Autism Spectrum Disorders: Translating human deficits into mouse behavior

Effects of agmatine on radial-arm maze memory performance and autistic-like behaviors in a male rat model of autism

BACKGROUND

Autism spectrum disorder (ASD) is the fastest-growing child neuropsychiatric condition. Cognitive dysfunctions such as memory impairments are experienced by patients along with social disturbances and repetitive/stereotypic movements. We have used the radial arm maze (RAM), for measurement of working and reference memory errors in an animal model of autism. In addition, the potential effects of agmatine, an endogenous NMDA antagonist, on RAM performance and autistic-like behaviors were assessed.

METHODS

Autism was modeled by valproic acid (VPA) administration at gestational Day 12.5. Autism-associated behaviors in male offspring were examined in an open field test (OFT) and three-chambered test (TCT) on postnatal days 50-51. Thereafter, the animals were trained in the RAM (PND 55) until they attained the criteria of 80% correct choices during five consecutive trials. Forty-eight hours after the acquisition of criteria, agmatine was injected 30 min before subsequent behavioral testing, which included the retention phase of the RAM, OFT, and TCT.

RESULTS

VPA-treated and intact rats showed the same performance in RAM, and acute injection of agmatine rescued social and anxiety-like behavior induced by VPA without the effect on RAM.

CONCLUSION

In a rat model of autism, spatial learning, and memory did not change. Agmatine rescued social and anxiety-like behavior in autistic animals.

Dynamic Foraging Behavior Performance Is Not Affected by Scn2a Haploinsufficiency

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

Behavioral characterization of Capn15 conditional knockout mice

Calpain 15 (CAPN15) is an intracellular cysteine protease belonging to the non-classical small optic lobe (SOL) family of calpains, which has an important role in development. Loss of Capn15 in mice leads to developmental eye anomalies and volumetric changes in the brain. Human individuals with biallelic variants in CAPN15 have developmental delay, neurodevelopmental disorders, as well as congenital malformations. In Aplysia, a reductionist model to study learning and memory, SOL calpain is important for non-associative long-term facilitation, the cellular analog of sensitization behavior. However, how CAPN15 is involved in adult behavior or learning and memory in vertebrates is unknown. Here, using Capn15 conditional knockout mice, we show that loss of the CAPN15 protein in excitatory forebrain neurons reduces self-grooming and marble burying, decreases performance in the accelerated roto-rod and reduces pre-tone freezing after strong fear conditioning. Thus, CAPN15 plays a role in regulating behavior in the adult mouse.

Microbial metabolites regulate social novelty via CaMKII neurons in the BNST

Social novelty is a cognitive process that is essential for animals to interact strategically with conspecifics based on their prior experiences. The commensal microbiome in the gut modulates social behavior through various routes, including microbe-derived metabolite signaling. Short-chain fatty acids (SCFAs), metabolites derived from bacterial fermentation in the gastrointestinal tract, have been previously shown to impact host behavior. Herein, we demonstrate that the delivery of SCFAs directly into the brain disrupts social novelty through distinct neuronal populations. We are the first to observe that infusion of SCFAs into the lateral ventricle disrupted social novelty in microbiome-depleted mice without affecting brain inflammatory responses. The deficit in social novelty can be recapitulated by activating calcium/calmodulin-dependent protein kinase II (CaMKII)-labeled neurons in the bed nucleus of the stria terminalis (BNST). Conversely, chemogenetic silencing of the CaMKII-labeled neurons and pharmacological inhibition of fatty acid oxidation in the BNST reversed the SCFAs-induced deficit in social novelty. Our findings suggest that microbial metabolites impact social novelty through a distinct neuron population in the BNST.

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.

The Shank3-InsG3680(+/+) mouse model of autism spectrum disorder displays auditory avoidance in a novel behavioral test

Introduction

Autism spectrum disorder (ASD) is characterized by deficits in communication and social interaction, restricted interests, repetitive behaviors, and sensory alterations, with auditory hypersensitivity being one of the most commonly reported sensory-perceptual abnormalities. Several candidate genes for involvement in this disorder have emerged from patient studies, including SHANK3, a gene that encodes a protein (SHANK3) in the postsynaptic density of excitatory synapses. Previous work has shown that mutant mice carrying a human ASD mutation in the Shank3 gene (InsG3680) exhibit repetitive behaviors and social interaction deficits, indicating important construct and face validity for this genotype as an animal model of ASD.

Methods

To further address whether these mice also present auditory sensory-perceptual alterations, we developed a novel behavioral test in which mice can choose between different soundscapes.

Results

Our results reveal that, in comparison to wild-type mice, Shank3 mutants display a strong behavioral preference toward silent regions of the arena.

Discussion

These data suggest that Shank3- mutant mice might express an auditory hypersensitivity phenotype, further adding to the face validity of this genotype as an animal model of ASD.

16p11.2 deletion mice exhibit compromised fronto-temporal connectivity, GABAergic dysfunction, and enhanced attentional ability

Autism spectrum disorders are more common in males, and have a substantial genetic component. Chromosomal 16p11.2 deletions in particular carry strong genetic risk for autism, yet their neurobiological impact is poorly characterised, particularly at the integrated systems level. Here we show that mice reproducing this deletion (16p11.2 DEL mice) have reduced GABAergic interneuron gene expression (decreased parvalbumin mRNA in orbitofrontal cortex, and male-specific decreases in Gad67 mRNA in parietal and insular cortex and medial septum). Metabolic activity was increased in medial septum, and in its efferent targets: mammillary body and (males only) subiculum. Functional connectivity was altered between orbitofrontal, insular and auditory cortex, and between septum and hippocampus/subiculum. Consistent with this circuit dysfunction, 16p11.2 DEL mice showed reduced prepulse inhibition, but enhanced performance in the continuous performance test of attentional ability. Level 1 autistic individuals show similarly heightened performance in the equivalent human test, also associated with parietal, insular-orbitofrontal and septo-subicular dysfunction. The data implicate cortical and septal GABAergic dysfunction, and resulting connectivity changes, as the cause of pre-attentional and attentional changes in autism.

Role of SHANK3 in concentrated ambient PM2. 5 exposure induced autism-like phenotype

Perinatal air pollution plays an important role in the development of autism. However, research on the pathogenic mechanism remains limited. In this study, the model of systemic inhalation of concentrated approximately 8-fold the level (mean concentration was 224 μg/m³) reported in ambient outdoor air of PM2.5 (particulate matters that are 2.5 μm or less in diameter)in early-postnatal male Sprague-Dawley (SD) rats was established. Through a series of autism-related behavioral tests, it was identified that young rats (postnatal day 1-day21, named PND1-PND21) exposed to PM2.5 exhibited typical autistic phenotypes, such as impaired language communication, abnormal repetitive and stereotyped behaviors, and impaired social skills. Moreover, synaptic abnormalities have been found in the brain tissues of young rats exposed to PM2.5. In terms of the molecular mechanism, we found that the levels of SH3 and multiple ankyrin repeat domains 3 (SHANK3) expression and key molecular proteins in the downstream signaling pathways were decreased in the brain tissues of the exposed rats. Finally, at the epigenetic level, SHANK3 methylation levels were increased in young rats exposed to PM2.5. In conclusion, the study revealed that PM2.5 exposure might induce the early postnatal autism through the SHANK3 signaling pathway by affecting the SHANK3 methylation levels and reducing the SHANK3 expression levels. The study could provide new ideas for autism etiology and a theoretical basis for the prevention and treatment of autism in children.

