Autism-related behavioral abnormalities in synapsin knockout mice

Memory Decline and Aberration of Synaptic Proteins in X-Linked Moesin Knockout Male Mice

OBJECTIVE

This study aims to investigate may moesin deficiency resulted in neurodevelopmental abnormalities caused by negative impact on synaptic signaling ultimately leading to synaptic structure and plasticity.

METHODS

Behavioral assessments measured neurodevelopment (surface righting, negative geotaxis, cliff avoidance), anxiety (open field test, elevated plus maze test), and memory (passive avoidance test, Y-maze test) in moesin-knockout mice (KO) compared to wild-type mice (WT). Whole exome sequencing (WES) of brain (KO vs. WT) and analysis of synaptic proteins were performed to determine the disruption of signal pathways downstream of moesin. Risperidone, a therapeutic agent, was utilized to reverse the neurodevelopmental aberrance in moesin KO.

RESULTS

Moesin-KO pups exhibited decrease in the surface righting ability on postnatal day 7 (p<0.05) and increase in time spent in the closed arms (p<0.01), showing increased anxiety-like behavior. WES revealed mutations in pathway aberration in neuron projection, actin filament-based processes, and neuronal migration in KO. Decreased cell viability (p<0.001) and expression of soluble NSF adapter protein 25 (SNAP25) (p<0.001) and postsynaptic density protein 95 (PSD95) (p<0.01) was observed in days in vitro 7 neurons. Downregulation of synaptic proteins, and altered phosphorylation levels of Synapsin I, mammalian uncoordinated 18 (MUNC18), extracellular signal-regulated kinase (ERK), and cAMP response element-binding protein (CREB) was observed in KO cortex and hippocampus. Risperidone reversed the memory impairment in the passive avoidance test and the spontaneous alternation percentage in the Y maze test. Risperidone also restored the reduced expression of PSD95 (p<0.01) and the phosphorylation of Synapsin at Ser605 (p<0.05) and Ser549 (p<0.001) in the cortex of moesin-KO.

CONCLUSION

Moesin deficiency leads to neurodevelopmental delay and memory decline, which may be caused through altered regulation in synaptic proteins and function.

Repurposing of niclosamide, an anthelmintic, by targeting ERK/MAPK signaling pathway in the experimental paradigm of autism spectrum disorders

AIM

The current study explores niclosamide's neuroprotective potential in an animal model of autism spectrum disorder (ASD) and goes further to understand how the ERK/MAPK signaling pathway is thought to contribute to this activity.

METHODS

In order to create an autism-like phenotype in rats, 4 μl of 1 M PPA was infused intracerebroventricularly. The oral treatment with niclosamide (50 and 100 mg/kg) and risperidone (1 mg/kg) (used as standard) was given from 3rd to 30th day. Between the 14th and 28th day, behavioral assessments were made for sociability, stereotypy, anxiety, depression, novelty preference, repetitive behavior, and perseverative behavior. The animals were euthanized on the 29th day, and oxidative stress markers were assessed in the brain homogenate. The levels of neuroinflammatory cytokines such as TNF-α, IL-6, NF-κB, IFN-γ and glutamate were estimated using ELISA kits. To assess the involvement of the ERK/MAPK signaling pathway, levels of Nrf2 and ERK2 were also measured.

KEY FINDINGS

Niclosamide therapy significantly restored behavioral, biochemical, neurological, and molecular impairments. Hence, niclosamide could be a potential neurotherapeutic candidate for further studies for use in ASD.

Mutation in the mitochondrial chaperone TRAP1 leads to autism with more severe symptoms in males

There is increasing evidence of mitochondrial dysfunction in autism spectrum disorders (ASD), but the causal relationships are unclear. In an ASD patient whose identical twin was unaffected, we identified a postzygotic mosaic mutation p.Q639* in the TRAP1 gene, which encodes a mitochondrial chaperone of the HSP90 family. Additional screening of 176 unrelated ASD probands revealed an identical TRAP1 variant in a male patient who had inherited it from a healthy mother. Notably, newly generated knock-in Trap1 p.Q641* mice display ASD-related behavioral abnormalities that are more pronounced in males than in females. Accordingly, Trap1 p.Q641* mutation also resulted in sex-specific changes in synaptic plasticity, the number of presynaptic mitochondria, and mitochondrial respiration. Thus, the TRAP1 p.Q639* mutation is the first example of a monogenic ASD caused by impaired mitochondrial protein homeostasis.

Molecular profiling of the hippocampus of children with autism spectrum disorder

Several lines of evidence point to a key role of the hippocampus in Autism Spectrum Disorders (ASD). Altered hippocampal volume and deficits in memory for person and emotion related stimuli have been reported, along with enhanced ability for declarative memories. Mouse models have demonstrated a critical role of the hippocampus in social memory dysfunction, associated with ASD, together with decreased synaptic plasticity. Chondroitin sulfate proteoglycans (CSPGs), a family of extracellular matrix molecules, represent a potential key link between neurodevelopment, synaptic plasticity, and immune system signaling. There is a lack of information regarding the molecular pathology of the hippocampus in ASD. We conducted RNAseq profiling on postmortem human brain samples containing the hippocampus from male children with ASD (n = 7) and normal male children (3-14 yrs old), (n = 6) from the NIH NeuroBioBank. Gene expression profiling analysis implicated molecular pathways involved in extracellular matrix organization, neurodevelopment, synaptic regulation, and immune system signaling. qRT-PCR and Western blotting were used to confirm several of the top markers identified. The CSPG protein BCAN was examined with multiplex immunofluorescence to analyze cell-type specific expression of BCAN and astrocyte morphology. We observed decreased expression of synaptic proteins PSD95 (p < 0.02) and SYN1 (p < 0.02), increased expression of the extracellular matrix (ECM) protease MMP9 (p < 0.03), and decreased expression of MEF2C (p < 0.03). We also observed increased BCAN expression with astrocytes in children with ASD, together with altered astrocyte morphology. Our results point to alterations in immune system signaling, glia cell differentiation, and synaptic signaling in the hippocampus of children with ASD, together with alterations in extracellular matrix molecules. Furthermore, our results demonstrate altered expression of genes implicated in genetic studies of ASD including SYN1 and MEF2C.

Deletion of VPS50 protein in mouse brain impairs synaptic function and behavior

BACKGROUND

The VPS50 protein functions in synaptic and dense core vesicle acidification, and perturbations of VPS50 function produce behavioral changes in Caenorhabditis elegans. Patients with mutations in VPS50 show severe developmental delay and intellectual disability, characteristics that have been associated with autism spectrum disorders (ASDs). The mechanisms that link VPS50 mutations to ASD are unknown.

RESULTS

To examine the role of VPS50 in mammalian brain function and behavior, we used the CRISPR/Cas9 system to generate knockouts of VPS50 in both cultured murine cortical neurons and living mice. In cultured neurons, KO of VPS50 did not affect the number of synaptic vesicles but did cause mislocalization of the V-ATPase V1 domain pump and impaired synaptic activity, likely as a consequence of defects in vesicle acidification and vesicle content. In mice, mosaic KO of VPS50 in the hippocampus altered synaptic transmission and plasticity and generated robust cognitive impairments.

CONCLUSIONS

We propose that VPS50 functions as an accessory protein to aid the recruitment of the V-ATPase V1 domain to synaptic vesicles and in that way plays a crucial role in controlling synaptic vesicle acidification. Understanding the mechanisms controlling behaviors and synaptic function in ASD-associated mutations is pivotal for the development of targeted interventions, which may open new avenues for therapeutic strategies aimed at ASD and related conditions.

Indoleamine 2,3-dioxygenase 2 deficiency associates with autism-like behavior via dopaminergic neuronal dysfunction

Indoleamine 2,3-dioxygenase 2 (IDO2) is an enzyme of the tryptophan-kynurenine pathway that is constitutively expressed in the brain. To provide insight into the physiological role of IDO2 in the brain, behavioral and neurochemical analyses in IDO2 knockout (KO) mice were performed. IDO2 KO mice showed stereotyped behavior, restricted interest and social deficits, traits that are associated with behavioral endophenotypes of autism spectrum disorder (ASD). IDO2 was colocalized immunohistochemically with tyrosine-hydroxylase-positive cells in dopaminergic neurons. In the striatum and amygdala of IDO2 KO mice, decreased dopamine turnover was associated with increased α-synuclein level. Correspondingly, levels of downstream dopamine D1 receptor signaling molecules such as brain-derived neurotrophic factor and c-Fos positive proteins were decreased. Furthermore, decreased abundance of ramified-type microglia resulted in increased dendritic spine density in the striatum of IDO2 KO mice. Both chemogenetic activation of dopaminergic neurons and treatment with methylphenidate, a dopamine reuptake inhibitor, ameliorated the ASD-like behavior of IDO2 KO mice. Sequencing analysis of exon regions in IDO2 from 309 ASD samples identified a rare canonical splice site variant in one ASD case. These results suggest that the IDO2 gene is, at least in part, a factor closely related to the development of psychiatric disorders.

