Decoding the contribution of dopaminergic genes and pathways to autism spectrum disorder (ASD)

The Role of Alpha-Synuclein in Neurodevelopmental Diseases

Neurodevelopmental disorders are a group of diseases with cognitive, motor, and emotional development deficits. Alpha-synuclein (α-syn) is a synaptic protein involved in transmission and neurodevelopment. This protein was previously shown to be associated with several disorders, including Parkinson's disease. Furthermore, a close link between neurodevelopmental disorders and Parkinson's has also been found. Changes in synaptic function have been noticed in neurodevelopmental disorders, including autism spectrum disorder. Impaired neurogenesis and related cognitive problems have been associated with altered expression of α-syn. Various studies reported α-syn in different body fluids and tissues such as blood and serum. Alpha-synuclein can help in better understanding the pathogenesis of neurodevelopmental diseases and facilitating their early diagnosis. This review aims to go over the recent advances in the role of α-syn in the pathophysiology of neurodevelopmental disorders, including autism spectrum disorder, attention deficit hyperactivity disorder, and motor and social impairment, and its value as a diagnostic biomarker.

Is cholesterol both the lock and key to abnormal transmembrane signals in Autism Spectrum Disorder?

Disturbances in cholesterol homeostasis have been associated with ASD. Lipid rafts are central in many transmembrane signaling pathways (including mTOR) and changes in raft cholesterol content affect their order function. Cholesterol levels are controlled by several mechanisms, including endoplasmic reticulum associated degradation (ERAD) of the rate limiting HMGCoA reductase. A new approach to increase cholesterol via temporary ERAD blockade using a benign bacterial toxin-derived competitor for the ERAD translocon is suggested.A new lock and key model for cholesterol/lipid raft dependent signaling is proposed in which the rafts provide both the afferent and efferent 'tumblers' across the membrane to allow 'lock and key' receptor transmembrane signals.

Amygdalar neurotransmission alterations in the BTBR mice model of idiopathic autism

Autism Spectrum Disorders (ASD) are principally diagnosed by three core behavioural symptoms, such as stereotyped repertoire, communication impairments and social dysfunctions. This complex pathology has been linked to abnormalities of corticostriatal and limbic circuits. Despite experimental efforts in elucidating the molecular mechanisms behind these abnormalities, a clear etiopathogenic hypothesis is still lacking. To this aim, preclinical studies can be really helpful to longitudinally study behavioural alterations resembling human symptoms and to investigate the underlying neurobiological correlates. In this regard, the BTBR T+ Itpr3tf/J (BTBR) mice are an inbred mouse strain that exhibits a pattern of behaviours well resembling human ASD-like behavioural features. In this study, the BTBR mice model was used to investigate neurochemical and biomolecular alterations, regarding Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF), together with GABAergic, glutamatergic, cholinergic, dopaminergic and noradrenergic neurotransmissions and their metabolites in four different brain areas, i.e. prefrontal cortex, hippocampus, amygdala and hypothalamus. In our results, BTBR strain reported decreased noradrenaline, acetylcholine and GABA levels in prefrontal cortex, while hippocampal measurements showed reduced NGF and BDNF expression levels, together with GABA levels. Concerning hypothalamus, no differences were retrieved. As regarding amygdala, we found reduced dopamine levels, accompanied by increased dopamine metabolites in BTBR mice, together with decreased acetylcholine, NGF and GABA levels and enhanced glutamate content. Taken together, our data showed that the BTBR ASD model, beyond its face validity, is a useful tool to untangle neurotransmission alterations that could be underpinned to the heterogeneous ASD-like behaviours, highlighting the crucial role played by amygdala.

The genetic landscape of autism spectrum disorder in the Middle Eastern population

Introduction: Autism spectrum disorder (ASD) is characterized by aberrations in social interaction and communication associated with repetitive behaviors and interests, with strong clinical heterogeneity. Genetic factors play an important role in ASD, but about 75% of ASD cases have an undetermined genetic risk. Methods: We extensively investigated an ASD cohort made of 102 families from the Middle Eastern population of Qatar. First, we investigated the copy number variations (CNV) contribution using genome-wide SNP arrays. Next, we employed Next Generation Sequencing (NGS) to identify de novo or inherited variants contributing to the ASD etiology and its associated comorbid conditions in families with complete trios (affected child and the parents). Results: Our analysis revealed 16 CNV regions located in genomic regions implicated in ASD. The analysis of the 88 ASD cases identified 41 genes in 39 ASD subjects with de novo (n = 24) or inherited variants (n = 22). We identified three novel de novo variants in new candidate genes for ASD (DTX4, ARMC6, and B3GNT3). Also, we have identified 15 de novo variants in genes that were previously implicated in ASD or related neurodevelopmental disorders (PHF21A, WASF1, TCF20, DEAF1, MED13, CREBBP, KDM6B, SMURF1, ADNP, CACNA1G, MYT1L, KIF13B, GRIA2, CHM, and KCNK9). Additionally, we defined eight novel recessive variants (RYR2, DNAH3, TSPYL2, UPF3B KDM5C, LYST, and WNK3), four of which were X-linked. Conclusion: Despite the ASD multifactorial etiology that hinders ASD genetic risk discovery, the number of identified novel or known putative ASD genetic variants was appreciable. Nevertheless, this study represents the first comprehensive characterization of ASD genetic risk in Qatar's Middle Eastern population.

Detecting Autism Spectrum Disorder and Attention Deficit Hyperactivity Disorder Using Multimodal Time-Frequency Analysis with Machine Learning Using the Electroretinogram from Two Flash Strengths

PURPOSE

Autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) are conditions that similarly alter cognitive functioning ability and challenge the social interaction, attention, and communication skills of affected individuals. Yet these are distinct neurological conditions that can exhibit diverse characteristics which require different management strategies. It is desirable to develop tools to assist with early distinction so that appropriate early interventions and support may be tailored to an individual's specific requirements. The current diagnostic procedures for ASD and ADHD require a multidisciplinary approach and can be lengthy. This study investigated the potential of electroretinogram (ERG), an eye test measuring retinal responses to light, for rapid screening of ASD and ADHD.

METHODS

Previous studies identified differences in ERG amplitude between ASD and ADHD, but this study explored time-frequency analysis (TFS) to capture dynamic changes in the signal. ERG data from 286 subjects (146 control, 94 ASD, 46 ADHD) was analyzed using two TFS techniques.

RESULTS

Key features were selected, and machine learning models were trained to classify individuals based on their ERG response. The best model achieved 70% overall accuracy in distinguishing control, ASD, and ADHD groups.

CONCLUSION

The ERG to the stronger flash strength provided better separation and the high frequency dynamics (80-300 Hz) were more informative features than lower frequency components. To further improve classification a greater number of different flash strengths may be required along with a discrimination comparison to participants who meet both ASD and ADHD classifications and carry both diagnoses.