Sex-Related Changes in the Clinical, Genetic, Electrophysiological, Connectivity, and Molecular Presentations of ASD: A Comparison between Human and Animal Models of ASD with Reference to Our Data

The etiology of autism spectrum disorder (ASD) is genetic, environmental, and epigenetic. In addition to sex differences in the prevalence of ASD, which is 3-4 times more common in males, there are also distinct clinical, molecular, electrophysiological, and pathophysiological differences between sexes. In human, males with ASD have more externalizing problems (i.e., attention-deficit hyperactivity disorder), more severe communication and social problems, as well as repetitive movements. Females with ASD generally exhibit fewer severe communication problems, less repetitive and stereotyped behavior, but more internalizing problems, such as depression and anxiety. Females need a higher load of genetic changes related to ASD compared to males. There are also sex differences in brain structure, connectivity, and electrophysiology. Genetic or non-genetic experimental animal models of ASD-like behavior, when studied for sex differences, showed some neurobehavioral and electrophysiological differences between male and female animals depending on the specific model. We previously carried out studies on behavioral and molecular differences between male and female mice treated with valproic acid, either prenatally or early postnatally, that exhibited ASD-like behavior and found distinct differences between the sexes, the female mice performing better on tests measuring social interaction and undergoing changes in the expression of more genes in the brain compared to males. Interestingly, co-administration of S-adenosylmethionine alleviated the ASD-like behavioral symptoms and the gene-expression changes to the same extent in both sexes. The mechanisms underlying the sex differences are not yet fully understood.

Transient reduction in dendritic spine density in brain-specific profilin1 mutant mice is associated with behavioral deficits

Actin filaments form the backbone of dendritic spines, the postsynaptic compartment of most excitatory synapses in the brain. Spine density changes affect brain function, and postsynaptic actin defects have been implicated in various neuropathies. It is mandatory to identify the actin regulators that control spine density. Based on previous studies, we hypothesized a role for the actin regulator profilin1 in spine formation. We report reduced hippocampal spine density in juvenile profilin1 mutant mice together with impairments in memory formation and reduced ultrasonic communication during active social behavior. Our results, therefore, underline a previously suggested function of profilin1 in controlling spine formation and behavior in juvenile mice.

Autism-like symptoms by exposure to air pollution and valproic acid-induced in male rats

Exposure to air pollution during prenatal or neonatal periods is associated with autism spectrum disorder (ASD) according to epidemiology studies. Furthermore, prenatal exposure to valproic acid (VPA) has also been found to be associated with an increased prevalence of ASD. To assess the association between simultaneous exposure to VPA and air pollutants, seven exposure groups of rats were included in current study (PM2.5 and gaseous pollutants exposed - high dose of VPA (PGE-high); PM2.5 and gaseous pollutants exposed - low dose of VPA (PGE-low); gaseous pollutants only exposed - high dose of VPA (GE-high); gaseous pollutants only exposed - low dose of VPA (GE-low); clean air exposed - high dose of VPA (CAE-high); clean air exposed - low dose of VPA (CAE-low) and clean air exposed (CAE)). The pollution-exposed rats were exposed to air pollutants from embryonic day (E0) to postnatal day 42 (PND42). In all the induced groups, decreased oxidative stress biomarkers, decreased oxytocin receptor (OXTR) levels, and increased the expression of interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor alpha (TNF-α) were found. The volumes of the cerebellum, hippocampus, striatum, and prefrontal decreased in all induced groups in comparison to CAE. Additionally, increased numerical density of glial cells and decreased of numerical density of neurons were found in all induced groups. Results show that simultaneous exposure to air pollution and VPA can cause ASD-related behavioral deficits and air pollution reinforced the mechanism of inducing ASD ̉s in VPA-induced rat model of autism.

A dorsal CA2 to ventral CA1 circuit contributes to oxytocinergic modulation of long-term social recognition memory

Background

Social recognition memory (SRM) is the ability to distinguish familiar from novel conspecifics and is crucial for survival and reproductive success across social species. We previously reported that oxytocin (OXT) receptor (OXTR) signaling in the CA2/CA3a of dorsal hippocampus is essential to promote the persistence of long-term SRM, yet how the endogenous OXT system influences CA2 outputs to regulate long-term SRM formation remains unclear.

Methods

To achieve a selective deletion of CA2 OXTRs, we crossed Amigo2-Cre mice with Oxtr-floxed mice to generate CA2-specific Oxtr conditional knockout (Oxtr^−/−) mice. A three-chamber paradigm test was used for studying SRM in mice. Chemogenetic and optogenetic targeting strategies were employed to manipulate neuronal activity.

Results

We show that selective ablation of Oxtr in the CA2 suffices to impair the persistence of long-term SRM but has no effect on sociability and social novelty preference in the three-chamber paradigm test. We find that cell-type specific activation of OXT neurons within the hypothalamic paraventricular nucleus enhances long-term SRM and this enhancement is blocked by local application of OXTR antagonist L-368,899 into dorsal hippocampal CA2 (dCA2) region. In addition, chemogenetic neuronal silencing in dCA2 demonstrated that neuronal activity is essential for forming long-term SRM. Moreover, chemogenetic terminal-specific inactivation reveals a crucial role for dCA2 outputs to ventral CA1 (vCA1), but not dorsal lateral septum, in long-term SRM. Finally, targeted activation of the dCA2-to-vCA1 circuit effectively ameliorates long-term SRM deficit observed in Oxtr^−/− mice.

Conclusions

These findings highlight the importance of hippocampal CA2 OXTR signaling in governing the persistence of long-term SRM and identify a hippocampal circuit linking dCA2 to vCA1 necessary for controlling long-term SRM formation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-022-00834-x.

