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Abstract Retinitis pigmentosa (RP), an inherited retinal disease, affects 1,5 million people worldwide. The initial mutation-driven photoreceptor degeneration leads to chronic inflammation, characterized by Müller cell activation and upregulation of CD44. CD44 is a cell surface transmembrane glycoprotein and the primary receptor for hyaluronic acid. It is involved in many pathological processes, but little is known about CD44’s retinal functions. CD44 expression is also increased in Müller cells from our Pde6b STOP/STOP RP mouse model. To gain a more detailed understanding of CD44’s role in healthy and diseased retinas, we analyzed Cd44 −/− and Cd44 −/− Pde6b STOP/STOP mice, respectively. The loss of CD44 led to enhanced photoreceptor degeneration, reduced retinal function, and increased inflammatory response. To understand the underlying mechanism, we performed proteomic analysis on isolated Müller cells from Cd44 −/− and Cd44 −/− Pde6b STOP/STOP retinas and identified a significant downregulation of glutamate transporter 1 (SLC1A2). This downregulation was accompanied by higher glutamate levels, suggesting impaired glutamate homeostasis. These novel findings indicate that CD44 stimulates glutamate uptake via SLC1A2 in Müller cells, which in turn, supports photoreceptor survival and function.

Retinitis pigmentosa (RP), an inherited retinal disease, affects 1,5 million people worldwide. The initial mutation-driven photoreceptor degeneration leads to chronic inflammation, characterized by Müller cell activation and upregulation of CD44. CD44 is a cell surface transmembrane glycoprotein and the primary receptor for hyaluronic acid. It is involved in many pathological processes, but little is known about CD44's retinal functions. CD44 expression is also increased in Müller cells from our Pde6bSTOP/STOP RP mouse model. To gain a more detailed understanding of CD44's role in healthy and diseased retinas, we analyzed Cd44−/− and Cd44−/−Pde6bSTOP/STOP mice, respectively. The loss of CD44 led to enhanced photoreceptor degeneration, reduced retinal function, and increased inflammatory response. To understand the underlying mechanism, we performed proteomic analysis on isolated Müller cells from Cd44−/− and Cd44−/−Pde6bSTOP/STOP retinas and identified a significant downregulation of glutamate transporter 1 (SLC1A2). This downregulation was accompanied by higher glutamate levels, suggesting impaired glutamate homeostasis. These novel findings indicate that CD44 stimulates glutamate uptake via SLC1A2 in Müller cells, which in turn, supports photoreceptor survival and function. [ABSTRACT FROM AUTHOR]

Abstract Background Silver–Russel syndrome (SRS) is a congenital disorder which is mainly characterized by intrauterine and postnatal growth retardation, relative macrocephaly, and characteristic (facial) dysmorphisms. The majority of patients shows a hypomethylation of the imprinting center region 1 (IC1) in 11p15 and maternal uniparental disomy of chromosome 7 (upd(7)mat), but in addition a broad spectrum of copy number variations (CNVs) and monogenetic variants (SNVs) has been reported in this cohort. These heterogeneous findings reflect the clinical overlap of SRS with other congenital disorders, but some of the CNVs are recurrent and have therefore been suggested as SRS-associated loci. However, this molecular heterogeneity makes the decision on the diagnostic workup of patients with SRS features challenging. Case presentation A girl with clinical features of SRS but negatively tested for the IC1 hypomethylation and upd(7)mat was analyzed by whole genome sequencing in order to address both CNVs and SNVs in the same run. We identified a 11p13 microduplication affecting a region overlapping with a variant reported in a previously published patient with clinical features of Silver–Russel syndrome. Conclusions The identification of a 11p13 microduplication in a patient with SRS features confirms the considerable contribution of CNVs to SRS-related phenotypes, and it strengthens the evidence for a 11p13 microduplication syndrome as a differential diagnosis SRS. Furthermore, we could confirm that WGS is a valuable diagnostic tool in patients with SRS and related disorders, as it allows CNVs and SNV detection in the same run, thereby avoiding a time-consuming diagnostic testing process.

