Contribution of SHANK3 mutations to autism spectrum disorder

The autophagy proteome in the brain

As one of the most important cellular housekeepers, autophagy directly affects cellular health, homeostasis, and function. Even though the mechanisms behind autophagy are well described, how molecular alterations and dysfunctions can lead to pathology in disease contexts still demands deeper investigation. Proteomics is a widely employed tool used to investigate molecular alterations associated with pathological states and has proven useful in identifying alterations in protein expression levels and post-translational modifications in autophagy. In this narrative review, we expand on the molecular mechanisms behind autophagy and its regulation, and further compile recent literature associating autophagy disturbances in context of brain disorders, utilizing discoveries from varying models and species from rodents and cellular models to human post-mortem brain samples. To outline, the canonical pathways of autophagy, the effects of post-translational modifications on regulating each step of autophagy, and the future directions of proteomics in autophagy will be discussed. We further aim to suggest how advancing proteomics can help further unveil molecular mechanisms with regard to neurological disorders.

The Medial Prefrontal Cortex-Basolateral Amygdala Circuit Mediates Anxiety in Shank3 InsG3680 Knock-in Mice

Anxiety disorder is a major symptom of autism spectrum disorder (ASD) with a comorbidity rate of ~40%. However, the neural mechanisms of the emergence of anxiety in ASD remain unclear. In our study, we found that hyperactivity of basolateral amygdala (BLA) pyramidal neurons (PNs) in Shank3 InsG3680 knock-in (InsG3680+/+) mice is involved in the development of anxiety. Electrophysiological results also showed increased excitatory input and decreased inhibitory input in BLA PNs. Chemogenetic inhibition of the excitability of PNs in the BLA rescued the anxiety phenotype of InsG3680+/+ mice. Further study found that the diminished control of the BLA by medial prefrontal cortex (mPFC) and optogenetic activation of the mPFC-BLA pathway also had a rescue effect, which increased the feedforward inhibition of the BLA. Taken together, our results suggest that hyperactivity of the BLA and alteration of the mPFC-BLA circuitry are involved in anxiety in InsG3680+/+ mice.

Deciphering the Role of Shank3 in Dendritic Morphology and Synaptic Function Across Postnatal Developmental Stages in the Shank3B KO Mouse

Autism Spectrum Disorder (ASD) is marked by early-onset neurodevelopmental anomalies, yet the temporal dynamics of genetic contributions to these processes remain insufficiently understood. This study aimed to elucidate the role of the Shank3 gene, known to be associated with monogenic causes of autism, in early developmental processes to inform the timing and mechanisms for potential interventions for ASD. Utilizing the Shank3B knockout (KO) mouse model, we examined Shank3 expression and its impact on neuronal maturation through Golgi staining for dendritic morphology and electrophysiological recordings to measure synaptic function in the anterior cingulate cortex (ACC) across different postnatal stages. Our longitudinal analysis revealed that, while Shank3B KO mice displayed normal neuronal morphology at one week postnatal, significant impairments in dendritic growth and synaptic activity emerged by two to three weeks. These findings highlight the critical developmental window during which Shank3 is essential for neuronal and synaptic maturation in the ACC.

Epigenetic Insights into Autism Spectrum Disorder: DNA Methylation Levels of NR3C1, ASCL1, and FOXO3 in Korean Autism Spectrum Disorder Sibling Pairs

Objective

Previous research on autism spectrum disorder (ASD) in Koreans has primarily focused on genetic diversity because of its high heritability. However, the emerging recognition of transgenerational epigenetic changes has recently shifted research attention towards epigenetic perspectives.

Methods

This study investigated the DNA methylation patterns of the promoter regions of candidate genes such as NR3C1, ASCL1, and FOXO3 in blood samples from ASD probands and their unaffected siblings. The analysis included 54 families (ASD proband group: 54; unaffected biological sibling group: 63). The diagnostic process involved screening the probands and their siblings for ASD based on the Diagnostic and Statistical Manual of Mental Disorders 5th edition. Intelligence, social ability, and medical history were thoroughly assessed using various scales and questionnaires. Genomic DNA from blood samples was analyzed using a methylation-sensitive quantitative polymerase chain reaction to examine the DNA methylation status of candidate genes.

Results

Methylation levels in candidate gene promoter regions differed significantly between the proband and sibling groups for all candidate genes. Correlation analysis between the proband and sibling groups revealed strong and significant correlations in NR3C1 and ASCL1 methylation. Additionally, in the analysis of the relationship between DNA and ASD phenotypes, FOXO3 methylation correlated with social quotient in probands, and ASCL1 methylation was associated with nonverbal communication, and daily living skills as measured by the Korean Vineland Adaptive Behavior Scale. Notably, ASCL1 methylation was significantly associated with parental age at pregnancy.

Conclusion

This study proposes DNA methylation of NR3C1, ASCL1, and FOXO3 in peripheral blood samples is a potential epigenetic biomarker of ASD.

Exploring the Landscape of Pre- and Post-Synaptic Pediatric Disorders with Epilepsy: A Narrative Review on Molecular Mechanisms Involved

Neurodevelopmental disorders (NDDs) are a group of conditions affecting brain development, with variable degrees of severity and heterogeneous clinical features. They include intellectual disability (ID), autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), often coexisting with epilepsy, extra-neurological comorbidities, and multisystemic involvement. In recent years, next-generation sequencing (NGS) technologies allowed the identification of several gene pathogenic variants etiologically related to these disorders in a large cohort of affected children. These genes encode proteins involved in synaptic homeostasis, such as SNARE proteins, implicated in calcium-triggered pre-synaptic release of neurotransmitters, or channel subunit proteins, such as post-synaptic ionotropic glutamate receptors involved in the brain's fast excitatory neurotransmission. In this narrative review, we dissected emerged molecular mechanisms related to NDDs and epilepsy due to defects in pre- and post-synaptic transmission. We focused on the most recently discovered SNAREopathies and AMPA-related synaptopathies.

Clinical, developmental and serotonemia phenotyping of a sample of 70 Italian patients with Phelan-McDermid Syndrome

BACKGROUND

Phelan-McDermid syndrome (PMS) is caused by monoallelic loss or inactivation at the SHANK3 gene, located in human chr 22q13.33, and is often associated with Autism Spectrum Disorder (ASD).

OBJECTIVES

To assess the clinical and developmental phenotype in a novel sample of PMS patients, including for the first time auxometric trajectories and serotonin blood levels.

METHODS

70 Italian PMS patients were clinically characterized by parental report, direct medical observation, and a thorough medical and psychodiagnostic protocol. Serotonin levels were measured in platelet-rich plasma by HPLC.