Ascorbate and its transporter SVCT2: The dynamic duo's integrated roles in CNS neurobiology and pathophysiology

Ascorbate is a small antioxidant molecule essential for the proper development and function of the brain. Ascorbate is transported into the brain and between brain cells via the Sodium vitamin C co-transporter 2 (SVCT2). This review provides an in-depth analysis of ascorbate's physiology, including how ascorbate is absorbed from food into the CNS, emphasizing cellular mechanisms of ascorbate recycling and release in different CNS compartments. Additionally, the review delves into the various functions of ascorbate in the CNS, including its impact on epigenetic modulation, synaptic plasticity, and neurotransmission. It also emphasizes ascorbate's role on neuromodulation and its involvement in neurodevelopmental processes and disorders. Furthermore, it analyzes the relationship between the duo ascorbate/SVCT2 in neuroinflammation, particularly its effects on microglial activation, cytokine release, and oxidative stress responses, highlighting its association with neurodegenerative diseases, such as Alzheimer's disease (AD). Overall, this review emphasizes the crucial role of the dynamic duo ascorbate/SVCT2 in CNS physiology and pathology and the need for further research to fully comprehend its significance in a neurobiological context and its potential therapeutic applications.

Assessing Trial-to-Trial Variability in Auditory ERPs in Autism and Schizophrenia

Sensory abnormalities are characteristic of autism and schizophrenia. In autism, greater trial-to-trial variability (TTV) in sensory neural responses suggest that the system is more unstable. However, these findings have only been identified in the amplitude and not in the timing of neural responses, and have not been fully explored in schizophrenia. TTV in event-related potential amplitudes and inter-trial coherence (ITC) were assessed in the auditory mismatch negativity (MMN) in autism, schizophrenia, and controls. MMN was largest in autism and smallest in schizophrenia, and TTV was greater in autism and schizophrenia compared to controls. There were no differences in ITC. Greater TTV appears to be characteristic of both autism and schizophrenia, implicating several neural mechanisms that could underlie sensory instability.

Effects of melatonin on dopaminergic neuron development via IP3-mediated mitochondrial Ca2+ regulation in autism spectrum disorder

Melatonin entrainment of suprachiasmatic nucleus-regulating circadian rhythms is mediated by MT1 and MT2 receptors. Melatonin also has neuroprotective and mitochondrial activating effects, suggesting it may affect neurodevelopment. We studied melatonin's pharmacological effects on autism spectrum disorder (ASD) neuropathology. Deciduous tooth-derived stem cells from children with ASD were used to model neurodevelopmental defects and differentiated into dopaminergic neurons (ASD-DNs) with or without melatonin. Without melatonin, ASD-DNs had reduced neurite outgrowth, mitochondrial dysfunction, lower mitochondrial Ca2+ levels, and Ca2+ accumulation in the endoplasmic reticulum (ER) compared to control DNs from typically developing children-derived stem cells. Melatonin enhanced IP3-dependent Ca2+ release from ER to mitochondria, improving mitochondrial function and neurite outgrowth in ASD-DNs. Luzindole, an MT1/MT2 antagonist, blocked these effects. Thus, melatonin supplementation may improve dopaminergic system development in ASD by modulating mitochondrial Ca2+ homeostasis via MT1/MT2 receptors.

The dopamine hypothesis of autism spectrum disorder: A comprehensive analysis of the evidence

Despite intensive research into the etiopathogenesis of autism spectrum disorder (ASD), limited progress has been achieved so far. Among the plethora of models seeking to clarify how ASD arises, a coherent dopaminergic model was lacking until recently. In 2017, we provided a theoretical framework that we designated "the dopamine hypothesis of ASD". In the meantime, numerous studies yielded empirical evidence for this model. 4 years later, we provided a second version encompassing a refined and reconceptualized framework that accounted for these novel findings. In this chapter, we will review the evidence backing the previous versions of our model and add the most recent developments to the picture. Along these lines, we intend to lay out a comprehensive analysis of the supporting evidence for the dopamine hypothesis of ASD.

Early cellular and synaptic changes in dopaminoceptive forebrain regions of juvenile mice following gestational exposure to valproate

Gestational exposure of mice to valproic acid (VPA) is one currently used experimental model for the investigation of typical failure symptoms associated with autism spectrum disorder (ASD). In the present study we hypothesized that the reduction of dopaminergic source neurons of the VTA, followed by perturbed growth of the mesotelencephalic dopamine pathway (MT), should also modify pattern formation in the dopaminoceptive target regions (particularly its mesoaccumbens/mesolimbic portion). Here, we investigated VPA-evoked cellular morphological (apoptosis-frequency detected by Caspase-3, abundance of Ca-binding proteins, CaBP), as well as synaptic proteomic (western blotting) changes, in selected dopaminoceptive subpallial, as compared to pallial, regions of mice, born to mothers treated with 500 mg/kg VPA on day 13.5 of pregnancy. We observed a surge of apoptosis on VPA treatment in nearly all investigated subpallial and pallial regions; with a non-significant trend of similar increase the nucleus accumbens (NAc) at P7, the age at which the MT pathway reduction has been reported (also supplemented by current findings). Of the CaBPs, calretinin (CR) expression was decreased in pallial regions, most prominently in retrosplenial cortex, but not in the subpallium of P7 mice. Calbindin-D 28K (CB) was selectively reduced in the caudate-putamen (CPu) of VPA exposed animals at P7 but no longer at P60, pointing to a potency of repairment. The VPA-associated overall increase in apoptosis at P7 did not correlate with the abundance and distribution of CaBPs, except in CPu, in which the marked drop of CB was negatively correlated with increased apoptosis. Abundance of parvalbumin (PV) at P60 showed no significant response to VPA treatment in any of the observed regions we did not find colocalization of apoptotic (Casp3+) cells with CaBP-immunoreactive neurons. The proteomic findings suggest reduction of tyrosine hydroxylase in the crude synaptosome fraction of NAc, but not in the CPu, without simultaneous decrease of the synaptic protein, synaptophysin, indicating selective impairment of dopaminergic synapses. The morpho-functional changes found in forebrain regions of VPA-exposed mice may signify dendritic and synaptic reorganization in dopaminergic target regions, with potential translational value to similar impairments in the pathogenesis of human ASD.

Analysis of neurotransmitters validates the importance of the dopaminergic system in autism spectrum disorder

BACKGROUND

The reasons behind the cardinal symptoms of communication deficits and repetitive, stereotyped behaviors that characterize autism spectrum disorder (ASD) remain unknown. The dopamine (DA) system, which regulates motor activity, goal-directed behaviors, and reward function, is believed to play a crucial role in ASD, although the exact mechanism is still unclear. Investigations have shown an association of the dopamine receptor D4 (DRD4) with various neurobehavioral disorders.

METHODS

We analyzed the association between ASD and four DRD4 genetic polymorphisms, 5' flanking 120-bp duplication (rs4646984), rs1800955 in the promoter, exon 1 12 bp duplication (rs4646983), and exon 3 48 bp repeats. We also examined plasma DA and its metabolite levels, DRD4 mRNA expression, and correlations of the studied polymorphisms with these parameters by case-control comparative analyses. The expression of DA transporter (DAT), which is important in regulating the circulating DA level, was also evaluated.

RESULTS

A significantly higher occurrence of rs1800955 "T/TT" was observed in the probands. ASD traits were affected by rs1800955 "T" and the higher repeat alleles of the exon 3 48 bp repeats, rs4646983 and rs4646984. ASD probands exhibited lower DA and norepinephrine levels together with higher homovanillic acid levels than the control subjects. DAT and DRD4 mRNA expression were down-regulated in the probands, especially in the presence of DAT rs3836790 "6R" and rs27072 "CC" and DRD4 rs4646984 higher repeat allele and rs1800955 "T".