Background: Silver–Russel syndrome (SRS) is a congenital disorder which is mainly characterized by intrauterine and postnatal growth retardation, relative macrocephaly, and characteristic (facial) dysmorphisms. The majority of patients shows a hypomethylation of the imprinting center region 1 (IC1) in 11p15 and maternal uniparental disomy of chromosome 7 (upd(7)mat), but in addition a broad spectrum of copy number variations (CNVs) and monogenetic variants (SNVs) has been reported in this cohort. These heterogeneous findings reflect the clinical overlap of SRS with other congenital disorders, but some of the CNVs are recurrent and have therefore been suggested as SRS-associated loci. However, this molecular heterogeneity makes the decision on the diagnostic workup of patients with SRS features challenging. Case presentation: A girl with clinical features of SRS but negatively tested for the IC1 hypomethylation and upd(7)mat was analyzed by whole genome sequencing in order to address both CNVs and SNVs in the same run. We identified a 11p13 microduplication affecting a region overlapping with a variant reported in a previously published patient with clinical features of Silver–Russel syndrome. Conclusions: The identification of a 11p13 microduplication in a patient with SRS features confirms the considerable contribution of CNVs to SRS-related phenotypes, and it strengthens the evidence for a 11p13 microduplication syndrome as a differential diagnosis SRS. Furthermore, we could confirm that WGS is a valuable diagnostic tool in patients with SRS and related disorders, as it allows CNVs and SNV detection in the same run, thereby avoiding a time-consuming diagnostic testing process. [ABSTRACT FROM AUTHOR]

Background: Personal variations in genetic risk for schizophrenia relate to its phenotypic heterogeneity—both in disorder development and clinical manifestations. Abnormal glutamatergic neurotransmitter system functioning is integrated in the pathogenesis of schizophrenia. Methods: A sample of 805 Russian schizophrenia patients from the Siberian Federal region was investigated. We examined the association of 39 single nucleotide polymorphisms in eight genes (GRIN2A, GRIN2B, SLC1A2, SLC1A3, SLC17A7, GRM3, GRM7, and GRM8) involved in the glutamatergic system with the development of clinical heterogeneity of schizophrenia. The MassARRAY Analyzer 4 was used for genotyping. Results: GRIN2A rs11644461, rs8057394 and GRIN2B rs7313149 are associated with the continuous type of schizophrenia. The GRIN2A rs8057394*G allele is a relative risk factor (p = 0.019) for developing the continuous type of schizophrenia. We found a nominally significant association between negative symptoms of schizophrenia and SLC17A7 rs62126236. The SLC17A7 rs62126236*T allele has a protective effect (p = 0.039) against predominant negative symptoms in schizophrenia. The total Positive and Negative Syndrome Scale (PANSS) scores were significantly associated with GRIN2A rs9788936 after adjusting for multiple testing (p = 0.001). Conclusions: In this study the contribution of the glutamatergic gene polymorphisms to the clinical heterogeneity of schizophrenia has been demonstrated. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disease that is characterized by a devastating decline in cognitive activities among all types of dementia, and it severely affects the quality of life. Late-onset AD (LOAD) occurs after the age of 65 years and develops sporadically. Although aging comes first along the main risk factors underlying LOAD, disease-causing susceptibility genes have been associated with disease pathogenesis. In our study, we included the genes PARP1, POLB, HTRA2, SLC1A2, HS1BP3, and DRD3 to be investigated in LOAD patients based on their expression levels. Within this framework, we aimed to determine the possible functions of these genes in the pathophysiology of the disease. We investigated whether the utilization of these genes as biomarkers in the early diagnosis of LOAD may help the treatment scheme to be applied in the clinic. We involved 50 individuals in the study and collected peripheral blood samples from the patients and control groups for molecular genetic analysis. Subsequently, RNA was extracted from the peripheral blood samples, and expression analyzes were performed using qualitative reverse transcription polymerase chain reaction. The results obtained were evaluated by using proper statistical methods. Our results demonstrated that there was no difference between patient and control groups in terms of HTRA2, DRD3, HS1BP3, and POLB genes. The expression levels of the SLC1A2 and PARP1 genes were significantly lower in the patient group compared with the control group. In conclusion, we presume that the PARP1 and SLC1A2 genes can be utilized as molecular biomarkers for LOAD.

Alzheimer’s disease (AD) is a neurodegenerative disease that is characterized by a devastating decline in cognitive activities among all types of dementia, and it severely affects the quality of life. Late-onset AD (LOAD) occurs after the age of 65 years and develops sporadically. Although aging comes first along the main risk factors underlying LOAD, disease-causing susceptibility genes have been associated with disease pathogenesis. In our study, we included the genes PARP1, POLB, HTRA2, SLC1A2, HS1BP3, and DRD3 to be investigated in LOAD patients based on their expression levels. Within this framework, we aimed to determine the possible functions of these genes in the pathophysiology of the disease.We investigated whether the utilization of these genes as biomarkers in the early diagnosis of LOAD may help the treatment scheme to be applied in the clinic.We involved 50 individuals in the study and collected peripheral blood samples from the patients and control groups for molecular genetic analysis. Subsequently, RNA was extracted from the peripheral blood samples, and expression analyzes were performed using qualitative reverse transcription polymerase chain reaction. The results obtained were evaluated by using proper statistical methods. Our results demonstrated that there was no difference between patient and control groups in terms of HTRA2, DRD3, HS1BP3, and POLB genes. The expression levels of the SLC1A2 and PARP1 genes were significantly lower in the patient group compared with the control group. In conclusion, we presume that the PARP1 and SLC1A2 genes can be utilized as molecular biomarkers for LOAD. [ABSTRACT FROM AUTHOR]