Heterozygous Nexmif female mice demonstrate mosaic NEXMIF expression, autism-like behaviors, and abnormalities in dendritic arborization and synaptogenesis

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with a strong genetic basis. ASDs are commonly characterized by impairments in language, restrictive and repetitive behaviors, and deficits in social interactions. Although ASD is a highly heterogeneous disease with many different genes implicated in its etiology, many ASD-associated genes converge on common cellular defects, such as aberrant neuronal morphology and synapse dysregulation. Our previous work revealed that, in mice, complete loss of the ASD-associated X-linked gene NEXMIF results in a reduction in dendritic complexity, a decrease in spine and synapse density, altered synaptic transmission, and ASD-like behaviors. Interestingly, human females of NEXMIF haploinsufficiency have recently been reported to demonstrate autistic features; however, the cellular and molecular basis for this haploinsufficiency-caused ASD remains unclear. Here we report that in the brains of Nexmif± female mice, NEXMIF shows a mosaic pattern in its expression in neurons. Heterozygous female mice demonstrate behavioral impairments similar to those of knockout male mice. In the mosaic mixture of neurons from Nexmif± mice, cells that lack NEXMIF have impairments in dendritic arborization and spine development. Remarkably, the NEXMIF-expressing neurons from Nexmif± mice also demonstrate similar defects in dendritic growth and spine formation. These findings establish a novel mouse model of NEXMIF haploinsufficiency and provide new insights into the pathogenesis of NEXMIF-dependent ASD.

Molecular and in silico analyses of SYN III gene variants in autism spectrum disorder

BACKGROUND

Defects in neurotransmission and synaptogenesis are noteworthy in the pathogenesis of ASD. Synapsin III (SYN III) is defined as a synaptic vesicle protein that plays an important role in synaptogenesis and regulation of neurotransmitter release and neurite outgrowth. Therefore, SYN III may associate with many neurodevelopmental diseases, including ASD.

AIM

The aim of this study was to investigate whether the SYN III gene -631 C > G (rs133946) and -196 G > A (rs133945) polymorphisms are associated with susceptibility to ASD.

METHODS

SYN III variants and the risk of ASD were investigated in 26 healthy children and 24 ASD children. SYN III gene variants were genotyped by PCR-RFLP methods. The differences in genotype and allele frequencies between the ASD and control groups were calculated using the chi-square (χ2). We analysed the SYN III gene using web-based tools.

RESULTS

Our results suggest that the presence of the AA genotype of the SYN III -196 G > A (rs133945) polymorphism affects the characteristics and development of ASD in children (p = 0.012). SYN III -631 C > G (rs133946) polymorphism was not associated with ASD (p = 0.524). We have shown the prediction of gene-gene interaction that SYN III is co-expressed with 17 genes, physical interaction with 3 genes, and co-localization with 12 genes. The importance of different genes (SYN I, II, III, GABRD, NOS1AP, GNAO1) for ASD pathogenesis was revealed by GO analysis.

CONCLUSION

Considering the role of SYN III and related genes, especially in the synaptic vesicle pathway and neurotransmission, its effect on ASD can be further investigated.

Low glycemic index diet restrains epileptogenesis in a gender-specific fashion

Dietary restriction, such as low glycemic index diet (LGID), have been successfully used to treat drug-resistant epilepsy. However, if such diet could also counteract antiepileptogenesis is still unclear. Here, we investigated whether the administration of LGID during the latent pre-epileptic period, prevents or delays the appearance of the overt epileptic phenotype. To this aim, we used the Synapsin II knockout (SynIIKO) mouse, a model of temporal lobe epilepsy in which seizures manifest 2-3 months after birth, offering a temporal window in which LGID may affect epileptogenesis. Pregnant SynIIKO mice were fed with either LGID or standard diet during gestation and lactation. Both diets were maintained in weaned mice up to 5 months of age. LGID delayed the seizure onset and induced a reduction of seizures severity only in female SynIIKO mice. In parallel with the epileptic phenotype, high-density multielectrode array recordings revealed a reduction of frequency, amplitude, duration, velocity of propagation and spread of interictal events by LGID in the hippocampus of SynIIKO females, but not mutant males, confirming the gender-specific effect. ELISA-based analysis revealed that LGID increased cortico-hippocampal allopregnanolone (ALLO) levels only in females, while it was unable to affect ALLO plasma concentrations in either sex. The results indicate that the gender-specific interference of LGID with the epileptogenic process can be ascribed to a gender-specific increase in cortical ALLO, a neurosteroid known to strengthen GABAergic transmission. The study highlights the possibility of developing a personalized gender-based therapy for temporal lobe epilepsy.

Multi-time point metabolomics reveals key metabolic features from the ultra-early stage of intracerebral hemorrhage in mice

Despite decades of intensive research, there are still very limited options for the effective treatment of intracerebral hemorrhage (ICH). Recently, mounting evidence has indicated that the ultra-early stage (<3 h), serving as the primary phase of ICH, plays a pivotal role and may even surpass other stages in terms of its significance. Therefore, uncovering the metabolic alterations induced by ICH in the ultra-early stage is of crucial importance. To investigate this, the collagenase ICH mouse model was employed in this study. ICH or sham-operated mice were euthanized at the ultra-early stage of 3 h and the acute stage of 24 h and 72 h after the operation. Then, the metabolic changes in the perihematomal tissues were detected by liquid chromatography coupled with tandem mass spectrometry. In total, alterations in the levels of 465 metabolites were detected. A total of 136 metabolites were significantly changed at 3 h. At 24 h and 72 h, the amounts were 132 and 126, respectively. Additionally, the key corresponding metabolic pathways for these time points were analyzed through KEGG. To gather additional information, quantitative real-time transcription polymerase chain reaction, enzyme-linked immunosorbent assay and Western blots were performed to validate the metabolic changes. Overall, ICH significantly alters important physiological functions such as cysteine metabolism, purine metabolism, synaptic alterations, the synaptic vesicle cycle, and the ATP-binding cassette transporter system. These might be the key pathologic mechanisms of the ultra-early stage induced by ICH.

Deletion of VPS50 protein in mice brain impairs synaptic function and behavior

VPS50, is an accessory protein, involved in the synaptic and dense core vesicle acidification and its alterations produce behavioral changes in C.elegans. Here, we produce the mosaic knock out (mKO) of VPS50 using CRISPR/Cas9 system in both cortical cultured neurons and whole animals to evaluate the effect of VPS50 in regulating mammalian brain function and behavior. While mKO of VPS50 does not change the number of synaptic vesicles, it produces a mislocalization of the V-ATPase pump that likely impact in vesicle acidification and vesicle content to impair synaptic and neuronal activity in cultured neurons. In mice, mKO of VPS50 in the hippocampus, alter synaptic transmission and plasticity, and generated robust cognitive impairments associate to memory formation. We propose that VPS50 is an accessory protein that aids the correct recruitment of the V-ATPase pump to synaptic vesicles, thus having a crucial role controlling synaptic vesicle acidification and hence synaptic transmission.

CSMD3 Deficiency Leads to Motor Impairments and Autism-Like Behaviors via Dysfunction of Cerebellar Purkinje Cells in Mice

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with highly heritable heterogeneity. Mutations of CUB and sushi multiple domains 3 (CSMD3) gene have been reported in individuals with ASD. However, the underlying mechanisms of CSMD3 for the onset of ASD remain unexplored. Here, using male CSMD3 knock-out (CSMD3 -/-) mice, we found that genetic deletion of CSMD3 produced core autistic-like symptoms (social interaction deficits, restricted interests, and repetitive and stereotyped behaviors) and motor dysfunction in mice, indicating that the CSMD3 gene can be considered as a candidate for ASD. Moreover, we discovered that the ablation of CSMD3 in mice led to abnormal cerebellar Purkinje cell (PC) morphology in Crus I/II lobules, including aberrant developmental dendritogenesis and spinogenesis of PCs. Furthermore, combining in vivo fiber photometry calcium imaging and ex vivo electrophysiological recordings, we showed that the CSMD3 -/- mice exhibited an increased neuronal activity (calcium fluorescence signals) in PCs of Crus I/II lobules in response to movement activity, as well as an enhanced intrinsic excitability of PCs and an increase of excitatory rather than inhibitory synaptic input to the PCs, and an impaired long-term depression at the parallel fiber-PC synapse. These results suggest that CSMD3 plays an important role in the development of cerebellar PCs. Loss of CSMD3 causes abnormal PC morphology and dysfunction in the cerebellum, which may underlie the pathogenesis of motor deficits and core autistic-like symptoms in CSMD3 -/- mice. Our findings provide novel insight into the pathophysiological mechanisms by which CSMD3 mutations cause impairments in cerebellar function that may contribute to ASD.SIGNIFICANCE STATEMENT Autism spectrum disorder (ASD) is a neurodevelopmental disorder with highly heritable heterogeneity. Advances in genomic analysis have contributed to numerous candidate genes for the risk of ASD. Recently, a novel giant gene CSMD3 encoding a protein with CUB and sushi multiple domains (CSMDs) has been identified as a candidate gene for ASD. However, the underlying mechanisms of CSMD3 for the onset of ASD remain largely unknown. Here, we unravel that loss of CSMD3 results in abnormal morphology, increased intrinsic excitabilities, and impaired synaptic plasticity in cerebellar PCs, subsequently leading to motor deficits and ASD-like behaviors in mice. These results provide novel insight into the pathophysiological mechanisms by which CSMD3 mutations cause impairments in cerebellar function that may contribute to ASD.

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.

Reduced epilepsy development in synapsin 2 knockout mice with autistic behavior following early systemic treatment with interleukin-6 receptor antibody

BACKGROUND

Individuals with autism spectrum disorder (ASD) have an increased risk of developing epilepsy. Both ASD and epilepsy have been associated with increased levels of immune factors in the blood, including the proinflammatory cytokine interleukin 6 (IL-6). Mice lacking the synapsin 2 gene (Syn2 KO) exhibit ASD-like behavior and develop epileptic seizures. Their brains display neuroinflammatory changes including elevated IL-6 levels. We aimed to investigate the effect of systemic IL-6 receptor antibody (IL-6R ab) treatment on seizure development and frequency in Syn2 KO mice.

