Autism Spectrum Disorder (ASD), we extrapolated these results to a cohort of children, now 6-7 years old, and found seven children with ASD diagnosis (5.14 %). Additionally, mice infected by ZIKV revealed autistic-like behaviors, with a significant increase of IL-6 mRNA levels in the brain. Considering these evidence, we inferred that ZIKV infection during pregnancy might lead to synaptogenesis impairment and neuroinflammation, which could increase the risk for ASD.

Establishment of animal models and behavioral studies for autism spectrum disorders

In recent years, the incidence of autism spectrum disorder (ASD) has increased, but the etiology and pathogenesis remain unclear. In this narrative review, we review and systematically summarize the methods used to construct animal models to study ASD and the related behavioral studies based on recent literature. Utilization of various ASD animal models can complement research on the etiology, pathogenesis, and core behaviors of ASD, providing information and a foundation for further basic research and clinical treatment of ASD.

Impaired neural circuitry of hippocampus in Pax2 nervous system-specific knockout mice leads to restricted repetitive behaviors

INTRODUCTION

Restricted repetitive behaviors (RRBs), which are associated with many different neurological and mental disorders, such as obsessive-compulsive disorder (OCD) and autism, are patterns of behavior with little variation and little obvious function. Paired Box 2 (Pax2) is a transcription factor that is expressed in many systems, including the kidney and the central nervous system. The protein that is encoded by Pax2 has been implicated in the development of the nervous system and neurodevelopmental disorders. In our previous study, Pax2 heterozygous gene knockout mice (Pax2+/- mice) showed abnormally increased self-grooming and impaired learning and memory abilities. However, it remains unclear which cell type is involved in this process. In this study, we deleted Pax2 only in the nervous system to determine the regulatory mechanism of Pax2 in RRBs.

METHODS

In this study, Pax2 nervous system-specific knockout mice (Nestin-Pax2 mice) aged 6-8 weeks and Pax2 flox mice of the same age were recruited as the experimental group. Tamoxifen and vehicle were administered via intraperitoneal injection to induce Pax2 knockout after gene identification. Western blotting was used to detect Pax2 expression. After that, we assessed the general health of these two groups of mice. The self-grooming test, marble burying test and T-maze acquisition and reversal learning test were used to observe the lower-order and higher-order RRBs. The three-chamber test, Y-maze, and elevated plus-maze were used to assess social ability, spatial memory ability, and anxiety. Neural circuitry tracing and transcriptome sequencing (RNA-seq) were used to observe the abnormal neural circuitry, differentially expressed genes (DEGs) and signaling pathways affected by Pax2 gene knockout in the nervous system and the putative molecular mechanism.

RESULTS

(1) The Nestin-Pax2 mouse model was successfully constructed, and the Nestin-Pax2 mice showed decreased expression of Pax2. (2) Nestin-Pax2 mice showed increased self-grooming behavior and impaired T-maze reversal behavior compared with Pax2 flox mice. (3) An increased number of projection fibers can be found in the mPFC projecting to the CA1 and BLA, and a reduction in IGFBP2 can be found in the hippocampus of Nestin-Pax2 mice.

CONCLUSION

The results demonstrated that loss of Pax2 in the nervous system leads to restricted repetitive behaviors. The mechanism may be associated with impaired neural circuitry and a reduction in IGFBP2.

Influence of maternal immune activation on autism-like symptoms and coping strategies in male offspring

Maternal immune activation (MIA) caused by exposure to pathogens or inflammation during critical periods of gestation increased susceptibility to neurodevelopmental disorders, including autism, in the offspring. In the present work, we aimed to provide characterization of the long-term consequences on anxiety-like behavior and cardiovascular stress response of MIA in the offspring. This study aimed to evaluate the effect of MIA by lipopolysaccharide (LPS) in adult male offspring. In our study, the animals were subjected to a range of behavioral and physiological tests, including the elevated plus maze, social interaction, cat odor response, open field behavior, contextual fear conditioning, and cardiovascular responses during restraint stress. In the offspring of MIA, our study unveiled distinct anxious behaviors. This was evident by fewer entries into the open arms of the maze, diminished anti-thigmotaxis in the open field, and a decrease in social interaction time. Moreover, these rats showed heightened sensitivity to cat odor, exhibited prolonged freezing during fear conditioning, and presented elevated 22 Hz ultrasonic vocalizations. Notably, during restraint stress, these animals manifested an augmented blood pressure response, and this was associated with an increase in c-fos expression in the locus coeruleus compared to the control group. These findings collectively underline the extensive behavioral and physiological alterations stemming from MIA. This study deepens our understanding of the significance of maternal health in predisposing offspring to neurobehavioral deficits and psychiatric disorders.

Behavioral and Molecular Characterization of Prenatal Stress Effects on the C57BL/6J Genetic Background for the Study of Autism Spectrum Disorder

Stress-inducing events during pregnancy are associated with aberrant neurodevelopment resulting in adverse psychiatric outcomes, including autism spectrum disorder (ASD). While numerous preclinical models for the study of ASD are frequently generated using C57BL/6J mice, few studies have investigated the effects of prenatal stress on this genetic background. In the current manuscript, we stressed C57BL/6 dams during gestation and examined numerous behavioral and molecular endophenotypes in the adult male and female offspring to characterize the resultant phenotype as compared with offspring born from nonstressed (NS) dams. Adult mice born from prenatal restraint stressed (PRS) dams demonstrated reduced sociability and reciprocal social interaction along with increased marble burying behaviors relative to mice born from nonstressed control dams. Differential expression of genes related to excitatory and inhibitory neurotransmission was evaluated in the medial prefrontal cortex, amygdala, hippocampus, nucleus accumbens and caudate putamen via qRT-PCR. The male PRS mouse behavioral phenotype coincided with aberrant expression of glutamate and GABA marker genes (e.g., Grin1, Grin2b, Gls, Gat1, Reln) in neural substrates of social behavior. Rescue of the male PRS sociability deficit by a known antipsychotic with epigenetic properties (i.e., clozapine (5 mg/kg) + 18 hr washout) indicated possible epigenetic regulation of genes that govern sociability. Clozapine treatment increased the expression levels of genes involved in DNA methylation, histone methylation, and histone acetylation in the nucleus accumbens. Identification of etiology-specific mechanisms underlying clinically relevant behavioral phenotypes may ultimately provide novel therapeutic interventions for the treatment of psychiatric disorders including ASD.

Umbelliprenin via increase in the MECP2 and attenuation of oxidative stress mitigates the autistic-like behaviors in mouse model of maternal separation stress

Introduction: Autism spectrum disorder (ASD) is a complex neurodevelopmental condition. Maternal separation (MS) stress is an early-life stress factor associated with behaviors resembling Autism. Both MECP2 and oxidative stress are implicated in the pathophysiology of Autism. Umbelliprenin (UMB) is a coumarin compound with various pharmacological properties. Our study aimed to investigate the potential effects of UMB in mitigating autistic-like behaviors in a mouse model subjected to MS stress, focusing on probable alterations in MECP2 gene expression in the hippocampus. Methods: MS paradigm was performed, and mice were treated with saline or UMB. Behavioral tests consisting of the three-chamber test (evaluating social interaction), shuttle box (assessing passive avoidance memory), elevated plus-maze (measuring anxiety-like behaviors), and marble-burying test (evaluating repetitive behaviors) were conducted. Gene expression of MECP2 and measurements of total antioxidant capacity (TAC), nitrite level, and malondialdehyde (MDA) level were assessed in the hippocampus. Results: The findings demonstrated that MS-induced behaviors resembling Autism, accompanied by decreased MECP2 gene expression, elevated nitrite, MDA levels, and reduced TAC in the hippocampus. UMB mitigated these autistic-like behaviors induced by MS and attenuated the adverse effects of MS on oxidative stress and MECP2 gene expression in the hippocampus. Conclusion: In conclusion, UMB likely attenuated autistic-like behaviors caused by MS stress, probably, through the reduction of oxidative stress and an increase in MECP2 gene expression.