Autism spectrum disorder-like behavior induced in rat offspring by perinatal exposure to di-(2-ethylhexyl) phthalate

Autism spectrum disorders (ASD), also known as childhood autism, is a common neurological developmental disorder. Although it is generally believed that genetic factors are a primary cause for ASD development, more and more studies show that an increasing number of ASD diagnoses are related to environmental exposure. Epidemiological studies indicated that perinatal exposure to endocrine disruptors might cause neurodevelopmental disorders in children. Di-(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in many products. To explore the neurodevelopmental effect induced by perinatal exposure to DEHP on rat offspring, and the potential mechanisms, female Wistar rats were exposed to 1, 10, and 100 mg/kg/day DEHP during pregnancy and lactation, while valproic acid (VPA) was used as a positive control. The behavior tests showed that rat pups exposed to VPA and 100 mg/kg/day DEHP were not good as those from the control group in both their socialability and social novelty. Expression of mTOR pathway-related components increased while the number of autophagosomes decreased in the brain tissue of the rat offspring exposed to 100 mg/kg/day DEHP. In addition, perinatal exposure to DEHP at all dosages decreased the level of autophagy proteins LC3II and Beclin1 in the brain tissue of rat pups. Our results indicated that perinatal DEHP exposure would induce ASD-like behavioral changes in rat offspring, which might be mediated by activation of the mTOR signaling pathway, and inhibition of autophagy in the brain.

Mice lacking full length Adgrb1 (Bai1) exhibit social deficits, increased seizure susceptibility, and altered brain development

The adhesion G protein-coupled receptor BAI1/ADGRB1 plays an important role in suppressing angiogenesis, mediating phagocytosis, and acting as a brain tumor suppressor. BAI1 is also a critical regulator of dendritic spine and excitatory synapse development and interacts with several autism-relevant proteins. However, little is known about the relationship between altered BAI1 function and clinically relevant phenotypes. Therefore, we studied the effect of reduced expression of full length Bai1 on behavior, seizure susceptibility, and brain morphology in Adgrb1 mutant mice. We compared homozygous (Adgrb1-/-), heterozygous (Adgrb1+/-), and wild-type (WT) littermates using a battery of tests to assess social behavior, anxiety, repetitive behavior, locomotor function, and seizure susceptibility. We found that Adgrb1-/- mice showed significant social behavior deficits and increased vulnerability to seizures. Adgrb1-/- mice also showed delayed growth and reduced brain weight. Furthermore, reduced neuron density and increased apoptosis during brain development were observed in the hippocampus of Adgrb1-/- mice, while levels of astrogliosis and microgliosis were comparable to WT littermates. These results show that reduced levels of full length Bai1 is associated with a broader range of clinically relevant phenotypes than previously reported.

Sex-Dependent Social and Repetitive Behavior and Neurochemical Profile in Mouse Model of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by deficits in social interaction, impaired communication, and repetitive behaviors. ASD presents a 3:1 ratio of diagnosed boys and girls, raising the question regarding sexual dimorphic mechanisms underlying ASD symptoms, and their molecular basis. Here, we performed in vivo proton magnetic resonance spectroscopy in juvenile male and female Tsc2^+/- mice (an established genetic animal model of ASD). Moreover, behavior and ultrasonic vocalizations during social and repetitive tasks were analyzed. We found significant sexual dimorphisms in the levels of metabolites in the hippocampus and prefrontal cortex. Further, we observed that female mutant animals had a differential social behavior and presented an increase in repetitive behavior. Importantly, while mutant females displayed a more simplified communication during social tasks, mutant males exhibited a similar less complex vocal repertoire but during repetitive tasks. These results hint toward sex-dependent alterations in molecular and metabolic pathways, which can lead to the sexual dimorphic behaviors and communication observed in social and repetitive environments.

6-Shogaol improves behavior and memory in Wistar rats prenatally exposed to lipopolysaccharide

OBJECTIVE

6-Shogaol, bioactive compound of Zingiber officinale Roscoe, has anti-inflammatory, antioxidant, and neuroprotective properties. The objective of the present study was to verify the effect of 6-shogaol on behavioral parameters in a preclinical model based on a maternal immune activation (MIA) by lipopolysaccharide (LPS).

METHODOLOGY

Twelve pregnant Wistar rats received 100-μg/kg LPS or saline solution on gestational day (GD) 9.5. Male offspring participated in the study and in the postnatal day (PND) 30 and 55 were supplemented with 6-shogaol or saline solution, by gavage at a dose of 10 mg/kg/day, orally for 5 days. In the PND 35 and 60 was performed the behavioral tests: grooming, crossing, and rearing that evaluated repetitive movements, anxiety, and interest in the new, respectively, and the inhibitory avoidance test that evaluated short-term (STM) and long-term memory (LTM).

RESULT

Prenatal exposure to LPS increased the grooming and crossing episodes at different ages and reduced rearing episodes in PND 37. Treatment with 6-shogaol reversed these parameters. In the inhibitory avoidance test, an improvement of memory was identified with 6-shogaol in the STM and LTM at both ages comparing training and test session of treated groups and between groups.

CONCLUSION

Administration of 6-shogaol reverses the stereotypy, exploratory behavior, and memory impairment in prenatal LPS-exposed offspring, acting as a promising therapeutic component against brain disorders associated with the process of MIA.

An overview of modeling and behavioral assessment of autism in the rodent

Autism Spectrum Disorders (ASDs) are common neurodevelopmental disorders with a growing incidence that generally present in the first 3 years of life. Behavioral symptoms, including impaired social interaction and increased repetitive or stereotypic movements, are hallmark characteristics of autism. Animal models are research tools used to study the biology of the disease and to develop new therapeutic approaches. The complexity of the etiology of autism makes it challenging to develop a comprehensive animal model that accurately mimics different clinical aspects of autism. Here, we reviewed the literature on modeling and behavioral assessment of autism in the rodent, and focused on ASD behavioral phenotypes that can be modeled in rodents. These animal models can be effective in gaining a better understanding of the pathophysiology of the disease.

Dual Profile of Environmental Enrichment and Autistic-Like Behaviors in the Maternal Separated Model in Rats

BACKGROUND

Environmental Enrichment (EE) has been suggested as a possible therapeutic intervention for neurodevelopmental disorders such as autism. Although the benefits of this therapeutic method have been reported in some animal models and human studies, the unknown pathophysiology of autism as well as number of conflicting results, urge for further examination of the therapeutic potential of EE in autism. Therefore, the aim of this study was to examine the effects of environmental enrichment on autism-related behaviors which were induced in the maternal separation (MS) animal model.

MATERIAL AND METHODS

Maternally separated (post-natal day (PND) 1-14, 3h/day) and control male rats were at weaning (PND21) age equally divided into rats housed in enriched environment and normal environment. At adolescence (PND42-50), the four groups were behaviorally tested for direct social interaction, sociability, repetitive behaviors, anxiety behavior, and locomotion. Following completion of the behavioral tests, the blood and brain tissue samples were harvested in order to assess plasma level of brain derived neurotrophic factor (BDNF) and structural plasticity of brain using ELISA and stereological methods respectively.