Objective: Mutations in the gene solute carrier family member 1A2 (SLC1A2) encoding the excitatory amino acid transporter 2 (EAAT2) are associated with severe forms of epileptic encephalopathy. EAAT2 is expressed in glial cells and presynaptic nerve terminals and represents the main l‐glutamate uptake carrier in the mammalian brain. It does not only function as a secondary active glutamate transporter, but also as an anion channel. How naturally occurring mutations affect these two transport functions of EAAT2 and how such alterations cause epilepsy is insufficiently understood. Methods: Here we studied the functional consequences of three disease‐associated mutations, which predict amino acid exchanges p.Gly82Arg (G82R), p.Leu85Pro (L85P), and p.Pro289Arg (P289R), by heterologous expression in mammalian cells, biochemistry, confocal imaging, and whole‐cell patch‐clamp recordings of EAAT2 l‐glutamate transport and anion current. Results: G82R and L85P exchange amino acid residues that contribute to the formation of the EAAT anion pore. They enlarge the pore diameter sufficiently to permit the passage of l‐glutamate and thus function as l‐glutamate efflux pathways. The mutation P289R decreases l‐glutamate uptake, but increases anion currents despite a lower membrane expression. Significance: l‐glutamate permeability of the EAAT anion pore is an unexpected functional consequence of naturally occurring single amino acid substitutions. l‐glutamate efflux through mutant EAAT2 anion channels will cause glutamate excitotoxicity and neuronal hyperexcitability in affected patients. Antagonists that selectively suppress the EAAT anion channel function could serve as therapeutic agents in the future. [ABSTRACT FROM AUTHOR]

Background Essential tremor (ET) is the most common disease among movement disorders. Genes such as essential tremor 1-4 (ETM 1-4), HS1-binding protein-3 (HS1BP3), dopamine receptor D3 (DRD3), leucine-rich repeat and Ig domain containing 1 (LINGO1), glial high affinity glutamate transporter member 2 (SLC1A2), FUS, high temperature requirement A2 (HTRA2) and TENM4 had been shown to be responsible for the genetic inheritance of the disease. The aim of the present study was to investigate the effect of propranolol on the expression of DRD3, SLC1A2, and HTRA2 genes in patients with ET. Methods A study of non-randomized experimental design was conducted involving 76 subjects. They were divided into two groups: 38 patients with ET in the patient group (Group 1) and 38 healthy people in the control group (Group 2). DRD3, SLC1A2 and HTRA2 gene expressions were assessed before and after 8 weeks of propranolol treatment. Fahn-Tolosa-Marin tremor scale results were compared before and after propranolol administration. Kruskal Wallis test was used to determine differences in gene expressions between the groups. Results D3 dopamine receptor and SLC1A2 gene expression in the patient group appeared to be lower than in the control group (p

Objective: The aim of this study was to investigate potential genetic overlap between essential tremor and Parkinson's disease in a cohort of 825 subjects from an Eastern Chinese population. Methods: A total of 441 Parkinson's disease patients and 384 healthy controls were recruited. The MassARRAY System was used to detect three essential tremor‐related single nucleotide polymorphisms. Odds ratio (OR) and 95% confidential interval (CI) were calculated to assess the relationship between polymorphisms and Parkinson's disease susceptibility. Results: Our results demonstrated that the odds ratios of rs3794087 of SLC1A2, rs9652490 of LINGO1, and rs17590046 of PPARGC1A were 0.71 (95% CI = 0.55‐0.91), 0.99 (95% CI = 0.78‐1.26), and 0.88 (95% CI = 0.62‐1.25), respectively. Conclusion: An essential tremor SNP (rs3794087 of SLC1A2) is associated with a decreased risk of PD in the Eastern Han Chinese population, while rs9652490 (LINGO1) and rs17590046 (PPARGC1A) do not show an association. [ABSTRACT FROM AUTHOR]

