Obsessive-compulsive disorder (OCD) is characterized by recurrent obtrusive and repetitive acts typically occurred following anxiety. In the last two decades, studies done on the gene sequences, large-scale and point mutations and gene-gene, gene-environment and gene-drug interactions have led to the discovery of hundreds of genes associated with OCD. Although each gene in turn is a part of the etiology of this disorder; however, OCD, like other mental disorders is complex and a comprehensive and integrated view is necessary to understand its genetic basis. In this study, through an extensive review of existing published studies, all genes associated with OCD were found. Then, in order to integrate the results, all the interactions between these genes were explored and the achievement was represented as an interactive genetic network. Furthermore, the reconstructed network was analyzed. It was found that GRIN2A, GRIN2B and GRIA2 are the most central nodes in the network. Functional and pathway enrichment analysis showed that glutamate-related pathways are the main deficient systems in patients with OCD. By studying genes shared between OCD and other diseases, it was cleared that OCD, epilepsy and some types of cancer have the most number of shared genes. The results of this study, in addition to reviewing the available results as a comprehensive and integrated manner, provide new hypotheses for future studies.

The majority of NMDA receptors (NMDARs) in the brain are composed of 2 GluN1 and 2 GluN2 subunits. The inclusion or exclusion of 1 N-terminal and 2 C-terminal domains of GluN1 results in 8 splicing variants that exhibit distinct temporal and spatial patterns of expression and functional properties. However, previous functional analyses of Grin1 variants have been done using heterologous expression and the in vivo function of Grin1 splicing is unknown. Here we show that N-terminal splicing of GluN1 has important functions in the maturation of excitatory synapses. The inclusion of exon 5 of Grin1 is up-regulated in several brain regions such as the thalamus and neocortex. We find that deletion of Grin1 exon 5 disrupts the developmental remodeling of NMDARs in thalamic neurons and the effect is distinct from that of Grin2a (GluN2A) deletion. Deletion of Grin2a or exon 5 of Grin1 alone partially attenuates the shortening of NMDAR-mediated excitatory postsynaptic currents (NMDAR-EPSCs) during early life, whereas deletion of both Grin2a and exon 5 of Grin1 completely abolishes the developmental change in NMDAR-EPSC decay time. Deletion of exon 5 of Grin1 leads to an overproduction of excitatory synapses in layer 5 pyramidal neurons in the cortex and increases seizure susceptibility in adult mice. Our findings demonstrate that N-terminal splicing of GluN1 has important functions in synaptic maturation and neuronal network excitability.

Landau-Kleffner syndrome (LKS) has been demonstrated in the past to respond to immunotherapy. Recently, some cases of LKS have been shown to be secondary to glutamate receptor (GRIN2A) mutations. Whether such cases respond to immunotherapy is not known. Here, we present the case of a 3-year-old boy with LKS found to have a GRIN2A heterozygous missense mutation, whose clinical symptoms and EEG responded to a course of combination oral steroids and monthly infusions of intravenous immunoglobulin. He then relapsed after discontinuation of this therapy, and responded again after a second course of intravenous immunoglobulin. We conclude that immunotherapy should be considered as a therapeutic option in patients with LKS who are also found to harbour GRIN2A mutations.

OBJECTIVE

To delineate the genetic, neurodevelopmental and epileptic spectrum associated with GRIN2A alterations with emphasis on epilepsy treatment.

METHODS

Retrospective study of 19 patients (7 females; age: 1-38 years; mean 10.1 years) with epilepsy and GRIN2A alteration. Genetic variants were classified according to the guidelines and recommendations of the American College of Medical Genetics (ACMG). Clinical findings including epilepsy classification, treatment, EEG findings, early childhood development and neurodevelopmental outcome were collected with an electronic questionnaire.