CONCLUSION

This pioneering investigation revealed a positive correlation between genetic variants, hypodopaminergic state, and impairment in socio-emotional and communication reciprocity in Indian subjects with ASD, warranting further in-depth analysis.

Cariprazine in Pediatric Patients with Autism Spectrum Disorder: Results of a Pharmacokinetic, Safety and Tolerability Study

Objective: Cariprazine is a dopamine D3-preferring D3/D2 and serotonin 5-HT1A receptor partial agonist approved to treat adults with schizophrenia and manic/mixed or depressive episodes associated with bipolar I disorder. This study, which is the first to evaluate cariprazine in pediatric patients with autism spectrum disorder (ASD) (including children 5-9 years of age) using an oral solution formulation, evaluated the safety, tolerability, pharmacokinetics (PK), and exploratory efficacy of cariprazine and its two major active metabolites, desmethyl cariprazine (DCAR) and didesmethyl cariprazine (DDCAR). Methods: This clinical pharmacology, open-label, multiple-dose study enrolled 25 pediatric patients from 5 to 17 years of age, who met the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria for ASD. All patients began treatment with cariprazine 0.5 mg once daily (QD) and underwent a titration over 7 days to maintenance doses of 1.5 or 3 mg QD for patients 13-17 years of age at Screening, 0.75 or 1.5 mg QD for patients 10-12 years of age at Screening, and 0.5 or 1.5 mg QD for patients 5-9 years of age at Screening. After 6 weeks total of dosing, there was a 6-week follow-up period. Study assessments included adverse events (AEs), safety parameters, noncompartmental PK parameters, and exploratory efficacy assessments, including the Aberrant Behavior Checklist-Irritability Subscale (ABC-I), Clinical Global Impressions (CGI-S), Caregiver Global Impressions (CgGI-S), Children's Yale-Brown Obsessive Compulsiveness Scale Modified for ASD (CYBOCS-ASD), Social Responsiveness Scale (SRS), and Vineland Adaptive Behavior Scale (VABS-III). Results: All AEs were mild or moderate in severity. Most frequent treatment-emergent adverse events (TEAEs) were increased weight, increased alanine aminotransferase, increased appetite, dizziness, agitation, and nasal congestion. Increases in weight were not considered clinically meaningful. Two subjects reported extrapyramidal symptom-related TEAEs that resolved without leading to discontinuation. Dose-normalized exposures of all analytes were modestly higher in pediatric patients from 5 to 9 years of age when compared to older patients. Consistent with previous studies, at steady state, the rank of exposure in plasma was DDCAR > cariprazine > DCAR. There was numerical improvement on all exploratory endpoints (ABC-I, CGI-S, CgGI-S, CYBOCS-ASD, SRS, and VABS-III). Conclusions: PK of cariprazine and its metabolites were characterized in pediatric patients with ASD at doses up to 3 mg QD (13-17 years) and 1.5 mg QD (5-12 years). Caripazine treatment was generally well tolerated and results from this study will inform the selection of appropriate pediatric doses for subsequent studies.

Brain-Derived Neurotrophic Factor (BDNF) in Mechanisms of Autistic-like Behavior in BTBR Mice: Crosstalk with the Dopaminergic Brain System

Disturbances in neuroplasticity undoubtedly play an important role in the development of autism spectrum disorders (ASDs). Brain neurotransmitters and brain-derived neurotrophic factor (BDNF) are known as crucial players in cerebral and behavioral plasticity. Such an important neurotransmitter as dopamine (DA) is involved in the behavioral inflexibility of ASD. Additionally, much evidence from human and animal studies implicates BDNF in ASD pathogenesis. Nonetheless, crosstalk between BDNF and the DA system has not been studied in the context of an autistic-like phenotype. For this reason, the aim of our study was to compare the effects of either the acute intracerebroventricular administration of a recombinant BDNF protein or hippocampal adeno-associated-virus-mediated BDNF overexpression on autistic-like behavior and expression of key DA-related and BDNF-related genes in BTBR mice (a widely recognized model of autism). The BDNF administration failed to affect autistic-like behavior but downregulated Comt mRNA in the frontal cortex and hippocampus; however, COMT protein downregulation in the hippocampus and upregulation in the striatum were insignificant. BDNF administration also reduced the receptor TrkB level in the frontal cortex and midbrain and the BDNF/proBDNF ratio in the striatum. In contrast, hippocampal BDNF overexpression significantly diminished stereotypical behavior and anxiety; these alterations were accompanied only by higher hippocampal DA receptor D1 mRNA levels. The results indicate an important role of BDNF in mechanisms underlying anxiety and repetitive behavior in ASDs and implicates BDNF-DA crosstalk in the autistic-like phenotype of BTBR mice.

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.

Dopaminergic Modulation of Prefrontal Cortex Inhibition

The prefrontal cortex is the highest stage of integration in the mammalian brain. Its functions vary greatly, from working memory to decision-making, and are primarily related to higher cognitive functions. This explains the considerable effort devoted to investigating this area, revealing the complex molecular, cellular, and network organization, and the essential role of various regulatory controls. In particular, the dopaminergic modulation and the impact of local interneurons activity are critical for prefrontal cortex functioning, controlling the excitatory/inhibitory balance and the overall network processing. Though often studied separately, the dopaminergic and GABAergic systems are deeply intertwined in influencing prefrontal network processing. This mini review will focus on the dopaminergic modulation of GABAergic inhibition, which plays a significant role in shaping prefrontal cortex activity.

Association between RIT2 rs16976358 Polymorphism and Autism Spectrum Disorder in Asian Populations: A Meta-analysis

Background

Recent studies have shown that Ras-like without CAAX2 (RIT2) polymorphism is a susceptible factor for Parkinson's disease (PD) and autism spectrum disorder (ASD). SNP rs12456492 and rs16976358 show the emerging evidence of increased risk of PD and ASD, respectively. A meta-analysis examining the relationship between rs12456492 and PD was reported, but the association between rs16976358 and ASD has not been investigated.

Methods

We searched literature from the databases PubMed, Embase, Google Scholar, ScienceDirect, EBSCOhost, OVID, Web of Science, and Wiley up to February 2021. Three studies including 1160 ASD cases and 1367 controls were eventually enrolled in the meta-analysis based on strict inclusion and exclusion criteria.

Results

All genetics models indicate a significant association between rs16976358 polymorphism and ASD susceptibility (C vs. T: p = 0.001; CC vs. TT: p = 0.001; CT vs. TT: p = 0.009; CC+CT vs. TT: p = 0.001; CC vs. CT+TT: p = 0.001; TT+CC vs. CT: p = 0.013). The results of sensitivity analysis and publication bias of Begg's and Egger's tests were stable in the models of allele (C vs. T), codominant (CC vs. TT), dominant (CC+CT vs. TT), and recessive (CC vs. CT+TT).

Conclusions

Our meta-analysis exhibits that the allele C, CC, and CT genotyping of rs16976358 suggest the risk for ASD, but additional studies using a large sample size and ethnically diverse populations need to be included in the future.

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.