RESULTS

Our sample includes 59 (84.3%) cases with chr. 22q13 terminal deletion, 5 (7.1%) disruptive SHANK3 mutations, and 6 (8.6%) ring chromosome 22. Intellectual disability was present in 69 (98.6%) cases, motor coordination disorder in 65 (92.9%), ASD in 20 (28.6%), and lifetime bipolar disorder in 12 (17.1%). Prenatal and postnatal complications were frequent (22.9%-48.6%). Expressive and receptive language were absent in 49 (70.0%) and 19 (27.1%) cases, respectively. Decreased pain sensitivity was reported in 56 (80.0%), hyperactivity in 49 (80.3%), abnormal sleep in 45 (64.3%), congenital dysmorphisms in 35 (58.3%), chronic stool abnormalities and especially constipation in 29 (41.4%). Parents reported noticing behavioral abnormalities during early childhood immediately after an infective episode in 34 (48.6%) patients. Brain MRI anomalies were observed in 53 (79.1%), EEG abnormalities in 16 (23.5%), kidney and upper urinary tract malformations in 18 (28.1%). Two novel phenotypes emerged: (a) a subgroup of 12/44 (27.3%) PMS patients displays smaller head size at enrollment (mean age 11.8 yrs) compared to their first year of neonatal life, documenting a deceleration of head growth (p < 0.001); (b) serotonin blood levels are significantly lower in 21 PMS patients compared to their 21 unaffected siblings (P < 0.05), and to 432 idiopathic ASD cases (p < 0.001).

CONCLUSIONS

We replicate and extend the description of many phenotypic characteristics present in PMS, and report two novel features: (1) growth trajectories are variable and head growth appears to slow down during childhood in some PMS patients; (2) serotonin blood levels are decreased in PMS, and not increased as frequently occurs in ASD. Further investigations of these novel features are under way.

Mapping the Behavioral Signatures of Shank3b Mice in Both Sexes

Autism spectrum disorders (ASD) are characterized by social and repetitive abnormalities. Although the ASD mouse model with Shank3b mutations is widely used in ASD research, the behavioral phenotype of this model has not been fully elucidated. Here, a 3D-motion capture system and linear discriminant analysis were used to comprehensively record and analyze the behavioral patterns of male and female Shank3b mutant mice. It was found that both sexes replicated the core and accompanied symptoms of ASD, with significant sex differences. Further, Shank3b heterozygous knockout mice exhibited distinct autistic behaviors, that were significantly different from those those observed in the wild type and homozygous knockout groups. Our findings provide evidence for the inclusion of both sexes and experimental approaches to efficiently characterize heterozygous transgenic models, which are more clinically relevant in autistic studies.

Structural Variations Identified in Patients with Autism Spectrum Disorder (ASD) in the Chinese Population: A Systematic Review of Case-Control Studies

Autistic spectrum disorder (ASD) is a neurodevelopmental disability characterised by the impairment of social interaction and communication ability. The alarming increase in its prevalence in children urged researchers to obtain a better understanding of the causes of this disease. Genetic factors are considered to be crucial, as ASD has a tendency to run in families. In recent years, with technological advances, the importance of structural variations (SVs) in ASD began to emerge. Most of these studies, however, focus on the Caucasian population. As a populated ethnicity, ASD shall be a significant health issue in China. This systematic review aims to summarise current case-control studies of SVs associated with ASD in the Chinese population. A list of genes identified in the nine included studies is provided. It also reveals that similar research focusing on other genetic backgrounds is demanded to manifest the disease etiology in different ethnic groups, and assist the development of accurate ethnic-oriented genetic diagnosis.

Transcriptional determinism and stochasticity contribute to the complexity of autism-associated SHANK family genes

Precision of transcription is critical because transcriptional dysregulation is disease causing. Traditional methods of transcriptional profiling are inadequate to elucidate the full spectrum of the transcriptome, particularly for longer and less abundant mRNAs. SHANK3 is one of the most common autism causative genes. Twenty-four Shank3-mutant animal lines have been developed for autism modeling. However, their preclinical validity has been questioned due to incomplete Shank3 transcript structure. We apply an integrative approach combining cDNA-capture and long-read sequencing to profile the SHANK3 transcriptome in humans and mice. We unexpectedly discover an extremely complex SHANK3 transcriptome. Specific SHANK3 transcripts are altered in Shank3-mutant mice and postmortem brain tissues from individuals with autism spectrum disorder. The enhanced SHANK3 transcriptome significantly improves the detection rate for potential deleterious variants from genomics studies of neuropsychiatric disorders. Our findings suggest that both deterministic and stochastic transcription of the genome is associated with SHANK family genes.

Trans-synaptic Association of Vesicular Zinc Transporter 3 and Shank3 Supports Synapse-Specific Dendritic Spine Structure and Function in the Mouse Auditory Cortex

Shank3 is a synaptic scaffolding protein that assists in tethering and organizing structural proteins and glutamatergic receptors in the postsynaptic density of excitatory synapses. The localization of Shank3 at excitatory synapses and the formation of stable Shank3 complexes is regulated by the binding of zinc to the C-terminal sterile-alpha-motif (SAM) domain of Shank3. Mutations in the SAM domain of Shank3 result in altered synaptic function and morphology, and disruption of zinc in synapses that express Shank3 leads to a reduction of postsynaptic proteins important for synaptic structure and function. This suggests that zinc supports the localization of postsynaptic proteins via Shank3. Many regions of the brain are highly enriched with free zinc inside glutamatergic vesicles at presynaptic terminals. At these synapses, zinc transporter 3 (ZnT3) moves zinc into vesicles where it is co-released with glutamate. Alterations in ZnT3 are implicated in multiple neurodevelopmental disorders, and ZnT3 knock-out (KO) mice-which lack synaptic zinc-show behavioral deficits associated with autism spectrum disorder and schizophrenia. Here we show that male and female ZnT3 KO mice have smaller dendritic spines and miniature excitatory postsynaptic current amplitudes than wildtype (WT) mice in the auditory cortex. Additionally, spine size deficits in ZnT3 KO mice are restricted to synapses that express Shank3. In WT mice, synapses that express both Shank3 and ZnT3 have larger spines compared to synapses that express Shank3 but not ZnT3. Together these findings suggest a mechanism whereby presynaptic ZnT3-dependent zinc supports postsynaptic structure and function via Shank3 in a synapse-specific manner.

Conditional knockout of Shank3 in the ventral CA1 by quantitative in vivo genome-editing impairs social memory in mice

Individuals with autism spectrum disorder (ASD) have a higher prevalence of social memory impairment. A series of our previous studies revealed that hippocampal ventral CA1 (vCA1) neurons possess social memory engram and that the neurophysiological representation of social memory in the vCA1 neurons is disrupted in ASD-associated Shank3 knockout mice. However, whether the dysfunction of Shank3 in vCA1 causes the social memory impairment observed in ASD remains unclear. In this study, we found that vCA1-specific Shank3 conditional knockout (cKO) by the adeno-associated virus (AAV)- or specialized extracellular vesicle (EV)- mediated in vivo gene editing was sufficient to recapitulate the social memory impairment in male mice. Furthermore, the utilization of EV-mediated Shank3-cKO allowed us to quantitatively examine the role of Shank3 in social memory. Our results suggested that there is a certain threshold for the proportion of Shank3-cKO neurons required for social memory disruption. Thus, our study provides insight into the population coding of social memory in vCA1, as well as the pathological mechanisms underlying social memory impairment in ASD.