Drug-resistant epilepsy is a common condition in patients with brain neoplasms. The pathogenesis of tumor-associated seizures is poorly understood. Among the possible pathogenetic mechanisms, the increase in glutamate concentration has been proposed. Glutamate transporters, glutamine synthetase and pyruvate carboxylase are involved in maintaining the physiological concentration of glutamate in the intersynaptic spaces. In our previous research on angiocentric gliomas, we demonstrated that all tumors lacked the expression of the main glutamate transporter EAAT2, while the expression of glutamine synthetase and pyruvate carboxylase was mostly preserved. In the present study, we evaluated the immunohistochemical expression of EAAT2, glutamine synthetase and pyruvate carboxylase in a heterogeneous series of 25 long-term epilepsy-associated tumors (10 dysembryoplastic neuroepithelial tumors, 7 gangliogliomas, 3 subependymal giant cell astrocytomas, 3 rosette forming glioneuronal tumors, 1 diffuse astrocytoma MYB- or MYBL1-altered and 1 angiocentric glioma). In order to evaluate the incidence of variants in the SLC1A2 gene, encoding EAAT2, in a large number of central nervous system tumors we also queried the PedcBioPortal. EAAT2 protein expression was lost in 9 tumors (36 %: 3 dysembryoplastic neuroepithelial tumors, 1 ganglioglioma, 3 subependymal giant cell astrocytomas, 1 diffuse astrocytoma MYB- or MYBL1-altered and 1 angiocentric glioma). Glutamine synthetase protein expression was completely lost in 2 tumors (8 %; 1 ganglioglioma and 1 diffuse astrocytoma MYB- or MYBL1-altered). All tumors of our series but rosette forming glioneuronal tumors (in which neurocytic cells were negative) were diffusely positive for pyruvate carboxylase. Consultation of the PedcBioPortal revealed that of 2307 pediatric brain tumors of different histotype and grade, 20 (< 1%) had variants in the SLC1A2 gene. Among the SLC1A2 -mutated tumors, there were no angiocentric gliomas or other LEATs In conclusion, unlike angiocentric gliomas where the EAAT2 loss is typical and constant, the current study shows the loss of EAAT2 expression only in a fraction of the LEATs. In these cases, we may hypothesize some possible epileptogenic role of the EAAT2 loss. The retained expression of pyruvate carboxylase may contribute to determining a pathological glutamate excess unopposed by glutamine synthetase that resulted expressed to a variable extent in the majority of the tumors. Furthermore, we can assume that the EAAT2 loss in brain tumors in general and in LEATs in particular is more conceivably epigenetic. • Drug-resistant epilepsy is a common condition in patients with brain neoplasms. • The pathogenesis of tumor-associated seizures is poorly understood. • EAAT2 removes glutamate excess from intersinaptic spaces. • Loss of EAAT2 expression may have an epiloptogenic role LEATs. • Loss of EAAT2 expression is more likely caused by epigenetic mechanisms. [ABSTRACT FROM AUTHOR]

Background: The excitatory amino-acid transporters EAAT1 and EAAT2 clear glutamate from the synaptic cleft and thus terminate neuronal excitation. The carriers are subject to regulation by various kinases. The EAAT3 isoform is regulated by mammalian target of rapamycin (mTOR). The present study thus explored whether mTOR influences transport by EAAT1 and/or EAAT2. Methods: cRNA encoding wild type EAAT1 (SLC1A3) or EAAT2 (SLC1A2) was injected into Xenopus oocytes without or with additional injection of cRNA encoding mTOR. Dual electrode voltage clamp was performed in order to determine electrogenic glutamate transport (IEAAT). EAAT2 protein abundance was determined utilizing chemiluminescence. Results: Appreciable IEAAT was observed in EAAT1 or EAAT2 expressing but not in water injected oocytes. IEAAT was significantly increased by coexpression of mTOR. Coexpression of mTOR increased significantly the maximal IEAAT in EAAT1 or EAAT2 expressing oocytes, without significantly modifying affinity of the carriers. Moreover, coexpression of mTOR increased significantly EAAT2 protein abundance in the cell membrane. Conclusions: The kinase mTOR up-regulates the excitatory amino acid transporters EAAT1 and EAAT2.

Background/Aims: Klotho, a transmembrane protein expressed in chorioid plexus of the brain, kidney, and several other tissues, is required for inhibition of 1,25(OH)2D3 formation by FGF23. The extracellular domain of Klotho protein could be cleaved off, thus being released into blood or cerebrospinal fluid. At least in part by exerting β-glucuronidase activity, soluble klotho regulates several ion channels and carriers. Klotho protein deficiency accelerates the appearance of age related disorders including neurodegeneration and muscle wasting and eventually leads to premature death. The present study explored the effect of Klotho protein on the excitatory glutamate transporters EAAT1 (SLC1A3) and EAAT2 (SLC1A2), Na+ coupled carriers clearing excitatory amino acids from the synaptic cleft and thus participating in the regulation of neuronal excitability. Methods: cRNA encoding EAAT1 or EAAT2 was injected into Xenopus laevis oocytes and glutamate (2 mM)-induced inward current (IGlu) taken as measure of glutamate transport. Measurements were made without or with prior 24 h treatment with soluble ß-Klotho protein (30 ng/ml) in the absence and presence of β-glucuronidase inhibitor D-saccharic acid 1,4-lactone monohydrate (DSAL,10 µM). Results: IGlu was observed in EAAT1 and in EAAT2 expressing oocytes but not in water injected oocytes. In both, EAAT1 and EAAT2 expressing oocytes IGlu was significantly increased by treatment with soluble ß-Klotho protein, an effect reversed by DSAL. Treatment with ß-klotho protein increased significantly the maximal transport rate without significantly modifying the affinity of the carriers. Conclusion: ß-Klotho up-regulates the excitatory glutamate transporters EAAT1 and EAAT2 and thus participates in the regulation of neuronal excitation.