MATERIAL AND METHODS

Weekly systemic (i.p.) injections of IL-6R ab or saline were given to Syn2 KO mice starting either early in life at 1 month of age, before seizure debut or at 3 months of age, directly after seizure debut and continued for 4 or 2 months, respectively. Seizures were provoked by handling the mice three times per week. The neuroinflammatory response and synaptic protein levels in the brain were determined by ELISA, immunohistochemistry and western blots. In an additional group of Syn2 KO mice, with IL-6R ab treatment early in life, ASD-related behavioral tests including social interaction and repetitive self-grooming, as well as cognitive memory and depressive-/anxiety-like tests, and actigraphy measurements of circadian sleep-awake rhythm were analyzed.

RESULTS

The IL-6R ab treatment reduced seizure development and frequency in Syn2 KO mice when initiated before, but not after, seizure debut. However, early treatment did not reverse the neuroinflammatory response or the imbalance in synaptic protein levels in the brain previously reported in Syn2 KO mice. The treatment did not affect social interaction, performance in memory, depressive-/anxiety-like tests or the sleep-awake rhythm of Syn2 KO mice.

CONCLUSION

These findings suggest the involvement of IL-6 receptor signaling during epilepsy development in Syn2 KO mice, without significant alterations of the immune reaction in the brain, and independently of cognitive performance, mood and circadian sleep-awake rhythm.

Simultaneous Antagonism at H3R/D2R/D3R Reduces Autism-like Self-Grooming and Aggressive Behaviors by Mitigating MAPK Activation in Mice

Dysregulation in brain neurotransmitters underlies several neuropsychiatric disorders, e.g., autism spectrum disorder (ASD). Also, abnormalities in the extracellular-signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway pave the way for neuroinflammation, neurodegeneration, and altered learning phenotype in ASD. Therefore, the effects of chronic systemic administration of the multiple-targeting antagonist ST-713 at the histamine H3 receptor (H3R) and dopamine D2/D3 receptors (D2/D3R) on repetitive self-grooming, aggressive behaviors, and abnormalities in the MAPK pathway in BTBR T + Itpr3tf/J (BTBR) mice were assessed. The results showed that ST-713 (2.5, 5, and 10 mg/kg, i.p.) mitigated repetitive self-grooming and aggression in BTBR mice (all p < 0.05), and the ameliorative effects of the most promising dose of ST-713 (5 mg/kg, i.p.) on behaviors were completely abrogated by co-administration of the H3R agonist (R)-α-methylhistamine or the anticholinergic drug scopolamine. Moreover, the elevated levels of several MAPK pathway proteins and induced proinflammatory markers such as tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), and IL-6 were significantly suppressed following chronic administration of ST-713 (5 mg/kg, i.p.) (all p < 0.01). Furthermore, ST-713 significantly increased the levels of histamine and dopamine in hippocampal tissue of treated BTBR mice (all p < 0.01). The current observations signify the potential role of such multiple-targeting compounds, e.g., ST-713, in multifactorial neurodevelopmental disorders such as ASD.

CRISPR/Cas9-Induced Inactivation of the Autism-Risk Gene setd5 Leads to Social Impairments in Zebrafish

Haploinsufficiency of the SETD5 gene, encoding a SET domain-containing histone methyltransferase, has been identified as a cause of intellectual disability and Autism Spectrum Disorder (ASD). Recently, the zebrafish has emerged as a valuable model to study neurodevelopmental disorders because of its genetic tractability, robust behavioral traits and amenability to high-throughput drug screening. To model human SETD5 haploinsufficiency, we generated zebrafish setd5 mutants using the CRISPR/Cas9 technology and characterized their morphological, behavioral and molecular phenotypes. According to our observation that setd5 is expressed in adult zebrafish brain, including those areas controlling social behavior, we found that setd5 heterozygous mutants exhibit defective aggregation and coordination abilities required for shoaling interactions, as well as indifference to social stimuli. Interestingly, impairment in social interest is rescued by risperidone, an antipsychotic drug used to treat behavioral traits in ASD individuals. The molecular analysis underscored the downregulation of genes encoding proteins involved in the synaptic structure and function in the adult brain, thus suggesting that brain hypo-connectivity could be responsible for the social impairments of setd5 mutant fishes. The zebrafish setd5 mutants display ASD-like features and are a promising setd5 haploinsufficiency model for drug screening aimed at reversing the behavioral phenotypes.

The different clinical facets of SYN1-related neurodevelopmental disorders

Synapsin-I (SYN1) is a presynaptic phosphoprotein crucial for synaptogenesis and synaptic plasticity. Pathogenic SYN1 variants are associated with variable X-linked neurodevelopmental disorders mainly affecting males. In this study, we expand on the clinical and molecular spectrum of the SYN1-related neurodevelopmental disorders by describing 31 novel individuals harboring 22 different SYN1 variants. We analyzed newly identified as well as previously reported individuals in order to define the frequency of key features associated with these disorders. Specifically, behavioral disturbances such as autism spectrum disorder or attention deficit hyperactivity disorder are observed in 91% of the individuals, epilepsy in 82%, intellectual disability in 77%, and developmental delay in 70%. Seizure types mainly include tonic-clonic or focal seizures with impaired awareness. The presence of reflex seizures is one of the most representative clinical manifestations related to SYN1. In more than half of the cases, seizures are triggered by contact with water, but other triggers are also frequently reported, including rubbing with a towel, fever, toothbrushing, fingernail clipping, falling asleep, and watching others showering or bathing. We additionally describe hyperpnea, emotion, lighting, using a stroboscope, digestive troubles, and defecation as possible triggers in individuals with SYN1 variants. The molecular spectrum of SYN1 variants is broad and encompasses truncating variants (frameshift, nonsense, splicing and start-loss variants) as well as non-truncating variants (missense substitutions and in-frame duplications). Genotype-phenotype correlation revealed that epileptic phenotypes are enriched in individuals with truncating variants. Furthermore, we could show for the first time that individuals with early seizures onset tend to present with severe-to-profound intellectual disability, hence highlighting the existence of an association between early seizure onset and more severe impairment of cognitive functions. Altogether, we present a detailed clinical description of the largest series of individuals with SYN1 variants reported so far and provide the first genotype-phenotype correlations for this gene. A timely molecular diagnosis and genetic counseling are cardinal for appropriate patient management and treatment.

Vinpocetine, a PDE1 modulator, regulates markers of cerebral health, inflammation, and oxidative stress in a rat model of prenatal alcohol-induced experimental attention deficit hyperactivity disorder

Prenatal alcohol exposure (PAE) has been shown to induce symptomatology associated with attention deficit hyperactivity disorder (ADHD) by altering neurodevelopmental trajectories. Phosphodiesterase-1 (PDE1) is expressed centrally and has been used in various experimental brain conditions. We investigated the role of vinpocetine, a PDE1 inhibitor, on behavioral phenotypes and important biochemical deficits associated with a PAE rat model of ADHD. Protein markers of cerebral health (synapsin-IIa, BDNF, and pCREB), inflammation (IL-6, IL-10, and TNF-α), and oxidative stress (TBARS, GSH, and SOD) were analyzed in three brain regions (frontal cortex, striatum, and cerebellum). Hyperactivity, inattention, and anxiety introduced in the offspring due to PAE were assayed using open-field, Y-maze, and elevated plus maze, respectively. Administration of vinpocetine (10 & 20 mg/kg, p.o. [by mouth]) to PAE rat offspring for 4 weeks resulted in improvement of the behavioral profile of the animals. Additionally, levels of protein markers such as synapsin-IIa, BDNF, pCREB, IL-10, SOD, and GSH were found to be significantly increased, with a significant reduction in markers such as TNF-α, IL-6, and TBARS in selected brain regions of vinpocetine-treated animals. Vinpocetine, a selective PDE1 inhibitor, rectified behavioral phenotypes associated with ADHD, possibly by improving cerebral function, reducing brain inflammation, and reducing brain oxidative stress. This study provides preliminary analysis and suggests that the PDE1 enzyme may be an important pharmacological tool to study ADHD as a result of PAE.

Synaptic genes and neurodevelopmental disorders: From molecular mechanisms to developmental strategies of behavioral testing

Synaptopathies are a class of neurodevelopmental disorders caused by modification in genes coding for synaptic proteins. These proteins oversee the process of neurotransmission, mainly controlling the fusion and recycling of synaptic vesicles at the presynaptic terminal, the expression and localization of receptors at the postsynapse and the coupling between the pre- and the postsynaptic compartments. Murine models, with homozygous or heterozygous deletion for several synaptic genes or knock-in for specific pathogenic mutations, have been developed. They have proved to be extremely informative for understanding synaptic physiology, as well as for clarifying the patho-mechanisms leading to developmental delay, epilepsy and motor, cognitive and social impairments that are the most common clinical manifestations of neurodevelopmental disorders. However, the onset of these disorders emerges during infancy and adolescence while the behavioral phenotyping is often conducted in adult mice, missing important information about the impact of synaptic development and maturation on the manifestation of the behavioral phenotype. Here, we review the main achievements obtained by behavioral testing in murine models of synaptopathies and propose a battery of behavioral tests to improve classification, diagnosis and efficacy of potential therapeutic treatments. Our aim is to underlie the importance of studying behavioral development and better focusing on disease onset and phenotypes.