RESULTS

7 out of 19 patients fulfilled the ACMG-criteria of carrying "pathogenic" or "likely pathogenic variants", in twelve patients the alterations were classified as variants of unknown significance. The spectrum of pathogenic/likely pathogenic mutations was as follows: nonsense n = 3, missense n = 2, duplications/deletions n = 1 and splice site n = 1. First seizures occurred at a mean age of 2.4 years with heterogeneous seizure types. Patients were treated with a mean of 5.6 AED. 4/5 patients with VPA had an improved seizure frequency (n = 3 with a truncation: n = 1 missense). 3/5 patients with STM reported an improvement of seizures (n = 2 truncation, n = 1 splicing). 3/5 CLB patients showed an improvement (n = 2: truncation; n = 1 splicing). Steroids were reported to have a positive effect on seizure frequency in 3/5 patients (n = 1 each truncation, splicing or deletion).

CONCLUSIONS

Our data indicate that children with epilepsy due to pathogenic GRIN2A mutations present with different clinical phenotypes and a spectrum of seizure types in the context of a pharmacoresistant epilepsy providing information for clinicians treating children with this form of genetically determined epileptic syndrome.

OBJECTIVE

Epilepsy-aphasia spectrum (EAS) are a group of epilepsy syndromes denoting an association between epilepsy, speech disorders and the EEG signature of centrotemporal spikes. Mutations in the GRIN2A gene, encoding the NMDA glutamate receptor α2 subunit were reported in focal epilepsy with speech disorder. We aimed to explore the role of GRIN2A mutations in patients with centrotemporal spikes related epileptic syndromes in a Chinese cohort.

METHODS

Patients with Landau-Kleffner syndrome (LKS), epileptic encephalopathy with continuous spike-and-wave during sleep (ECSWS), atypical benign partial epilepsy (ABPE), and benign epilepsy with centrotemporal spikes (BECTS) were recruited. GRIN2A mutation screening was performed using PCR and Sanger sequencing.

RESULTS

122 patients, including 9 LKS, 26 ECSWS, 42 ABPE and 45 BECTS were enrolled. The mean age of seizure or aphasia onset was 5 years, ranging from 10 months to 11 years. Heterozygous GRIN2A mutations were detected in four patients (G760S, D1385Y, C455Y and C231R) GRIN2A mutation was found in 11.1% (1 out of 9 cases) of LKS, and in 7.1% (3 out of 42 cases) of ABPE, but in none with ECSWS and BECTS. No GRIN2A mutation was found in patients with a family history of febrile seizures or epilepsy.

CONCLUSIONS

GRIN2A mutation is a genetic cause in less than 11% patients with LKS or ABPE. GRIN2A gene is a rare causative gene in Chinese patients with EAS, suggesting the possibility of other gene involved in the pathogenesis.

Astrocytes are known as structural and supporting cells in the central nervous system (CNS). Glutamate, as a main excitatory amino acid neurotransmitter in the mammalian central nervous system, can be excitotoxic, playing a key role in many chronic neurodegenerative diseases. The aim of the current study was to elucidate the potential of vitamin E in protecting glutamate-injured primary astrocytes. Hence, primary astrocytes were isolated from mixed glial cells of C57BL/6 mice by applying the EasySep® Mouse CD11b Positive Selection Kit, cultured in Dulbecco's modified Eagle medium (DMEM) and supplemented with special nutrients. The IC20 and IC50 values of glutamate, as well as the cell viability of primary astrocytes, were assessed with 100 ng/mL, 200 ng/mL, and 300 ng/mL of tocotrienol-rich fraction (TRF) and alpha-tocopherol (α-TCP), as determined by an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The mitochondrial membrane potential (MMP) detected in primary astrocytes was assessed with the same concentrations of TRF and α-TCP. The expression levels of the ionotropic glutamate receptor genes (Gria2, Grin2A, GRIK1) were independently determined using RT-PCR. The purification rate of astrocytes was measured by a flow-cytometer as circa 79.4%. The IC20 and IC50 values of glutamate were determined as 10 mM and 100 mM, respectively. Exposure to 100 mM of glutamate in primary astrocytes caused the inhibition of cell viability of approximately 64.75% and 61.10% in pre- and post-study, respectively (p < 0.05). Both TRF and α-TCP (at the lowest and highest concentrations, respectively) were able to increase the MMP to 88.46% and 93.31% pre-treatment, and 78.43% and 81.22% post-treatment, respectively. Additionally, the findings showed a similar pattern for the expression level of the ionotropic glutamate receptor genes. Increased extracellular calcium concentrations were also observed, indicating that the presence of vitamin E altered the polarization of astrocytes. In conclusion, α-TCP showed better recovery and prophylactic effects as compared to TRF in the pre-treatment of glutamate-injured primary astrocytes.