RESULTS

We found that environmental enrichment reduced repetitive behaviors but failed to improve the impaired sociability and anxiety behaviors which were induced by maternal separation. Indeed, EE exacerbated anxiety and social behaviors deficits in association with increased plasma BDNF level, larger volume of the hippocampus and infra-limbic region and higher number of neurons in the infra-limbic area (p < 0.05). Conclusion: We conclude that environmental enrichment has a significant improvement effect on the repetitive behavior as one of the core autistic-like behaviors induced by maternal separation but has negative effect on the anxiety and social behaviors which might have been modulated by BDNF.

The effect of background strain on the behavioral phenotypes of the MDGA2+/- mouse model of autism spectrum disorder

The membrane-associated mucin (MAM) domain containing glycosylphosphatidylinositol anchor 2 protein single knock-out mice (MDGA2^+/- ) are models of ASD. We examined the behavioral phenotypes of male and female MDGA2^+/- and wildtype mice on C57BL6/NJ and C57BL6/N backgrounds at 2 months of age and measured MDGA2, neuroligin 1 and neuroligin 2 levels at 7 months. Mice on the C57BL6/NJ background performed better than those on the C57BL6/N background in visual ability and in learning and memory performance in the Morris water maze and differed in measures of motor behavior and anxiety. Mice with the MDGA2^+/- genotype differed from WT mice in motor, social and repetitive behavior and anxiety, but most of these effects involved interactions between MDGA2^+/- genotype and background strain. The background strain also influenced MDGA2 levels and NLGN2 association in MDGA2^+/- mice. Our findings emphasize the importance of the background strain used in studies of genetically modified mice.

Pesticides used in Europe and autism spectrum disorder risk: can novel exposure hypotheses be formulated beyond organophosphates, organochlorines, pyrethroids and carbamates? - A systematic review

BACKGROUND

A growing body of evidences suggests an association between early exposure to organophosphates (OPs), organochlorines (OCs), pyrethroids or carbamates and autism spectrum disorder (ASD). However, there are limited data about the other pesticide groups, especially in Europe.

OBJECTIVES

Based on a systematic review, we aimed to assess the influence of neuro- and thyrotoxic agricultural and domestic pesticides (other than OPs, OCs, pyrethroids and carbamates) authorized in Europe on risk of ASD in children or ASD behavioral phenotypes in rodents.

METHODS

Pesticides were initially identified in the Hazardous Substances Data Bank. 20 currently used (10 pesticide groups) were retained based on the higher exposure potential. Epidemiological (children) and in vivo (rodents) studies were identified through PubMed, Web of Science and TOXLINE, without restriction of publication date or country (last update: November 2019). The risk of bias and level of evidence were also assessed. This systematic review is registered at the International Prospective Register of Systematic Reviews (PROSPERO, registration number CRD42019145384).

RESULTS

In total, two epidemiological and 15 in vivo studies were retained, focusing on the azole, neonicotinoid, phenylpyrazole and phosphonoglycine pesticide groups. No study was conducted in Europe. Glyphosate, imidacloprid, clothianidin, myclobutanil, acetamiprid, tebuconazole, thiabendazole and fipronil, globally reported an association with an increased risk of ASD in children and/or ASD behavioral phenotypes in rodents. In children, glyphosate and myclobutanil showed a "moderate level of evidence" in their association with ASD, whereas imidacloprid showed an "inadequate level of evidence". In rodents, clothianidin, imidacloprid and glyphosate showed a "high level of evidence" in their association with altered behavioral, learning and memory skills.

CONCLUSION

In the framework of environmental risk factors of ASD, novel hypotheses can be formulated about early exposure to eight pesticides. Glyphosate presented the most salient level of evidence. Given their neuro- and thyrotoxic properties, additional studies are needed for the 12 other pesticides not yet studied as potential ASD risk factors according to our inclusion criteria.

Increased repetitive self-grooming occurs in Pax2 mutant mice generated using CRISPR/Cas9

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interaction and communication, and repetitive or restricted interest and behaviors. However, the specific pathogenesis of ASD is still unclear. It has been widely accepted that genetic and environmental risk factors are associated with the pathogenesis of ASD. Paired box2 (Pax2) gene encodes a transcription factor that plays an important role in the development of the central nervous system of humans and mice. In this study, we constructed Pax2 heterozygous gene knockout (Pax2^+/-) mice using CRISPR/Cas9 technology and performed several autistic-like behavioral assays, including self-grooming test, sociability approach, the elevated plus maze test and Y maze test. Results showed increased repetitive self-grooming and possible abnormal anxiety-like behavior occur in Pax2^+/- mice. Furthermore, no changes were observed in the abilities of sociability and working memory in Pax2^+/- mice compared to wild-type C57BL/6 J mice. Finally, we speculated that possible mechanism of abnormal autistic-like behaviors due to the deletion of Pax2 gene.

Autistic-like behaviours and associated brain structural plasticity are modulated by oxytocin in maternally separated rats

BACKGROUND

Early psycho-social experiences influence the developing brain and possible onset of various neurodevelopmental disorders, such as Autism Spectrum Disorder (ASD). ASD is characterized by a variety of brain abnormalities, including alteration of oxytocin receptors in the brain. Recently, early life adverse experiences, such as maternal separation (MS), have been shown to constitute risk factors for ASD in preclinical studies. Therefore, the main aims of the current study were to i) explore the association between onset of autistic-like behaviours and molecular/structural changes in the brain following MS, and ii) evaluate the possible beneficial effects of oxytocin treatment on the same parameters.

METHOD AND MATERIAL

Male rats were exposed to the maternal separation from post-natal day (PND) 1 to PND14. After weaning, daily injections of oxytocin (1 mg/kg, ip) were administered (PND 22-30), followed by examination of autism-related behaviours at adolescence (PND 42-50). Brain structural plasticity was examined using stereological methods, and the plasma level of brain derived neurotrophic factor (BDNF) was analysed using ELISA.

RESULTS

We found that maternal separation induced autistic-like behaviours, which was associated with increase in the hippocampal CA1 stratum radiatum (CA1.SR) volume. In addition, we observed increase in the infralimbic brain region volume and in the number of the pyramidal neurons in the same brain region. Maternal separation significantly increased the plasma BDNF levels. Treatment with oxytocin improved autistic like behaviours, normalized the number of neurons and the volume of the infralimbic region as well as the plasma BDNF level (p < 0.05).

CONCLUSION

Maternal separation induced autistic-like behaviours, brain structural impairment together with plasma BDNF level abnormality, which could be improved by oxytocin treatment.