The Role of Short-Chain Fatty Acids and Altered Microbiota Composition in Autism Spectrum Disorder: A Comprehensive Literature Review

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by deficits in communication and social interactions, restrictive and repetitive behavior, and a wide range of cognitive impediments. The prevalence of ASD tripled in the last 20 years and now affects 1 in 44 children. Although ASD's etiology is not yet elucidated, a growing body of evidence shows that it stems from a complex interplay of genetic and environmental factors. In recent years, there has been increased focus on the role of gut microbiota and their metabolites, as studies show that ASD patients show a significant shift in their gut composition, characterized by an increase in specific bacteria and elevated levels of short-chain fatty acids (SCFAs), especially propionic acid (PPA). This review aims to provide an overview of the role of microbiota and SCFAs in the human body, as well as possible implications of microbiota shift. Also, it highlights current studies aiming to compare the composition of the gut microbiome of ASD-afflicted patients with neurotypical control. Finally, it highlights studies with rodents where ASD-like symptoms or molecular hallmarks of ASD are evoked, via the grafting of microbes obtained from ASD subjects or direct exposure to PPA.

Automated movement tracking of young autistic children during free play is correlated with clinical features associated with autism

LAY ABSTRACT

Play-based observations allow researchers to observe autistic children across a wide range of ages and skills. We recorded autistic children playing with toys in the center of a room and at a corner table while a caregiver remained seated off to the side and used video tracking technology to track children's movement and location. We examined how time children spent in room regions and whether or not they approached each region during play related to their cognitive, social, communication, and adaptive skills to determine if tracking child movement and location can meaningfully demonstrate clinical variation among autistic children representing a range of ages and skills. One significant finding was that autistic children who spent more time in the toy-containing center of the room had higher cognitive and language abilities, whereas those who spent less time in the center had higher levels of autism-related behaviors. In contrast, children who spent more time in the caregiver region had lower daily living skills and those who were quicker to approach the caregiver had lower adaptive behavior and language skills. These findings support the use of movement tracking as a complementary method of measuring clinical differences among autistic children. Furthermore, over 90% of autistic children representing a range of ages and skills in this study provided analyzable play observation data, demonstrating that this method allows autistic children of all levels of support needs to participate in research and demonstrate their social, communication, and attention skills without wearing any devices.

Exposure to nonylphenol in early life causes behavioural deficits related with autism spectrum disorders in rats

Early-life exposure to environmental endocrine disruptors (EDCs) is a potential risk factor for autism spectrum disorder (ASD). Exposure to nonylphenol (NP), a typical EDC, is known to cause some long-term behavioural abnormalities. Moreover, these abnormal behaviours are the most frequent psychiatric co-morbidities in ASD. However, the direct evidence for the link between NP exposure in early life and ASD-like behavioural phenotypes is still missing. In the present study, typical ASD-like behaviours induced by valproic acid treatment were considered as a positive behavioural control. We investigated impacts on social behaviours following early-life exposure to NP, and explored effects of this exposure on neuronal dendritic spines, mitochondria function, oxidative stress, and endoplasmic reticulum (ER) stress. Furthermore, primary cultured rat neurons were employed as in vitro model to evaluate changes in dendritic spine caused by exposure to NP, and oxidative stress and ER stress were specifically modulated to further explore their roles in these changes. Our results indicated rats exposed to NP in early life showed mild ASD-like behaviours. Moreover, we also found the activation of ER stress triggered by oxidative stress may contribute to dendritic spine decrease and synaptic dysfunction, which may underlie neurobehavioural abnormalities induced by early-life exposure to NP.

microRNA as a Maternal Marker for Prenatal Stress-Associated ASD, Evidence from a Murine Model

Autism Spectrum Disorder (ASD) has been associated with a complex interplay between genetic and environmental factors. Prenatal stress exposure has been identified as a possible risk factor, although most stress-exposed pregnancies do not result in ASD. The serotonin transporter (SERT) gene has been linked to stress reactivity, and the presence of the SERT short (S)-allele has been shown to mediate the association between maternal stress exposure and ASD. In a mouse model, we investigated the effects of prenatal stress exposure and maternal SERT genotype on offspring behavior and explored its association with maternal microRNA (miRNA) expression during pregnancy. Pregnant female mice were divided into four groups based on genotype (wildtype or SERT heterozygous knockout (Sert-het)) and the presence or absence of chronic variable stress (CVS) during pregnancy. Offspring behavior was assessed at 60 days old (PD60) using the three-chamber test, open field test, elevated plus-maze test, and marble-burying test. We found that the social preference index (SPI) of SERT-het/stress offspring was significantly lower than that of wildtype control offspring, indicating a reduced preference for social interaction on social approach, specifically for males. SERT-het/stress offspring also showed significantly more frequent grooming behavior compared to wildtype controls, specifically for males, suggesting elevated repetitive behavior. We profiled miRNA expression in maternal blood samples collected at embryonic day 21 (E21) and identified three miRNAs (mmu-miR-7684-3p, mmu-miR-5622-3p, mmu-miR-6900-3p) that were differentially expressed in the SERT-het/stress group compared to all other groups. These findings suggest that maternal SERT genotype and prenatal stress exposure interact to influence offspring behavior, and that maternal miRNA expression late in pregnancy may serve as a potential marker of a particular subtype of ASD pathogenesis.

Early-life exposure to endocrine-disrupting chemicals and autistic traits in childhood and adolescence: a systematic review of epidemiological studies

Aims

Exposure to endocrine-disrupting chemicals (EDCs) during critical neurodevelopmental windows has been associated with the risk of autistic traits. This systematic review of epidemiological studies examined the association between maternal exposure to EDCs during pregnancy and the risk of autism spectrum disorder (ASD) in the offspring.

Methods

We searched PubMed, Web of Science, Scopus, and Google Scholar from inception to November 17, 2022, for studies investigating the association between prenatal exposure to EDCs and outcomes related to ASD. Two independent reviewers screened studies for eligibility, extracted data, and assessed the risk of bias. The review was registered in PROSPERO (CRD42023389386).

Results

We included 27 observational studies assessing prenatal exposure to phthalates (8 studies), polychlorinated biphenyls (8 studies), organophosphate pesticides (8 studies), phenols (7 studies), perfluoroalkyl substances (6 studies), organochlorine pesticides (5 studies), brominated flame retardants (3 studies), dioxins (1 study), and parabens (1 study). The number of examined children ranged from 77 to 1,556, the age at the assessment of autistic traits ranged from 3 to 14 years, and most studies assessed autistic traits using the Social Responsiveness Scale. All but one study was considered to have a low risk of bias. Overall, there was no association between maternal exposure to specific ECDs during pregnancy and the occurrence of autistic traits in offspring.

Conclusions

Findings from the epidemiological studies evaluated here do not support an association between prenatal exposure to ECDs and the likelihood of autistic traits in later in life. These findings should not be interpreted as definitive evidence of the absence of neurodevelopment effects of EDCs affecting ASD risk, given the limitations of current studies such as representative exposure assessment, small sample sizes, inadequacy to assess sexually dimorphic effects, or the effects of EDC mixtures. Future studies should carefully address these limitations.