A cross-talk between nitric oxide and the glutamatergic system in a Shank3 mouse model of autism

Nitric oxide (NO) is a multifunctional signaling molecule that plays a crucial role in synaptic transmission and neuronal function. Pioneering studies show that nitric oxide (NO) and S-nitrosylation (SNO, the NO-mediated posttranslational modification) can engender nitrosative stress in the brain, contributing to neurodegenerative diseases. Little is known, however, about the aberrant NO signaling in neurodevelopmental disorders including autism spectrum disorder (ASD). We have recently shown that the Shank3 mutation in mice representing a model of ASD causes excessive NO levels and aberrant protein SNO. The glutamatergic system is involved in ASD, specifically in SHANK3 pathology. We used SNOTRAP technology to identify the SNO-proteome in the brain of the Shank3 mutant mice to understand the role of SNO in the glutamatergic system during the development of these mice. We conducted a systems biology analysis of the SNO-proteome to investigate the biological processes and signaling pathways in the brain of juvenile and adult Shank3 mutant and wild-type mice. The Shank3 mutation caused significant SNO-enrichment of a glutamate signaling pathway in the juvenile and adult mutant mice, although different protein subsets were S-nitrosylated in both ages. Cellular compartments analysis showed that "glutamatergic Synapse" is SNO-enriched significantly in the mutant mice of both ages. We also found eight S-nitrosylated proteins involved in glutamate transmission in both ages. 38 SNO-proteins found in the mutant mice are among the high-risk SFARI gene list. Biochemical examination shows a reduction in the levels of NMDA Receptor (NR1) in the cortex and striatum of the mutant mice of both ages. Neuronal NOS knockdown in SHSY-5Y rescued NR1 levels. In conclusion, this study reveals novel SNO of key glutamatergic proteins in Shank3 mutant mice and a cross-talk between nitric oxide and the glutamatergic system.

Prkn knockout mice show autistic-like behaviors and aberrant synapse formation

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with high genetic heterogeneity, affecting one in 44 children in the United States. Recent genomic sequencing studies from autistic human individuals indicate that PARK2, a gene that has long been considered in the pathogenesis of Parkinson's disease, is involved in ASD. Here, we report that Prkn knockout (KO) mice demonstrate autistic-like behaviors including impaired social interaction, elevated repetitive behaviors, and deficits in communication. In addition, Prkn KO mice show reduced neuronal activity in the context of sociability in the prelimbic cortex. Cell morphological examination of layer 5 prelimbic cortical neurons shows a reduction in dendritic arborization and spine number. Furthermore, biochemistry and immunocytochemistry analyses reveal alterations in synapse density and the molecular composition of synapses. These findings indicate that Prkn is implicated in brain development and suggest the potential use of the Prkn KO mouse as a model for autism research.

Loss of neurodevelopmental-associated miR-592 impairs neurogenesis and causes social interaction deficits

microRNA-592 (miR-592) has been linked to neurogenesis, but the influence of miR-592 knockout in vivo remains unknown. Here, we report that miR-592 knockout represses IPC-to-mature neuron transition, impairs motor coordination and reduces social interaction. Combining the RNA-seq and tandem mass tagging-based quantitative proteomics analysis (TMT protein quantification) and luciferase reporter assays, we identified MeCP2 as the direct targetgene of miR-592 in the mouse cortex. In Tg(MECP2) mice, lipofection of miR-592 efficiently reduced MECP2 expression in the brains of Tg(MECP2) mice at E14.5. Furthermore, treatment with miR-592 partially ameliorated the autism-like phenotypes observed in adult Tg(MECP2) mice. The findings demonstrate that miR-592 might play a novel role in treating the neurodevelopmental-associated disorder.

[Mechanism of valproic acid-induced dendritic spine and synaptic impairment in the prefrontal cortex for causing core autistic symptoms in mice]

OBJECTIVE

To investigate the mechanism of valproic acid (VPA) -induced impairment of the dendritic spines and synapses in the prefrontal cortex (PFC) for causing core symptoms of autism spectrum disorder (ASD) in mice.

METHODS

Female C57 mice were subjected to injections of saline or VPA on gestational days 10 and 12, and the male offspring mice in the two groups were used as the normal control group and ASD model group (n=10), respectively. Another 20 male mice with fetal exposure to VPA were randomized into two groups for stereotactic injection of DMSO or Wortmannin into the PFC (n=10). Open field test, juvenile play test and 3-chamber test were used to evaluate autistic behaviors of the mice. The density of dendrite spines in the PFC was observed with Golgi staining. Western blotting and immunofluorescence staining were used to detect the expressions of p-PI3K, PI3K, p-AKT, AKT, p-mTOR, mTOR and the synaptic proteins PSD95, p-Syn, and Syn in the PFC of the mice.

RESULTS

Compared with the normal control mice, the mice with fetal exposure to VPA exhibited obvious autism-like behaviors with significantly decreased density of total, mushroom and stubby dendritic spines (P < 0.05) and increased filopodia dendritic spines (P < 0.05) in the PFC. The VPA-exposed mice also showed significantly increased expressions of p-PI3K/PI3K, p-AKT/AKT, and p-mTOR/mTOR (P < 0.01) and lowered expressions of PSD95 and p-Syn/Syn in the PFC (P < 0.05 or 0.001). Wortmannin injection into the PFC obviously improved the ASD-like phenotype and dendritic spine development, down-regulated PI3K/Akt/mTOR signaling pathway and up-regulated the synaptic proteins in VPA-exposed mice.

CONCLUSION

In male mice with fetal exposure to VPA, excessive activation of PI3K/Akt/mTOR signaling pathway and decreased expressions of the synaptic proteins PSD95 and p-Syn cause dendritic spine damage and synaptic development disturbance in the PFC, which eventually leads to ASD-like phenotype.

Ca2+ binding to synapsin I regulates resting Ca2+ and recovery from synaptic depression in nerve terminals

Synapsin I (SynI) is a synaptic vesicle (SV)-associated phosphoprotein that modulates neurotransmission by controlling SV trafficking. The SynI C-domain contains a highly conserved ATP binding site mediating SynI oligomerization and SV clustering and an adjacent main Ca²⁺ binding site, whose physiological role is unexplored. Molecular dynamics simulations revealed that the E373K point mutation irreversibly deletes Ca²⁺ binding to SynI, still allowing ATP binding, but inducing a destabilization of the SynI oligomerization interface. Here, we analyzed the effects of this mutation on neurotransmitter release and short-term plasticity in excitatory and inhibitory synapses from primary hippocampal neurons. Patch-clamp recordings showed an increase in the frequency of miniature excitatory postsynaptic currents (EPSCs) that was totally occluded by exogenous Ca²⁺ chelators and associated with a constitutive increase in resting terminal Ca²⁺ concentrations. Evoked EPSC amplitude was also reduced, due to a decreased readily releasable pool (RRP) size. Moreover, in both excitatory and inhibitory synapses, we observed a marked impaired recovery from synaptic depression, associated with impaired RRP refilling and depletion of the recycling pool of SVs. Our study identifies SynI as a novel Ca²⁺ buffer in excitatory terminals. Blocking Ca²⁺ binding to SynI results in higher constitutive Ca²⁺ levels that increase the probability of spontaneous release and disperse SVs. This causes a decreased size of the RRP and an impaired recovery from depression due to the failure of SV reclustering after sustained high-frequency stimulation. The results indicate a physiological role of Ca²⁺ binding to SynI in the regulation of SV clustering and trafficking in nerve terminals.

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.

Exploring nordihydroguaretic acid (NDGA) as a plausible neurotherapeutic in the experimental paradigm of autism spectrum disorders targeting nitric oxide pathway

The present study investigates the neuro-protective ability of nordihydroguaretic acid (NDGA) in the experimental paradigm of autism spectrum disorders (ASD) and further decipher the nitric oxide pathway's role in its proposed action. An intracerebroventricular infusion of 4 μl of 1 M PPA was given in the lateral ventricle's anterior region to induce autism-like phenotype in male rats. Oral administration of NDGA (5, 10 & 15 mg/kg) was initiated from the 3^rd day lasting till the 28th day. L-NAME (50 mg/kg) and L-Arginine (800 mg/kg) were also given individually and combined to explore NDGA's ability to act via the nitric oxide pathway. Behavior tests for sociability, stereotypy, anxiety, depression, novelty, repetitive and perseverative behavior were carried out between the 14th and 28th day. On the 29th day, animals were sacrificed, and 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 assess the involvement of the nitric oxide pathway, levels of iNOS and homocysteine were estimated. Treatment with NDGA significantly restored behavioral, biochemical, neurological, and molecular deficits. Hence, NDGA can be used as a neurotherapeutic agent in ASD. Targeting nitric oxide pathway mediated oxidative & nitrosative stress responsible for behavioral, biochemical, and molecular alterations via modulating nitric oxide pathway. The evaluation of iNOS and homocysteine levels conclusively establishes the nitric oxide pathway's role in causing behavioral, biochemical & molecular deficits and NDGA's beneficial effect in restoring these alterations.