Pharmacological modulation of developmental and synaptic phenotypes in human SHANK3 deficient stem cell-derived neuronal models

Phelan-McDermid syndrome (PMDS) arises from mutations in the terminal region of chromosome 22q13, impacting the SHANK3 gene. The resulting deficiency of the postsynaptic density scaffolding protein SHANK3 is associated with autism spectrum disorder (ASD). We examined 12 different PMDS patient and CRISPR-engineered stem cell-derived neuronal models and controls and found that reduced expression of SHANK3 leads to neuronal hyperdifferentiation, increased synapse formation, and decreased neuronal activity. We performed automated imaging-based screening of 7,120 target-annotated small molecules and identified three compounds that rescued SHANK3-dependent neuronal hyperdifferentiation. One compound, Benproperine, rescued the decreased colocalization of Actin Related Protein 2/3 Complex Subunit 2 (ARPC2) with ß-actin and rescued increased synapse formation in SHANK3 deficient neurons when administered early during differentiation. Neuronal activity was only mildly affected, highlighting Benproperine's effects as a neurodevelopmental modulator. This study demonstrates that small molecular compounds that reverse developmental phenotypes can be identified in human neuronal PMDS models.

Sex-specific modulation of safety learning in Shank2-deficient mice

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by impaired perceptual processing and social communication, intellectual disabilities, and repetitive behaviors. Interestingly, while not a core symptom, anxiety disorders frequently co-occur in individuals with ASD and deficits in safety learning have been described in patients with anxiety-related disorders. Because genetic factors, such as SHANK deficiency (loss-of-function mutations), have been linked to ASD, the aim of the present study was to investigate whether Shank2 deficiency interferes with associative fear and safety signal learning. To first investigate trait anxiety, male and female Shank2-deficient mice were exposed to a light-dark box test. Mice were then submitted to a combination of contextual fear conditioning and single-cue safety conditioning. The results show that Shank2 deficiency increases trait anxiety but reduces contextual fear learning. In male but not female Shank2-deficient mice, reduced single-cued safety learning was observed. This safety learning deficit was not caused by altered anxiety levels, increased locomotor activity, or reduced contextual fear since these changes were also observed in female Shank2-deficient mice. Concluding, our data indicate that the observed safety learning deficits in Shank2-deficient male mice could contribute to the emotional symptoms observed in ASD and the high comorbidity with anxiety-related disorders.

Increased number of excitatory synapsis and decreased number of inhibitory synapsis in the prefrontal cortex in autism

Previous studies in autism spectrum disorder demonstrated an increased number of excitatory pyramidal cells and a decreased number of inhibitory parvalbumin+ chandelier interneurons in the prefrontal cortex of postmortem brains. How these changes in cellular composition affect the overall abundance of excitatory and inhibitory synapses in the cortex is not known. Herein, we quantified the number of excitatory and inhibitory synapses in the prefrontal cortex of 10 postmortem autism spectrum disorder brains and 10 control cases. To identify excitatory synapses, we used VGlut1 as a marker of the presynaptic component and postsynaptic density protein-95 as marker of the postsynaptic component. To identify inhibitory synapses, we used the vesicular gamma-aminobutyric acid transporter as a marker of the presynaptic component and gephyrin as a marker of the postsynaptic component. We used Puncta Analyzer to quantify the number of co-localized pre- and postsynaptic synaptic components in each area of interest. We found an increase in the number of excitatory synapses in upper cortical layers and a decrease in inhibitory synapses in all cortical layers in autism spectrum disorder brains compared with control cases. The alteration in the number of excitatory and inhibitory synapses could lead to neuronal dysfunction and disturbed network connectivity in the prefrontal cortex in autism spectrum disorder.

Transcriptional Determinism and Stochasticity Contribute to the Complexity of Autism Associated SHANK Family Genes

Precision of transcription is critical because transcriptional dysregulation is disease causing. Traditional methods of transcriptional profiling are inadequate to elucidate the full spectrum of the transcriptome, particularly for longer and less abundant mRNAs. SHANK3 is one of the most common autism causative genes. Twenty-four Shank3 mutant animal lines have been developed for autism modeling. However, their preclinical validity has been questioned due to incomplete Shank3 transcript structure. We applied an integrative approach combining cDNA-capture and long-read sequencing to profile the SHANK3 transcriptome in human and mice. We unexpectedly discovered an extremely complex SHANK3 transcriptome. Specific SHANK3 transcripts were altered in Shank3 mutant mice and postmortem brains tissues from individuals with ASD. The enhanced SHANK3 transcriptome significantly improved the detection rate for potential deleterious variants from genomics studies of neuropsychiatric disorders. Our findings suggest the stochastic transcription of genome associated with SHANK family genes.

From synapses to circuits: What mouse models have taught us about how autism spectrum disorder impacts hippocampal function

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that impacts a variety of cognitive and behavioral domains. While a genetic component of ASD has been well-established, none of the numerous syndromic genes identified in humans accounts for more than 1% of the clinical patients. Due to this large number of target genes, numerous mouse models of the disorder have been generated. However, the focus on distinct brain circuits, behavioral phenotypes and diverse experimental approaches has made it difficult to synthesize the overwhelming number of model animal studies into concrete throughlines that connect the data across levels of investigation. Here we chose to focus on one circuit, the hippocampus, and one hypothesis, a shift in excitatory/inhibitory balance, to examine, from the level of the tripartite synapse up to the level of in vivo circuit activity, the key commonalities across disparate models that can illustrate a path towards a better mechanistic understanding of ASD's impact on hippocampal circuit function.

Impaired synaptic function and hyperexcitability of the pyramidal neurons in the prefrontal cortex of autism-associated Shank3 mutant dogs

BACKGROUND

SHANK3 gene is a highly replicated causative gene for autism spectrum disorder and has been well characterized in multiple Shank3 mutant rodent models. When compared to rodents, domestic dogs are excellent animal models in which to study social cognition as they closely interact with humans and exhibit similar social behaviors. Using CRISPR/Cas9 editing, we recently generated a dog model carrying Shank3 mutations, which displayed a spectrum of autism-like behaviors, such as social impairment and heightened anxiety. However, the neural mechanism underlying these abnormal behaviors remains to be identified.

METHODS

We used Shank3 mutant dog models to examine possible relationships between Shank3 mutations and neuronal dysfunction. We studied electrophysiological properties and the synaptic transmission of pyramidal neurons from acute brain slices of the prefrontal cortex (PFC). We also examined dendrite elaboration and dendritic spine morphology in the PFC using biocytin staining and Golgi staining. We analyzed the postsynaptic density using electron microscopy.

RESULTS

We established a protocol for the electrophysiological recording of canine brain slices and revealed that excitatory synaptic transmission onto PFC layer 2/3 pyramidal neurons in Shank3 heterozygote dogs was impaired, and this was accompanied by reduced dendrite complexity and spine density when compared to wild-type dogs. Postsynaptic density structures were also impaired in Shank3 mutants; however, pyramidal neurons exhibited hyperexcitability.

LIMITATIONS

Causal links between impaired PFC pyramidal neuron function and behavioral alterations remain unclear. Further experiments such as manipulating PFC neuronal activity or restoring synaptic transmission in Shank3 mutant dogs are required to assess PFC roles in altered social behaviors.

CONCLUSIONS

Our study demonstrated the feasibility of using canine brain slices as a model system to study neuronal circuitry and disease. Shank3 haploinsufficiency causes morphological and functional abnormalities in PFC pyramidal neurons, supporting the notion that Shank3 mutant dogs are new and valid animal models for autism research.