Dysregulation of synaptic pruning as a possible link between intestinal microbiota dysbiosis and neuropsychiatric disorders

The prenatal and early postnatal stages represent a critical time window for human brain development. Interestingly, this window partly overlaps with the maturation of the intestinal flora (microbiota) that play a critical role in the bidirectional communication between the central and the enteric nervous systems (microbiota-gut-brain axis). The microbial composition has important influences on general health and the development of several organ systems, such as the gastrointestinal tract, the immune system, and also the brain. Clinical studies have shown that microbiota alterations are associated with a wide range of neuropsychiatric disorders including autism spectrum disorder, attention deficit hyperactivity disorder, schizophrenia, and bipolar disorder. In this review, we dissect the link between these neuropsychiatric disorders and the intestinal microbiota by focusing on their effect on synaptic pruning, a vital process in the maturation and establishing efficient functioning of the brain. We discuss in detail how synaptic pruning is dysregulated differently in the aforementioned neuropsychiatric disorders and how it can be influenced by dysbiosis and/or changes in the intestinal microbiota composition. We also review that the improvement in the intestinal microbiota composition by a change in diet, probiotics, prebiotics, or fecal microbiota transplantation may play a role in improving neuropsychiatric functioning, which can be at least partly explained via the optimization of synaptic pruning and neuronal connections. Altogether, the demonstration of the microbiota's influence on brain function via microglial-induced synaptic pruning addresses the possibility that the manipulation of microbiota-immune crosstalk represents a promising strategy for treating neuropsychiatric disorders.

Effects of PM2.5 and gases exposure during prenatal and early-life on autism-like phenotypes in male rat offspring

BACKGROUND

Epidemiological studies have reported associations between elevated air pollution and autism spectrum disorders (ASD). However, we hypothesized that exposure to air pollution that mimics real world scenarios, is a potential contributor to ASD. The exact etiology and molecular mechanisms underlying ASD are not well understood. Thus, we assessed whether changes in OXTR levels may be part of the mechanism linking PM_2.5/gaseous pollutant exposure and ASD. The current in-vivo study investigated the effect of exposure to fine particulate matter (PM_2.5) and gaseous pollutants on ASD using behavioral and molecular experiments. Four exposure groups of Wistar rats were included in this study: 1) particulate matter and gaseous pollutants exposed (PGE), 2) gaseous pollutants only exposed (GE), 3) autism-like model (ALM) with VPA induction, and 4) clean air exposed (CAE) as the control. Pregnant dams and male pups were exposed to air pollutants from embryonic day (E0) to postnatal day (PND21).

RESULTS

The average ± SD concentrations of air pollutants were: PM_2.5: 43.8 ± 21.1 μg/m³, CO: 13.5 ± 2.5 ppm, NO₂: 0.341 ± 0.100 ppm, SO₂: 0.275 ± 0.07 ppm, and O₃: 0.135 ± 0.01 ppm. The OXTR protein level, catalase activity (CAT), and GSH concentrations in the ALM, PGE, and GE rats were lower than those in control group (CAE). However, the decrements in the GE rats were smaller than other groups. Also in behavioral assessments, the ALM, PGE, and GE rats demonstrated a repetitive /restricted behavior and poor social interaction, but the GE rats had weaker responses compared to other groups of rats. The PGE and GE rats showed similar trends in these tests compared to the VPA rats.

CONCLUSIONS

This study suggested that exposure to ambient air pollution contributed to ASD and that OXTR protein may serve as part of the mechanism linking them.

Regulation of Central Nervous System Development by Class I Histone Deacetylases

Neurodevelopment is a highly complex process composed of several carefully regulated events starting from the proliferation of neuroepithelial cells and culminating with and refining of neural networks and synaptic transmission. Improper regulation of any of these neurodevelopmental events often results in severe brain dysfunction. Accumulating evidence indicates that epigenetic modifications of chromatin play a key role in neurodevelopmental regulation. Among these modifications are histone acetylation and deacetylation, which control access of transcription factors to DNA, thereby regulating gene transcription. Histone deacetylation, which restricts access of transcription factor repressing gene transcription, involves the action of members of a family of 18 enzymes, the histone deacetylases (HDAC), which are subdivided in 4 subgroups. This review focuses on the Group 1 HDACs - HDAC 1, 2, 3, and 8. Although much of the evidence for HDAC involvement in neurodevelopment has come from the use of pharmacological inhibitors, because these agents are generally nonselective with regard to their effects on individual members of the HDAC family, this review is limited to evidence garnered from the use of molecular genetic approaches. Our review describes that Class I HDACs play essential roles in all phases of neurodevelopment. Modulation of the activity of individual HDACs could be an important therapeutic approach for neurodevelopmental and psychiatric disorders.

Identification of a molecular locus for normalizing dysregulated GABA release from interneurons in the Fragile X brain

Principal neurons encode information by varying their firing rate and patterns precisely fine-tuned through GABAergic interneurons. Dysregulation of inhibition can lead to neuropsychiatric disorders, yet little is known about the molecular basis underlying inhibitory control. Here, we find that excessive GABA release from basket cells (BCs) attenuates the firing frequency of Purkinje neurons (PNs) in the cerebellum of Fragile X Mental Retardation 1 (Fmr1) knockout (KO) mice, a model of Fragile X Syndrome (FXS) with abrogated expression of the Fragile X Mental Retardation Protein (FMRP). This over-inhibition originates from increased excitability and Ca²⁺ transients in the presynaptic terminals, where Kv1.2 potassium channels are downregulated. By paired patch-clamp recordings, we further demonstrate that acutely introducing an N-terminal fragment of FMRP into BCs normalizes GABA release in the Fmr1-KO synapses. Conversely, direct injection of an inhibitory FMRP antibody into BCs, or membrane depolarization of BCs, enhances GABA release in the wild type synapses, leading to abnormal inhibitory transmission comparable to the Fmr1-KO neurons. We discover that the N-terminus of FMRP directly binds to a phosphorylated serine motif on the C-terminus of Kv1.2; and that loss of this interaction in BCs exaggerates GABA release, compromising the firing activity of PNs and thus the output from the cerebellar circuitry. An allosteric Kv1.2 agonist, docosahexaenoic acid, rectifies the dysregulated inhibition in vitro as well as acoustic startle reflex and social interaction in vivo of the Fmr1-KO mice. Our results unravel a novel molecular locus for targeted intervention of FXS and perhaps autism.

Impaired regulation of KCC2 phosphorylation leads to neuronal network dysfunction and neurodevelopmental pathology

KCC2 is a vital neuronal K+/Cl- cotransporter that is implicated in the etiology of numerous neurological diseases. In normal cells, KCC2 undergoes developmental dephosphorylation at Thr906 and Thr1007 We engineered mice with heterozygous phosphomimetic mutations T906E and T1007E (KCC2E/+ ) to prevent the normal developmental dephosphorylation of these sites. Immature (postnatal day 15) but not juvenile (postnatal day 30) KCC2E/+ mice exhibited altered GABAergic inhibition, an increased glutamate/GABA synaptic ratio, and greater susceptibility to seizure. KCC2E/+ mice also had abnormal ultrasonic vocalizations at postnatal days 10 to 12 and impaired social behavior at postnatal day 60. Postnatal bumetanide treatment restored network activity by postnatal day 15 but failed to restore social behavior by postnatal day 60. Our data indicate that posttranslational KCC2 regulation controls the GABAergic developmental sequence in vivo, indicating that deregulation of KCC2 could be a risk factor for the emergence of neurological pathology.