Vinpocetine amended prenatal valproic acid induced features of ASD possibly by altering markers of neuronal function, inflammation, and oxidative stress

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with complex etiology and phenotypes. Phosphodiesterase-1 (PDE1) inhibitors are known to provide benefits in various brain conditions manifesting similar behavioral phenotypes. The pharmacological consequences of vinpocetine administration a PDE1 inhibitor in prenatal-valproic acid (pre-VPA) induced ASD related behavioral phenotypes (social behavior deficits, repetitive behavior, anxiety, hyperlocomotion, and nociception) was assessed. Also, effects on important biochemical markers of neuronal function (DCX-neurogenesis, BDNF-neuronal survival, synapsin-IIa-synaptic transmission, pCREB-neuronal transcription factor), inflammation (interleukin [IL]-6, IL-10, and TNF-α) and oxidative stress (thiobarbituric acid reactive substance [TBARS] and glutathione (GSH) were studied in important brain areas (frontal cortex, cerebral cortex, hippocampus, and striatum). Further, neuronal cell viability was determined in dentate gyrus using Nissl staining. Pre-VPA administration resulted into impaired behavior, brain biochemistry, and neuronal cell viability. Administration of vinpocetine resulted in improvements of pre-VPA impaired social behavior, repetitive behavior, anxiety, locomotion, and nociception. Also, vinpocetine resulted in a significant increase in the levels of BDNF, synapsin-IIa, DCX, pCREB/CREB, IL-10, and GSH along with significant decrease in TNF-α, IL-6, TBARS, number of pyknotic and chromatolytic cells in different brain areas of pre-VPA group. Finally, high association between behavioral parameters and biochemical parameters was observed upon Pearson's correlation analysis. Vinpocetine, a PDE1 inhibitor rectified important behavioral phenotypes related with ASD, possibly by improving neuronal function, brain inflammation and brain oxidative stress. Thus, PDE1 may be a possible target for further understanding ASD. LAY SUMMARY: ASD is a brain developmental disorder with a wide array of genetic and environmental factors. Many targets have been identified till date, but a clinical treatment is still afar. The results of this study indicate that vinpocetine administration resulted in amelioration of ASD associated symptomatology in rats, prenatally exposed to VPA. Our research adds a widely expressed brain enzyme PDE1, as a possible novel pharmacological target and opens-up a new line of enquiry for ASD treatment.

An updated reappraisal of synapsins: structure, function and role in neurological and psychiatric disorders

Synapsins (Syns) are phosphoproteins strongly involved in neuronal development and neurotransmitter release. Three distinct genes SYN1, SYN2 and SYN3, with elevated evolutionary conservation, have been described to encode for Synapsin I, Synapsin II and Synapsin III, respectively. Syns display a series of common features, but also exhibit distinctive localization, expression pattern, post-translational modifications (PTM). These characteristics enable their interaction with other synaptic proteins, membranes and cytoskeletal components, which is essential for the proper execution of their multiple functions in neuronal cells. These include the control of synapse formation and growth, neuron maturation and renewal, as well as synaptic vesicle mobilization, docking, fusion, recycling. Perturbations in the balanced expression of Syns, alterations of their PTM, mutations and polymorphisms of their encoding genes induce severe dysregulations in brain networks functions leading to the onset of psychiatric or neurological disorders. This review presents what we have learned since the discovery of Syn I in 1977, providing the state of the art on Syns structure, function, physiology and involvement in central nervous system disorders.

Familial SYN1 variants related neurodevelopmental disorders in Asian pediatric patients

BACKGROUND

SYN1 encodes synapsin I, which is a neuronal phosphoprotein involving in regulating axonogenesis and synaptogenesis. Variants in the gene have been associated with X-linked neurodevelopmental disorders in recent years.

METHODS

In the study, we reported two male patients with familial SYN1 variants related neurodevelopmental disorders from Asian population. Previously published cases with significant SYN1 variants from the literature were also included to analyze the phenotype and genotype of the disorder.

RESULTS

Two maternally inherited SYN1 variants, including c.C1076A, p.T359K in proband A and c.C1444T, p. Q482X in proband B (NM_133499) were found, which have never been described in detail. Combining with our research, all reported probands were male in the condition, whose significant SYN1 variants were inherited from their asymptomatic or mild affected mother. Although the disorder encompasses three main clinical presentations: mental deficiency, easily controlled reflex seizure and behavior problems, patients' clinical manifestations vary in genders and individuals, even in the same pedigree.

CONCLUSION

We firstly reported two familial SYN1-related neurodevelopmental disorders in Asian pediatric patients. Gender and phenotype differences should be highly valued in the disorder.

Aberrant Early in Life Stimulation of the Stress-Response System Affects Emotional Contagion and Oxytocin Regulation in Adult Male Mice

Results over the last decades have provided evidence suggesting that HPA axis dysfunction is a major risk factor predisposing to the development of psychopathological behaviour. This susceptibility can be programmed during developmental windows of marked neuroplasticity, allowing early-life adversity to convey vulnerability to mental illness later in life. Besides genetic predisposition, also environmental factors play a pivotal role in this process, through embodiment of the mother's emotions, or via nutrients and hormones transferred through the placenta and the maternal milk. The aim of the current translational study was to mimic a severe stress condition by exposing female CD-1 mouse dams to abnormal levels of corticosterone (80 µg/mL) in the drinking water either during the last week of pregnancy (PreCORT) or the first one of lactation (PostCORT), compared to an Animal Facility Rearing (AFR) control group. When tested as adults, male mice from PostCORT offspring and somewhat less the PreCORT mice exhibited a markedly increased corticosterone response to acute restraint stress, compared to perinatal AFR controls. Aberrant persistence of adolescence-typical increased interest towards novel social stimuli and somewhat deficient emotional contagion also characterised profiles in both perinatal-CORT groups. Intranasal oxytocin (0 or 20.0 µg/kg) generally managed to reduce the stress response and restore a regular behavioural phenotype. Alterations in density of glucocorticoid and mineralocorticoid receptors, oxytocin and µ- and κ-opioid receptors were found. Changes differed as a function of brain areas and the specific age window of perinatal aberrant stimulation of the HPA axis. Present results provided experimental evidence in a translational mouse model that precocious adversity represents a risk factor predisposing to the development of psychopathological behaviour.

Kv1.1 deficiency alters repetitive and social behaviors in mice and rescues autistic-like behaviors due to Scn2a haploinsufficiency

BACKGROUND

Autism spectrum disorder (ASD) and epilepsy are highly comorbid, suggesting potential overlap in genetic etiology, pathophysiology, and neurodevelopmental abnormalities; however, the nature of this relationship remains unclear. This work investigated how two ion channel mutations, one associated with autism (Scn2a-null) and one with epilepsy (Kcna1-null), interact to modify genotype-phenotype relationships in the context of autism. Previous studies have shown that Scn2a+/- ameliorates epilepsy in Kcna1-/- mice, improving survival, seizure characteristics, and brain-heart dynamics. Here, we tested the converse, whether Kcna1 deletion modifies ASD-like repetitive and social behaviors in Scn2a+/- mice.

METHODS

Mice were bred with various combinations of Kcna1 and Scn2a knockout alleles. Animals were assessed for repetitive behaviors using marble burying, grooming, and nestlet shredding tests and for social behaviors using sociability and social novelty preference tests.

RESULTS

Behavioral testing revealed drastic reductions in all repetitive behaviors in epileptic Kcna1-/- mice, but relatively normal social interactions. In contrast, mice with partial Kcna1 deletion (Kcna1+/- ) exhibited increased self-grooming and decreased sociability suggestive of ASD-like features similar to those observed in Scn2a+/- mice. In double-mutant Scn2a+/- ; Kcna1+/- mice, the two mutations interacted to partially normalize ASD-like behaviors associated with each mutation independently.

CONCLUSIONS

Taken together, these findings suggest that Kv1.1 subunits are important in pathways and neural networks underlying ASD and that Kcna1 may be a therapeutic target for treatment of Scn2a-associated ASD.

Dysfunction of the serotonergic system in the brain of synapsin triple knockout mice is associated with behavioral abnormalities resembling synapsin-related human pathologies

Synapsins (Syns) are a family of phosphoproteins associated with synaptic vesicles (SVs). Their main function is to regulate neurotransmitter release by maintaining a reserve pool of SVs at the presynaptic terminal. Previous studies reported that the deletion of one or more Syn genes in mice results in an epileptic phenotype and autism-related behavioral abnormalities. Here we aimed at characterizing the behavioral phenotype and neurobiological correlates of the deletion of Syns in a Syn triple knockout (TKO) mouse model. Wild type (WT) and TKO mice were tested in the open field, novelty suppressed feeding, light-dark box, forced swim, tail suspension and three-chamber sociability tests. Using in vivo electrophysiology, we recorded the spontaneous activity of dorsal raphe nucleus (DRN) serotonin (5-HT) and ventral tegmental area (VTA) dopamine (DA) neurons. Levels of 5-HT and DA in the frontal cortex and hippocampus of WT and TKO mice were also assessed using a High-Performance Liquid Chromatography. TKO mice displayed hyperactivity and impaired social and anxiety-like behavior. Behavioral dysfunctions were accompanied by reduced firing activity of DRN 5-HT, but not VTA DA, neurons. TKO mice also showed increased responsiveness of DRN 5-HT-1A autoreceptors, measured as a reduced dose of the 5-HT-1A agonist 8-OH-DPAT necessary to inhibit DRN 5-HT firing activity by 50%. Finally, hippocampal 5-HT levels were lower in TKO than in WT mice. Overall, Syns deletion in mice leads to a reduction in DRN 5-HT firing activity and hippocampal 5-HT levels along with behavioral alterations reminiscent of human neuropsychiatric conditions associated with Syn dysfunction.

Spectrum of social alterations in the Neurobeachin haploinsufficiency mouse model of autism

Autism spectrum disorder (ASD) is a common and pervasive neurodevelopmental disorder, characterized by sexually divergent social deficits. Its etiology is multifactorial with an important contribution of genetic factors. Neurobeachin (Nbea), a brain-enriched multidomain scaffolding protein, is an ASD candidate gene that was found to be translocated or deleted in ASD patients. Nbea haploinsufficient (^+/-) mice have been proposed as an ASD mouse model, but its broad-spectrum social phenotype, sexual divergence and age-related robustness remain unstudied. This study compared one-year-old male and female Nbea^+/- mice and their control littermates in an extensive behavioral battery that focused on social behaviors and communication. Nbea haploinsufficiency was associated with selective, sex-dependent, quantitative and qualitative changes, including alterations in social interest and approach, ultrasonic vocalization (USV) between same-sex adult conspecifics, and preferred types of social interaction. Notably, Nbea^+/- females (but not males) displayed a significantly higher number of calls, and the mean principal frequency of their calls was higher than those of normal female littermates. Our results demonstrate that Nbea haploinsufficiency alters various aspects of social performance that are also altered in clinical ASD. The phenotype was often different between male and female mice, even though this sexual divergence was sometimes counterintuitive to observations in people with ASD, and probably influenced by differences in social interaction between male and female mice. By and large, however, this study demonstrates the clinical validity and robustness of the ASD-like phenotype of Nbea^+/- mice.