Prenatal low-dose methylmercury exposure causes premature neuronal differentiation and autism-like behaviors in a rodent model

Aberrant neurodevelopment is a core deficit of autism spectrum disorder (ASD). Here we ask whether a non-genetic factor, prenatal exposure to the environmental pollutant methylmercury (MeHg), is a contributing factor in ASD onset. We showed that adult mice prenatally exposed to non-apoptotic MeHg exhibited key ASD characteristics, including impaired communication, reduced sociability, and increased restrictive repetitive behaviors, whereas in the embryonic cortex, prenatal MeHg exposure caused premature neuronal differentiation. Further single-cell RNA sequencing (scRNA-seq) analysis disclosed that prenatal exposure to MeHg resulted in cortical radial glial precursors (RGPs) favoring asymmetric differentiation to directly generate cortical neurons, omitting the intermediate progenitor stage. In addition, MeHg exposure in cultured RGPs increased CREB phosphorylation and enhanced the interaction between CREB and CREB binding protein (CBP). Intriguingly, metformin, an FDA-approved drug, can reverse MeHg-induced premature neuronal differentiation via CREB/CBP repulsion. These findings provide insights into ASD etiology, its underlying mechanism, and a potential therapeutic strategy.

Deletion of Arrb2 Down-regulates Autophagy in the Mouse Hippocampus via Akt-mTOR Pathway Activation

The cytoplasmic multifunctional adaptor protein β-arrestin 2 (Arrb2) is involved in the occurrence of various nervous system diseases, such as Alzheimer's disease and Parkinson's disease. Previous laboratory studies have shown that the expression and function of the Arrb2 gene was increased in valproic acid-induced autistic mice models. However, few reports have examined the possible role of Arrb2 in the pathogenesis of autism spectrum disorder. Therefore, Arrb2-deficient (Arrb2^-/-) mice were further studied to uncover the physiological function of Arrb2 in the nervous system. In this study, we found that Arrb2^-/- mice had normal behavioral characteristics compared with wild-type mice. The autophagy marker protein LC3B was decreased in the hippocampus of Arrb2^-/- mice compared to wild-type mice. Western blot analysis revealed that deletion of Arrb2 caused hyperactivation of Akt-mTOR signaling in the hippocampus. In addition, abnormal mitochondrial dysfunction was observed in Arrb2^-/- hippocampal neurons, which was characterized by a reduction in mitochondrial membrane potential and adenosine triphosphate production and an increase in reactive oxygen species levels. Therefore, this study elucidates the interaction between Arrb2 and the Akt-mTOR signaling pathway and provides insights into the role of Arrb2 in hippocampal neuron autophagy.

Seizure susceptibility to various convulsant stimuli in the BTBR mouse model of autism spectrum disorders

Background: Autism spectrum disorders (ASDs) are one of the most severe chronic childhood disorders in terms of prevalence, morbidity, and impact on society. Interestingly, several systematic reviews and meta-analyses documented a bidirectional link between epilepsy and ASD, supporting the hypothesis that both disorders may have common neurobiological pathways. According to this hypothesis, an imbalance of the excitatory/inhibitory (E/I) ratio in several brain regions may represent a causal mechanism underpinning the co-occurrence of these neurological diseases. Methods: To investigate this bidirectional link, we first tested the seizure susceptibility to chemoconvulsants acting on GABAergic and glutamatergic systems in the BTBR mice, in which an imbalance between E/I has been previously demonstrated. Subsequently, we performed the PTZ kindling protocol to study the impact of seizures on autistic-like behavior and other neurological deficits in BTBR mice. Results: We found that BTBR mice have an increased susceptibility to seizures induced by chemoconvulsants impairing GABA_A neurotransmission in comparison to C57BL/6J control mice, whereas no significant difference in seizure susceptibility was observed after administration of AMPA, NMDA, and Kainate. This data suggests that deficits in GABAergic neurotransmission can increase seizure susceptibility in this strain of mice. Interestingly, BTBR mice showed a longer latency in the development of kindling compared to control mice. Furthermore, PTZ-kindling did not influence autistic-like behavior in BTBR mice, whereas it was able to significantly increase anxiety and worsen cognitive performance in this strain of mice. Interestingly, C57BL/6J displayed reduced sociability after PTZ injections, supporting the hypothesis that a tight connection exists between ASD and epilepsy. Conclusion: BTBR mice can be considered a good model to study epilepsy and ASD contemporarily. However, future studies should shed light on the mechanisms underpinning the co-occurrence of these neurological disorders in the BTBR model.

Leaky Gut Plays a Critical Role in the Pathophysiology of Autism in Mice by Activating the Lipopolysaccharide-Mediated Toll-Like Receptor 4–Myeloid Differentiation Factor 88–Nuclear Factor Kappa B Signaling Pathway

Increased intestinal barrier permeability, leaky gut, has been reported in patients with autism. However, its contribution to the development of autism has not been determined. We selected dextran sulfate sodium (DSS) to disrupt and metformin to repair the intestinal barrier in BTBR T+tf/J autistic mice to test this hypothesis. DSS treatment resulted in a decreased affinity for social proximity; however, autistic behaviors in mice were improved after the administration of metformin. We found an increased affinity for social proximity/social memory and decreased repetitive and anxiety-related behaviors. The concentration of lipopolysaccharides in blood decreased after the administration of metformin. The expression levels of the key molecules in the toll-like receptor 4 (TLR4)–myeloid differentiation factor 88 (MyD88)–nuclear factor kappa B (NF-κB) pathway and their downstream inflammatory cytokines in the cerebral cortex were both repressed. Thus, “leaky gut” could be a trigger for the development of autism via activation of the lipopolysaccharide-mediated TLR4–MyD88–NF-κB pathway.

Cellular mechanisms underlying central sensitization in a mouse model of chronic muscle pain

Chronic pain disorders are often associated with negative emotions, including anxiety and depression. The central nucleus of the amygdala (CeA) has emerged as an integrative hub for nociceptive and affective components during central pain development. Prior adverse injuries are precipitating factors thought to transform nociceptors into a primed state for chronic pain. However, the cellular basis underlying the primed state and the subsequent development of chronic pain remains unknown. Here, we investigated the cellular and synaptic alterations of the CeA in a mouse model of chronic muscle pain. In these mice, local infusion of pregabalin, a clinically approved drug for fibromyalgia and other chronic pain disorders, into the CeA or chemogenetic inactivation of the somatostatin-expressing CeA (CeA-SST) neurons during the priming phase prevented the chronification of pain. Further, electrophysiological recording revealed that the CeA-SST neurons had increased excitatory synaptic drive and enhanced neuronal excitability in the chronic pain states. Finally, either chemogenetic inactivation of the CeA-SST neurons or pharmacological suppression of the nociceptive afferents from the brainstem to the CeA-SST neurons alleviated chronic pain and anxio-depressive symptoms. These data raise the possibility of targeting treatments to CeA-SST neurons to prevent central pain sensitization.

The socially enriched environment test: a new approach to evaluate social behavior in a mouse model of social anxiety disorder

Social anxiety disorder (SAD) is a common anxiety disorder characterized by a marked fear of social situations. Treatments for SAD, including exposure therapy and medication, are not satisfactory for all patients. This has led to the development of several paradigms to study social fear in rodents. However, there are still some social impairments observed in SAD patients that have never been examined in rodent models. Indeed, social situations avoided by SAD patients include not only social interactions but also public performances and being observed by others. Nevertheless, tests used to assess sociability in rodents evaluate mostly social interaction in pairs. Thus, we developed a new test-a socially enriched environment test-that evaluates sociability within a group of three unfamiliar conspecifics in an enriched environment. In this study, we induced a SAD-like behavior (i.e., social fear) in male mice using social fear conditioning (SFC) and then tested social fear using the socially enriched environment test and the three-chamber test. Finally, we tested the effects of fear extinction and acute diazepam treatment in reversing social fear. Results revealed, in conditioned mice, decreased object exploration in proximity to conspecifics, social interaction, and mouse-like object exploration. Extinction training, but not acute diazepam treatment, reversed SFC-induced behavioral changes. These findings demonstrate that the socially enriched environment test provides an appropriate behavioral approach to better understand the etiology of SAD. This test may also have important implications in the exploration of new treatments.