This study aimed to identify the genes related to epilepsy and their effects on epilepsy, as well as the underlying mechanism. Using microarray analysis, differentially expressed genes (DEGs) were screened out and then used to build weighted gene coexpression networks using WGCNA. Module membership and evaluation of gene significance (GS) were adopted to detect hub genes. The DAVID online tool was used to understand the function of modules and target genes. The Licl‐pilocarpine chronic rat epilepsy model was used to simulate mesial temporal lobe epilepsy with an initial precipitating injury. Hippocampal expression of the proteins solute carrier family 1 member 2 (SLC1A2), glial fibrillary acidic protein, interleukin‐1β (IL‐1β), tumor necrosis factor α (TNF‐α), and N‐methyl‐d‐aspartic acid receptor (NMDAR) was determined by ELISA and Western blot. Nissl staining was used to measure neuronal loss. Immunohistochemistry was performed to assess the percentage of positive cells to reflect the distribution of NMDAR1. Here, 3232 potential genes highly correlated with epilepsy were selected from the screened DEGs, among which SLC1A2 was related to brain development and its expression was significantly decreased in epilepsy patients. According to Gene Ontology and KEGG analysis, SLC1A2 mediates epilepsy through the glutamatergic synapse pathway. Tissue experiments suggested that Slc1a2 could genuinely ameliorate epilepsy through the glutamatergic synapse pathway, mitigate neuronal loss, and suppress astrocytosis and inflammatory responses. Our study suggested that low hippocampal content of SLC1A2 is a potential biomarker of epilepsy and may affect the function of neurons through the glutamatergic synapse pathway. © 2018 IUBMB Life, 71(1):213–222, 2019 [ABSTRACT FROM AUTHOR]

Glutamate is the principal excitatory neurotransmitter in the central nervous system. In mature brains, it is critically involved in neuroplasticity and, at high levels, neurotoxicity. The concentrations of glutamate in the extracellular space are maintained at low physiological levels by molecular glutamate transporters (excitatory amino acid transporters-EAATs). Adverse childhood experiences (ACEs) are highly reported in bipolar disorder (BD) and interact with the glutamatergic system in the brain. The aim of the study is to investigate the effect of a glutamate transporter polymorphism EAAT2-181A > C (rs4354668) and exposure to ACE on white matter microstructure in patients with BD. We assessed 175 bipolar subjects using diffusion tensor imaging, Risky Families Questionnaire, and EEAT2 rs4354668 variants. We observed an interaction between ACE and rs4354668: carriers of the G allele showed lower axial diffusivity compared to T/T homozygotes when exposed to high stress and higher axial diffusivity than T/T when exposed to low stress. Since the mutant G allele has been associated with a reduced transcriptional activity and expression of the transporter protein, and early stress is associated with a reduced expression of the EAAT2, we could hypothesize that after exposure to high levels of ACE G/G homozygotes are more vulnerable to stress reporting the highest damage as a consequence of an excess of free glutamate. [ABSTRACT FROM AUTHOR]

Recently, a genome-wide association study of a Caucasian population identified variant rs3794087 in intron 4 of the SLC1A2 gene, which may increase the risk of essential tremor (ET). Considering the overlap in the pathological features and clinical manifestations of ET and Parkinson's disease (PD), several studies on the association between rs3794087 and PD were later performed in other populations. However, results about the role of SLC1A2 rs3794087 in PD were inconsistent. We thus performed a case-control study in a Chinese Han population to investigate the role of SLC1A2 rs3794087 in Chinese patients with PD. Overall, 1096 subjects comprising 546 patients with PD and 550 control subjects were genotyped. A meta-analysis of the data obtained from the current sample-set and those available from prior studies was performed. Taking all patients and controls into consideration, rs3794087 was found to have no significant effect on PD susceptibility in analyses using allelic ( p  = .486), genotype ( p  = .736), additive ( p  = .764), dominant ( p  = .438), and recessive ( p  = .878) genetic models. The results of the meta-analysis were in agreement with our findings (the pooled OR was 0.97 and 95% CI = 0.85, 1.10). Our study suggested that rs3794087 does not lead to an increased risk of PD in the Chinese Han population. The role of single nucleotide polymorphism rs3794087 in the development of PD remains to be further studied. [ABSTRACT FROM AUTHOR]