Attenuation of neurobehavioural abnormalities by papaverine in prenatal valproic acid rat model of ASD

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with complex aetiology and phenotypes. Phosphodiesterase-10A (PDE10A) inhibition has shown to provide benefits in various brain conditions. We investigated the role of a PDE10A inhibitor, papaverine on core phenotypes in prenatal-valproic acid (Pre-VPA) model of ASD. In order to identify probable mechanisms involved, the effects on several protein markers of neuronal function such as, neurogenesis-DCX, neuronal survival-BDNF, synaptic transmission-synapsin-IIa, neuronal transcription factor-pCREB, neuronal inflammation (IL-6, IL-10 and TNF-α) and neuronal oxidative stress (TBARS and GSH) were studied in frontal cortex, cerebellum, hippocampus and striatum. Pre-VPA induced impairments in social behaviour, presence of repetitive behaviour, hyper-locomotion, anxiety, and diminished nociception were studied in male Albino Wistar rats. Administration of papaverine to Pre-VPA animals resulted in improvements of social behaviour, corrected repetitive behaviour, anxiety, locomotor, and nociceptive changes. Also, papaverine resulted in a significant increase in the levels of BDNF, synapsin-IIa, DCX, pCREB, IL-10 and GSH along with significant decrease in TNF-α, IL-6 and TBARS in different brain areas of Pre-VPA group. Finally, high association between behavioural parameters and biochemical parameters was observed upon Pearson's correlation analysis. Papaverine, administration rectified core behavioural phenotype of ASD, possibly by altering protein markers associated with neuronal survival, neurogenesis, neuronal transcription factor, neuronal transmission, neuronal inflammation, and neuronal oxidative stress. Implicating PDE10A as a possible target for furthering our understanding of ASD phenotypes.

Autism spectrum disorder-like behavior caused by reduced excitatory synaptic transmission in pyramidal neurons of mouse prefrontal cortex

Autism spectrum disorder (ASD) is thought to result from deviation from normal development of neural circuits and synaptic function. Many genes with mutation in ASD patients have been identified. Here we report that two molecules associated with ASD susceptibility, contactin associated protein-like 2 (CNTNAP2) and Abelson helper integration site-1 (AHI1), are required for synaptic function and ASD-related behavior in mice. Knockdown of CNTNAP2 or AHI1 in layer 2/3 pyramidal neurons of the developing mouse prefrontal cortex (PFC) reduced excitatory synaptic transmission, impaired social interaction and induced mild vocalization abnormality. Although the causes of reduced excitatory transmission were different, pharmacological enhancement of AMPA receptor function effectively restored impaired social behavior in both CNTNAP2- and AHI1-knockdown mice. We conclude that reduced excitatory synaptic transmission in layer 2/3 pyramidal neurons of the PFC leads to impaired social interaction and mild vocalization abnormality in mice.

CNTNAP2 or AHI1 are autism-associated genes. Here the authors show using knockdown of the genes that this results in reduced excitatory synaptic transmission in layer 2/3 pyramidal neurons in the prefrontal cortex and is associated with impaired social interaction in mice.

Recent advances in gene therapy for neurodevelopmental disorders with epilepsy

Neurodevelopmental disorders can be caused by mutations in neuronal genes fundamental to brain development. These disorders have severe symptoms ranging from intellectually disability, social and cognitive impairments, and a subset are strongly linked with epilepsy. In this review, we focus on those neurodevelopmental disorders that are frequently characterized by the presence of epilepsy (NDD + E). We loosely group the genes linked to NDD + E with different neuronal functions: transcriptional regulation, intrinsic excitability and synaptic transmission. All these genes have in common a pivotal role in defining the brain architecture and function during early development, and when their function is altered, symptoms can present in the first stages of human life. The relationship with epilepsy is complex. In some NDD + E, epilepsy is a comorbidity and in others seizures appear to be the main cause of the pathology, suggesting that either structural changes (NDD) or neuronal communication (E) can lead to these disorders. Furthermore, grouping the genes that cause NDD + E, we review the uses and limitations of current models of the different disorders, and how different gene therapy strategies are being developed to treat them. We highlight where gene replacement may not be a treatment option, and where innovative therapeutic tools, such as CRISPR‐based gene editing, and new avenues of delivery are required. In general this group of genetically defined disorders, supported increasing knowledge of the mechanisms leading to neurological dysfunction serve as an excellent collection for illustrating the translational potential of gene therapy, including newly emerging tools.

Social subordination induced by early life adversity rewires inhibitory control of the prefrontal cortex via enhanced Npy1r signaling

Social hierarchies are present in most mammalian species. In nature, hierarchies offer a tradeoff between reduction of in-group fighting between males, at the expense of an asymmetric sharing of resources. Early life experiences and stress are known to influence the rank an individual attains in adulthood, but the associated cellular and synaptic alterations are poorly understood. Using a maternal separation protocol, we show that care-deprived mice display a long-lasting submissive phenotype, increased social recognition, and enhanced explorative behavior. These alterations are consistent with an adaptation that favors exploration rather than confrontation within a group setting. At the neuronal level, these animals display dendritic atrophy and enhanced inhibitory synaptic inputs in medial prefrontal cortex (mPFC) neurons. To determine what could underlie this synaptic modification, we first assessed global gene expression changes via RNAseq, and next focused on a smaller subset of putatively altered synaptic receptors that could explain the changes in synaptic inhibition. Using different cohorts of maternally deprived mice, we validated a significant increase in the expression of Npy1r, a receptor known to play a role in maternal care, anxiety, foraging, and regulation of group behavior. Using electrophysiological recordings in adult mice while blocking NPY1R signaling, we determined that this receptor plays a key role in enhancing GABAergic currents in mice that experience maternal deprivation. Taken together, our work highlights the potential of regulating NPY1R in social anxiety disorders and the alterations induced in brain circuitry as a consequence of early life stress and adversity.

The Synaptic Vesicle Cycle Revisited: New Insights into the Modes and Mechanisms

Neurotransmission is sustained by endocytosis and refilling of synaptic vesicles (SVs) locally within the presynapse. Until recently, a consensus formed that after exocytosis, SVs are recovered by either fusion pore closure (kiss-and-run) or clathrin-mediated endocytosis directly from the plasma membrane. However, recent data have revealed that SV formation is more complex than previously envisaged. For example, two additional recycling pathways have been discovered, ultrafast endocytosis and activity-dependent bulk endocytosis, in which SVs are regenerated from the internalized membrane and synaptic endosomes. Furthermore, these diverse modes of endocytosis appear to influence both the molecular composition and subsequent physiological role of individual SVs. In addition, previously unknown complexity in SV refilling and reclustering has been revealed. This review presents a modern view of the SV life cycle and discusses how neuronal subtype, physiological temperature, and individual activity patterns can recruit different endocytic modes to generate new SVs and sculpt subsequent presynaptic performance.

IGF-1 treatment causes unique transcriptional response in neurons from individuals with idiopathic autism

BACKGROUND

Research evidence accumulated in the past years in both rodent and human models for autism spectrum disorders (ASD) have established insulin-like growth factor 1 (IGF-1) as one of the most promising ASD therapeutic interventions to date. ASD is phenotypically and etiologically heterogeneous, making it challenging to uncover the underlying genetic and cellular pathophysiology of the condition; and to efficiently design drugs with widespread clinical benefits. While IGF-1 effects have been comprehensively studied in the literature, how IGF-1 activity may lead to therapeutic recovery in the ASD context is still largely unknown.

METHODS

In this study, we used a previously characterized neuronal population derived from induced pluripotent stem cells (iPSC) from neurotypical controls and idiopathic ASD individuals to study the transcriptional signature of acutely and chronically IGF-1-treated cells.

RESULTS

We present a comprehensive list of differentially regulated genes and molecular interactions resulting from IGF-1 exposure in developing neurons from controls and ASD individuals. Our results indicate that IGF-1 treatment has a different impact on neurons from ASD patients compared to controls. Response to IGF-1 treatment in neurons derived from ASD patients was heterogeneous and correlated with IGF-1 receptor expression, indicating that IGF-1 response may have responder and non-responder distinctions across cohorts of ASD patients. Our results suggest that caution should be used when predicting the effect of IGF-1 treatment on ASD patients using neurotypical controls. Instead, IGF-1 response should be studied in the context of ASD patients' neural cells.

LIMITATIONS

The limitation of our study is that our cohort of eight sporadic ASD individuals is comorbid with macrocephaly in childhood. Future studies will address weather downstream transcriptional response of IGF-1 is comparable in non-macrocephalic ASD cohorts.

CONCLUSIONS

The results presented in this study provide an important resource for researchers in the ASD field and underscore the necessity of using ASD patient lines to explore ASD neuronal-specific responses to drugs such as IGF-1. This study further helps to identify candidate pathways and targets for effective clinical intervention and may help to inform clinical trials in the future.