Ketamine administration in early postnatal life as a tool for mimicking Autism Spectrum Disorders core symptoms

Autism Spectrum Disorders (ASD) core symptoms include deficits of social interaction, stereotyped behaviours, dysfunction in language and communication. Beyond them, several additional symptoms, such as cognitive impairment, anxiety-like states and hyperactivity are often occurring, mainly overlapping with other neuropsychiatric diseases. To untangle mechanisms underlying ASD etiology, and to identify possible pharmacological approaches, different factors, such as environmental, immunological and genetic ones, need to be considered. In this context, ASD animal models, aiming to reproduce the wide range of behavioural phenotypes of this uniquely human disorder, represent a very useful tool. Ketamine administration in early postnatal life of mice has already been studied as a suitable animal model resembling psychotic-like symptoms. Here, we investigated whether ketamine administration, at postnatal days 7, 9 and 11, might induce behavioural features able to mimic ASD typical symptoms in adult mice. To this aim, we developed a 4-days behavioural tests battery, including Marble Burying, Hole Board, Olfactory and Social tests, to assess repetitive and stereotyped behaviour, social deficits and anxiety-like symptoms. Moreover, by using this mouse model, we performed neurochemical and biomolecular analyses, quantifying neurotransmitters belonging to excitatory-inhibitory pathways, such as glutamate, glutamine and gamma-aminobutyric acid (GABA), as well as immune activation biomarkers related to ASD, such as CD11b and glial fibrillary acidic protein (GFAP), in the hippocampus and amygdala. Possible alterations in levels of brain-derived neurotrophic factor (BDNF) expression in the hippocampus and amygdala were also evaluated. Our results showed an increase in stereotyped behaviours, together with social impairments and anxiety-like behaviour in adult mice, receiving ketamine administration in early postnatal life. In addition, we found decreased BDNF and enhanced GFAP hippocampal expression levels, accompanied by elevations in glutamate amount, as well as reduction in GABA content in amygdala and hippocampus. In conclusion, early ketamine administration may represent a suitable animal model of ASD, exhibiting face validity to mimic specific ASD symptoms, such as social deficits, repetitive repertoire and anxiety-like behaviour.

Generation and characterization of Ccdc28b mutant mice links the Bardet-Biedl associated gene with mild social behavioral phenotypes

CCDC28B (coiled-coil domain-containing protein 28B) was identified as a modifier in the ciliopathy Bardet-Biedl syndrome (BBS). Our previous work in cells and zebrafish showed that CCDC28B plays a role regulating cilia length in a mechanism that is not completely understood. Here we report the generation of a Ccdc28b mutant mouse using CRISPR/Cas9 (Ccdc28b mut). Depletion of CCDC28B resulted in a mild phenotype. Ccdc28b mut animals i) do not present clear structural cilia affectation, although we did observe mild defects in cilia density and cilia length in some tissues, ii) reproduce normally, and iii) do not develop retinal degeneration or obesity, two hallmark features of reported BBS murine models. In contrast, Ccdc28b mut mice did show clear social interaction defects as well as stereotypical behaviors. This finding is indeed relevant regarding CCDC28B as a modifier of BBS since behavioral phenotypes have been documented in BBS. Overall, this work reports a novel mouse model that will be key to continue evaluating genetic interactions in BBS, deciphering the contribution of CCDC28B to modulate the presentation of BBS phenotypes. In addition, our data underscores a novel link between CCDC28B and behavioral defects, providing a novel opportunity to further our understanding of the genetic, cellular, and molecular basis of these complex phenotypes.

BBS is caused by mutations in any one of 22 genes known to date. In some families, BBS can be inherited as an oligogenic trait whereby mutations in more than one BBS gene collaborate in the presentation of the syndrome. In addition, CCDC28B was originally identified as a modifier of BBS, whereby a reduction in CCDC28B levels was associated with a more severe presentation of the syndrome. Different mechanisms, all relying on functional redundancy, have been proposed to explain these genetic interactions. The characterization of BBS proteins supported this functional redundancy hypothesis: BBS proteins play a role in cilia maintenance/function and subsets of BBS proteins can even interact directly in multiprotein complexes.

We have previously shown that CCDC28B also participates in cilia biology regulating the length of the organelle: knockdown of CCDC28B in cells results in cilia shortening and targeting ccdc28b in zebrafish also results in early embryonic phenotypes characteristic of other cilia mutants. In this work, we generated a Ccdc28b mutant mouse to determine whether abrogating Ccdc28b function would be sufficient to cause a ciliopathy phenotype in mammals, and to generate a tool to continue dissecting its modifying role in the context of BBS. Overall, Ccdc28b mutant mice presented a mild phenotype, a finding fully compatible with its role as a modifier, rather than a causal BBS gene. In addition, we found that Ccdc28b mutants showed behavioral phenotypes, similar to the deficits observed in rodent autism spectrum disorder (ASD) models. Thus, our results underscore a novel causal link between CCDC28B and behavioral phenotypes in mice.

Lifelong Exposure to a Low-Dose of the Glyphosate-Based Herbicide RoundUp® Causes Intestinal Damage, Gut Dysbiosis, and Behavioral Changes in Mice

RoundUp® (RUp) is a comercial formulation containing glyphosate (N-(phosphono-methyl) glycine), and is the world's leading wide-spectrum herbicide used in agriculture. Supporters of the broad use of glyphosate-based herbicides (GBH) claim they are innocuous to humans, since the active compound acts on the inhibition of enzymes which are absent in human cells. However, the neurotoxic effects of GBH have already been shown in many animal models. Further, these formulations were shown to disrupt the microbiome of different species. Here, we investigated the effects of a lifelong exposure to low doses of the GBH-RUp on the gut environment, including morphological and microbiome changes. We also aimed to determine whether exposure to GBH-RUp could harm the developing brain and lead to behavioral changes in adult mice. To this end, animals were exposed to GBH-RUp in drinking water from pregnancy to adulthood. GBH-RUp-exposed mice had no changes in cognitive function, but developed impaired social behavior and increased repetitive behavior. GBH-Rup-exposed mice also showed an activation of phagocytic cells (Iba-1-positive) in the cortical brain tissue. GBH-RUp exposure caused increased mucus production and the infiltration of plama cells (CD138-positive), with a reduction in phagocytic cells. Long-term exposure to GBH-RUp also induced changes in intestinal integrity, as demonstrated by the altered expression of tight junction effector proteins (ZO-1 and ZO-2) and a change in the distribution of syndecan-1 proteoglycan. The herbicide also led to changes in the gut microbiome composition, which is also crucial for the establishment of the intestinal barrier. Altogether, our findings suggest that long-term GBH-RUp exposure leads to morphological and functional changes in the gut, which correlate with behavioral changes that are similar to those observed in patients with neurodevelopmental disorders.