Christianson syndrome (CS) is a X-linked neurodevelopmental disorder, including severe intellectual disability (ID), progressive microcephaly, ataxia, autistic behaviour (ASD), near absent speech, and epilepsy. Electrical status epilepticus in sleep (ESES) has been reported in two patients. We describe five male patients from three unrelated families with Christianson syndrome caused by a pathogenic nucleotide variation or a copy-number variation involving SLC9A6. ESES was present in three out of the five patients in the critical age window between 4 and 8 years. All patients presented with severe intellectual disability, autistic features, and hyperactivity. Epilepsy onset occurred within the first two years of life. Seizures were of various types. In the two boys with a 20-years follow-up, epilepsy was drug-resistant during childhood, and became less active in early adolescence. Psychomotor regression was noted in two patients presenting with ESES. It was difficult to assess to what extent ESES could have contributed to the pathophysiological process, leading to regression of the already very limited communication skills. The two published case reports and our observation suggests that ESES could be a constitutive feature of Christianson syndrome, as it has already been shown for other Mendelian epileptic disorders, such as GRIN2A and CNKSR2-related developmental epileptic encephalopathies. Sleep EEG should be performed in patients with Christianson syndrome between 4 and 8 years of age. ESES occurring in the context of ID, ASD and severe speech delay, could be helpful to make a diagnosis of CS.

BACKGROUND

Electrical status epilepticus during slow-wave sleep (ESESS) which is also known as continuous spike-wave of slow sleep (CSWSS) is type of electroencephalographic (EEG) pattern which is seen in ESESS/CSWSS/epilepsy aphasia spectrum. This EEG pattern can occur alone or with other syndromes. Its etiology is not clear, however, brain malformations, immune disorders, and genetic etiologies are suspected to contribute. We aimed to perform a systematic review of all genetic etiologies which have been reported to associate with ESESS/CSWSS/epilepsy-aphasia spectrum. We further aimed to identify the common underlying pathway which can explain it. To our knowledge, there is no available systematic review of genetic etiologies of ESESS/CSWSS/epilepsy-aphasia spectrum. MEDLINE, EMBASE, PubMed and Cochrane review database were searched, using terms specific to electrical status epilepticus during sleep or continuous spike-wave discharges during slow sleep or epilepsy-aphasia spectrum and of studies of genetic etiologies. These included monogenic mutations and copy number variations (CNVs). For each suspected dosage-sensitive gene, further studies were performed through OMIM and PubMed database.

RESULTS

Twenty-six studies out of the 136 identified studies satisfied our inclusion criteria. I51 cases were identified among those 26 studies. 16 studies reported 11 monogenic mutations: SCN2A (N = 6), NHE6/SLC9A6 (N = 1), DRPLA/ ATN1 (N = 1), Neuroserpin/SRPX2 (N = 1), OPA3 (N = 1), KCNQ2 (N = 2), KCNA2 (N = 5), GRIN2A (N = 34), CNKSR2 (N = 2), SLC6A1 (N = 2) and KCNB1 (N = 5). 10 studies reported 89 CNVs including 9 recurrent ones: Xp22.12 deletion encompassing CNKSR2 (N = 6), 16p13 deletion encompassing GRIN2A (N = 4), 15q11.2-13.1 duplication (N = 15), 3q29 duplication (N = 11), 11p13 duplication (N = 2), 10q21.3 deletion (N = 2), 3q25 deletion (N = 2), 8p23.3 deletion (N = 2) and 9p24.2 (N = 2). 68 of the reported genetic etiologies including monogenic mutations and CNVs were detected in patients with ESESS/CSWSS/epilepsy aphasia spectrum solely. The most common underlying pathway was channelopathy (N = 56).