Resveratrol ameliorates the effect of maternal immune activation associated with schizophrenia in adulthood offspring

Maternal exposure to infectious agents such as arboviruses, bacteria, or other protozoans has been associated with an elevated risk of schizophrenia (SZ). Evidence suggests that immunological processes occurring during infection may disturb the neural progenitor, impacting the central nervous system (CNS) functions. Moreover, growing evidence suggests that resveratrol (RSV) has neuroprotective activity through anti-oxidant and anti-inflammatory mechanisms. Therefore, we investigated if the treatment with RSV during pregnancy would prevent the abnormalities associated with a SZ-like phenotype induced by maternal immune activation (MIA). Pregnant dams stimulated with a subcutaneous (s.c.) injection of polyriboinosinic-polyribocytidylic acid (poly I:C; 50 mg/kg), a viral nucleic acid mimetic or vehicle, on gestational day (GD) 12.5, were treated with RSV (40 mg/kg, s.c.) or saline, from GD 9.5 to GD 14.5. On day 45 after birth, the offspring was evaluated using a three-compartment social interaction test, elevated plus maze, and hyperlocomotion test induced by amphetamine. After the behavioral tests, the relative expression of mRNA to synapsin 1 (Syn1), oligodendrocyte transcription factor 1 (Olig1), and SRY (sex-determining region Y)-box 2 (Sox2) was determined in the hippocampus and cortex. Treatment with RSV restored the social behavior and attenuated the hyperlocomotion of the offspring bred by dams submitted to MIA. RSV prevented the effects of MIA on Syn1 and Olig1 expression in the hippocampus and Syn1 in the cortex. The present study showed that maternal treatment with RSV attenuates some of the negative behavioral impacts caused by MIA, with modulation of synaptic and oligodendrogenesis processes.

Factors Associated With Seizure Onset in Children With Autism Spectrum Disorder

BACKGROUND AND OBJECTIVES

Children with autism spectrum disorder (ASD) have a higher prevalence of epilepsy compared with general populations. In this pilot study, we prospectively identified baseline risk factors for the development of seizures in individuals with ASD and also identified characteristics sensitive to seizure onset up to 6 years after enrollment in the Autism Speaks Autism Treatment Network.

METHODS

Children with ASD and no history of seizures at baseline who either experienced onset of seizures after enrollment in the Autism Treatment Network or remained seizure free were included in the analysis.

RESULTS

Among 472 qualifying children, 22 (4.7%) experienced onset of seizures after enrollment. Individuals who developed seizures after enrollment exhibited lower scores at baseline on all domains of the Vineland Adaptive Behavior Scales, greater hyperactivity on the Aberrant Behavior Checklist (25.4 ± 11.8 vs 19.2 ± 11.1; P = .018), and lower physical quality of life scores on the Pediatric Quality of Life Inventory (60.1 ± 24.2 vs 76.0 ± 18.2; P < .001). Comparing change in scores from entry to call-back, adjusting for age, sex, length of follow-up, and baseline Vineland II composite score, individuals who developed seizures experienced declines in daily living skills (-8.38; 95% confidence interval -14.50 to -2.50; P = .005). Adjusting for baseline age, sex, and length of follow-up, baseline Vineland II composite score was predictive of seizure development (risk ratio = 0.95 per unit Vineland II composite score, 95% confidence interval 0.92 to 0.99; P = .007).

CONCLUSIONS

Individuals with ASD at risk for seizures exhibited changes in adaptive functioning and behavior.

The Regulation of Reactive Neuroblastosis, Neuroplasticity, and Nutraceuticals for Effective Management of Autism Spectrum Disorder

Autism spectrum disorder (ASD) encompasses a cluster of neurodevelopmental and genetic disorders that has been characterized mainly by social withdrawal, repetitive behavior, restricted interests, and deficits in language processing mainly in children. ASD has been known to severely impair behavioral patterns and cognitive functions including learning and memory due to defects in neuroplasticity. The biology of the ASD appears to be highly complex and heterogeneous, and thus, finding a therapeutic target for autism remains obscure. There has been no complete prevention or disease-modifying cure for this disorder. Recently, individuals with autism have been characterized by reactive neurogenesis, obstructions in axonal growth, heterotopia, resulting from dysplasia of neuroblasts in different brain regions. Therefore, it can be assumed that the aforementioned neuropathological correlates seen in the autistic individuals might originate from the defects mainly in the regulation of neuroblasts in the developing as well as adult brain. Nutrient deficiencies during early brain development and intake of certain allergic foods have been proposed as main reasons for the development of ASD. However, the integrated understanding of neurodevelopment and functional aspects of neuroplasticity working through neurogenesis in ASD is highly limited. Moreover, neurogenesis at the level of neuroblasts can be regulated by nutrition. Hence, defects in neuroblastosis underlying the severity of autism potentially could be rectified by appropriate implementation of nutraceuticals.

Physical Activity Reduces Epilepsy Incidence: a Retrospective Cohort Study in Swedish Cross-Country Skiers and an Experimental Study in Seizure-Prone Synapsin II Knockout Mice

BACKGROUND

Epilepsy patients commonly exercise less than the general population. Animal studies indicate beneficial effects of physical activity in established epilepsy, while its effect on the development is currently less known.

METHODS

Here, we investigated the incidence of epilepsy during 20 years in a cohort of participants from the long-distance Swedish cross-country ski race Vasaloppet (n = 197,685) and compared it to the incidence of non-participating-matched controls included in the Swedish population register (n = 197,684). Individuals diagnosed with diseases such as stroke and epilepsy before entering the race were excluded from both groups. Experimentally, we also determined how physical activity could affect the development of epilepsy in epilepsy-prone synapsin II knockout mice (SynIIKO), with and without free access to a running wheel.

RESULTS

We identified up to 40-50% lower incidence of epilepsy in the Vasaloppet participants of all ages before retirement. A lower incidence of epilepsy in Vasaloppet participants was seen regardless of gender, education and occupation level compared to controls. The participants included both elite and recreational skiers, and in a previous survey, they have reported a higher exercise rate than the general Swedish population. Sub-analyses revealed a significantly lower incidence of epilepsy in participants with a faster compared to slower finishing time. Dividing participants according to specified epilepsy diagnoses revealed 40-50% decrease in focal and unspecified epilepsy, respectively, but no differences in generalized epilepsy. Voluntary exercise in seizure-prone SynIIKO mice for 1 month before predicted epilepsy development decreased seizure manifestation from > 70 to 40%. Brain tissue analyses following 1 month of exercise showed increased hippocampal neurogenesis (DCX-positive cells), while microglial (Iba1) and astrocytic activation (GFAP), neuronal Map2, brain-derived neurotrophic factor and its receptor tyrosine receptor kinase B intensity were unaltered. Continued exercise for additionally 2 months after predicted seizure onset in SynIIKO mice resulted in a 5-fold reduction in seizure manifestation (from 90 to 20%), while 2 months of exercise initiated at the time of predicted seizure development gave no seizure relief, suggesting exercise-induced anti-epileptogenic rather than anti-convulsive effect.

CONCLUSION

The clinical study and the experimental findings in mice indicate that physical activity may prevent or delay the development of epilepsy.

NEXMIF/KIDLIA Knock-out Mouse Demonstrates Autism-Like Behaviors, Memory Deficits, and Impairments in Synapse Formation and Function

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disability that demonstrates impaired social interactions, communication deficits, and restrictive and repetitive behaviors. ASD has a strong genetic basis and many ASD-associated genes have been discovered thus far. Our previous work has shown that loss of expression of the X-linked gene NEXMIF/KIDLIA is implicated in patients with autistic features and intellectual disability (ID). To further determine the causal role of the gene in the disorder, and to understand the cellular and molecular mechanisms underlying the pathology, we have generated a NEXMIF knock-out (KO) mouse. We find that male NEXMIF KO mice demonstrate reduced sociability and communication, elevated repetitive grooming behavior, and deficits in learning and memory. Loss of NEXMIF/KIDLIA expression results in a significant decrease in synapse density and synaptic protein expression. Consistently, male KO animals show aberrant synaptic function as measured by excitatory miniatures and postsynaptic currents in the hippocampus. These findings indicate that NEXMIF KO mice recapitulate the phenotypes of the human disorder. The NEXMIF KO mouse model will be a valuable tool for studying the complex mechanisms involved in ASD and for the development of novel therapeutics for this disorder.SIGNIFICANCE STATEMENT Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder characterized by behavioral phenotypes. Based on our previous work, which indicated the loss of NEXMIF/KIDLIA was associated with ASD, we generated NEXMIF knock-out (KO) mice. The NEXMIF KO mice demonstrate autism-like behaviors including deficits in social interaction, increased repetitive self-grooming, and impairments in communication and in learning and memory. The KO neurons show reduced synapse density and a suppression in synaptic transmission, indicating a role for NEXMIF in regulating synapse development and function. The NEXMIF KO mouse faithfully recapitulates the human disorder, and thus serves as an animal model for future investigation of the NEXMIF-dependent neurodevelopmental disorders.