Recently, heterozygous de novo mutations in SCL1A2 have been reported to underlie severe early-onset epileptic encephalopathy. In one male presenting with epileptic seizures and visual impairment, we identified a novel homozygous splicing variant in SCL1A2 (c.1421 + 1G > C) by using exome sequencing. Functional studies on cDNA level confirmed a consecutive loss of function. Our findings suggest that not only de novo mutations but also biallelic variants in SLC1A2 can cause epilepsy and that there is an additional autosomal recessive mode of inheritance. These findings also contribute to the understanding of the genetic mechanism of autosomal dominant SLC1A2-related epileptic encephalopathy as they exclude haploinsufficiency as exclusive genetic mechanism. [ABSTRACT FROM AUTHOR]

Massively parallel sequencing has revealed many de novo mutations in the etiology of developmental and epileptic encephalopathies (EEs), highlighting their genetic heterogeneity. Additional candidate genes have been prioritized in silico by their co-expression in the brain. Here, we evaluate rare coding variability in 20 candidates nominated with the use of a reference gene set of 51 established EE-associated genes. Variants within the 20 candidate genes were extracted from exome-sequencing data of 42 subjects with EE and no previous genetic diagnosis. We identified 7 rare non-synonymous variants in 7 of 20 genes and performed Sanger sequence validation in affected probands and parental samples. De novo variants were found only in SLC1A2 (aka EAAT2 or GLT1 ) (c.244G>A [p.Gly82Arg]) and YWHAG (aka 14-3-3γ) (c.394C>T [p.Arg132Cys]), highlighting the potential cause of EE in 5% (2/42) of subjects. Seven additional subjects with de novo variants in SLC1A2 (n = 1) and YWHAG (n = 6) were subsequently identified through online tools. We identified a highly significant enrichment of de novo variants in YWHAG , establishing their role in early-onset epilepsy, and we provide additional support for the prior assignment of SLC1A2 . Hence, in silico modeling of brain co-expression is an efficient method for nominating EE-associated genes to further elucidate the disorder’s etiology and genotype-phenotype correlations. [ABSTRACT FROM AUTHOR]

Background: The excitatory amino-acid transporters EAAT1 and EAAT2 clear glutamate from the synaptic cleft and thus terminate neuronal excitation. The carriers are subject to regulation by various kinases. The EAAT3 isoform is regulated by mammalian target of rapamycin (mTOR). The present study thus explored whether mTOR influences transport by EAAT1 and/or EAAT2. Methods: cRNA encoding wild type EAAT1 (SLC1A3) or EAAT2 (SLC1A2) was injected into Xenopus oocytes without or with additional injection of cRNA encoding mTOR. Dual electrode voltage clamp was performed in order to determine electrogenic glutamate transport (IEAAT). EAAT2 protein abundance was determined utilizing chemiluminescence. Results: Appreciable IEAAT was observed in EAAT1 or EAAT2 expressing but not in water injected oocytes. IEAAT was significantly increased by coexpression of mTOR. Coexpression of mTOR increased significantly the maximal IEAAT in EAAT1 or EAAT2 expressing oocytes, without significantly modifying affinity of the carriers. Moreover, coexpression of mTOR increased significantly EAAT2 protein abundance in the cell membrane. Conclusions: The kinase mTOR up-regulates the excitatory amino acid transporters EAAT1 and EAAT2. [ABSTRACT FROM AUTHOR]

Background The association between the polymorphism rs3794087 in the solute carrier family 1, member 2 ( SLC1A2 ) and the risk of essential tremor (ET) among different studies is controversial. Considering the overlap of the clinical manifestations and pathological characteristics of ET, Parkinson's disease (PD), multiple system atrophy (MSA), as well as amyotrophic lateral sclerosis (ALS), we explored the possible genetic association of rs3794087 with ET, PD, MSA and ALS in a Chinese cohort. Methods A total of 112 ET, 621 PD, 356 MSA, 513 sporadic ALS (SALS) patients and 437 healthy controls (HCs) were genotyped for rs3794087 using the Sequenom iPLEX Assay technology. Results Significant association was found between SLC1A2 rs3794087 and PD in the additive model ( p = 0.006), which was more obvious in early onset PD. The minor allele of rs3794087 decreased the risk for early onset PD ( p = 0.011, OR: 0.73, 95% CI: 0.56–0.94). However, no significant differences in the genotype distributions and allele frequency were observed in the allelic, additive, dominant or recessive genetic models of SLC1A2 rs3794087 between ET patients and HCs, between SALS patients and HCs, and between MSA and HCs. Conclusions Our results suggested SLC1A2 rs3794087 may decrease the risk for PD in a Chinese cohort, but do not support a role in the susceptibility to SALS or MSA. [ABSTRACT FROM AUTHOR]