Cross-country comparison of parental reports and objective measures of sleep patterns of typically developing children and autistic children between the UK and South Korea

Sleep duration and disturbances in typically developing (TD) children have been found to vary across countries. Given the impact of culture on sleep patterns in TD children, it is also necessary to examine the impact of culture on sleep patterns in children with atypical development. However, previous studies have often relied only on parent reports of children's sleep. Hence, the present study conducted a cross-cultural comparison of sleep duration and disturbances of school-aged TD children and autistic children in the UK and South Korea (hereafter Korea) using both subjective and objective sleep measurements. Cultural differences were observed in both actigraphy measures and parent reports of children's sleep duration and disturbances. Both TD children and autistic children in Korea had a later bedtime, later getting up time and shorter nocturnal sleep duration than their peers in the UK (p < .05). Furthermore, greater parent-reported sleep disturbances were reported in TD children in Korea compared to TD children in the UK and in autistic children in the UK compared to autistic children in Korea. Correlational analyses indicated that most parent-reported measures of children's sleep did not significantly correlate with objective measures and child reports, suggesting that studies on children's sleep can benefit by collecting data from multiple sources. Taken together, these findings suggest a cultural influence on sleep duration and disturbances of both TD children and autistic children. This study raises questions for further research to identify factors underlying cultural differences in children's sleep duration and disturbances.

Synthesis of genetic association studies on autism spectrum disorders using a genetic model-free approach

BACKGROUND

Autism spectrum disorder (ASD) is a clinically and genetically heterogeneous group of neurodevelopmental disorders. Despite the extensive efforts of scientists, the etiology of ASD is far from completely elucidated. In an effort to enlighten the genetic architecture of ASDs, a meta-analysis of all available genetic association studies (GAS) was conducted.

METHODS

We searched in the Human Genome Epidemiology Navigator (HuGE Navigator) and PubMed for available case-control GAS of ASDs. The threshold for meta-analysis was two studies per genetic variant. The association between genotype distribution and ASDs was examined using the generalized linear odds ratio (ORG). For variants with available allele frequencies, the examined model was the allele contrast.

RESULTS

Overall, 57 candidate genes and 128 polymorphisms were investigated in 159 articles. In total 28 genetic polymorphisms have been shown to be associated with ASDs, that are harbored in 19 genes. Statistically significant results were revealed for the variants of the following genes adenosine deaminase (ADA), bone marrow stromal cell antigen-1 (CD157/BST1), Dopamine receptor D1 (DRD1), engrailed homolog 2 (EN2), met proto-oncogene (MET), methylenetetrahydrofolate reductase (MTHFR), solute carrier family 6 member 4 (SLC6A4), Synaptosomal-associated protein, 25kDa (SNAP-25) and vitamin D receptor (VDR). In the allele contrast model of cases versus healthy controls, significant associations were observed for Adrenoceptor Alpha 1B (ADRA1B), acetyl serotonin O - methyltransferase (ASMT), complement component 4B (C4B), dopamine receptor D3 (DRD3), met proto-oncogene (MET), neuroligin 4, X-linked (NLGN4), neurexin 1 (NRXN1), oxytocin receptor (OXTR), Serine/Threonine-Protein Kinase PFTAIRE-1 (PFTK1), Reelin (RELN) and Ras-like without CAAX 2 (RIT2).

CONCLUSION

These significant findings provide further evidence for genetic factors' implication in ASDs offering new perspectives in means of prevention and prognosis.

Dopamine‐related oxidative stress and mitochondrial dysfunction in dopaminergic neurons differentiated from deciduous teeth‐derived stem cells of children with Down syndrome

Down syndrome (DS) is one of the common genetic disorders caused by the trisomy of human chromosome 21 (HSA21). Mitochondrial dysfunction and redox imbalance play important roles in DS pathology, and altered dopaminergic regulation has been demonstrated in the brain of individuals with DS. However, the pathological association of these elements is not yet fully understood. In this study, we analyzed dopaminergic neurons (DNs) differentiated from deciduous teeth‐derived stem cells of children with DS or healthy control children. As previously observed in the analysis of a single case of DS, compared to controls, patient‐derived DNs (DS‐DNs) displayed shorter neurite outgrowth and fewer branches, as well as downregulated vesicular monoamine transporter 2 and upregulated dopamine transporter 1, both of which are key regulators of dopamine homeostasis in DNs. In agreement with these expression profiles, DS‐DNs accumulated dopamine intracellularly and had increased levels of cellular and mitochondrial reactive oxygen species (ROS). DS‐DNs showed downregulation of non‐canonical Notch ligand, delta‐like 1, which may contribute to dopamine accumulation and increased ROS levels through DAT1 upregulation. Furthermore, DS‐DNs showed mitochondrial dysfunction in consistent with lower expression of peroxisome proliferator‐activated receptor‐gamma coactivator 1 alpha (PGC‐1α) and upregulation of a HSA21‐encoded negative regulator of PGC‐1α, nuclear receptor‐interacting protein 1. These results suggest that dysregulated dopamine homeostasis may participate in oxidative stress and mitochondrial dysfunction of the dopaminergic system in DS.

Pathophysiological Studies of Monoaminergic Neurotransmission Systems in Valproic Acid-Induced Model of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with complex etiology. The core syndromes of ASD are deficits in social communication and self-restricted interests and repetitive behaviors. Social communication relies on the proper integration of sensory and motor functions, which is tightly interwoven with the limbic function of reward, motivation, and emotion in the brain. Monoamine neurotransmitters, including serotonin, dopamine, and norepinephrine, are key players in the modulation of neuronal activity. Owing to their broad distribution, the monoamine neurotransmitter systems are well suited to modulate social communication by coordinating sensory, motor, and limbic systems in different brain regions. The complex and diverse functions of monoamine neurotransmission thus render themselves as primary targets of pathophysiological investigation of the etiology of ASD. Clinical studies have reported that children with maternal exposure to valproic acid (VPA) have an increased risk of developing ASD. Extensive animal studies have confirmed that maternal treatments of VPA include ASD-like phenotypes, including impaired social communication and repetitive behavior. Here, given that ASD is a neurodevelopmental disorder, we begin with an overview of the neural development of monoaminergic systems with their neurochemical properties in the brain. We then review and discuss the evidence of human clinical and animal model studies of ASD with a focus on the VPA-induced pathophysiology of monoamine neurotransmitter systems. We also review the potential interactions of microbiota and monoamine neurotransmitter systems in ASD pathophysiology. Widespread and complex changes in monoamine neurotransmitters are detected in the brains of human patients with ASD and validated in animal models. ASD animal models are not only essential to the characterization of pathogenic mechanisms, but also provide a preclinical platform for developing therapeutic approaches to ASD.

Dopaminergic Dysregulation in Syndromic Autism Spectrum Disorders: Insights From Genetic Mouse Models

Autism spectrum disorder (ASD) is a neurodevelopmental disorder defined by altered social interaction and communication, and repetitive, restricted, inflexible behaviors. Approximately 1.5-2% of the general population meet the diagnostic criteria for ASD and several brain regions including the cortex, amygdala, cerebellum and basal ganglia have been implicated in ASD pathophysiology. The midbrain dopamine system is an important modulator of cellular and synaptic function in multiple ASD-implicated brain regions via anatomically and functionally distinct dopaminergic projections. The dopamine hypothesis of ASD postulates that dysregulation of dopaminergic projection pathways could contribute to the behavioral manifestations of ASD, including altered reward value of social stimuli, changes in sensorimotor processing, and motor stereotypies. In this review, we examine the support for the idea that cell-autonomous changes in dopaminergic function are a core component of ASD pathophysiology. We discuss the human literature supporting the involvement of altered dopamine signaling in ASD including genetic, brain imaging and pharmacologic studies. We then focus on genetic mouse models of syndromic neurodevelopmental disorders in which single gene mutations lead to increased risk for ASD. We highlight studies that have directly examined dopamine neuron number, morphology, physiology, or output in these models. Overall, we find considerable support for the idea that the dopamine system may be dysregulated in syndromic ASDs; however, there does not appear to be a consistent signature and some models show increased dopaminergic function, while others have deficient dopamine signaling. We conclude that dopamine dysregulation is common in syndromic forms of ASD but that the specific changes may be unique to each genetic disorder and may not account for the full spectrum of ASD-related manifestations.