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

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

Early-onset catatonia associated with SHANK3 mutations: looking at the autism spectrum through the prism of psychomotor phenomena

Background

Individuals with Phelan-McDermid syndrome (PMS) present with a wide range of diagnoses: autism spectrum disorder, intellectual disability, or schizophrenia. Differences in the genetic background could explain these different neurodevelopmental trajectories. However, a more parsimonious hypothesis is to consider that they may be the same phenotypic entity. Catatonic disturbances occasionally reported from adolescence onwards in PMS prompts exploration of the hypothesis that this clinical entity may be an early-onset form of catatonia. The largest cohort of children with childhood catatonia was studied by the Wernicke-Kleist-Leonhard school (WKL school), which regards catatonia as a collection of qualitative abnormalities of psychomotricity that predominantly affecting involuntary motricity (reactive and expressive). The aim of this study was to investigate the presence of psychomotor signs in three young adults carrying a mutation or intragenic deletion of the SHANK3 gene through the prism of the WKL school conception of catatonia.

Methods

This study was designed as an exploratory case study. Current and childhood psychomotor phenomena were investigated through semi-structured interviews with the parents, direct interaction with the participants, and the study of documents reporting observations of the participants at school or by other healthcare professionals.

Results

The findings show catatonic manifestations from childhood that evolved into a chronic form, with possible phases of sub-acute exacerbations starting from adolescence.

Conclusion

The presence of catatonic symptoms from childhood associated with autistic traits leads us to consider that this singular entity fundamentally related to SHANK3 mutations could be a form of early-onset catatonia. Further case studies are needed to confirm our observations.

SHANK3 Mutations Associated with Autism and Schizophrenia Lead to Shared and Distinct Changes in Dendritic Spine Dynamics in the Developing Mouse Brain

Autism Spectrum Disorders (ASD) and schizophrenia are distinct neurodevelopmental disorders that share certain symptoms and genetic components. Both disorders show abnormalities in dendritic spines, which are the main sites of excitatory synaptic inputs. Recent studies have identified the synaptic scaffolding protein Shank3 as a leading candidate gene for both disorders. Mutations in the SHANK3 gene have been linked to both ASD and schizophrenia; however, how patient-derived mutations affect the structural plasticity of dendritic spines during brain development is unknown. Here we use live two photon in vivo imaging to examine dendritic spine structural plasticity in mice with SHANK3 mutations associated with ASD and schizophrenia. We identified shared and distinct phenotypes in dendritic spine morphogenesis and plasticity in the ASD-associated InsG3680 mutant mice and the schizophrenia-associated R1117X mutant mice. No significant changes in dendritic arborization were observed in either mutant, raising the possibility that synaptic dysregulation may be a key contributor to the behavioral defects previously reported in these mice. These findings shed light on how patient-linked mutations in SHANK3 affect dendritic spine dynamics in the developing brain, which provides insight into the synaptic basis for the distinct phenotypes observed in ASD and schizophrenia.

Intranasal Oxytocin in Pediatric Populations: Exploring the Potential for Reducing Irritability and Modulating Neural Responses: A Mini Review

Endogenous neuropeptide Oxytocin (OXT) plays a crucial role in modulating pro-social behavior and the neural response to social/emotional stimuli. Intranasal administration is the most common method of delivering OXT. Intranasal OXT has been implemented in clinical studies of various psychiatric disorders with mixed results, mainly related to lack of solid pharmacodynamics and pharmacokinetics model. Due to intranasal OXT's mechanism of reducing the activation of neural areas implicated in emotional responding and emotion regulation, a psychopathology with this target mechanism could be potentially excellent candidate for future clinical trial. In this regard, irritability in youth may be a very promising target for clinical studies of intranasal OXT. Here we provide a mini-review of fifteen randomized controlled trials in pediatric patients with diagnoses of autism spectrum disorder (ASD), Prader-Willi syndrome (PWS), or Phelan-McDermid syndrome (PMS). Most studies had small sample sizes and varying dosages, with changes in irritability, mainly as adverse events (AEs). Neuroimaging results showed modulation of the reward processing system and the neural areas implicated in social-emotional information processing by intranasal OXT administration. Further research is needed to determine the most effective dose and duration of OXT treatment, carefully select target psychopathologies, verify target engagement, and measure adverse event profiles.

Reduced neurite density index in the prefrontal cortex of adults with autism assessed using neurite orientation dispersion and density imaging

Background

Core symptoms of autism-spectrum disorder (ASD) have been associated with prefrontal cortex abnormalities. However, the mechanisms behind the observation remain incomplete, partially due to the challenges of modeling complex gray matter (GM) structures. This study aimed to identify GM microstructural alterations in adults with ASD using neurite orientation dispersion and density imaging (NODDI) and voxel-wise GM-based spatial statistics (GBSS) to reduce the partial volume effects from the white matter and cerebrospinal fluid.

Materials and methods

A total of 48 right-handed participants were included, of which 22 had ASD (17 men; mean age, 34.42 ± 8.27 years) and 26 were typically developing (TD) individuals (14 men; mean age, 32.57 ± 9.62 years). The metrics of NODDI (neurite density index [NDI], orientation dispersion index [ODI], and isotropic volume fraction [ISOVF]) were compared between groups using GBSS. Diffusion tensor imaging (DTI) metrics and surface-based cortical thickness were also compared. The associations between magnetic resonance imaging-based measures and ASD-related scores, including ASD-spectrum quotient, empathizing quotient, and systemizing quotient were also assessed in the region of interest (ROI) analysis.

Results

After controlling for age, sex, and intracranial volume, GBSS demonstrated significantly lower NDI in the ASD group than in the TD group in the left prefrontal cortex (caudal middle frontal, lateral orbitofrontal, pars orbitalis, pars triangularis, rostral middle frontal, and superior frontal region). In the ROI analysis of individuals with ASD, a significantly positive correlation was observed between the NDI in the left rostral middle frontal, superior frontal, and left frontal pole and empathizing quotient score. No significant between-group differences were observed in all DTI metrics, other NODDI (i.e., ODI and ISOVF) metrics, and cortical thickness.

Conclusion

GBSS analysis was used to demonstrate the ability of NODDI metrics to detect GM microstructural alterations in adults with ASD, while no changes were detected using DTI and cortical thickness evaluation. Specifically, we observed a reduced neurite density index in the left prefrontal cortices associated with reduced empathic abilities.

Updated consensus guidelines on the management of Phelan-McDermid syndrome

Phelan-McDermid syndrome (PMS) is a genetic condition caused by SHANK3 haploinsufficiency and characterized by a wide range of neurodevelopmental and systemic manifestations. The first practice parameters for assessment and monitoring in individuals with PMS were published in 2014; recently, knowledge about PMS has grown significantly based on data from longitudinal phenotyping studies and large-scale genotype-phenotype investigations. The objective of these updated clinical management guidelines was to: (1) reflect the latest in knowledge in PMS and (2) provide guidance for clinicians, researchers, and the general community. A taskforce was established with clinical experts in PMS and representatives from the parent community. Experts joined subgroups based on their areas of specialty, including genetics, neurology, neurodevelopment, gastroenterology, primary care, physiatry, nephrology, endocrinology, cardiology, gynecology, and dentistry. Taskforce members convened regularly between 2021 and 2022 and produced specialty-specific guidelines based on iterative feedback and discussion. Taskforce leaders then established consensus within their respective specialty group and harmonized the guidelines. The knowledge gained over the past decade allows for improved guidelines to assess and monitor individuals with PMS. Since there is limited evidence specific to PMS, intervention mostly follows general guidelines for treating individuals with developmental disorders. Significant evidence has been amassed to guide the management of comorbid neuropsychiatric conditions in PMS, albeit mainly from caregiver report and the experience of clinical experts. These updated consensus guidelines on the management of PMS represent an advance for the field and will improve care in the community. Several areas for future research are also highlighted and will contribute to subsequent updates with more refined and specific recommendations as new knowledge accumulates.