Excitatory amino acid transporters EAAT1 (SLC1A3), EAAT2 (SLC1A2), EAAT3 (SLC1A1), and EAAT4 (SLC1A6) serve to clear L-glutamate from the synaptic cleft and are thus important for the limitation of neuronal excitation. EAAT3 has previously been shown to form complexes with caveolin-1, a major component of caveolae, which participate in the regulation of transport proteins. The present study explored the impact of caveolin-1 on electrogenic transport by excitatory amino acid transporter isoforms EAAT1-4. To this end cRNA encoding EAAT1, EAAT2, EAAT3, or EAAT4 was injected into Xenopus oocytes without or with additional injection of cRNA encoding caveolin-1. The L-glutamate (2 mM)-induced inward current (I Glu) was taken as a measure of glutamate transport. As a result, I Glu was observed in EAAT1-, EAAT2-, EAAT3-, or EAAT4-expressing oocytes but not in water-injected oocytes, and was significantly decreased by coexpression of caveolin-1. Caveolin-1 decreased significantly the maximal transport rate. Treatment of EAATs-expressing oocytes with brefeldin A (5 µM) was followed by a decrease in conductance, which was similar in oocytes expressing EAAT together with caveolin-1 as in oocytes expressing EAAT1-4 alone. Thus, caveolin-1 apparently does not accelerate transporter protein retrieval from the cell membrane. In conclusion, caveolin-1 is a powerful negative regulator of the excitatory glutamate transporters EAAT1, EAAT2, EAAT3, and EAAT4. [ABSTRACT FROM AUTHOR]

Background/Aims: Klotho, a transmembrane protein expressed in chorioid plexus of the brain, kidney, and several other tissues, is required for inhibition of 1,25(OH)2D3 formation by FGF23. The extracellular domain of Klotho protein could be cleaved off, thus being released into blood or cerebrospinal fluid. At least in part by exerting β-glucuronidase activity, soluble klotho regulates several ion channels and carriers. Klotho protein deficiency accelerates the appearance of age related disorders including neurodegeneration and muscle wasting and eventually leads to premature death. The present study explored the effect of Klotho protein on the excitatory glutamate transporters EAAT1 (SLC1A3) and EAAT2 (SLC1A2), Na+ coupled carriers clearing excitatory amino acids from the synaptic cleft and thus participating in the regulation of neuronal excitability. Methods: cRNA encoding EAAT1 or EAAT2 was injected into Xenopus laevis oocytes and glutamate (2 mM)-induced inward current (IGlu) taken as measure of glutamate transport. Measurements were made without or with prior 24 h treatment with soluble ß-Klotho protein (30 ng/ml) in the absence and presence of β-glucuronidase inhibitor D-saccharic acid 1,4-lactone monohydrate (DSAL,10 µM). Results: IGlu was observed in EAAT1 and in EAAT2 expressing oocytes but not in water injected oocytes. In both, EAAT1 and EAAT2 expressing oocytes IGlu was significantly increased by treatment with soluble ß-Klotho protein, an effect reversed by DSAL. Treatment with ß-klotho protein increased significantly the maximal transport rate without significantly modifying the affinity of the carriers. Conclusion: ß-Klotho up-regulates the excitatory glutamate transporters EAAT1 and EAAT2 and thus participates in the regulation of neuronal excitation. © 2015 The Author(s) Published by S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The glutamate transporter GLT-1 (also called EAAT2 in humans) plays a critical role in regulating extracellular glutamate levels in the central nervous system (CNS). In Alzheimer's disease (AD), EAAT2 loss is associated with neuropathology and cognitive impairment. In keeping with this, we have reported that partial GLT-1 loss (GLT-1+/-) causes early-occurring cognitive deficits in mice harboring familial AD AβPPswe/PS1ΔE9 mutations. GLT-1 plays important roles in several molecular pathways that regulate brain metabolism, including Akt and insulin signaling in astrocytes. Significantly, AD pathogenesis also involves chronic Akt activation and reduced insulin signaling in the CNS. In this report we tested the hypothesis that GLT-1 heterozygosity (which reduces GLT-1 to levels that are comparable to losses in AD patients) in AβPPswe/PS1ΔE9 mice would induce sustained activation of Akt and disturb components of the CNS insulin signaling cascade. We found that partial GLT-1 loss chronically increased Akt activation (reflected by increased phosphorylation at serine 473), impaired insulin signaling (reflected by decreased IRβ phosphorylation of tyrosines 1150/1151 and increased IRS-1 phosphorylation at serines 632/635 - denoted as 636/639 in humans), and reduced insulin degrading enzyme (IDE) activity in brains of mice expressing familial AβPPswe/PS1ΔE9 AD mutations. GLT-1 loss also caused an apparent compensatory increase in IDE activity in the liver, an organ that has been shown to regulate peripheral amyloid-β levels and expresses GLT-1. Taken together, these findings demonstrate that partial GLT-1 loss can cause insulin/Akt signaling abnormalities that are in keeping with those observed in AD. [ABSTRACT FROM AUTHOR]