Ilex kudingcha C.J. Tseng Mitigates Phenotypic Characteristics of Human Autism Spectrum Disorders in a Drosophila Melanogaster Rugose Mutant

Autism spectrum disorders (ASD) have heterogeneous etiologies involving dysfunction of central nervous systems, for which no effective pan-specific treatments are available. Ilex kudingcha (IK) C.J. Tseng is a nootropic botanical used in Asia for neuroprotection and improvement of cognition. This study establishes that a chemically characterized extract from IK (IKE) mitigates behavioral traits in the Drosophila melanogaster rugose mutant, whose traits resemble human ASD, and examines possible mechanisms. IKE treatment significantly ameliorated deficits in social interaction, short-term memory, and locomotor activity in Drosophila rugose, and significantly increased synaptic bouton number of size more than 2 μm² in the neuromuscular junctions (NMJs) of Drosophila rugose. To clarify mechanism(s) of IKE action, methylphenidate (MPH), a dopamine transporter inhibitor, was included as a reference drug in the behavioral assays: MPH significantly improved social interaction and short-term memory deficit in Drosophila rugose; administration of the dopamine D1 receptor antagonist SCH23390 and dopamine D2 receptor antagonist sulpiride reversed the ameliorative effects of both MPH and IKE on the social interaction deficits of Drosophila rugose. To extend analysis of IKE treatment to the vertebrate central nervous system, ASD-associated gene expression in mouse hippocampus was studied by RNA-seq: IKE treatment altered the expression of genes coding phosphoinositide 3-kinases/protein kinase B (PI3K-Akt), proteins in glutamatergic, dopaminergic, serotonergic, and GABAergic synapses, cAMP response element-binding protein (CREB), and RNA transporter proteins. These results provide a foundation for further analysis of IKE as a candidate for treatment of some forms of ASD.

Dental Pulp-Derived Mesenchymal Stem Cells for Modeling Genetic Disorders

A subpopulation of mesenchymal stem cells, developmentally derived from multipotent neural crest cells that form multiple facial tissues, resides within the dental pulp of human teeth. These stem cells show high proliferative capacity in vitro and are multipotent, including adipogenic, myogenic, osteogenic, chondrogenic, and neurogenic potential. Teeth containing viable cells are harvested via minimally invasive procedures, based on various clinical diagnoses, but then usually discarded as medical waste, indicating the relatively low ethical considerations to reuse these cells for medical applications. Previous studies have demonstrated that stem cells derived from healthy subjects are an excellent source for cell-based medicine, tissue regeneration, and bioengineering. Furthermore, stem cells donated by patients affected by genetic disorders can serve as in vitro models of disease-specific genetic variants, indicating additional applications of these stem cells with high plasticity. This review discusses the benefits, limitations, and perspectives of patient-derived dental pulp stem cells as alternatives that may complement other excellent, yet incomplete stem cell models, such as induced pluripotent stem cells, together with our recent data.

Gene x responsive parenting interactions in social development: Characterizing heterogeneity in autism spectrum disorder

Emerging research suggests that caregiving environments and genetic variants independently contribute to social functioning in children with typical development or autism spectrum disorder (ASD). However, biologically plausible interactive models and complimentary assessment of mechanisms are needed to: (a) explain considerable social heterogeneity, (b) resolve inconsistencies in the literature, and (c) develop and select optimal treatments based on individual differences. This study examined the role of child genotypes and responsive parenting in the social development of 104 children with ASD (ages 4-7 years). We utilized a longitudinal, multi-informant design and structural equation models to evaluate: (a) the additive and interactive effects of biologically plausible candidate genes (5-HTTLPR, OXTR, DRD4) and responsive parenting in predicting prospective social development in ASD across three time points spanning 1.5 years, and (b) whether child emotion regulation mediated observed gene x environment interactions (GxEs). Responsive parenting positively predicted prospective change in child social skills; these associations were moderated by 5-HTTLPR and DRD4 in teacher-report models, and DRD4 in parent-report models. No GxE effects were found for OXTR. Emotion regulation did not significantly mediate the GxEs involving 5-HTTLPR and DRD4. Acknowledging the complexities of GxE research, implications for future research, and targeted intervention efforts are discussed.

Plasma Levels of Alpha and Gamma Synucleins in Autism Spectrum Disorder: An Indicator of Severity

OBJECTIVES

The aim of this study was to correlate plasma levels of the synaptic proteins α-synuclein and γ-synuclein in autism spectrum disorder (ASD) children in order to elucidate their possible contribution to the pathogenesis of ASD and to study their association with the severity of the disorder.

SUBJECTS AND METHODS

Plasma levels of α-synuclein and γ-synuclein were measured in 38 male children diagnosed with ASD and 40 healthy age-matched male children by ELISA.

RESULTS

Our results showed that plasma levels of α-synuclein (18.02 ± 5.3 pg/mL) were significantly higher in ASD children than in control children (14.39 ± 2 pg/mL), and plasma levels of γ-synuclein were decreased in the ASD group (23.74 ± 7.7 pg/mL) compared to the control group (32.40 ± 6.8 pg/mL) (p < 0.0001). Our data also indicate that plasma levels of both α-synuclein and γ-synuclein are significantly associated with the severity of ASD.

CONCLUSIONS

Our study showed that alteration in α-synuclein and γ-synuclein might be associated with ASD pathogenesis and could be an indicator of the severity of the disorder.

Facial Emotion Recognition and Polymorphisms of Dopaminergic Pathway Genes in Children with ASD

Background

It is inconclusive whether children with autism spectrum disorder (ASD) experience a deficit in facial emotion recognition. The dopaminergic pathway has been implicated in the pathogenesis of ASD. This study was aimed at determining facial emotion recognition and its correlation with polymorphisms in the dopaminergic pathway genes in children with ASD.

Methods

Facial emotion recognition was examined in 98 children with ASD and 60 age- and gender-matched healthy controls. The severity of ASD was evaluated using the Childhood Autism Rating Scale (CARS). DNA from blood cells was used to analyze the genotypes of single-nucleotide polymorphisms (SNPs) in dopaminergic pathway genes. SNPs of DBH rs1611115, DDC rs6592961, DRD1 rs251937, DRD2 rs4630328, and DRD3 rs167771 were analyzed.

Results

Children with ASD took a significantly longer time to recognize all facial emotions, and their interpretations were less accurate for anger at low intensity and fear at both low and high intensities. The severity of the disease was associated with significant delays in recognition of all facial emotions and with a decrease in accuracy in recognition of happiness and anger at low intensity. Accuracy in recognizing fear at high intensity and sadness at low intensity was associated with rs251937 and rs4630328, respectively, in children with ASD. Multivariate logistic regression analysis revealed that SNP rs167771, response time for the recognition of happiness, sadness and fear, and accuracy in recognition of anger and fear were all associated with the risk of childhood ASD.