Acupuncture at ST36 Alleviates the Behavioral Disorder of Autistic Rats by Inhibiting TXNIP-Mediated Activation of NLRP3

Autism is a common neurodevelopmental disorder that severely affects patients' quality of life. We aimed to investigate whether acupuncture at Zusanli (ST36) could alleviate the behavior disorder of autistic rats by inhibiting thioredoxin-interacting protein (TXNIP)-mediated activation of NLRP3. An autism model was induced by intraperitoneal injection of pregnant rats with valproic acid (VPA). The pups' behaviors were analyzed using hot plate, open field, Morris water maze, and 3-chamber social interaction tests. Nissl staining was used to visualize neurons in prefrontal cortex. Levels of TXNIP, NLRP3, interleukin (IL)-1β, and caspase were determined by Western blot or quantitative real-time PCR. After ST36 acupuncture, pain sensitivity, autonomous activity, sociability index, sociability preference index, and learning and memory were improved in the autism model rats. Levels of TXNIP, NLRP3, IL-1β, and caspase 1 were decreased after acupuncture. Interference with TXNIP alleviated the behavior disorders and inhibited NLRP3, caspase 1, and IL-1β levels. In summary, ST36 acupuncture reduced TXNIP expression, inhibited the activation of the NLRP3 inflammasome, and alleviated the behavior disorder related to the prefrontal cortex of the autistic rats. These results point to a potential mechanism for acupuncture-induced improvement of autistic behavioral disorders.

Maternal Immune Activation and Interleukin 17A in the Pathogenesis of Autistic Spectrum Disorder and Why It Matters in the COVID-19 Era

Autism spectrum disorder (ASD) is the commonest neurodevelopmental disability. It is a highly complex disorder with an increasing prevalence and an unclear etiology. Consensus indicates that ASD arises as a genetically modulated, and environmentally influenced condition. Although pathogenic rare genetic variants are detected in around 20% of cases of ASD, no single factor is responsible for the vast majority of ASD cases or that explains their characteristic clinical heterogeneity. However, a growing body of evidence suggests that ASD susceptibility involves an interplay between genetic factors and environmental exposures. One such environmental exposure which has received significant attention in this regard is maternal immune activation (MIA) resulting from bacterial or viral infection during pregnancy. Reproducible rodent models of ASD are well-established whereby induction of MIA in pregnant dams, leads to offspring displaying neuroanatomical, functional, and behavioral changes analogous to those seen in ASD. Blockade of specific inflammatory cytokines such as interleukin-17A during gestation remediates many of these observed behavioral effects, suggesting a causative or contributory role. Here, we review the growing body of animal and human-based evidence indicating that interleukin-17A may mediate the observed effects of MIA on neurodevelopmental outcomes in the offspring. This is particularly important given the current corona virus disease-2019 (COVID-19) pandemic as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during pregnancy is a potent stimulator of the maternal immune response, however the long-term effects of maternal SARS-CoV-2 infection on neurodevelopmental outcomes is unclear. This underscores the importance of monitoring neurodevelopmental outcomes in children exposed to SARS-CoV-2-induced MIA during gestation.

The Zonulin-transgenic mouse displays behavioral alterations ameliorated via depletion of the gut microbiota

The gut-brain axis hypothesis suggests that interactions in the intestinal milieu are critically involved in regulating brain function. Several studies point to a gut-microbiota-brain connection linking an impaired intestinal barrier and altered gut microbiota composition to neurological disorders involving neuroinflammation. Increased gut permeability allows luminal antigens to cross the gut epithelium, and via the blood stream and an impaired blood-brain barrier (BBB) enters the brain impacting its function. Pre-haptoglobin 2 (pHP2), the precursor protein to mature HP2, is the first characterized member of the zonulin family of structurally related proteins. pHP 2 has been identified in humans as the thus far only endogenous regulator of epithelial and endothelial tight junctions (TJs). We have leveraged the Zonulin-transgenic mouse (Ztm) that expresses a murine pHP2 (zonulin) to determine the role of increased gut permeability and its synergy with a dysbiotic intestinal microbiota on brain function and behavior. Here we show that Ztm mice display sex-dependent behavioral abnormalities accompanied by altered gene expression of BBB TJs and increased expression of brain inflammatory genes. Antibiotic depletion of the gut microbiota in Ztm mice downregulated brain inflammatory markers ameliorating some anxiety-like behavior. Overall, we show that zonulin-dependent alterations in gut permeability and dysbiosis of the gut microbiota are associated with an altered BBB integrity, neuroinflammation, and behavioral changes that are partially ameliorated by microbiota depletion. Our results suggest the Ztm model as a tool for the study of the cross-talk between the microbiome/gut and the brain in the context of neurobehavioral/neuroinflammatory disorders.

Effects of chronic exposure to bisphenol A in adult female mice on social behavior, vasopressin system, and estrogen membrane receptor (GPER1)

Bisphenol A (BPA), an organic synthetic compound found in some plastics and epoxy resins, is classified as an endocrine disrupting chemical. Exposure to BPA is especially dangerous if it occurs during specific "critical periods" of life, when organisms are more sensitive to hormonal changes (i.e., intrauterine, perinatal, juvenile or puberty periods). In this study, we focused on the effects of chronic exposure to BPA in adult female mice starting during pregnancy. Three months old C57BL/6J females were orally exposed to BPA or to vehicle (corn oil). The treatment (4 µg/kg body weight/day) started the day 0 of pregnancy and continued throughout pregnancy, lactation, and lasted for a total of 20 weeks. BPA-treated dams did not show differences in body weight or food intake, but they showed an altered estrous cycle compared to the controls. In order to evidence alterations in social and sociosexual behaviors, we performed the Three-Chamber test for sociability, and analyzed two hypothalamic circuits (well-known targets of endocrine disruption) particularly involved in the control of social behavior: the vasopressin and the oxytocin systems. The test revealed some alterations in the displaying of social behavior: BPA-treated dams have higher locomotor activity compared to the control dams, probably a signal of high level of anxiety. In addition, BPA-treated dams spent more time interacting with no-tester females than with no-tester males. In brain sections, we observed a decrease of vasopressin immunoreactivity (only in the paraventricular and suprachiasmatic nuclei) of BPA-treated females, while we did not find any alteration of the oxytocin system. In parallel, we have also observed, in the same hypothalamic nuclei, a significant reduction of the membrane estrogen receptor GPER1 expression.

Effects of catechin on a rodent model of autism spectrum disorder: implications for the role of nitric oxide in neuroinflammatory pathway

AIM

The present research work aims at deciphering the involvement of nitric oxide pathway and its modulation by ( ±)catechin hydrate in experimental paradigm of autism spectrum disorders (ASD).

METHOD

An intracerebroventricular infusion of 4 μl of 1 M propanoic acid was given in the anterior region of the lateral ventricle to induce autism-like phenotype in male rats. Oral administration of ( ±)catechin hydrate (25, 50, and 100 mg/kg) was initiated from the 3rd day lasting till the 28th day. L-NAME (50 mg/kg) and L-arginine (800 mg/kg) were also given individually as well as in combination to explore the ability of ( ±)catechin hydrate to act via nitric oxide pathway. Behavior test for sociability, stereotypy, anxiety, depression, and novelty, repetitive, and perseverative behavior was carried out between the 14th and 28th day. On the 29th day, animals were sacrificed, and levels of mitochondrial complexes and oxidative stress parameters were evaluated. We also estimated the levels of neuroinflammatory and apoptotic markers such as TNF-α, IL-6, NF-κB, IFN-γ, HSP-70, and caspase-3. To evaluate the involvement of nitric oxide pathway, the levels of iNOS and homocysteine were estimated.

RESULTS

Treatment with ( ±)catechin hydrate significantly ameliorated behavioral, biochemical, neurological, and molecular deficits. Hence, ( ±)catechin hydrate has potential to be used as neurotherapeutic agent in ASD targeting nitric oxide pathway-mediated oxidative and nitrosative stress responsible for behavioral, biochemical, and molecular alterations via modulating nitric oxide pathway.

CONCLUSION

The evaluation of the levels of iNOS and homocysteine conclusively establishes the role of nitric oxide pathway in causing behavioral, biochemical, and molecular deficits and the beneficial effect of ( ±)catechin hydrate in restoring these alterations.