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.

Inhibitory interneurons mediate autism-associated behaviors via 4E-BP2

Translational control plays a key role in regulation of neuronal activity and behavior. Deletion of the translational repressor 4E-BP2 in mice alters excitatory and inhibitory synaptic functions, engendering autistic-like behaviors. The contribution of 4E-BP2-dependent translational control in excitatory and inhibitory neurons and astrocytic cells to these behaviors remains unknown. To investigate this, we generated cell-type-specific conditional 4E-BP2 knockout mice and tested them for the salient features of autism, including repetitive stereotyped behaviors (self-grooming and marble burying), sociability (3-chamber social and direct social interaction tests), and communication (ultrasonic vocalizations in pups). We found that deletion of 4E-BP2 in GABAergic inhibitory neurons, defined by Gad2, resulted in impairments in social interaction and vocal communication. In contrast, deletion of 4E-BP2 in forebrain glutamatergic excitatory neurons, defined by Camk2a, or in astrocytes, defined by Gfap, failed to cause autistic-like behavioral abnormalities. Taken together, we provide evidence for an inhibitory-cell-specific role of 4E-BP2 in engendering autism-related behaviors.

Neonatal social isolation increases the proportion of the immature spines in the layer 2/3 pyramidal neurons of the somatosensory cortex

Social isolation during the juvenile period is postulated to leave specific sequelae, such as attention deficits and emotion recognition. Miswiring of the cortical neuronal circuit during postnatal development may underlie such behavioral impairments, but the details of the circuit-level impairment associated with social isolation have not yet been clarified. In this study, we evaluated the possibility that environmental factors may induce alternation in spine characteristics and dynamics. We isolated mice from the mother and siblings from postnatal day 7 to 11 for 6 h per day. Both dynamics and structural properties of spines in the layer 2/3 pyramidal neurons of the somatosensory cortex were measured at postnatal 3 weeks by in vivo two-photon microscopy. We found decrease in the ratio of PSD-95-positive dendritic spines in the mice after social isolation. These mice did not show alteration in spine dynamics. Those results suggest that the neonatal social isolation results in less mature spines, with normal rate of their turnover, which is distinct from spine phenotype seen in multiple models of autism spectrum disorders.

The Autism-Associated Gene Scn2a Contributes to Dendritic Excitability and Synaptic Function in the Prefrontal Cortex

Autism spectrum disorder (ASD) is strongly associated with de novo gene mutations. One of the most commonly affected genes is SCN2A. ASD-associated SCN2A mutations impair the encoded protein Na_V1.2, a sodium channel important for action potential initiation and propagation in developing excitatory cortical neurons. The link between an axonal sodium channel and ASD, a disorder typically attributed to synaptic or transcriptional dysfunction, is unclear. Here we show that Na_V1.2 is unexpectedly critical for dendritic excitability and synaptic function in mature pyramidal neurons in addition to regulating early developmental axonal excitability. Na_V1.2 loss reduced action potential backpropagation into dendrites, impairing synaptic plasticity and synaptic strength, even when Na_V1.2 expression was disrupted in a cell-autonomous fashion late in development. These results reveal a novel dendritic function for Na_V1.2, providing insight into cellular mechanisms probably underlying circuit and behavioral dysfunction in ASD.

Prenatal exposure to TiO2 nanoparticles in mice causes behavioral deficits with relevance to autism spectrum disorder and beyond

Environmental factors are involved in the etiology of autism spectrum disorder (ASD) and may contribute to the raise in its incidence rate. It is currently unknown whether the increasing use of nanoparticles such as titanium dioxide (TiO₂ NPs) in consumer products and biomedical applications may play a role in these associations. While nano-sized TiO₂ is generally regarded as safe and non-toxic, excessive exposure to TiO₂ NPs may be associated with negative health consequences especially when occurring during sensitive developmental periods. To test if prenatal exposure to TiO₂ NPs alters fetal development and behavioral functions relevant to ASD, C57Bl6/N dams were subjected to a single intravenous injection of a low (100 µg) or high (1000 µg) dose of TiO₂ NPs or vehicle solution on gestation day 9. ASD-related behavioral functions were assessed in the offspring using paradigms that index murine versions of ASD symptoms. Maternal exposure to TiO₂ NPs led to subtle and dose-dependent impairments in neonatal vocal communication and juvenile sociability, as well as a dose-dependent increase in prepulse inhibition of the acoustic startle reflex of both sexes. These behavioral alterations emerged in the absence of pregnancy complications. Prenatal exposure to TiO₂ NPs did not cause overt fetal malformations or changes in pregnancy outcomes, nor did it affect postnatal growth of the offspring. Taken together, our study provides a first set of preliminary data suggesting that prenatal exposure to nano-sized TiO₂ can induce behavioral deficits relevant to ASD and related neurodevelopmental disorders without inducing major changes in physiological development. If extended further, our preclinical findings may provide an incentive for epidemiological studies examining the role of prenatal TiO₂ NPs exposure in the etiology of ASD and other neurodevelopmental disorders.

Prenatal stress disrupts social behavior, cortical neurobiology and commensal microbes in adult male offspring

In utero and early neonatal exposure to maternal stress is linked with psychiatric disorders, and the underlying mechanisms are currently being elucidated. We used a prenatal stressor in pregnant mice to examine novel relationships between prenatal stress exposure, changes in the gut microbiome, and social behavior. Here, we show that males exposed to prenatal stress had a significant reduction in social behavior in adulthood, with increased corticosterone release following social interaction. Male offspring exposed to prenatal stress also had neuroinflammation, decreased oxytocin receptor, and decreased serotonin metabolism in their cortex in adulthood, which are linked to decreased social behavior. Finally, we found a significant difference in commensal microbes, including decreases in Bacteroides and Parabacteroides, in adult male offspring exposed to prenatal stress when compared to non-stressed controls. Our findings indicate that gestation is a critical window where maternal stress contributes to the development of aberrant social behaviors and alterations in cortical neurobiology, and that prenatal stress is sufficient to disrupt the male gut-brain axis into adulthood.