CONCLUSIONS

Our review suggests that genetic etiologies have a role to play in the occurrence of ESESS/CSWSS/epilepsy-aphasia spectrum. The common underlying pathway is channelopathy. Therefore we propose more genetic studies to be done for more discoveries which can pave a way for proper drug identification. We also suggest development of common cut-off value for spike-wave index to ensure common language among clinicians and researchers.

Depressive disorder is a common mental disorder characterized by depressed mood and loss of interest or pleasure. As the Herbal medicines are mainly used as complementary and alternative therapy for depression. This study aimed at exploring antidepressant activity of Huang-lian Jie-du Decoction (HLJDD), and evaluating active components and potential depression-associated targets. HLJDD was administered on chronic unpredictable mild stress-induced (CUMS) depressive mice. Behavior evaluation was performed through force swimming test (FST), novelty-suppressed feeding test (NSF), and open field test (OFT). Active components of HLJDD, potential targets, and metabolic pathways involved in depression were explored through systemic biology-based network pharmacology assay, molecular docking and metabonomics. FST assay showed that CUMS mice administered with HLJDD had significantly shorter immobility time compared with control mice. Further, HLJDD alleviated feeding latency of CUMS mice in NSFand increased moving distance and duration in OFT. In the following network pharmacology assay, thirty-eight active compounds in HLJDD were identified based on drug-like characteristics, and pharmacokinetics and pharmacodynamics profiles. Moreover, forty-eight molecular targets and ten biochemical pathways were uncovered through molecular docking and metabonomics. GRIN2B, DRD, PRKCA, HTR, MAOA, SLC6A4, GRIN2A, and CACNA1A are implicated in inhibition of depressive symptoms through modulating tryptophan metabolism, serotonergic and dopaminergic synaptic activities, cAMP signaling pathway, and calcium signaling pathway. Further network pharmacology-based analysis showed a correlation between HLJDD and tryptophan metabolism. A total of thirty-seven active compounds, seventy-six targets, and sixteen biochemical pathways were involved in tryptophan metabolism. These findings show that HLJDD acts on potential targets such as SLC6A4, HTR, INS, MAO, CAT, and FoxO, PI3K/Akt, calcium, HIF-1, and mTOR signaling pathways, and modulates serotoninergic and dopaminergic synaptic functions. In addition, metabonomics showed that tryptophan metabolism is the primary target for HLJDD in CUMS mice. The findings of the study show that HLJDD exhibited antidepressant effects. SLC6A4 and MAOA in tryptophan metabolism were modulated by berberine, baicalein, tetrahydroberberine, candicine and may be the main antidepressant targets for HLJDD.

Keywords: depression; huang-lian jie-du decoction; metabolomics; network pharmacology; tryptophan metabolism.

A 9-year-old boy presented with intolerance to noise that was a trigger for violent temper tantrums that occasionally resembled complex partial seizures. The condition was also a cause for withdrawal from all activities and settings that could potentially be associated with noise. Both electroencephalography and magnetoencephalography clearly demonstrated a left temporal (T5) epileptic focus, although the child never had convulsive seizures. Genetic studies failed to reveal a GRIN2A mutation. We suggest that the hyperacusis in the reported child is another variation of the Landau-Kleffner spectrum.