A systematic-review of olfactory deficits in neurodevelopmental disorders: From mouse to human

Olfactory impairment is a common clinical motif across neurodevelopmental disorders, suggesting olfactory circuits are particularly vulnerable to disease processes and can provide insight into underlying disease mechanisms. The mouse olfactory bulb is an ideal model system to study mechanisms of neurodevelopmental disease due to its anatomical accessibility, behavioral relevance, ease of measuring circuit input and output, and the feature of adult neurogenesis. Despite the clinical relevance and experimental benefits, olfactory testing across animal models of neurodevelopmental disease has been inconsistent and non-standardized. Here we performed a systematic literature review of olfactory function testing in mouse models of neurodevelopmental disorders, and identified intriguing inconsistencies that include evidence for both increased and decreased acuity in odor detection in various mouse models of Autism Spectrum Disorder (ASD). Based on our identified gaps in the literature, we recommend direct comparison of different mouse models of ASD using standardized tests for odor detection and discrimination. This review provides a framework to guide future olfactory function testing in mouse models of neurodevelopmental diseases.

Genetic disruption of Grm5 causes complex alterations in motor activity, anxiety and social behaviors

Autism is a neurodevelopmental disorder characterized by impaired social interactions and restricted and repetitive behaviors. Although group 1 metabotropic glutamate receptors (mGluRs), and in particular mGluR5, have been extensively proposed as potential targets for intervention in autism and other neurodevelopmental disorders, there has not been a comprehensive analysis of the effect of mGluR5 loss on behaviors typically assessed in autism mouse models thought to be correlates of behavioral symptoms of human disorders. Here we present a behavioral characterization of mice with complete or partial loss of mGluR5 (homozygous or heterozygous null mutations in Grm5 gene). We tested several autism related behaviors including social interaction, repetitive grooming, digging and locomotor behaviors. We found that digging and marble burying behaviors were almost completely abolished in mGluR5 ko mice, although self-grooming was not altered. Social interaction was impaired in ko but not in heterozygote (het) mice. In tests of locomotor activity and anxiety related behaviors, mGluR5 ko mice exhibited hyperactivity and reduced anxiety in the open field test but unexpectedly, showed hypoactivity in the elevated zero-maze test. There was no impairment in motor learning in the accelerating rotarod in both ko and het mutant. Together these results provide support for the importance of mGluR5 in motor and social behaviors that are specifically affected in autism disorders.

Differential effects by sex with Kmt5b loss

Lysine methyl transferase 5B (KMT5B) has been recently highlighted as a risk gene in genetic studies of neurodevelopmental disorders (NDDs), specifically, autism spectrum disorder (ASD) and intellectual disability (ID); yet, its role in the brain is not known. The goal of this work was to neurodevelopmentally characterize the effect(s) of KMT5B haploinsufficiency using a mouse model. A Kmt5b gene-trap mouse line was obtained from the Knockout Mouse Project. Wild type (WT) and heterozygous (HET) mice were subjected to a comprehensive neurodevelopmental test battery to assess reflexes, motor behavior, learning/memory, social behavior, repetitive movement, and common ASD comorbidities (obsessive compulsion, depression, and anxiety). Given the strong sex bias observed in the ASD patient population, we tested both a male and female cohort of animals and compared differences between genotypes and sexes. HET mice were significantly smaller than WT littermates starting at postnatal day 10 through young adulthood which was correlated with smaller brain size (i.e., microcephaly). This was more severe in males than females. HET male neonates also had delayed eye opening and significantly weaker reflexes than WT littermates. In young adults, significant differences between genotypes relative to anxiety, depression, fear, and extinction learning were observed. Interestingly, several sexually dimorphic differences were noted including increased repetitive grooming behavior in HET females and an increased latency to hot plate response in HET females versus a decreased latency in HET males. LAY SUMMARY: Lysine methyl transferase 5B (KMT5B) has been recently highlighted as a risk gene in neurodevelopmental disorders (NDDs), specifically, autism spectrum disorder (ASD) and intellectual disability (ID); yet its role in the brain is not known. Our study indicates that mice lacking one genomic copy of Kmt5b show deficits in neonatal reflexes, sociability, repetitive stress-induced grooming, changes in thermal pain sensing, decreased depression and anxiety, increased fear, slower extinction learning, and lower body weight, length, and brain size. Furthermore, several outcomes differed by sex, perhaps mirroring the sex bias in ASD.

Altered gut microbiome and autism like behavior are associated with parental high salt diet in male mice

Neurodevelopmental disorders are conditions caused by the abnormal development of the central nervous system. Autism spectrum disorder (ASD) is currently the most common form of such disorders, affecting 1% of the population worldwide. Despite its prevalence, the mechanisms underlying ASD are not fully known. Recent studies have suggested that the maternal gut microbiome can have profound effects on neurodevelopment. Considering that the gut microbial composition is modulated by diet, we tested the hypothesis that ASD-like behavior could be linked to maternal diet and its associated gut dysbiosis. Therefore, we used a mouse model of parental high salt diet (HSD), and specifically evaluated social and exploratory behaviors in their control-fed offspring. Using 16S genome sequencing of fecal samples, we first show that (1) as expected, HSD changed the maternal gut microbiome, and (2) this altered gut microbiome was shared with the offspring. More importantly, behavioral analysis of the offspring showed hyperactivity, increased repetitive behaviors, and impaired sociability in adult male mice from HSD-fed parents. Taken together, our data suggests that parental HSD consumption is strongly associated with offspring ASD-like behavioral abnormalities via changes in gut microbiome.

Assessment of autism-relevant behaviors in C57BKS/J leptin receptor deficient mice

Gestational diabetes mellitus (GDM) was associated with greater autism risk in epidemiological studies. Disrupted leptin signaling may contribute to their coincidence, as it is found in both disorders. Given this we examined leptin receptor (Lepr) deficient (BKS.Cg-Dock7^m +/+ Lepr^db/J diabetic (db)) heterozygous (db/+) mice for autism-relevant behaviors. BKS db/+ females are lean with normal blood glucose, but they develop GDM while pregnant. We hypothesized BKS db/+ offspring might exhibit physiological and behavior traits consistent with autism. Adolescent body weight, fasting blood glucose, serum corticosterone, social preferences, self-grooming, marble burying, social dominance and cognitive flexibility of BKS db/+ mice was compared to C57BLKS/J (BKS) and C57BL/6J (BL6) mice. Male db/+ weighed more and had higher blood glucose and corticosterone relative to BL6, but not BKS mice. Also, male db/+ lacked social interaction preference, explored arenas less, and buried more marbles than BL6, but not BKS males. Male and female db/+ were more dominant and made more mistakes in water T-mazes locating a sunken platform after its position was reversed than BL6, but not BKS mice. Overall BKS db/+, particularly males, exhibited some autism-like social deficits and restrictive-repetitive behaviors relative to BL6, but BKS strain contributions to BKS db/+ behaviors were evident. Since BKS db/+ and BKS behavioral and physiological phenotypes are already so similar, it will be difficult to use these models in studies designed to detect contributions of fetal GDM exposures to offspring behaviors.