Glutamate is the most abundant free amino acid in the brain and is at the crossroad between multiple metabolic pathways. Considering this, it was a surprise to discover that glutamate has excitatory effects on nerve cells, and that it can excite cells to their death in a process now referred to as 'excitotoxicity'. This effect is due to glutamate receptors present on the surface of brain cells. Powerful uptake systems (glutamate transporters) prevent excessive activation of these receptors by continuously removing glutamate from the extracellular fluid in the brain. Further, the blood-brain barrier shields the brain from glutamate in the blood. The highest concentrations of glutamate are found in synaptic vesicles in nerve terminals from where it can be released by exocytosis. In fact, glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. It took, however, a long time to realize that. The present review provides a brief historical description, gives a short overview of glutamate as a transmitter in the healthy brain, and comments on the so-called glutamate-glutamine cycle. The glutamate transporters responsible for the glutamate removal are described in some detail. [ABSTRACT FROM AUTHOR]

Background: Schizophrenia and bipolar disorder together affect approximately 2.5% of the world population, and their etiologies are thought to involve multiple genetic variants and environmental influences. The analysis of gene expression patterns in brain may provide a characteristic signature for each disorder. Methods: RNA samples from the dorsolateral prefrontal cortex (Brodmann area 46) consisting of individuals with schizophrenia (SZ), bipolar disorder (BPD), and control subjects were tested on the Codelink Human 20K Bioarray platform. Selected transcripts were validated by quantitative real-time polymerase chain reaction (PCR). The strong effects of age, gender, and pH in the analysis of differential gene expression were controlled by analysis of covariance (ANCOVA). Criteria for differential gene expression were 1) a gene was significantly dysregulated in both BPD and SZ compared with control subjects and 2) significant in ANCOVA analysis with samples that have a pH above the median of the sample. Results: A list of 78 candidate genes passed these two criteria in BPD and SZ and was overrepresented for functional categories of nervous system development, immune system development and response, and cell death. Five dysregulated genes were confirmed with quantitative Q-PCR in both BPD and SZ. Three genes were highly enriched in brain expression (AGXT2L1, SLC1A2, and TU3A). The distribution of AGXT2L1 expression in control subjects versus BPD and SZ was highly significant (Fisher''s Exact Test, p < 10−06). Conclusions: These results suggest a partially shared molecular profile for both disorders and offer a window into discovery of common pathophysiology that might lead to core treatments. [Copyright &y& Elsevier]

Presents abstracts of several articles on ruminant nutrition for animals. "Monensin or Decoquinate in High Concentrate Diets Fed to Santa Ines Lambs," by I. Susin, C. Q. Mendes, A. V. Pires and I. U. Packer; "Rate and Extent of In Situ DM Disappearance of Feedstuffs in Cows Fed Different Strains of Yeast," by J. C, Silva and L. W. Greene; "Fermentable and Nutritional Characteristics of Fermented Feedstuffs Added Aspergillus Oryzae and Saccharomyces Cerevisiae," by P. Byung Ki, R. Chang Six and S. Jong Suh; "Effect of Supplemental Chromium on Tissue Chromium Concentrations in Cattle," by J. W. Spears, K. E. Lloyd, M. E. Tiffany and M. T. Socha.

Presents abstracts of several articles on ruminant nutrition for animals. "Monensin or Decoquinate in High Concentrate Diets Fed to Santa Ines Lambs," by I. Susin, C. Q. Mendes, A. V. Pires and I. U. Packer; "Rate and Extent of In Situ DM Disappearance of Feedstuffs in Cows Fed Different Strains of Yeast," by J. C, Silva and L. W. Greene; "Fermentable and Nutritional Characteristics of Fermented Feedstuffs Added Aspergillus Oryzae and Saccharomyces Cerevisiae," by P. Byung Ki, R. Chang Six and S. Jong Suh; "Effect of Supplemental Chromium on Tissue Chromium Concentrations in Cattle," by J. W. Spears, K. E. Lloyd, M. E. Tiffany and M. T. Socha.

Presents abstracts of several articles on ruminant nutrition for animals. "Monensin or Decoquinate in High Concentrate Diets Fed to Santa Ines Lambs," by I. Susin, C. Q. Mendes, A. V. Pires and I. U. Packer; "Rate and Extent of In Situ DM Disappearance of Feedstuffs in Cows Fed Different Strains of Yeast," by J. C, Silva and L. W. Greene; "Fermentable and Nutritional Characteristics of Fermented Feedstuffs Added Aspergillus Oryzae and Saccharomyces Cerevisiae," by P. Byung Ki, R. Chang Six and S. Jong Suh; "Effect of Supplemental Chromium on Tissue Chromium Concentrations in Cattle," by J. W. Spears, K. E. Lloyd, M. E. Tiffany and M. T. Socha.