Conclusions

Children with ASD experience a deficit in facial emotion recognition. Certain SNPs in the dopaminergic pathway genes are associated with accuracy in recognizing selective facial emotions in children with ASD.

Modelling Learning and Memory in Drosophila to Understand Intellectual Disabilities

Neurodevelopmental disorders (NDDs) include a large number of conditions such as Fragile  X  syndrome, autism spectrum disorders and Down syndrome, among others. They are characterized by limitations in adaptive and social behaviors, as well as intellectual disability (ID). Whole-exome and whole-genome sequencing studies have highlighted a large number of NDD/ID risk genes. To dissect the genetic causes and underlying biological pathways, in vivo experimental validation of the effects of these mutations is needed. The fruit fly, Drosophila melanogaster, is an ideal model to study NDDs, with highly tractable genetics, combined with simple behavioral and circuit assays, permitting rapid medium-throughput screening of NDD/ID risk genes. Here, we review studies where the use of well-established assays to study mechanisms of learning and memory in Drosophila has permitted insights into molecular mechanisms underlying IDs. We discuss how technologies in the fly model, combined with a high degree of molecular and physiological conservation between flies and mammals, highlight the Drosophila system as an ideal model to study neurodevelopmental disorders, from genetics to behavior.

Integrated Systems Analysis Explores Dysfunctional Molecular Modules and Regulatory Factors in Children with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a genetic neurodevelopmental disorder involving multiple genes that occurs in early childhood, and a number of risk genes have been reported in previous studies. However, the molecular mechanism of the polygenic regulation leading to pathological changes in ASD remains unclear. First, we identified 8 dysregulated gene coexpression modules by analyzing blood transcriptome data from 96 children with ASD and 42 controls. These modules are rich in ASD risk genes and function related to metabolism, immunity, neurodevelopment, and signaling. The regulatory factors of each module including microRNA (miRNA) and transcription factors (TFs) were subsequently predicted based on transcriptional and posttranscriptional regulation. We identified a set of miRNAs that regulate metabolic and immune modules, as well as transcription factors that cause dysregulation of the modules, and we constructed a coregulatory network between the regulatory factors and modules. Our work reveals dysfunctional modules in children with ASD, elucidates the role of miRNA and transcription factor dysregulation in the pathophysiology of ASD, and helps us to further understand the underlying molecular mechanism of ASD.

Gestational Exposure to Sodium Valproate Disrupts Fasciculation of the Mesotelencephalic Dopaminergic Tract, With a Selective Reduction of Dopaminergic Output From the Ventral Tegmental Area

Gestational exposure to valproic acid (VPA) is known to cause behavioral deficits of sociability, matching similar alterations in human autism spectrum disorder (ASD). Available data are scarce on the neuromorphological changes in VPA-exposed animals. Here, we focused on alterations of the dopaminergic system, which is implicated in motivation and reward, with relevance to social cohesion. Whole brains from 7-day-old mice born to mothers given a single injection of VPA (400 mg/kg b.wt.) on E13.5 were immunostained against tyrosine hydroxylase (TH). They were scanned using the iDISCO method with a laser light-sheet microscope, and the reconstructed images were analyzed in 3D for quantitative morphometry. A marked reduction of mesotelencephalic (MT) axonal fascicles together with a widening of the MT tract were observed in VPA treated mice, while other major brain tracts appeared anatomically intact. We also found a reduction in the abundance of dopaminergic ventral tegmental (VTA) neurons, accompanied by diminished tissue level of DA in ventrobasal telencephalic regions (including the nucleus accumbens (NAc), olfactory tubercle, BST, substantia innominata). Such a reduction of DA was not observed in the non-limbic caudate-putamen. Conversely, the abundance of TH+ cells in the substantia nigra (SN) was increased, presumably due to a compensatory mechanism or to an altered distribution of TH+ neurons occupying the SN and the VTA. The findings suggest that defasciculation of the MT tract and neuronal loss in VTA, followed by diminished dopaminergic input to the ventrobasal telencephalon at a critical time point of embryonic development (E13-E14) may hinder the patterning of certain brain centers underlying decision making and sociability.

Interaction Between Prematurity and the MAOA Gene on Mental Development in Children: A Longitudinal View

This study aimed to examine the association of dopamine-related genes with mental and motor development and the gene-environment interaction in preterm and term children. A total of 201 preterm and 111 term children were examined for their development at 6, 12, 18, 24, and 36 months and were genotyped for 15 single-nucleotide polymorphisms (SNPs) in dopamine-related genes (DRD2, DRD3, DAT1, COMT, and MAOA). An independent sample of 256 preterm children was used for replication. Since the developmental age trends of preterm children differed from those of term children, the analyses were stratified by prematurity. Among the 8 SNPs on the MAOA gene examined in the whole learning sample, the results of linkage disequilibrium analysis indicated that they were located in one block (all D' > 0.9), and rs2239448 was chosen as the tag (r² > 0.85). In the analysis of individual SNPs in each dopamine-related gene, the tag SNP (rs2239448) in MAOA remained significantly associated with the mental scores of preterm children for the interaction with age trend (p < 0.0001; largest effect size of 0.65 at 24 months) after Bonferroni correction for multiple testing. Similar findings for rs2239448 were replicated in the independent sample (p = 0.026). However, none of the SNPs were associated with the motor scores of preterm children, and none were related to the mental or motor scores of term children. The genetic variants of the MAOA gene exert influence on mental development throughout early childhood for preterm, but not term, children.

[Chronic Activation of the Dopaminergic Neuronal Pathway Improves Behavioral Abnormalities in the Prenatal Valproic Acid Exposure Mouse Model of Autism Spectrum Disorder]

Over the last decade there has been an increase in the prevalence of autism spectrum disorder (ASD); however, its pathogenic mechanisms remain unclear. To date, no effective drug has been developed to treat the core symptoms of ASD, especially social interaction deficits. Previous studies have mainly focused on the glutamatergic, GABAergic, and serotonergic signaling pathways; however, a growing number of studies have reported abnormalities in the dopaminergic pathway, such as mutations and functional alterations of dopamine-related molecules, in ASD patients. Furthermore, atypical antipsychotic drugs risperidone and aripiprazole are prescribed for the treatment of non-core symptoms, such as irritability, in patients with ASD. These observations suggest that the dopaminergic pathway is involved in the pathogenesis of ASD. Previously, we have established a mouse model of ASD based on clinical research, which shows that exposure to valproic acid, an antiepileptic drug, during pregnancy causes an increase in the risk of developing ASD in children. This review summarizes our recent studies, which have assessed alterations in the prefrontal dopaminergic pathway. In addition, we discuss the effects of treatment with attention deficit/hyperactivity disorder drugs and atypical antipsychotic drugs, which activate the prefrontal dopaminergic pathway, on ASD-like behavioral abnormalities in the valproic acid exposure mouse model of ASD.