The Multi-Targeting Ligand ST-2223 with Histamine H3 Receptor and Dopamine D2/D3 Receptor Antagonist Properties Mitigates Autism-Like Repetitive Behaviors and Brain Oxidative Stress in Mice

Autism spectrum disorder (ASD) is a complex heterogeneous neurodevelopmental disorder characterized by social and communicative impairments, as well as repetitive and restricted behaviors (RRBs). With the limited effectiveness of current pharmacotherapies in treating repetitive behaviors, the present study determined the effects of acute systemic treatment of the novel multi-targeting ligand ST-2223, with incorporated histamine H₃ receptor (H₃R) and dopamine D₂/D₃ receptor affinity properties, on ASD-related RRBs in a male Black and Tan BRachyury (BTBR) mouse model of ASD. ST-2223 (2.5, 5, and 10 mg/kg, i.p.) significantly mitigated the increase in marble burying and self-grooming, and improved reduced spontaneous alternation in BTBR mice (all p < 0.05). Similarly, reference drugs memantine (MEM, 5 mg/kg, i.p.) and aripiprazole (ARP, 1 mg/kg, i.p.), reversed abnormally high levels of several RRBs in BTBR (p < 0.05). Moreover, ST-2223 palliated the disturbed anxiety levels observed in an open field test (all p < 0.05), but did not restore the hyperactivity parameters, whereas MEM failed to restore mouse anxiety and hyperactivity. In addition, ST-2223 (5 mg/kg, i.p.) mitigated oxidative stress status by decreasing the elevated levels of malondialdehyde (MDA), and increasing the levels of decreased glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) in different brain parts of treated BTBR mice (all p < 0.05). These preliminary in vivo findings demonstrate the ameliorative effects of ST-2223 on RRBs in a mouse model of ASD, suggesting its pharmacological prospective to rescue core ASD-related behaviors. Further confirmatory investigations on its effects on various brain neurotransmitters, e.g., dopamine and histamine, in different brain regions are still warranted to corroborate and expand these initial data.

Corticostriatal dysfunction and social interaction deficits in mice lacking the cystine/glutamate antiporter

The astrocytic cystine/glutamate antiporter system x_c^- represents an important source of extracellular glutamate in the central nervous system, with potential impact on excitatory neurotransmission. Yet, its function and importance in brain physiology remain incompletely understood. Employing slice electrophysiology and mice with a genetic deletion of the specific subunit of system x_c^-, xCT (xCT^-/- mice), we uncovered decreased neurotransmission at corticostriatal synapses. This effect was partly mitigated by replenishing extracellular glutamate levels, indicating a defect linked with decreased extracellular glutamate availability. We observed no changes in the morphology of striatal medium spiny neurons, the density of dendritic spines, or the density or ultrastructure of corticostriatal synapses, indicating that the observed functional defects are not due to morphological or structural abnormalities. By combining electron microscopy with glutamate immunogold labeling, we identified decreased intracellular glutamate density in presynaptic terminals, presynaptic mitochondria, and in dendritic spines of xCT^-/- mice. A proteomic and kinomic screen of the striatum of xCT^-/- mice revealed decreased expression of presynaptic proteins and abnormal kinase network signaling, that may contribute to the observed changes in postsynaptic responses. Finally, these corticostriatal deregulations resulted in a behavioral phenotype suggestive of autism spectrum disorder in the xCT^-/- mice; in tests sensitive to corticostriatal functioning we recorded increased repetitive digging behavior and decreased sociability. To conclude, our findings show that system x_c^- plays a previously unrecognized role in regulating corticostriatal neurotransmission and influences social preference and repetitive behavior.

KDM5A mutations identified in autism spectrum disorder using forward genetics

Autism spectrum disorder (ASD) is a constellation of neurodevelopmental disorders with high phenotypic and genetic heterogeneity, complicating the discovery of causative genes. Through a forward genetics approach selecting for defective vocalization in mice, we identified Kdm5a as a candidate ASD gene. To validate our discovery, we generated a Kdm5a knockout mouse model (Kdm5a^-/-) and confirmed that inactivating Kdm5a disrupts vocalization. In addition, Kdm5a^-/- mice displayed repetitive behaviors, sociability deficits, cognitive dysfunction, and abnormal dendritic morphogenesis. Loss of KDM5A also resulted in dysregulation of the hippocampal transcriptome. To determine if KDM5A mutations cause ASD in humans, we screened whole exome sequencing and microarray data from a clinical cohort. We identified pathogenic KDM5A variants in nine patients with ASD and lack of speech. Our findings illustrate the power and efficacy of forward genetics in identifying ASD genes and highlight the importance of KDM5A in normal brain development and function.

DNMT3A Haploinsufficiency Results in Behavioral Deficits and Global Epigenomic Dysregulation Shared across Neurodevelopmental Disorders

Mutations in DNA methyltransferase 3A (DNMT3A) have been detected in autism and related disorders, but how these mutations disrupt nervous system function is unknown. Here, we define the effects of DNMT3A mutations associated with neurodevelopmental disease. We show that diverse mutations affect different aspects of protein activity but lead to shared deficiencies in neuronal DNA methylation. Heterozygous DNMT3A knockout mice mimicking DNMT3A disruption in disease display growth and behavioral alterations consistent with human phenotypes. Strikingly, in these mice, we detect global disruption of neuron-enriched non-CG DNA methylation, a binding site for the Rett syndrome protein MeCP2. Loss of this methylation leads to enhancer and gene dysregulation that overlaps with models of Rett syndrome and autism. These findings define the effects of DNMT3A haploinsufficiency in the brain and uncover disruption of the non-CG methylation pathway as a convergence point across neurodevelopmental disorders.

Driessen T, J. Lee P, Tejwani L, Sami A, Nawaz M, Mehmood Baig S, Lim J, Kaukab Raja G. Genetic Risk of Autism Spectrum Disorder in a Pakistani Population

Autism spectrum disorder (ASD) is a group of complex multifactorial neurodevelopmental and neuropsychiatric disorders in children characterized by impairment of communication and social interaction. Several genes with associated single nucleotide polymorphisms (SNPs) have been identified for ASD in different genetic association studies, meta-analyses, and genome-wide association studies (GWAS). However, associations between different SNPs and ASD vary from population to population. Four SNPs in genes CNTNAP2, EIF4E, ATP2B2, CACNA1C, and SNP rs4307059 (which is found between CDH9 and CDH10 genes) have been identified and reported as candidate risk factors for ASD. The aim of the present study was, for the first time, to assess the association of SNPs in these genes with ASD in the Pakistani population. PCR-based genotyping was performed using allele-specific primers in 93 ASD and 93 control Pakistani individuals. All genetic associations, genotype frequencies, and allele frequencies were computed as odds’ ratios (ORs) using logistic regression with a threshold of p ≤ 0.01 to determine statistical significance. We found that the homozygous genotypes of mutant T alleles of CNTNAP2 and ATP2B2 were significantly associated with Pakistani ASD patients in unadjusted ORs (p < 0.01), but their significance score was lost in the adjusted model. Other SNPs such as rs4307059, rs17850950 of EIF4E, and rs1006737 of CACNA1C were not statistically significant. Based on this, we conclude that SNPs are not associated with, or are not the main cause of, autism in the Pakistani population, indicating the involvement of additional players, which need to be investigated in future studies in a large population size. One of the limitations of present study is its small sample size. However, this study, being the first on Pakistani ASD patients, may lay the foundations for future studies in larger samples.

Behavioral Phenotyping for Down Syndrome in Mice

Down syndrome (DS) is the most frequent genetic cause of intellectual disability, characterized by alterations in different behavioral symptom domains: neurodevelopment, motor behavior, and cognition. As mouse models have the potential to generate data regarding the neurological basis for the specific behavioral profile of DS, and may indicate pharmacological treatments with the potential to affect their behavioral phenotype, it is important to be able to assess disease-relevant behavioral traits in animal models in order to provide biological plausibility to the potential findings. The field is at a juncture that requires assessments that may effectively translate the findings acquired in mouse models to humans with DS. In this article, behavioral tests are described that are relevant to the domains affected in DS. A neurodevelopmental behavioral screen, the balance beam test, and the Multivariate Concentric Square Field test to assess multiple behavioral phenotypes and locomotion are described, discussing the ways to merge these findings to more fully understand cognitive strengths and weaknesses in this population. New directions for approaches to cognitive assessment in mice and humans are discussed. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Preweaning neurodevelopmental battery Basic Protocol 2: Balance beam Basic Protocol 3: Multivariate concentric square field test (MCSF).