Sulfur dioxide (SO2 ) is a ubiquitous air pollutant. The previous studies have documented the adverse effects of SO2 on nervous system health, suggesting that acutely SO2 inhalation at high concentration may be associated with neurotoxicity and increase risk of hospitalization and mortality of many brain disorders. However, the remarkable features of air pollution exposure are lifelong duration and at low concentration; and it is rarely reported that whether there are different responses on synapse when rats inhaled same mass of SO2 at low concentration with a longer term. In this study, we evaluated the synaptic plasticity in rat hippocampus after exposure to same mass of SO2 at various concentrations and durations (3.5 and 7 mg/m(3) , 6 h/day, for 4 weeks; and 14 and 28 mg/m(3) , 6 h/day, for 1 week). The results showed that the mRNA level of synaptic plasticity marker Arc, glutamate receptors (GRIA1, GRIA2, GRIN1, GRIN2A, and GRIN2B) and the protein expression of memory related kinase p-CaMKпα were consistently inhibited by SO2 both in 1 week and 4 weeks exposure cases; the protein expression of presynaptic marker synaptophysin, postsynaptic density protein 95 (PSD-95), protein kinase A (PKA), and protein kinase C (PKC) were increased in 1 week exposure case, and decreased in 4 weeks exposure case. Our results indicated that SO2 inhalation caused differential synaptic injury in 1 week and 4 weeks exposure cases, and implied the differential effects might result from different PKA- and/or PKC-mediated signal pathway. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 820-829, 2016.

De novo GRIN variants, encoding for the ionotropic glutamate NMDA receptor subunits, have been recently associated with GRIN-related disorders (GRDs), a group of rare paediatric encephalopathies. Current investigational and clinical efforts are focused to functionally stratify GRIN variants, towards precision therapies of this primary disturbance of glutamatergic transmission that affects neuronal function and brain. In the present study, we aimed to comprehensively delineate the functional outcomes and clinical phenotypes of GRIN protein truncating variants (PTVs) -accounting for ~ 20% of disease-associated GRIN variants- hypothetically provoking NMDAR hypofunctionality. To tackle this question, we created a comprehensive GRIN PTVs variants database compiling a cohort of 9 individuals harbouring GRIN PTVs, together with previously identified variants, to build-up an extensive GRIN PTVs repertoire composed of 293 unique variants. Genotype-phenotype correlation studies were conducted, followed by cell-based assays of selected paradigmatic GRIN PTVs, allowing their functional annotation. Genetic and clinical phenotypes metaanalysis revealed that heterozygous GRIN1, GRIN2C, GRIN2D, GRIN3A and GRIN3B PTVs are non-pathogenic. In contrast, heterozygous GRIN2A and GRIN2B PTVs are associated with specific neurological clinical phenotypes in a subunit- and domain-dependent manner. Mechanistically, cell-based assays showed that paradigmatic pathogenic GRIN2A and GRIN2B PTVs result on a decrease of NMDAR surface expression and NMDAR-mediated currents, ultimately leading to NMDAR functional haploinsufficiency.. Overall, these findings contribute to delineate GRIN PTVs genotype-phenotype association, and GRIN variants stratification. Functional studies showed that GRIN2A and GRIN2B pathogenic PTVs trigger NMDAR hypofunctionality, and thus accelerate therapeutic decisions for this neurodevelopmental condition.

Age of onset (AO) of Huntington disease (HD) is mainly determined by the length of the CAG repeat expansion (CAGexp) in exon 1 of the HTT gene. Additional genetic variation has been suggested to contribute to AO, although the mechanism by which it could affect AO is presently unknown. The aim of this study is to explore the contribution of candidate genetic factors to HD AO in order to gain insight into the pathogenic mechanisms underlying this disorder. For that purpose, two AO definitions were used: the earliest age with unequivocal signs of HD (earliest AO or eAO), and the first motor symptoms age (motor AO or mAO). Multiple linear regression analyses were performed between genetic variation within 20 candidate genes and eAO or mAO, using DNA and clinical information of 253 HD patients from REGISTRY project. Gene expression analyses were carried out by RT-qPCR with an independent sample of 35 HD patients from Basque Country Hospitals. We found suggestive association signals between HD eAO and/or mAO and genetic variation within the E2F2, ATF7IP, GRIN2A, GRIN2B, LINC01559, HIP1 and GRIK2 genes. Among them, the most significant was the association between eAO and rs2742976, mapping to the promoter region of E2F2 transcription factor. Furthermore, rs2742976 T allele patient carriers exhibited significantly lower lymphocyte E2F2 gene expression, suggesting a possible implication of E2F2-dependent transcriptional activity in HD pathogenesis. Thus, E2F2 emerges as a new potential HD AO modifier factor.