Adolescent sleep defects and dopaminergic hyperactivity in mice with a schizophrenia-linked Shank3 mutation

Shank3 is a shared risk gene for autism spectrum disorders and schizophrenia. Sleep defects have been characterized for autism models with Shank3 mutations; however, evidence has been lacking for the potential sleep defects caused by Shank3 mutation associated with schizophrenia and how early in development these defects may occur. Here we characterized the sleep architecture of adolescent mice carrying a schizophrenia-linked, R1117X mutation in Shank3. We further employed GRABDA dopamine sensor and fiber photometry to record dopamine release in the nucleus accumbens during sleep/wake states. Our results show that homozygous mutant R1117X mice have significantly reduced sleep in the dark phase during adolescence, altered electroencephalogram power, especially during the rapid-eye-movement sleep, and dopamine hyperactivity during sleep but not during wakefulness. Further analyses suggest that these adolescent defects in sleep architecture and dopaminergic neuromodulation tightly correlate with the social novelty preference later in adulthood and predict adult social performance during same-sex social interactions. Our results provide novel insights into the sleep phenotypes in mouse models of schizophrenia and the potential use of developmental sleep as a predictive metric for adult social symptoms. Together with recent studies in other Shank3 models, our work underscores the idea that Shank3-involved circuit disruptions may be one of the shared pathologies in certain types of schizophrenia and autism. Future research is needed to establish the causal relationship among adolescent sleep defects, dopaminergic dysregulation, and adult behavioral changes in Shank3 mutation animals and other models.

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

BACKGROUND

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

METHODS

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

RESULTS

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

LIMITATIONS

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

CONCLUSIONS

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

Progranulin is an FMRP target that influences macroorchidism but not behaviour in a mouse model of Fragile X Syndrome

A growing body of evidence has implicated progranulin in neurodevelopment and indicated that aberrant progranulin expression may be involved in neurodevelopmental disease. Specifically, increased progranulin expression in the prefrontal cortex has been suggested to be pathologically relevant in male Fmr1 knockout (Fmr1 KO) mice, a mouse model of Fragile X Syndrome (FXS). Further investigation into the role of progranulin in FXS is warranted to determine if therapies that reduce progranulin expression represent a viable strategy for treating patients with FXS. Several key knowledge gaps remain. The mechanism of increased progranulin expression in Fmr1 KO mice is poorly understood and the extent of progranulin's involvement in FXS-like phenotypes in Fmr1 KO mice has been incompletely explored. To this end, we have performed a thorough characterization of progranulin expression in Fmr1 KO mice. We find that the phenomenon of increased progranulin expression is post-translational and tissue-specific. We also demonstrate for the first time an association between progranulin mRNA and FMRP, suggesting that progranulin mRNA is an FMRP target. Subsequently, we show that progranulin over-expression in Fmr1 wild-type mice causes reduced repetitive behaviour engagement in females and mild hyperactivity in males but is largely insufficient to recapitulate FXS-associated behavioural, morphological, and electrophysiological abnormalities. Lastly, we determine that genetic reduction of progranulin expression on an Fmr1 KO background reduces macroorchidism but does not alter other FXS-associated behaviours or biochemical phenotypes.

Advances in Genetics and Epigenetics of Developmental Coordination Disorder in Children

Developmental coordination disorder (DCD) is a developmental disorder characterized by impaired motor coordination, often co-occurring with attention deficit disorder, autism spectrum disorders, and other psychological and behavioural conditions. The aetiology of DCD is believed to involve brain changes and environmental factors, with genetics also playing a role in its pathogenesis. Recent research has identified several candidate genes and genetic factors associated with motor impairment, including deletions, copy number variations, single nucleotide polymorphisms, and epigenetic modifications. This review provides an overview of the current knowledge in genetic research on DCD, highlighting the importance of continued research into the underlying genetic mechanisms. While evidence suggests a genetic contribution to DCD, the evidence is still in its early stages, and much of the current evidence is based on studies of co-occurring conditions. Further research to better understand the genetic basis of DCD could have important implications for diagnosis, treatment, and our understanding of the condition's aetiology.

Sleep disturbances in autism spectrum disorder: Animal models, neural mechanisms, and therapeutics

Sleep is crucial for brain development. Sleep disturbances are prevalent in children with autism spectrum disorder (ASD). Strikingly, these sleep problems are positively correlated with the severity of ASD core symptoms such as deficits in social skills and stereotypic behavior, indicating that sleep problems and the behavioral characteristics of ASD may be related. In this review, we will discuss sleep disturbances in children with ASD and highlight mouse models to study sleep disturbances and behavioral phenotypes in ASD. In addition, we will review neuromodulators controlling sleep and wakefulness and how these neuromodulatory systems are disrupted in animal models and patients with ASD. Lastly, we will address how the therapeutic interventions for patients with ASD improve various aspects of sleep. Together, gaining mechanistic insights into the neural mechanisms underlying sleep disturbances in children with ASD will help us to develop better therapeutic interventions.

The gut-brain connection: Exploring the influence of the gut microbiota on neuroplasticity and neurodevelopmental disorders

Neuroplasticity refers to the ability of brain circuits to reorganize and change the properties of the network, resulting in alterations in brain function and behavior. It is traditionally believed that neuroplasticity is influenced by external stimuli, learning, and experience. Intriguingly, there is new evidence suggesting that endogenous signals from the body's periphery may play a role. The gut microbiota, a diverse community of microorganisms living in harmony with their host, may be able to influence plasticity through its modulation of the gut-brain axis. Interestingly, the maturation of the gut microbiota coincides with critical periods of neurodevelopment, during which neural circuits are highly plastic and potentially vulnerable. As such, dysbiosis (an imbalance in the gut microbiota composition) during early life may contribute to the disruption of normal developmental trajectories, leading to neurodevelopmental disorders. This review aims to examine the ways in which the gut microbiota can affect neuroplasticity. It will also discuss recent research linking gastrointestinal issues and bacterial dysbiosis to various neurodevelopmental disorders and their potential impact on neurological outcomes.