Classifying sex and strain from mouse ultrasonic vocalizations using deep learning

Vocalizations are widely used for communication between animals. Mice use a large repertoire of ultrasonic vocalizations (USVs) in different social contexts. During social interaction recognizing the partner's sex is important, however, previous research remained inconclusive whether individual USVs contain this information. Using deep neural networks (DNNs) to classify the sex of the emitting mouse from the spectrogram we obtain unprecedented performance (77%, vs. SVM: 56%, Regression: 51%). Performance was even higher (85%) if the DNN could also use each mouse's individual properties during training, which may, however, be of limited practical value. Splitting estimation into two DNNs and using 24 extracted features per USV, spectrogram-to-features and features-to-sex (60%) failed to reach single-step performance. Extending the features by each USVs spectral line, frequency and time marginal in a semi-convolutional DNN resulted in a performance mid-way (64%). Analyzing the network structure suggests an increase in sparsity of activation and correlation with sex, specifically in the fully-connected layers. A detailed analysis of the USV structure, reveals a subset of male vocalizations characterized by a few acoustic features, while the majority of sex differences appear to rely on a complex combination of many features. The same network architecture was also able to achieve above-chance classification for cortexless mice, which were considered indistinguishable before. In summary, spectrotemporal differences between male and female USVs allow at least their partial classification, which enables sexual recognition between mice and automated attribution of USVs during analysis of social interactions.

Rapid well-plate assays for motor and social behaviors in larval zebrafish

Behavior phenotypes are a powerful means of uncovering subtle xenobiotic chemical impacts on vertebrate nervous system development. Rodents manifest complex and informative behavior phenotypes but are generally not practical models in which to screen large numbers of chemicals. Zebrafish recapitulate much of the behavioral complexity of higher vertebrates, develop externally and are amenable to assay automation. Short duration automated assays can be leveraged to screen large numbers of chemicals or comprehensive dose-response for fewer chemicals. Here we describe a series of mostly automated assays including larval photomotor response, strobe light response, blue color avoidance, shoaling and mirror stimulus-response performed on the ZebraBox (ViewPoint Behavior Technologies) instrument platform. To explore the sensitivity and uniqueness of each assay endpoint, larval cohorts from 5 to 28 days post fertilization were acutely exposed to several chemicals broadly understood to impact different neuro-activities. We highlight the throughput advantages of using the same instrument platform for multiple assays and the ability of different assays to detect unique phenotypes among different chemicals.

Prefrontal parvalbumin interneurons require juvenile social experience to establish adult social behavior

Social isolation during the juvenile critical window is detrimental to proper functioning of the prefrontal cortex (PFC) and establishment of appropriate adult social behaviors. However, the specific circuits that undergo social experience-dependent maturation to regulate social behavior are poorly understood. We identify a specific activation pattern of parvalbumin-positive interneurons (PVIs) in dorsal-medial PFC (dmPFC) prior to an active bout, or a bout initiated by the focal mouse, but not during a passive bout when mice are explored by a stimulus mouse. Optogenetic and chemogenetic manipulation reveals that brief dmPFC-PVI activation triggers an active social approach to promote sociability. Juvenile social isolation decouples dmPFC-PVI activation from subsequent active social approach by freezing the functional maturation process of dmPFC-PVIs during the juvenile-to-adult transition. Chemogenetic activation of dmPFC-PVI activity in the adult animal mitigates juvenile isolation-induced social deficits. Therefore, social experience-dependent maturation of dmPFC-PVI is linked to long-term impacts on social behavior.

Evaluating the stability of individual variation in social and nonsocial behavioural types using prairie voles (Microtus ochrogaster)

Prairie voles (Microtus ochrogaster) exhibit remarkable individual variation in social behaviour, suggesting differences in behavioural types. To date, however, there has been little assessment of whether these behavioural types are stable across test sessions, nor to what extent internal states and external contexts (domains) drive individual differences. Here we examined the individual consistency of social (huddling) and non-social (distance moved) behaviour across repeated, long-duration tests, in same-sex cagemate (SS-CM), same-sex stranger (SS-S), opposite-sex stranger (OS-S), and standard partner preference test (PPT) contexts. The SS-CM and SS-S tests were repeated multiple times (SS-CM 1-2; SS-S 1-5) to assess state-dependent variation. A second cohort was used to determine the replicability of findings. Overall, there was a general lack of stability in huddling behavior. It was inconsistent across repeated sessions of the same test type and between types of tests, suggesting a strong contribution of state-dependent variation. Non-social behaviour was more consistent and appeared more domain-dependent and less state-dependent than huddling. Translational and comparative studies of individual variation would likely benefit from testing across multiple contexts and employing repetitive testing paradigms to account for state-dependent variation.

Flexible and Lightweight Devices for Wireless Multi-Color Optogenetic Experiments Controllable via Commercial Cell Phones

Optogenetics provide a potential alternative approach to the treatment of chronic pain, in which complex pathology often hampers efficacy of standard pharmacological approaches. Technological advancements in the development of thin, wireless, and mechanically flexible optoelectronic implants offer new routes to control the activity of subsets of neurons and nerve fibers in vivo. This study reports a novel and advanced design of battery-free, flexible, and lightweight devices equipped with one or two miniaturized LEDs, which can be individually controlled in real time. Two proof-of-concept experiments in mice demonstrate the feasibility of these devices. First, we show that blue-light devices implanted on top of the lumbar spinal cord can excite channelrhodopsin expressing nociceptors to induce place aversion. Second, we show that nocifensive withdrawal responses can be suppressed by green-light optogenetic (Archaerhodopsin-mediated) inhibition of action potential propagation along the sciatic nerve. One salient feature of these devices is that they can be operated via modern tablets and smartphones without bulky and complex lab instrumentation. In addition to the optical stimulation, the design enables the simultaneously wireless recording of the temperature in proximity of the stimulation area. As such, these devices are primed for translation to human patients with implications in the treatment of neurological and psychiatric conditions far beyond chronic pain syndromes.

CYFIP1 overexpression increases fear response in mice but does not affect social or repetitive behavioral phenotypes

Background

CYFIP1, a protein that interacts with FMRP and regulates protein synthesis and actin dynamics, is overexpressed in Dup15q syndrome as well as autism spectrum disorder (ASD). While CYFIP1 heterozygosity has been rigorously studied due to its loss in 15q11.2 deletion, Prader-Willi and Angelman syndrome, the effects of CYFIP1 overexpression, as is observed in patients with CYFIP1 duplication, are less well understood.

Methods

We developed and validated a mouse model of human CYFIP1 overexpression (CYFIP1 OE) using qPCR and western blot analysis. We performed a large battery of behavior testing on these mice, including ultrasonic vocalizations, three-chamber social assay, home-cage behavior, Y-maze, elevated plus maze, open field test, Morris water maze, fear conditioning, prepulse inhibition, and the hot plate assay. We also performed RNA sequencing and analysis on the basolateral amygdala.

Results

Extensive behavioral testing in CYFIP1 OE mice reveals no changes in the core behaviors related to ASD: social interactions and repetitive behaviors. However, we did observe mild learning deficits and an exaggerated fear response. Using RNA sequencing of the basolateral amygdala, a region associated with fear response, we observed changes in pathways related to cytoskeletal regulation, oligodendrocytes, and myelination. We also identified GABA-A subunit composition changes in basolateral amygdala neurons, which are essential components of the neural fear conditioning circuit.

Conclusion

Overall, this research identifies the behavioral and molecular consequences of CYFIP1 overexpression and how they contribute to the variable phenotype seen in Dup15q syndrome and in ASD patients with excess CYFIP1.