Decreased Expression of Synaptophysin 1 (SYP1 Major Synaptic Vesicle Protein p38) and Contactin 6 (CNTN6/NB3) in the Cerebellar Vermis of reln Haplodeficient Mice

Reeler heterozygous mice (reln+/-) are seemingly normal but haplodeficient in reln, a gene implicated in autism. Structural/neurochemical alterations in the reln+/- brain are subtle and difficult to demonstrate. Therefore, the usefulness of these mice in translational research is still debated. As evidence implicated several synapse-related genes in autism and the cerebellar vermis is structurally altered in the condition, we have investigated the expression of synaptophysin 1 (SYP1) and contactin 6 (CNTN6) within the vermis of reln+/- mice. Semi-thin plastic sections of the vermis from adult mice of both sexes and different genotypes (reln+/- and reln+/+) were processed with an indirect immunofluorescence protocol. Immunofluorescence was quantified on binary images and statistically analyzed. Reln+/- males displayed a statistically significant reduction of 11.89% in the expression of SYP1 compared to sex-matched wild-type animals, whereas no differences were observed between reln+/+ and reln+/- females. In reln+/- male mice, reductions were particularly evident in the molecular layer: 10.23% less SYP1 than reln+/+ males and 5.84% < reln+/+ females. In reln+/- females, decrease was 9.84% versus reln+/+ males and 5.43% versus reln+/+ females. Both reln+/- males and females showed a stronger decrease in CNTN6 expression throughout all the three cortical layers of the vermis: 17-23% in the granular layer, 24-26% in the Purkinje cell layer, and 9-14% in the molecular layer. Altogether, decrease of vermian SYP1 and CNTN6 in reln+/- mice displayed patterns compatible with the structural modifications of the autistic cerebellum. Therefore, these mice may be a good model in translational studies.

Perturbation of synapsins homeostasis through HIV-1 Tat-mediated suppression of BAG3 in primary neuronal cells

HIV-1 Tat is known to be released by HIV infected non-neuronal cells in the brain, and after entering neurons, compromises brain homeostasis by impairing pro-survival pathways, thus contributing to the development of HIV-associated CNS disorders commonly observed in individuals living with HIV. Here, we demonstrate that synapsins, phosphoproteins that are predominantly expressed in neuronal cells and play a vital role in modulating neurotransmitter release at the pre-synaptic terminal, and neuronal differentiation become targets for Tat through autophagy and protein quality control pathways. We demonstrate that the presence of Tat in neurons results in downregulation of BAG3, a co-chaperone for heat shock proteins (Hsp70/Hsc70) that is implicated in protein quality control (PQC) processes by eliminating mis-folded and damaged proteins, and selective macroautophagy. Our results show that treatment of cells with Tat or suppression of BAG3 expression by siRNA in neuronal cells disturbs subcellular distribution of synapsins and synaptotagmin 1 (Syt1) leading to their accumulation in the neuronal soma and along axons in a punctate pattern, rather than being properly distributed at axon-terminals. Further, our results revealed that synapsins partially lost their stability and their removal via lysosomal autophagy was noticeably impaired in cells with low levels of BAG3. The observed impairment of lysosomal autophagy, under this condition, is likely caused by cells losing their ability to process LC3-I to LC3-II, in part due to a decrease in the ATG5 levels upon BAG3 knockdown. These observations ascribe a new function for BAG3 in controlling synaptic communications and illuminate a new downstream target for Tat to elicit its pathogenic effect in impacting neuronal cell function and behavior.

Strain differences in the susceptibility to the gut-brain axis and neurobehavioural alterations induced by maternal immune activation in mice

There is a growing realization that the severity of the core symptoms of autism spectrum disorders and schizophrenia is associated with gastrointestinal dysfunction. Nonetheless, the mechanisms underlying such comorbidities remain unknown. Several genetic and environmental factors have been linked to a higher susceptibility to neurodevelopmental abnormalities. The maternal immune activation (MIA) rodent model is a valuable tool for elucidating the basis of this interaction. We induced MIA with polyinosinic-polycytidylic acid (poly I:C) at gestational day 12.5 and assessed behavioural, physiological and molecular aspects relevant to the gut-brain axis in the offspring of an outbred (NIH Swiss) and an inbred (C57BL6/J) mouse strain. Our results showed that the specific MIA protocol employed induces social deficits in both strains. However, alterations in anxiety and depression-like behaviours were more pronounced in NIH Swiss mice. These strain-specific behavioural effects in the NIH Swiss mice were associated with marked changes in important components of gut-brain axis communication: the endocrine response to stress and gut permeability. In addition, MIA-induced changes in vasopressin receptor 1a mRNA expression in the hypothalamus were observed in NIH Swiss mice only. Taken together, these data suggest that genetic background is a critical factor in susceptibility to the gut-brain axis effects induced by MIA.

Retinal alterations in a pre-clinical model of an autism spectrum disorder

Background

Autism spectrum disorders (ASD) affect around 1.5% of people worldwide. Symptoms start around age 2, when children fail to maintain eye contact and to develop speech and other forms of communication. Disturbances in glutamatergic and GABAergic signaling that lead to synaptic changes and alter the balance between excitation and inhibition in the developing brain are consistently found in ASD. One of the hallmarks of these disorders is hypersensitivity to sensory stimuli; however, little is known about its underlying causes. Since the retina is the part of the CNS that converts light into a neuronal signal, we set out to study how it is affected in adolescent mice prenatally exposed to valproic acid (VPA), a useful tool to study ASD endophenotypes.

Methods

Pregnant female mice received VPA (600 mg/kg, ip) or saline at gestational day 11. Their male adolescent pups (P29–35) were behaviorally tested for anxiety and social interaction. Proteins known to be related with ASD were quantified and visualized in their retinas by immunoassays, and retinal function was assessed by full-field scotopic electroretinograms (ERGs).

Results

Early adolescent mice prenatally exposed to VPA displayed impaired social interest and increased anxiety-like behaviors consistent with an ASD phenotype. The expression of GABA, GAD, synapsin-1, and FMRP proteins were reduced in their retinas, while mGluR5 was increased. The a-wave amplitudes of VPA-exposed were smaller than those of CTR animals, whereas the b-wave and oscillatory potentials were normal.

Conclusions

This study establishes that adolescent male mice of the VPA-induced ASD model have alterations in retinal function and protein expression compatible with those found in several brain areas of other autism models. These results support the view that synaptic disturbances with excitatory/inhibitory imbalance early in life are associated with ASD and point to the retina as a window to understand their subjacent mechanisms.

Electronic supplementary material

The online version of this article (10.1186/s13229-019-0270-8) contains supplementary material, which is available to authorized users.

Postsynaptic Mechanisms Render Syn I/II/III Mice Highly Responsive to Psychostimulants

BACKGROUND

Synapsins are encoded by SYN I, SYN II, and SYN III, and they regulate neurotransmitter release by maintaining a reserve pool of synaptic vesicles.

METHODS

Presynaptic dopamine responses to cocaine were examined by microdialysis, and postsynaptic responses were evaluated to various dopamine receptor agonists in the open field with SynI/SynII/SynIII triple knockout mice.

RESULTS

Triple knockout mice showed enhanced spontaneous locomotion in a novel environment and were hyper-responsive to indirect and direct D1 and D2 dopamine agonists. Triple knockout animals appeared sensitized to cocaine upon first open field exposure; sensitization developed across days in wild-type controls. When mutants were preexposed to a novel environment before injection, cocaine-stimulated locomotion was reduced and behavioral sensitization retarded. Baseline dopamine turnover was enhanced in mutants and novel open field exposure increased their striatal dopamine synthesis rates. As KCl-depolarization stimulated comparable dopamine release in both genotypes, their readily releasable pools appeared indistinguishable. Similarly, cocaine-induced hyperlocomotion was indifferent to blockade of newly synthesized dopamine and depletion of releasable dopamine pools. Extracellular dopamine release was similar in wild-type and triple knockout mice preexposed to the open field and given cocaine or placed immediately into the arena following injection. Since motor effects to novelty and psychostimulants depend upon frontocortical-striatal inputs, we inhibited triple knockout medial frontal cortex with GABA agonists. Locomotion was transiently increased in cocaine-injected mutants, while their supersensitive cocaine response to novelty was lost.

CONCLUSIONS

These results reveal presynaptic dopamine release is not indicative of agonist-induced triple knockout hyperlocomotion. Instead, their novelty response occurs primarily through postsynaptic mechanisms and network effects.

Enhanced Social Dominance and Altered Neuronal Excitability in the Prefrontal Cortex of Male KCC2b Mutant Mice

The K-Cl cotransporter KCC2 is essential in the development of the "GABA switch" that produces a change in neuronal responses to GABA signaling from excitatory to inhibitory early in brain development, and alterations in this progression have previously been hypothesized to play a causal role in autism spectrum disorder (ASD). We investigated the KCC2b (Slc12a5) heterozygous knockout mouse using a battery of rodent behavioral tests relevant to core and comorbid ASD symptoms. Compared to wild-type littermates, KCC2^+/- mice were normal in standard measures of locomotor activity, grooming and digging behaviors, and social, vocalization, and anxiety-like behaviors. However, KCC2^+/- mice exhibited increased social dominance behaviors and increased amplitude of spontaneous postsynaptic currents in the medial prefrontal cortex (PFC) that were previously implicated in governing social hierarchy and dominance behaviors. Treatment of wild-type mouse brain slices with the KCC2 inhibitor VU0240511 increased the amplitude and frequency of excitatory postsynaptic currents, partially recapitulating the phenotype of KCC2^+/- mice. These findings indicate that the activity of KCC2 plays a role in social dominance, in parallel with effects on PFC signaling, further suggesting that KCC2 function has some relevance to social behavior but without the breadth of impact on autism-like behavior suggested by previous studies. Further testing could assess whether KCC2 alters other circuits and whether additional factors such as environmental insults may precipitate autism-related behavioral phenotypes. Autism Research 2019, 12: 732-743. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: A mouse model of altered chloride transporter expression was used to look for a role in behaviors and brain function relevant to autism. There was an imbalance in signaling in the prefrontal cortex, and increased social dominance behavior, although other autism-related behaviors were not changed. These findings indicate that altered chloride transporter function affects prefrontal cortex function and social dominance without a broader impact on autism-like behaviors.