Current Enlightenment About Etiology and Pharmacological Treatment of Autism Spectrum Disorder

Autistic Spectrum Disorder (ASD) is a complex neurodevelopmental brain disorder characterized by two core behavioral symptoms, namely impairments in social communication and restricted/repetitive behavior. The molecular mechanisms underlying ASD are not well understood. Recent genetic as well as non-genetic animal models contributed significantly in understanding the pathophysiology of ASD, as they establish autism-like behavior in mice and rats. Among the genetic causes, several chromosomal mutations including duplications or deletions could be possible causative factors of ASD. In addition, the biochemical basis suggests that several brain neurotransmitters, e.g., dopamine (DA), serotonin (5-HT), gamma-amino butyric acid (GABA), acetylcholine (ACh), glutamate (Glu) and histamine (HA) participate in the onset and progression of ASD. Despite of convincible understanding, risperidone and aripiprazole are the only two drugs available clinically for improving behavioral symptoms of ASD following approval by Food and Drug Administration (FDA). Till date, up to our knowledge there is no other drug approved for clinical usage specifically for ASD symptoms. However, many novel drug candidates and classes of compounds are underway for ASD at different phases of preclinical and clinical drug development. In this review, the diversity of numerous aetiological factors and the alterations in variety of neurotransmitter generation, release and function linked to ASD are discussed with focus on drugs currently used to manage neuropsychiatric symptoms related to ASD. The review also highlights the clinical development of drugs with emphasis on their pharmacological targets aiming at improving core symptoms in ASD.

Oral sensitization to whey proteins induces age- and sex-dependent behavioral abnormality and neuroinflammatory responses in a mouse model of food allergy: a potential role of mast cells

BACKGROUND

Growing evidence has strengthened the association of food allergy with neuropsychiatric symptoms such as depression, anxiety, and autism. However, underlying mechanisms by which peripheral allergic responses lead to behavioral dysfunction are yet to be determined. Allergen-activated mast cells may serve as mediators by releasing histamine and other inflammatory factors that could adversely affect brain function. We hypothesized that eliciting food allergy in experimental animals would result in behavioral changes accompanied by mast cell accumulation in the brain. Our hypothesis was tested in a mouse model of milk allergy using bovine milk whey proteins (WP) as the allergen.

METHODS

Male and female C57BL/6 mice at 4 weeks (young) and 10 months (old) of age underwent 5-week WP sensitization with weekly intragastric administration of 20 mg WP and 10 μg cholera toxin as an adjuvant. Age-matched sham animals were given the vehicle containing only the adjuvant. All animals were orally challenged with 50 mg WP in week 6 and their intrinsic digging behavior was assessed the next day. Animals were sacrificed 3 days after the challenge, and WP-specific serum IgE, intestinal and brain mast cells, glial activation, and epigenetic DNA modification in the brain were examined.

RESULTS

WP-sensitized males showed significantly less digging activity than the sham males in both age groups while no apparent difference was observed in females. Mast cells and their activities were evident in the intestines in an age- and sex-dependent manner. Brain mast cells were predominantly located in the region between the lateral midbrain and medial hippocampus, and their number increased in the WP-sensitized young, but not old, male brains. Noticeable differences in for 5-hydroxymethylcytosine immunoreactivity were observed in WP mice of both age groups in the amygdala, suggesting epigenetic regulation. Increased microglial Iba1 immunoreactivity and perivascular astrocytes hypertrophy were also observed in the WP-sensitized old male mice.

CONCLUSIONS

Our results demonstrated that food allergy induced behavioral abnormality, increases in the number of mast cells, epigenetic DNA modification in the brain, microgliosis, and astrocyte hypertrophy in a sex- and age-dependent manner, providing a potential mechanism by which peripheral allergic responses evoke behavioral dysfunction.

Impaired Object Recognition but Normal Social Behavior and Ultrasonic Communication in Cofilin1 Mutant Mice

Autism spectrum disorder (ASD), schizophrenia (SCZ) and intellectual disability (ID) show a remarkable overlap in symptoms, including impairments in cognition, social behavior and communication. Human genetic studies revealed an enrichment of mutations in actin-related genes for these disorders, and some of the strongest candidate genes control actin dynamics. These findings led to the hypotheses: (i) that ASD, SCZ and ID share common disease mechanisms; and (ii) that, at least in a subgroup of affected individuals, defects in the actin cytoskeleton cause or contribute to their pathologies. Cofilin1 emerged as a key regulator of actin dynamics and we previously demonstrated its critical role for synaptic plasticity and associative learning. Notably, recent studies revealed an over-activation of cofilin1 in mutant mice displaying ASD- or SCZ-like behavioral phenotypes, suggesting that dysregulated cofilin1-dependent actin dynamics contribute to their behavioral abnormalities, such as deficits in social behavior. These findings let us hypothesize: (i) that, apart from cognitive impairments, cofilin1 mutants display additional behavioral deficits with relevance to ASD or SCZ; and (ii) that our cofilin1 mutants represent a valuable tool to study the underlying disease mechanisms. To test our hypotheses, we compared social behavior and ultrasonic communication of juvenile mutants to control littermates, and we did not obtain evidence for impaired direct reciprocal social interaction, social approach or social memory. Moreover, concomitant emission of ultrasonic vocalizations was not affected and time-locked to social activity, supporting the notion that ultrasonic vocalizations serve a pro-social communicative function as social contact calls maintaining social proximity. Finally, cofilin1 mutants did not display abnormal repetitive behaviors. Instead, they performed weaker in novel object recognition, thereby demonstrating that cofilin1 is relevant not only for associative learning, but also for “non-matching-to-sample” learning. Here we report the absence of an ASD- or a SCZ-like phenotype in cofilin1 mutants, and we conclude that cofilin1 is relevant specifically for non-social cognition.

CD38 is Required for Dendritic Organization in Visual Cortex and Hippocampus

Morphological screening of mouse brains with known behavioral deficits can give great insight into the relationship between brain regions and their behavior. Oxytocin- and CD38-deficient mice have previously been shown to have behavioral phenotypes, such as restrictions in social memory, social interactions, and maternal behavior. CD38 is reported as an autism spectrum disorder (ASD) candidate gene and its behavioral phenotypes may be linked to ASD. To address whether these behavioral phenotypes relate to brain pathology and neuronal morphology, here we investigate the morphological changes in the CD38-deficient mice brains, with focus on the pathology and neuronal morphology of the cortex and hippocampus, using Nissl staining, immunohistochemistry, and Golgi staining. No difference was found in terms of cortical layer thickness. However, we found abnormalities in the number of neurons and neuronal morphology in the visual cortex and dentate gyrus (DG). In particular, there were arborisation differences between CD38^-/- and CD38^+/+ mice in the apical dendrites of the visual cortex and hippocampal CA1 pyramidal neurons. The data suggest that CD38 is implicated in appropriate development of brain regions important for social behavior.