The rat provides valuable and sometimes unique models of human complex diseases. To fully exploit the rat models in biomedical research, it is important to have access to detailed knowledge of the rat genome organization as well as its relation to the human genome. Rat Chromosome 10 (RNO10) harbors several important cancer-related genes. Deletions in the proximal part of RNO10 were repeatedly found in a rat model for endometrial cancer. To identify functional and positional candidate genes in the affected region, we used radiation hybrid (RH) mapping and single- and dual-color fluorescence in situ hybridization (FISH) techniques to construct a detailed chromosomal map of the proximal part of RNO10. The regional localization of 14 genes, most of them cancer-related ( Grin2a, Gspt1, Crebbp, Gfer, Tsc2, Tpsb1, Il9r, Il4, Irf1, Csf2, Sparc, Tp53, Thra1, Gh1), and of five microsatellite markers ( D10Mit10, D10Rat42, D10Rat50, D10Rat72, and D10Rat165) was determined on RNO10. For a fifteenth gene, Ppm1b, which had previously been assigned to RNO10, the map position was corrected to RNO6q12-q13.

Expectation of salient rewards and novelty seeking are processes implicated in substance use disorders but the neurobiological substrates underlying these associations are not well understood. To better understand the regional circuitry of novelty and reward preference, rats were conditioned to pair unique cues with bacon, an initially novel food, or chow, a familiar food. In the same animals, after training, cue-induced brain activity was measured, and the relationships between activity and preference for three rewards, the conditioned foods and ethanol (EtOH), were separately determined. Activity in response to the food paired cues was measured using brain glucose metabolism (BGluM). Rats favoring bacon-paired (BAP) cues had increased BGluM in mesocorticolimbic brain regions after exposure to these cues, while rats favoring chow-paired (CHP) cues showed relative deactivation in these regions. Rats exhibiting BAP cue-induced activation in prefrontal cortex (PFC) also consumed more EtOH while rats with cortical activation in response to CHP cues showed lower EtOH consumption. Additionally, long-term stable expression levels of PFC Grin2a, a subunit of the NMDA receptor, correlated with individual differences in EtOH preference insomuch that rats with high EtOH preference had enduringly low PFC Grin2a mRNA expression. No other glutamatergic, dopaminergic or endocannabinoid genes studied showed this relationship. Overall, these results suggest that natural variation in mesocorticolimbic sensitivity to reward-paired cues underlies behavioral preferences for and vulnerability to alcohol abuse, and support the notion of common neuronal circuits involved in food- and drug-seeking behavior. The findings also provide evidence that PFC NMDA-mediated glutamate signaling may modulate these associations.

Hypoxia preconditioning is an effective strategy of intrinsic cell protection. An acute repetitive hypoxic mice model was developed. High-throughput microarray analysis was performed to explore the integrative alterations of gene expression in repetitive hypoxic mice. Data obtained was analyzed via multiple bioinformatics approaches to identify the hub genes, pathways and biological processes related to hypoxia preconditioning. The current study, for the first time, provides insights into the gene expression profiles in repetitive hypoxic mice. It was found that a total of 1175 genes expressed differentially between the hypoxic mice and normal mice. Overall, 113 significantly up-regulated and 138 significantly down-regulated functions were identified from the differentially expressed genes in repetitive hypoxic brains. Among them, at least fourteen of these genes were very associated with hypoxia preconditioning. The change trends of these genes were validated by reverse-transcription polymerase chain reaction and were found to be consistent with the microarray data. Combined the results of pathway and gene co-expression networks, we defined Plcb1, Cacna2d1, Atp2b4, Grin2a, Grin2b and Glra1 as the main hub genes tightly related with hypoxia preconditioning. The differential functions mainly included the mitogen-activated protein kinase pathway and ion or neurotransmitter transport. The multiple reactions in cell could be initiated by activating MAPK pathway to prevent hypoxia damage. Plcb1 was an important and hub gene and node in the hypoxia preconditioning signal networks. The findings in the hub genes and integrated gene networks provide very useful information for further exploring the molecular mechanisms of hypoxia preconditioning.