Neuromedin U induces self-grooming in socially-stimulated mice

Emerging evidence suggest that appetite-regulating peptides modulate social behaviors. We here investigate whether the anorexigenic peptide neuromedin U (NMU) modulates sexual behavior in male mice. However, instead of modulating sexual behaviors, NMU administered into the third ventricle increased self-grooming behavior. In addition, NMU-treatment increased self-grooming behavior when exposed to other mice or olfactory social-cues, but not when exposed to non-social environments. As the neuropeptide oxytocin is released during social investigation and exogenous oxytocin induces self-grooming, its role in NMU-induced self-grooming behavior was investigated. In line with our hypothesis, the oxytocin receptor antagonist inhibited NMU-induced self-grooming behavior in mice exposed to olfactory social-cues. Moreover, dopamine in the mesocorticolimbic system is known to be a key regulator of self-grooming behavior. In line with this, we proved that infusion of NMU into nucleus accumbens increased self-grooming behavior in mice confronted with an olfactory social-cue and that this behavior was inhibited by antagonism of dopamine D2, but not D1/D5, receptors. Moreover repeated NMU treatment enhanced ex vivo dopamine levels and decreased the expression of dopamine D2 receptors in nucleus accumbens in socially housed mice. On the other hand, the olfactory stimuli-dependent NMU-induced self-grooming was not affected by a corticotrophin-releasing hormone antagonist, and NMU-treatment did not influence repetitive behaviors in the marble burying test. In conclusion, our results suggest that NMU treatment and, social cues - potentially triggering oxytocin release - together induce excessive grooming behavior in male mice. The mesolimbic dopamine system, including accumbal dopamine D2 receptors, was identified as a crucial downstream mechanism.

Lower serum retinoic acid level for prediction of higher risk of mortality in ischemic stroke

OBJECTIVE

To explore the association between serum retinoic acid (RA) level in patients with acute ischemic stroke (AIS) and mortality risk in the 6 months after admission.

METHODS

From January 2015 through December 2016, patients admitted to 3 stroke centers in China for first-ever AIS were screened. The primary endpoint was all-cause mortality or cardiovascular disease (CVD) mortality in the 6 months after admission. The significance of serum RA level, NIH Stroke Scale score, and established risk factors in predicting mortality were determined. The integrated discrimination improvement (IDI) and net reclassification improvement (NRI) statistics were applied in statistical analysis.

RESULTS

Of the 1,530 patients enrolled, 325 died within 6 months of admission, with an all-cause mortality of 21.2% and CVD-related mortality of 13.1%. In multivariable analysis, RA levels were expressed as quartiles with the clinical variables. The results of the second to fourth quartiles (Q2-Q4) were compared with the first quartile (Q1); RA levels showed prognostic significance, with decreased all-cause and CVD mortality of 55% and 63%, respectively. After RA was added to the existing risk factors, all-cause mortality could be better reclassified, in association with only the NRI statistic (p = 0.005); CVD mortality could be better reclassified with significance, in association with both the IDI and NRI statistics (p < 0.01).

CONCLUSIONS

Low circulating levels of RA were associated with increased risk of all-cause and CVD mortality in a cohort of patients with first-incidence AIS, indicating that RA level could be a predictor independent of established conventional risk factors.

Conserved regulation of neurodevelopmental processes and behavior by FoxP in Drosophila

FOXP proteins form a subfamily of evolutionarily conserved transcription factors involved in the development and functioning of several tissues, including the central nervous system. In humans, mutations in FOXP1 and FOXP2 have been implicated in cognitive deficits including intellectual disability and speech disorders. Drosophila exhibits a single ortholog, called FoxP, but due to a lack of characterized mutants, our understanding of the gene remains poor. Here we show that the dimerization property required for mammalian FOXP function is conserved in Drosophila. In flies, FoxP is enriched in the adult brain, showing strong expression in ~1000 neurons of cholinergic, glutamatergic and GABAergic nature. We generate Drosophila loss-of-function mutants and UAS-FoxP transgenic lines for ectopic expression, and use them to characterize FoxP function in the nervous system. At the cellular level, we demonstrate that Drosophila FoxP is required in larvae for synaptic morphogenesis at axonal terminals of the neuromuscular junction and for dendrite development of dorsal multidendritic sensory neurons. In the developing brain, we find that FoxP plays important roles in α-lobe mushroom body formation. Finally, at a behavioral level, we show that Drosophila FoxP is important for locomotion, habituation learning and social space behavior of adult flies. Our work shows that Drosophila FoxP is important for regulating several neurodevelopmental processes and behaviors that are related to human disease or vertebrate disease model phenotypes. This suggests a high degree of functional conservation with vertebrate FOXP orthologues and established flies as a model system for understanding FOXP related pathologies.

Kami-shoyo-san improves ASD-like behaviors caused by decreasing allopregnanolone biosynthesis in an SKF mouse model of autism

Dysfunctions in the GABAergic system are associated with the pathogenesis of autism spectrum disorder (ASD). However, the mechanisms by which GABAergic system dysfunctions induce the pathophysiology of ASD remain unclear. We previously demonstrated that a selective type I 5α-reductase inhibitor SKF105111 (SKF) induced ASD-like behaviors, such as impaired sociability-related performance and repetitive grooming behaviors, in male mice. Moreover, the effects of SKF were caused by a decrease in the endogenous levels of allopregnanolone (ALLO), a positive allosteric modulator of the GABAA receptor. In this study, we used SKF-treated male mice as a putative animal model of ASD and examined the effects of Kami-shoyo-san (KSS) as an experimental therapeutic strategy for ASD. KSS is a traditional Kampo formula consisting of 10 different crude drugs and has been used for the treatment of neuropsychiatric symptoms. KSS dose-dependently attenuated sociability deficits and suppressed an increase in grooming behaviors in SKF-treated mice without affecting ALLO content in the prefrontal cortex. The systemic administration of the dopamine D1 receptor antagonist SCH23390 reversed the ameliorative effects of KSS. On the other hand, the dopamine D2 receptor antagonist sulpiride and GABAA receptor antagonist bicuculline only attenuated the ameliorative effect of KSS on repetitive self-grooming behaviors. The present results indicate that KSS improves SKF-induced ASD-like behaviors by facilitating dopamine receptor-mediated mechanisms and partly by neurosteroid-independent GABAA receptor-mediated neurotransmission. Therefore, KSS is a potential candidate for the treatment of ASD.

Molecular Pathology and Pharmacological Treatment of Autism Spectrum Disorder-Like Phenotypes Using Rodent Models

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder with a high prevalence rate. The core symptoms of ASD patients are impaired social communication and repetitive behavior. Genetic and environmental factors contribute to pathophysiology of ASD. Regarding environmental risk factors, it is known that valproic acid (VPA) exposure during pregnancy increases the chance of ASD among offspring. Over a decade of animal model studies have shown that maternal treatment with VPA in rodents recapitulates ASD-like pathophysiology at a molecular, cellular and behavioral level. Here, we review the prevailing theories of ASD pathogenesis, including excitatory/inhibitory imbalance, neurotransmitter dysfunction, dysfunction of mTOR and endocannabinoid signaling pathways, neuroinflammation and epigenetic alterations that have been associated with ASD. We also describe the evidence linking neuropathological changes to ASD-like behavioral abnormalities in maternal VPA-treated rodents. In addition to obtaining an understanding of the neuropathological mechanisms, the VPA-induced ASD-like animal models also serve as a good platform for testing pharmacological reagents that might be use treating ASD. We therefore have summarized the various pharmacological studies that have targeted the classical neurotransmitter systems, the endocannabinoids, the Wnt signal pathway and neuroinflammation. These approaches have been shown to often be able to ameliorate the ASD-like phenotypes induced by maternal VPA treatments.