Hippocampal oxytocin receptors are necessary for discrimination of social stimuli

Oxytocin receptor (Oxtr) signaling in neural circuits mediating discrimination of social stimuli and affiliation or avoidance behavior is thought to guide social recognition. Remarkably, the physiological functions of Oxtrs in the hippocampus are not known. Here we demonstrate using genetic and pharmacological approaches that Oxtrs in the anterior dentate gyrus (aDG) and anterior CA2/CA3 (aCA2/CA3) of mice are necessary for discrimination of social, but not non-social, stimuli. Further, Oxtrs in aCA2/CA3 neurons recruit a population-based coding mechanism to mediate social stimuli discrimination. Optogenetic terminal-specific attenuation revealed a critical role for aCA2/CA3 outputs to posterior CA1 for discrimination of social stimuli. In contrast, aCA2/CA3 projections to aCA1 mediate discrimination of non-social stimuli. These studies identify a role for an aDG-CA2/CA3 axis of Oxtr expressing cells in discrimination of social stimuli and delineate a pathway relaying social memory computations in the anterior hippocampus to the posterior hippocampus to guide social recognition.

The Endocannabinoid System and Autism Spectrum Disorders: Insights from Animal Models

Autism spectrum disorder (ASD) defines a group of neurodevelopmental disorders whose symptoms include impaired communication and social interaction with restricted or repetitive motor movements, frequently associated with general cognitive deficits. Although it is among the most severe chronic childhood disorders in terms of prevalence, morbidity, and impact to the society, no effective treatment for ASD is yet available, possibly because its neurobiological basis is not clearly understood hence specific drugs have not yet been developed. The endocannabinoid (EC) system represents a major neuromodulatory system involved in the regulation of emotional responses, behavioral reactivity to context, and social interaction. Furthermore, the EC system is also affected in conditions often present in subsets of patients diagnosed with ASD, such as seizures, anxiety, intellectual disabilities, and sleep pattern disturbances. Despite the indirect evidence suggestive of an involvement of the EC system in ASD, only a few studies have specifically addressed the role of the EC system in the context of ASD. This review describes the available data on the investigation of the presence of alterations of the EC system as well as the effects of its pharmacological manipulations in animal models of ASD-like behaviors.

Bridging Autism Spectrum Disorders and Schizophrenia through inflammation and biomarkers - pre-clinical and clinical investigations

In recent years, evidence supporting a link between inflammation and neuropsychiatric disorders has been mounting. Autism spectrum disorders (ASD) and schizophrenia share some clinical similarities which we hypothesize might reflect the same biological basis, namely, in terms of inflammation. However, the diagnosis of ASD and schizophrenia relies solely on clinical symptoms, and to date, there is no clinically useful biomarker to diagnose or monitor the course of such illnesses.

The focus of this review is the central role that inflammation plays in ASD and schizophrenia. It spans from pre-clinical animal models to clinical research and excludes in vitro studies. Four major areas are covered: (1) microglia, the inflammatory brain resident myeloid cells, (2) biomarkers, including circulating cytokines, oxidative stress markers, and microRNA players, known to influence cellular processes at brain and immune levels, (3) effect of anti-psychotics on biomarkers and other predictors of response, and (4) impact of gender on response to immune activation, biomarkers, and response to anti-psychotic treatments.

The non-coding RNA BC1 regulates experience-dependent structural plasticity and learning

The brain cytoplasmic (BC1) RNA is a non-coding RNA (ncRNA) involved in neuronal translational control. Absence of BC1 is associated with altered glutamatergic transmission and maladaptive behavior. Here, we show that pyramidal neurons in the barrel cortex of BC1 knock out (KO) mice display larger excitatory postsynaptic currents and increased spontaneous activity in vivo. Furthermore, BC1 KO mice have enlarged spine heads and postsynaptic densities and increased synaptic levels of glutamate receptors and PSD-95. Of note, BC1 KO mice show aberrant structural plasticity in response to whisker deprivation, impaired texture novel object recognition and altered social behavior. Thus, our study highlights a role for BC1 RNA in experience-dependent plasticity and learning in the mammalian adult neocortex, and provides insight into the function of brain ncRNAs regulating synaptic transmission, plasticity and behavior, with potential relevance in the context of intellectual disabilities and psychiatric disorders.

Brain cytoplasmic (BC1) RNA is a non-coding RNA that has been implicated in translational regulation, seizure, and anxiety. Here, the authors show that in the cortex, BC1 RNA is required for sensory deprivation-induced structural plasticity of dendritic spines, as well as for correct sensory learning and social behaviors.

Advances in nonhuman primate models of autism: Integrating neuroscience and behavior

Given the prevalence and societal impact of autism spectrum disorders (ASD), there is an urgent need to develop innovative preventative strategies and treatments to reduce the alarming number of cases and improve core symptoms for afflicted individuals. Translational efforts between clinical and preclinical research are needed to (i) identify and evaluate putative causes of ASD, (ii) determine the underlying neurobiological mechanisms, (iii) develop and test novel therapeutic approaches and (iv) ultimately translate basic research into safe and effective clinical practices. However, modeling a uniquely human brain disorder, such as ASD, will require sophisticated animal models that capitalize on unique advantages of diverse species including drosophila, zebra fish, mice, rats, and ultimately, species more closely related to humans, such as the nonhuman primate. Here we discuss the unique contributions of the rhesus monkey (Macaca mulatta) model to ongoing efforts to understand the neurobiology of the disorder, focusing on the convergence of brain and behavior outcome measures that parallel features of human ASD.

Basal ganglia and autism - a translational perspective

The basal ganglia are a collection of nuclei below the cortical surface that are involved in both motor and non-motor functions, including higher order cognition, social interactions, speech, and repetitive behaviors. Motor development milestones that are delayed in autism such as gross motor, fine motor and walking can aid in early diagnosis of autism. Neuropathology and neuroimaging findings in autism cases revealed volumetric changes and altered cell density in select basal ganglia nuclei. Interestingly, in autism, both the basal ganglia and the cerebellum are impacted both in their motor and non-motor domains and recently, found to be connected via the pons through a short disynaptic pathway. In typically developing individuals, the basal ganglia plays an important role in: eye movement, movement coordination, sensory modulation and processing, eye-hand coordination, action chaining, and inhibition control. Genetic models have proved to be useful toward understanding cellular and molecular changes at the synaptic level in the basal ganglia that may in part contribute to these autism-related behaviors. In autism, basal ganglia functions in motor skill acquisition and development are altered, thus disrupting the normal flow of feedback to the cortex. Taken together, there is an abundance of emerging evidence that the basal ganglia likely plays critical roles in maintaining an inhibitory balance between cortical and subcortical structures, critical for normal motor actions and cognitive functions. In autism, this inhibitory balance is disturbed thus impacting key pathways that affect normal cortical network activity. Autism Res 2017, 10: 1751-1775. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

Habit learning, action selection and performance are modulated by the basal ganglia, a collection of groups of neurons located below the cerebral cortex in the brain. In autism, there is emerging evidence that parts of the basal ganglia are structurally and functionally altered disrupting normal information flow. The basal ganglia through its interconnected circuits with the cerebral cortex and the cerebellum can potentially impact various motor and cognitive functions in the autism brain.