Genetic mutations are the major pathogenic factor of Autism Spectrum Disorder (ASD). In recent years, more and more ASD risk genes have been revealed, among which there are a group of transcriptional regulators. Considering the similarity of the core clinical phenotypes, it is possible that these different factors may regulate the expression levels of certain key targets. Identification of these targets could facilitate the understanding of the etiology and developing of novel diagnostic and therapeutic methods. Therefore, we performed integrated transcriptome analyses of RNA-Seq and microarray data in multiple ASD mouse models and identified a number of common downstream genes in various brain regions, many of which are related to the structure and function of the synapse components or drug addiction. We then established protein-protein interaction networks of the overlapped targets and isolated the hub genes by 11 algorithms based on the topological structure of the networks, including Sdc4, Vegfa, and Cp in the Cortex-Adult subgroup, Gria1 in the Cortex-Juvenile subgroup, and Kdr, S1pr1, Ubc, Grm2, Grin2b, Nrxn1, Pdyn, Grin3a, Itgam, Grin2a, Gabra2, and Camk4 in the Hippocampus-Adult subgroup, many of which have been associated with ASD in previous studies. Finally, we cross compared our results with human brain transcriptional data sets and verified several key candidates, which may play important role in the pathology process of ASD, including SDC4, CP, S1PR1, UBC, PDYN, GRIN2A, GABRA2, and CAMK4. In summary, by integrated bioinformatics analysis, we have identified a series of potentially important molecules for future ASD research. Autism Res 2019. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Abnormal transcriptional regulation accounts for a significant portion of Autism Spectrum Disorder. In this study, we performed transcriptome analyses of mouse models to identify common downstream targets of transcriptional regulators involved in ASD. We identified several recurrent target genes that are close related to the common pathological process of ASD, including SDC4, CP, S1PR1, UBC, PDYN, GRM2, NRXN1, GRIN3A, ITGAM, GRIN2A, GABRA2, and CAMK4. These results provide potentially important targets for understanding the molecular mechanism of ASD.

The glutamate system including N-methyl-d-aspartate (NMDA) affects synaptic formation, plasticity and maintenance. Recent studies have shown a variable (GT)n polymorphism in the promoter region of the NMDA subunit gene (GRIN2A) and a length-dependent inhibition of transcriptional activity by the (GT)n repeat. In the present study, we examined whether the GRIN2A polymorphism is associated with regional brain volume especially in medial temporal lobe structures, in which the NMDA-dependent synaptic processes have been most extensively studied. Gray matter regions of interest (ROIs) for the bilateral amygdala and hippocampus were outlined manually on the magnetic resonance images of 144 healthy individuals. In addition, voxel-based morphometry (VBM) was conducted to explore the association of genotype with regional gray matter volume from everywhere in the brain in the same sample. The manually measured hippocampal and amygdala volumes were significantly larger in subjects with short allele carriers (n = 89) than in those with homozygous long alleles (n = 55) when individual differences in intracranial volume were accounted for. The VBM showed no significant association between the genotype and regional gray matter volume in any brain region. These findings suggest that the functional GRIN2A (GT)n polymorphism could weakly but significantly impact on human medial temporal lobe volume in a length-dependent manner, providing in vivo evidence of the role of the NMDA receptor in human brain development.