Head Size in Phelan-McDermid Syndrome: A Literature Review and Pooled Analysis of 198 Patients Identifies Candidate Genes on 22q13

Phelan-McDermid syndrome (PMS) is a multisystem disorder that is associated with deletions of the 22q13 genomic region or pathogenic variants in the SHANK3 gene. Notable features include developmental issues, absent or delayed speech, neonatal hypotonia, seizures, autism or autistic traits, gastrointestinal problems, renal abnormalities, dolichocephaly, and both macro- and microcephaly. Assessment of the genetic factors that are responsible for abnormal head size in PMS has been hampered by small sample sizes as well as a lack of attention to these features. Therefore, this study was conducted to investigate the relationship between head size and genes on chromosome 22q13. A review of the literature was conducted to identify published cases of 22q13 deletions with information on head size to conduct a pooled association analysis. Across 56 studies, we identified 198 cases of PMS with defined deletion sizes and head size information. A total of 33 subjects (17%) had macrocephaly, 26 (13%) had microcephaly, and 139 (70%) were normocephalic. Individuals with macrocephaly had significantly larger genomic deletions than those with microcephaly or normocephaly (p < 0.0001). A genomic region on 22q13.31 was found to be significantly associated with macrocephaly with CELSR1, GRAMD4, and TBCD122 suggested as candidate genes. Investigation of these genes will aid the understanding of head and brain development.

Targeting Shank3 deficiency and paresthesia in autism spectrum disorder: A brief review

Autism spectrum disorder (ASD) includes a group of multifactorial neurodevelopmental disorders characterized by impaired social communication, social interaction, and repetitive behaviors. Several studies have shown an association between cases of ASD and mutations in the genes of SH3 and multiple ankyrin repeat domain protein 3 (SHANK3). These genes encode many cell adhesion molecules, scaffold proteins, and proteins involved in synaptic transcription, protein synthesis, and degradation. They have a profound impact on all aspects of synaptic transmission and plasticity, including synapse formation and degeneration, suggesting that the pathogenesis of ASD may be partially attributable to synaptic dysfunction. In this review, we summarize the mechanism of synapses related to Shank3 in ASD. We also discuss the molecular, cellular, and functional studies of experimental models of ASD and current autism treatment methods targeting related proteins.

Transient hearing abnormalities precede social deficits in a mouse model of autism

Hearing abnormalities are important symptoms of autism spectrum disorders (ASDs), a neurological and developmental disorder. However, the characteristics of hearing abnormalities associated with ASD during development have not been fully investigated. We found that in Shank3B knockout mice (a high-confidence mouse model of ASD), transient hearing abnormalities can be found in auditory brainstem response, auditory cortical activity, as well as acoustic startle response. More importantly, all hearing abnormalities at 4 weeks were most prominent and preceded the onset of social deficits at 6 weeks. These hearing abnormalities gradually recovered with age. In addition, analysis of ABR data at 4 weeks using Support Vector Machine (SVM) can faithfully predict the genotype of mice with an accuracy of 85.71%. These findings not only revealed hearing changes in Shank3B knockout autistic-like mice during development, but also suggested that hearing abnormalities could potentially be used as an early and effective indicator of ASD risk.

Therapeutic modulation of JAK-STAT, mTOR, and PPAR-γ signaling in neurological dysfunctions

The cytokine-activated Janus kinase (JAK)-signal transducer and activator of transcription (STAT) cascade is a pleiotropic pathway that involves receptor subunit multimerization. The mammalian target of rapamycin (mTOR) is a ubiquitously expressed serine-threonine kinase that perceives and integrates a variety of intracellular and environmental stimuli to regulate essential activities such as cell development and metabolism. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a prototypical metabolic nuclear receptor involved in neural differentiation and axon polarity. The JAK-STAT, mTOR, and PPARγ signaling pathways serve as a highly conserved signaling hub that coordinates neuronal activity and brain development. Additionally, overactivation of JAK/STAT, mTOR, and inhibition of PPARγ signaling have been linked to various neurocomplications, including neuroinflammation, apoptosis, and oxidative stress. Emerging research suggests that even minor disruptions in these cellular and molecular processes can have significant consequences manifested as neurological and neuropsychiatric diseases. Of interest, target modulators have been proven to alleviate neuronal complications associated with acute and chronic neurological deficits. This research-based review explores the therapeutic role of JAK-STAT, mTOR, and PPARγ signaling modulators in preventing neuronal dysfunctions in preclinical and clinical investigations.

Catecholaminergic and cholinergic neuromodulation in autism spectrum disorder: A comparison to attention-deficit hyperactivity disorder

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder characterized by social impairments and restricted, repetitive behaviors. Treatment of ASD is notoriously difficult and might benefit from identification of underlying mechanisms that overlap with those disturbed in other developmental disorders, for which treatment options are more obvious. One example of the latter is attention-deficit hyperactivity disorder (ADHD), given the efficacy of especially stimulants in treatment of ADHD. Deficiencies in catecholaminergic systems [dopamine (DA), norepinephrine (NE)] in ADHD are obvious targets for stimulant treatment. Recent findings suggest that dysfunction in catecholaminergic systems may also be a factor in at least a subgroup of ASD. In this review we scrutinize the evidence for catecholaminergic mechanisms underlying ASD symptoms, and also include in this analysis a third classic ascending arousing system, the acetylcholinergic (ACh) network. We complement this with a comprehensive review of DA-, NE-, and ACh-targeted interventions in ASD, and an exploratory search for potential treatment-response predictors (biomarkers) in ASD, genetically or otherwise. Based on this review and analysis we propose that (1) stimulant treatment may be a viable option for an ASD subcategory, possibly defined by genetic subtyping; (2) cerebellar dysfunction is pronounced for a relatively small ADHD subgroup but much more common in ASD and in both cases may point toward NE- or ACh-directed intervention; (3) deficiency of the cortical salience network is sizable in subgroups of both disorders, and biomarkers such as eye blink rate and pupillometric data may predict the efficacy of targeting this underlying deficiency via DA, NE, or ACh in both ASD and ADHD.

Construction of copy number variation landscape and characterization of associated genes in a Bangladeshi cohort of neurodevelopmental disorders

Introduction: Copy number variations (CNVs) play a critical role in the pathogenesis of neurodevelopmental disorders (NDD) among children. In this study, we aim to identify clinically relevant CNVs, genes and their phenotypic characteristics in an ethnically underrepresented homogenous population of Bangladesh. Methods: We have conducted chromosomal microarray analysis (CMA) for 212 NDD patients with male to female ratio of 2.2:1.0 to identify rare CNVs. To identify candidate genes within the rare CNVs, gene constraint metrics [i.e., "Critical-Exon Genes (CEGs)"] were applied to the population data. Autism Diagnostic Observation Schedule-Second Edition (ADOS-2) was followed in a subset of 95 NDD patients to assess the severity of autism and all statistical tests were performed using the R package. Results: Of all the samples assayed, 12.26% (26/212) and 57.08% (121/212) patients carried pathogenic and variant of uncertain significance (VOUS) CNVs, respectively. While 2.83% (6/212) patients' pathogenic CNVs were found to be located in the subtelomeric regions. Further burden test identified females are significant carriers of pathogenic CNVs compared to males (OR = 4.2; p = 0.0007). We have observed an increased number of Loss of heterozygosity (LOH) within cases with 23.85% (26/109) consanguineous parents. Our analyses on imprinting genes show, 36 LOH variants disrupting 69 unique imprinted genes and classified these variants as VOUS. ADOS-2 subset shows severe social communication deficit (p = 0.014) and overall ASD symptoms severity (p = 0.026) among the patients carrying duplication CNV compared to the CNV negative group. Candidate gene analysis identified 153 unique CEGs in pathogenic CNVs and 31 in VOUS. Of the unique genes, 18 genes were found to be in smaller (<1 MB) focal CNVs in our NDD cohort and we identified PSMC3 gene as a strong candidate gene for Autism Spectrum Disorder (ASD). Moreover, we hypothesized that KMT2B gene duplication might be associated with intellectual disability. Conclusion: Our results show the utility of CMA for precise genetic diagnosis and its integration into the diagnosis, therapy and management of NDD patients.