Impaired neurite development associated with mitochondrial dysfunction in dopaminergic neurons differentiated from exfoliated deciduous tooth-derived pulp stem cells of children with autism spectrum disorder

Autism spectrum disorder (ASD) is a highly heterogeneous neurodevelopmental disorder characterized by impaired social interactions, restrictive interests, and repetitive stereotypic behaviors. Among the various mechanisms underlying the pathogenesis of ASD, dysfunctions of dopaminergic signaling and mitochondria have been hypothesized to explain the core symptoms of children with ASD. However, only a few studies focusing on the pathological association between dopaminergic neurons (DN) and mitochondria in ASD have been performed using patient-derived stem cells and in vitro differentiated neurons. Stem cells from human exfoliated deciduous teeth (SHED) are neural crest-derived mesenchymal stem cells present in the dental pulp of exfoliated deciduous teeth; these cells can differentiate into dopaminergic neurons (DN) in vitro. This study aimed to investigate the pathological association between development of DN and mitochondria in ASD by using SHED as a disease- or patient-specific cellular model. The SHED obtained from three children with ASD and three typically developing children were differentiated into DN, and the neurobiology of these cells was examined. The DN derived from children with ASD showed impaired neurite outgrowth and branching, associated with decreased mitochondrial membrane potential, ATP production, number of mitochondria within the neurites, amount of mitochondria per cell area and intracellular calcium level. In addition, impaired neurite outgrowth and branching of ASD-derived DN were not improved by brain-derived neurotrophic factor (BDNF), suggesting impairment of the BDNF signaling pathway in ASD. These results imply that intracerebral dopamine production may have decreased in these children. The earliest age at which deciduous teeth spontaneously exfoliate in humans, and SHED can be noninvasively collected, is approximately 6 years. Our results suggest that in vitro analysis of SHED-derived DN obtained from children with ASD provides neurobiological information that may be useful in determining treatment strategies in the early stages of ASD.

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Dental pulp stem cells of autistic patient differentiate into dopaminergic neurons.

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These neurons show impaired neurite development compared with those from controls.

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This impairment is associated with mitochondrial dysfunction.

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Dental pulp stem cells may help establish treatment strategies against autism.

Current Enlightenment About Etiology and Pharmacological Treatment of Autism Spectrum Disorder

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

The dopamine transporter role in psychiatric phenotypes

The dopamine transporter (DAT) is one of the most relevant and investigated neurotransmitter transporters. DAT is a plasma membrane protein which plays a homeostatic role, controlling both extracellular and intracellular concentrations of dopamine (DA). Since unbalanced DA levels are known to be involved in numerous mental disorders, a wealth of investigations has provided valuable insights concerning DAT role into normal brain functioning and pathological processes. Briefly, this extensive but non-systematic review discusses what is recently known about the role of SLC6A3 gene which encodes the dopamine transporter in psychiatric phenotypes. DAT protein, SLC6A3 gene, animal models, neuropsychology, and neuroimaging investigations are also concisely discussed. To conclude, current challenges are reviewed in order to provide perspectives for future studies.

Pathophysiological and neurobehavioral characteristics of a propionic acid-mediated autism-like rat model

Autism spectrum disorder (ASD) is induced by complex hereditary and environmental factors. However, the mechanisms of ASD development are poorly understood. The purpose of this study was to identify standard indicators of this condition by comparing clinical, pathophysiological, and neurobehavioral features in an autism-like animal model. A total of 22 male Sprague-Dawley rats were randomly divided into control and 500 mg/kg propionic acid (PPA)-treated groups. Rats were subjected to behavioral tests, gene expression analyses, and histological analyses to detect pathophysiological and neurobehavioral alterations. Exploratory activity and non-aggressive behavior were significantly reduced in PPA-treated rats, whereas enhanced aggressive behavior during adjacent interactions was observed on day 14 after PPA administration. To evaluate gene expression after PPA administration, we analyzed hippocampal tissue using reverse transcription PCR. Glial fibrillary acidic protein was augmented in the PPA-treated group on day 14 after appearance of ASD-like behaviors by PPA administration, whereas octamer-binding transcription factor 4 expression was significantly decreased in the PPA-treated group. Histological evaluation revealed significantly reduced diameter and layer thickness of granule cells in PPA-treated rats compared with control rats. We conclude that PPA administration induced abnormal neural cell organization, which may have led to autism-like neurobehaviors, including increased aggressive behavior, reduced exploratory activity, and isolative and passive behaviors.

DHA Mitigates Autistic Behaviors Accompanied by Dopaminergic Change in a Gene/Prenatal Stress Mouse Model

Autism Spectrum Disorder (ASD) is characterized by impairments in social interaction, social communication, and repetitive and stereotyped behaviors. Recent work has begun to explore gene × environmental interactions in the etiology of ASD. We previously reported that prenatal stress exposure in stress-susceptible heterozygous serotonin transporter (SERT) KO pregnant dams in a mouse model resulted in autism-like behavior in the offspring (SERT/S mice). The association between prenatal stress and ASD appears to be affected by maternal SERT genotype in clinical populations as well. Using the mouse model, we examined autistic-like behaviors in greater detail, and additionally explored whether diet supplementation with docosahexaenoic acid (DHA) may mitigate the behavioral changes. Only male SERT/S mice showed social impairment and stereotyped behavior, and DHA supplementation ameliorated some of these behaviors. We also measured monoamine levels in the SERT/S mice after three treatment paradigms: DHA-rich diet continuously from breeding (DHA diet), DHA-rich diet only after weaning (CTL/DHA diet) and control diet only (CTL diet). The dopamine (DA) content in the striatum was significantly increased in the SERT/S mice compared with wild-type (WT) mice, whereas no difference was observed with noradrenaline and serotonin content. Moreover, DA content in the striatum was significantly reduced in the SERT/S mice with the DHA-rich diet provided continuously from breeding. The results indicate that autism-associated behaviors and changes in the dopaminergic system in this setting can be mitigated with DHA supplementation.

CSNK2B splice site mutations in patients cause intellectual disability with or without myoclonic epilepsy

De novo mutations are a frequent cause of disorders related to brain development. We report the results from the screening of two patients diagnosed with intellectual disability (ID) using exome sequencing to identify new causative de novo mutations. Exome sequencing was conducted in two patient-parent trios to identify de novo variants. In silico and expression studies were also performed to evaluate the functional consequences of these variants. The two patients presented developmental delay with minor facial dysmorphy. One of them presented pharmacoresistant myoclonic epilepsy. We identified two de novo splice variants (c.175+2T>G; c.367+2T>C) in the CSNK2B gene encoding the β subunit of the Caseine kinase 2 (CK2). CK2 is a ubiquitously expressed kinase that is present in high levels in brain and it appears to be constitutively active. The mRNA transcripts were abnormal and significantly reduced in affected fibroblasts and most likely produced truncated proteins. Taking into account that mutations in CSNK2A1, encoding the α subunit of CK2, were previously identified in patients with neurodevelopmental disorders and dysmorphic features, our study confirmed that the protein kinase CK2 plays a major role in brain, and showed that CSNK2, encoding the β subunit, is a novel ID gene. This study adds knowledge to the increasingly growing list of causative and candidate genes in ID and epilepsy, and highlights CSNK2B as a new gene for neurodevelopmental disorders.