Ionotropic glutamate receptors (iGluRs) are large integral membrane multi-protein complexes that create ion channels in plasma membranes. Upon binding of receptor specific ligands (e.g., glutamate), increased efflux or influx of mono- or divalent cations (e.g., Ca2+) promotes synaptic transmission, cellular migration, and survival. Three classes of iGluRs were originally defined after their respective agonists: AMPA, kainate, and NMDA receptors (NMDARs). Recently, we examined iGluR families at the genetic level using Next-Generation Sequencing (NGS) (whole-exome sequencing (WES)) and discovered a high prevalence of somatic mutations within the gene for one of the NMDAR subunits, GRIN2A, specifically in malignant melanoma. Following confirmation of the somatic mutations, we focused on functional characterization of a subset of the GRIN2A mutants that demonstrated a loss of NMDAR functionality. We used gene expression and protein biochemistry to examine complex formation between GluN1 subunit (encoded by GRIN1) and GluN2A subunit (encoded by GRIN2A), anchorage-independent growth in soft agar and cellular migration. Furthermore, we used shRNA depletion of endogenous GRIN2A in melanoma cells expressing either wild-type GRIN2A or mutant GRIN2A and measured cellular proliferation compared to negative controls. Our data show that somatic mutation of certain residues in GluN2A results in increased survival and is the first such report to demonstrate the functional importance of GRIN2A mutations in melanoma and the significance ionotropic glutamate receptor signaling plays in malignant melanoma.

BACKGROUND

Drug addiction, a leading health problem, is a chronic brain disease with a significant genetic component. Animal models and clinical studies established the involvement of glutamate and GABA neurotransmission in drug addiction. This study was designed to assess if 258 variants in 27 genes of these systems contribute to the vulnerability to develop drug addiction.

METHODS

Four independent analyses were conducted in a sample of 1860 subjects divided according to drug of abuse (heroin or cocaine) and ancestry (African and European).

RESULTS

A total of 11 SNPs in eight genes showed nominally significant associations (P<0.01) with heroin and/or cocaine addiction in one or both ancestral groups but the associations did not survive correction for multiple testing. Of these SNPs, the GAD1 upstream SNP rs1978340 is potentially functional as it was shown to affect GABA concentrations in the cingulate cortex. In addition, SNPs GABRB3 rs7165224; DBI rs12613135; GAD1 SNPs rs2058725, rs1978340, rs2241164; and GRIN2A rs1650420 were previously reported in associations with drug addiction or related phenotypes.

CONCLUSIONS

The study supports the involvement of genetic variation in the glutamatergic and GABAergic systems in drug addiction with partial overlap in susceptibility loci between cocaine and heroin addiction.

CONCLUSIONS

Fragile X syndrome (FXS) is a genetic condition that is the most common form of inherited intellectual impairment and causes a range of neurodevelopmental complications including learning disabilities and intellectual disability and shares many characteristics with autism spectrum disorder (ASD). In the FXS mouse model, Fmr1-/y , impaired synaptic plasticity was restored by pharmacologically inhibiting GluN2A-containing NMDA receptors but not GluN2B-containing receptors. Similar results were obtained by crossing Fmr1-/y with GluN2A knock-out (Grin2A-/- ) mice. These results suggest that dampening the elevated levels of GluN2A-containing NMDA receptors in Fmr1-/y mice has the potential to restore hyperexcitability of the neural circuitry to (a more) normal-like level of brain activity.

UNASSIGNED

NMDA receptors (NMDARs) play important roles in synaptic plasticity at central excitatory synapses, and dysregulation of their function may lead to severe disorders such Fragile X syndrome (FXS). FXS is caused by transcriptional silencing of the FMR1 gene followed by lack of the encoding protein. Here we examined the effects of pharmacological and genetic manipulation of hippocampal NMDAR functions in long-term potentiation (LTP) and depression (LTD). We found impaired NMDAR-dependent LTP in the Fmr1-deficient mice, which could be fully restored when GluN2A-containing NMDARs was pharmacological inhibited. Interestingly, similar LTP effects were observed when the GluN2A gene (Grin2a) was deleted in Fmr1-/y mice (Fmr1-/y /Grin2a-/- double knockout). In addition, GluN2A inhibition improved elevated mGluR5-dependent LTD to normal level in the Fmr1-/y mouse. These findings suggest that GluN2A is a promising target in FXS research that could help us better understand the disorder.