The Evolving Role of Animal Models in the Discovery and Development of Novel Treatments for Psychiatric Disorders

Historically, animal models have been routinely used in the characterization of novel chemical entities (NCEs) for various psychiatric disorders. Animal models have been essential in the in vivo validation of novel drug targets, establishment of lead compound pharmacokinetic to pharmacodynamic relationships, optimization of lead compounds through preclinical candidate selection, and development of translational measures of target occupancy and functional target engagement. Yet, with decades of multiple NCE failures in Phase II and III efficacy trials for different psychiatric disorders, the utility and value of animal models in the drug discovery process have come under intense scrutiny along with the widespread withdrawal of the pharmaceutical industry from psychiatric drug discovery. More recently, the development and utilization of animal models for the discovery of psychiatric NCEs has undergone a dynamic evolution with the application of the Research Domain Criteria (RDoC) framework for better design of preclinical to clinical translational studies combined with innovative genetic, neural circuitry-based, and automated testing technologies. In this chapter, the authors will discuss this evolving role of animal models for improving the different stages of the discovery and development in the identification of next generation treatments for psychiatric disorders.

Genetic diagnostic yields of 354 Chinese ASD children with rare mutations by a pipeline of genomic tests

Purpose: To establish an effective genomic diagnosis pipeline for children with autism spectrum disorder (ASD) for its genetic etiology and intervention. Methods: A cohort of 354 autism spectrum disorder patients were obtained from Beijing Children's Hospital, Capital Medical University. Peripheral blood samples of the patients were collected for whole genome sequencing (WGS) and RNA sequencing (RNAseq). Sequencing data analyses were performed for mining the single nucleotide variation (SNV), copy number variation (CNV) and structural variation (SV). Sanger sequencing and quantitative PCR were used to verify the positive results. Results: Among 354 patients, 9 cases with pathogenic/likely pathogenic copy number variation and 10 cases with pathogenic/likely pathogenic single nucleotide variations were detected, with a total positive rate of 5.3%. Among these 9 copy number variation cases, 5 were de novo and 4 were inherited. Among the 10 de novo single nucleotide variations, 7 were previously unreported. The pathological de novo mutations account for 4.2% in our cohort. Conclusion: Rare mutations of copy number variations and single nucleotide variations account for a relatively small proportion of autism spectrum disorder children, which can be easily detected by a genomic testing pipeline of combined whole genome sequencing and RNA sequencing. This is important for early etiological diagnosis and precise management of autism spectrum disorder with rare mutations.

Reversibility and therapeutic development for neurodevelopmental disorders, insights from genetic animal models

Neurodevelopmental Disorders (NDDs) encompass a broad spectrum of conditions resulting from atypical brain development. Over the past decades, we have had the fortune to witness enormous progress in diagnosis, etiology discovery, modeling, and mechanistic understanding of NDDs from both fundamental and clinical research. Here, we review recent neurobiological advances from experimental models of NDDs. We introduce several examples and highlight breakthroughs in reversal studies of phenotypes using genetically engineered models of NDDs. The in-depth understanding of brain pathophysiology underlying NDDs and evaluations of reversibility in animal models paves the foundation for discovering novel treatment options. We discuss how the expanding property of cutting-edge technologies, such as gene editing and AAV-mediated gene delivery, are leveraged in animal models for the therapeutic development of NDDs. We envision opportunities and challenges toward faithful modeling and fruitful clinical translation.

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.

Age, brain region, and gene dosage-differential transcriptomic changes in Shank3-mutant mice

Shank3 is an abundant excitatory postsynaptic scaffolding protein implicated in various neurodevelopmental disorders, including autism spectrum disorder (ASD), Phelan-McDermid syndrome, intellectual disability, and schizophrenia. Shank3-mutant mice show various molecular, synaptic, and behavioral deficits, but little is known about how transcriptomic phenotypes vary across different ages, brain regions, and gene dosages. Here, we report transcriptomic patterns in the forebrains of juvenile and adult homozygous Shank3-mutant mice that lack exons 14-16 and also the prefrontal, hippocampal, and striatal transcriptomes in adult heterozygous and homozygous Shank3-mutant mice. The juvenile and adult mutant transcriptomes show patterns opposite from and similar to those observed in ASD (termed reverse-ASD and ASD-like patterns), respectively. The juvenile transcriptomic changes accompany synaptic upregulations and ribosomal and mitochondrial downregulations, whereas the adult transcriptome show opposite changes. The prefrontal, hippocampal, and striatal transcriptomes show differential changes in ASD-related gene expressions and biological functions associated with synapse, ribosome, mitochondria, and spliceosome. These patterns also differ across heterozygous and homozygous Shank3-mutant mice. These results suggest age, brain region, and gene dosage-differential transcriptomic changes in Shank3-mutant mice.

Epigenome-wide association study of global cortical volumes in generation Scotland: Scottish family health study

A complex interplay of genetic and environmental risk factors influence global brain structural alterations associated with brain health and disease. Epigenome-wide association studies (EWAS) of global brain imaging phenotypes have the potential to reveal the mechanisms of brain health and disease and can lead to better predictive analytics through the development of risk scores.We perform an EWAS of global brain volumes in Generation Scotland using peripherally measured whole blood DNA methylation (DNAm) from two assessments, (i) at baseline recruitment, ~6 years prior to MRI assessment (N = 672) and (ii) concurrent with MRI assessment (N=565). Four CpGs at baseline were associated with global cerebral white matter, total grey matter, and whole-brain volume (Bonferroni p≤7.41×10-8, βrange = -1.46x10-6 to 9.59 × 10-7). These CpGs were annotated to genes implicated in brain-related traits, including psychiatric disorders, development, and ageing. We did not find significant associations in the meta-analysis of the EWAS of the two sets concurrent with imaging at the corrected level.These findings reveal global brain structural changes associated with DNAm measured ~6 years previously, indicating a potential role of early DNAm modifications in brain structure. Although concurrent DNAm was not associated with global brain structure, the nominally significant findings identified here present a rationale for future investigation of associations between DNA methylation and structural brain phenotypes in larger population-based samples.

Molecular mechanisms of synaptogenesis

Synapses are the basic units for information processing and storage in the nervous system. It is only when the synaptic connection is established, that it becomes meaningful to discuss the structure and function of a circuit. In humans, our unparalleled cognitive abilities are correlated with an increase in the number of synapses. Additionally, genes involved in synaptogenesis are also frequently associated with neurological or psychiatric disorders, suggesting a relationship between synaptogenesis and brain physiology and pathology. Thus, understanding the molecular mechanisms of synaptogenesis is the key to the mystery of circuit assembly and neural computation. Furthermore, it would provide therapeutic insights for the treatment of neurological and psychiatric disorders. Multiple molecular events must be precisely coordinated to generate a synapse. To understand the molecular mechanisms underlying synaptogenesis, we need to know the molecular components of synapses, how these molecular components are held together, and how the molecular networks are refined in response to neural activity to generate new synapses. Thanks to the intensive investigations in this field, our understanding of the process of synaptogenesis has progressed significantly. Here, we will review the molecular mechanisms of synaptogenesis by going over the studies on the identification of molecular components in synapses and their functions in synaptogenesis, how cell adhesion molecules connect these synaptic molecules together, and how neural activity mobilizes these molecules to generate new synapses. Finally, we will summarize the human-specific regulatory mechanisms in synaptogenesis and results from human genetics studies on synaptogenesis and brain disorders.

The complexity of ventral CA1 and its multiple functionalities

The hippocampus is one of the most widely investigated brain regions with its massive contributions to multiple behaviours. Especially, the hippocampus is subdivided into the dorsal and ventral parts playing distinct roles. In this review, we will focus on the ventral hippocampus, especially the ventral CA1 (vCA1), whose role is being actively discovered. vCA1 is well known to be associated with emotion-like behaviour, in both positive (reward) and negative (aversive) stimuli. How can this small region in volume mediate such variety of responses? This question will be answered with technologies up to date that have allowed us to study in-depth the specific neural circuit and to map the complex connectivity.

Yield of array-CGH analysis in Tunisian children with autism spectrum disorder

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with strong genetic underpinnings. Microarray-based comparative genomic hybridization (aCGH) technology has been proposed as a first-level test in the genetic diagnosis of ASD and of neurodevelopmental disorders in general.

METHODS

We performed aCGH on 98 Tunisian children (83 boys and 15 girls) diagnosed with ASD according to DSM-IV criteria.

RESULTS

"Pathogenic" or "likely pathogenic" copy number variants (CNVs) were detected in 11 (11.2%) patients, CNVs of "uncertain clinical significance" in 26 (26.5%), "likely benign" or "benign" CNVs were found in 37 (37.8%) and 24 (24.5%) patients, respectively. Gene set enrichment analysis involving genes spanning rare "pathogenic," "likely pathogenic," or "uncertain clinical significance" CNVs, as well as SFARI database "autism genes" in common CNVs, detected eight neuronal Gene Ontology classes among the top 10 most significant, including synapse, neuron differentiation, synaptic signaling, neurogenesis, and others. Similar results were obtained performing g: Profiler analysis. Neither transcriptional regulation nor immune pathways reached significance.

CONCLUSIONS

aCGH confirms its sizable diagnostic yield in a novel sample of autistic children from North Africa. Recruitment of additional families is under way, to verify whether genetic contributions to ASD in the Tunisian population, differently from other ethnic groups, may involve primarily neuronal genes, more than transcriptional regulation and immune-related pathways.

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.

Prefrontal Circuits guiding Social Preference: Implications in Autism Spectrum Disorder

Although Autism Spectrum Disorder (ASD) is increasing in diagnostic prevalence, treatment options are inadequate largely due to limited understanding of ASD's underlying neural mechanisms. Contributing to difficulties in treatment development is the vast heterogeneity of ASD, from physiological causes to clinical presentations. Recent studies suggest that distinct genetic and neurological alterations may converge onto similar underlying neural circuits. Therefore, an improved understanding of neural circuit-level dysfunction in ASD may be a more productive path to developing broader treatments that are effective across a greater spectrum of ASD. Given the social preference behavioral deficits commonly seen in ASD, dysfunction in circuits mediating social preference may contribute to the atypical development of social cognition. We discuss some of the animal models used to study ASD and examine the function and effects of dysregulation of the social preference circuits, notably the medial prefrontal cortex-amygdala and the medial prefrontal cortex-nucleus accumbens circuits, in these animal models. Using the common circuits underlying similar behavioral disruptions of social preference behaviors as an example, we highlight the importance of identifying disruption in convergent circuits to improve the translational success of animal model research for ASD treatment development.

Differential Methylation Profile in Fragile X Syndrome-Prone Offspring Mice after in Utero Exposure to Lactobacillus Reuteri

Environmental factors such as diet, gut microbiota, and infections have proven to have a significant role in epigenetic modifications. It is known that epigenetic modifications may cause behavioral and neuronal changes observed in neurodevelopmental disabilities, including fragile X syndrome (FXS) and autism (ASD). Probiotics are live microorganisms that provide health benefits when consumed, and in some cases are shown to decrease the chance of developing neurological disorders. Here, we examined the epigenetic outcomes in offspring mice after feeding of a probiotic organism, Lactobacillus reuteri (L. reuteri), to pregnant mother animals. In this study, we tested a cohort of Western diet-fed descendant mice exhibiting a high frequency of behavioral features and lower FMRP protein expression similar to what is observed in FXS in humans (described in a companion manuscript in this same GENES special topic issue). By investigating 17,735 CpG sites spanning the whole mouse genome, we characterized the epigenetic profile in two cohorts of mice descended from mothers treated and non-treated with L. reuteri to determine the effect of prenatal probiotic exposure on the prevention of FXS-like symptoms. We found several genes involved in different neurological pathways being differentially methylated (p ≤ 0.05) between the cohorts. Among the key functions, synaptogenesis, neurogenesis, synaptic modulation, synaptic transmission, reelin signaling pathway, promotion of specification and maturation of neurons, and long-term potentiation were observed. The results of this study are relevant as they could lead to a better understanding of the pathways involved in these disorders, to novel therapeutics approaches, and to the identification of potential biomarkers for early detection of these conditions.

SHANK3 genetic polymorphism and susceptibility to ASD: evidence from molecular, in silico, and meta-analysis approaches

BACKGROUND

The SHANK3 gene encodes a master synaptic scaffolding protein at the excitatory synapse's postsynaptic density, which is predominantly responsible for constructing a synapse, maintaining synaptic structure, and functions. Recently, evidence from rare mutations and copy number variation provided an important clue about SHANK3 which acts as a strong candidate gene in the pathogenesis of Autism Spectrum Disorder (ASD).

MATERIALS AND METHODS

To investigate potential allelic variants for the SHANK3 (rs9616915) gene as a genetic risk factor, we performed PCR-RFLP analysis and Sanger sequencing for 90 ASD and 90 healthy subjects. Moreover, to understand the functional and structural impacts of our selected non-synonymous SHANK3 SNP rs9616915, we have performed an in silico analysis. Subsequently, a meta-analysis of rs9616915 with a total of 6 eligible studies (including the present study) containing a total of 795 cases and 12,947 controls was obtained from a comprehensive online database search to evaluate the overall association with ASD.

RESULTS

Our retrieved data, such as Pearson's chi-square test (p = 0.081) as well as logistic regression analysis of co-dominant (p = 0.1131), dominant (p = 0.3656) and recessive models (p = 0.0569) speculated no significant association between rs9616915 and our studied sample. Interestingly, by in silico analysis, we have observed two hydrogen bonds between amino acids instead of one hydrogen bond in the protein structure of rs9616915, which indicates this mutant structure could affect the proteins' stability. The findings of the meta-analysis revealed that four genetic association models were associated with ASD susceptibility.

CONCLUSIONS

Our study suggested that targeted SHANK3 SNP of interest rs9616915 might not be associated with ASD in the southern part of the Bangladeshi population.