Association between the gamma-aminobutyric acid A3 receptor gene and multiple sclerosis

MicroRNA-7188-5p and miR-7235 regulates Multiple sclerosis in an experimental mouse model

The short non-coding microRNAs (miRNAs) have emerged as reliable modulators of various pathological conditions including autoimmune diseases in mammals. The current study, aims to identify new potential differential expressed miRNAs and their downstream mRNA targets of the autoimmune disease, Multiple sclerosis (MS). The study identifies a new set of miRNA(s) that are probably implicated in MS using computational tools. The study further carried-out different in vivo and in vitro experiments to check these identified miRNAs could be role in as therapeutic and prognostic applications. Preliminary insilico screening revealed that miR-659-3p, miR-659-5p, miR-684, miR-3607-3p, miR-3607-5p, miR-3682-3p, miR-3682-5p miR-4647, miR-7188-3p, miR-7188-5p and miR-7235 are specifically elevated in the secondary lymphoid cells of EAE mice. In addition, expression of the downstream target mRNA of these miRNAs such as FXBO33, SGMS-1, ZDHHC-9, GABRA-3, NRXN-2 were reciprocal to miRNA expression in lymphoid cells. These confirmed by applying the mimic and silencing miRNA models, suggesting new inflammatory target genes of these promising miRNA markers. The in vivo adoptive transfer model revealed that the suppression of miRNA-7188-5p and miR-7235 changed the pattern of astrocytes and CNS pathophysiology. The current study opens a new miRNA and their mRNA targets in MS disease. The absence of miRNA-7188-5p and miR-7235 enhanced the disease alleviation, confirms the regulatory effect of these targets. These optimized results highlights new set of miRNA's with therapeutic potential in experimental MS. Further studies are required to confirm these miRNA as therapeutic biomarker.

GABAA receptors in GtoPdb v.2021.3

The GABA_A receptor is a ligand-gated ion channel of the Cys-loop family that includes the nicotinic acetylcholine, 5-HT₃ and strychnine-sensitive glycine receptors. GABA_A receptor-mediated inhibition within the CNS occurs by fast synaptic transmission, sustained tonic inhibition and temporally intermediate events that have been termed 'GABA_A, slow' [45]. GABA_A receptors exist as pentamers of 4TM subunits that form an intrinsic anion selective channel. Sequences of six α, three β, three γ, one δ, three ρ, one ε, one π and one θ GABA_A receptor subunits have been reported in mammals [278, 235, 236, 283]. The π-subunit is restricted to reproductive tissue. Alternatively spliced versions of many subunits exist (e.g. α4- and α6- (both not functional) α5-, β2-, β3- and γ2), along with RNA editing of the α3 subunit [71]. The three ρ-subunits, (ρ1-3) function as either homo- or hetero-oligomeric assemblies [359, 50]. Receptors formed from ρ-subunits, because of their distinctive pharmacology that includes insensitivity to bicuculline, benzodiazepines and barbiturates, have sometimes been termed GABA_C receptors [359], but they are classified as GABA _A receptors by NC-IUPHAR on the basis of structural and functional criteria [16, 235, 236]. Many GABA_A receptor subtypes contain α-, β- and γ-subunits with the likely stoichiometry 2α.2β.1γ [168, 235]. It is thought that the majority of GABA_A receptors harbour a single type of α- and β - subunit variant. The α1β2γ2 hetero-oligomer constitutes the largest population of GABA_A receptors in the CNS, followed by the α2β3γ2 and α3β3γ2 isoforms. Receptors that incorporate the α4- α5-or α 6-subunit, or the β1-, γ1-, γ3-, δ-, ε- and θ-subunits, are less numerous, but they may nonetheless serve important functions. For example, extrasynaptically located receptors that contain α6- and δ-subunits in cerebellar granule cells, or an α4- and δ-subunit in dentate gyrus granule cells and thalamic neurones, mediate a tonic current that is important for neuronal excitability in response to ambient concentrations of GABA [209, 272, 83, 19, 288]. GABA binding occurs at the β+/α- subunit interface and the homologous γ+/α- subunits interface creates the benzodiazepine site. A second site for benzodiazepine binding has recently been postulated to occur at the α+/β- interface ([254]; reviewed by [282]). The particular α-and γ-subunit isoforms exhibit marked effects on recognition and/or efficacy at the benzodiazepine site. Thus, receptors incorporating either α4- or α6-subunits are not recognised by 'classical' benzodiazepines, such as flunitrazepam (but see [356]). The trafficking, cell surface expression, internalisation and function of GABA_A receptors and their subunits are discussed in detail in several recent reviews [52, 140, 188, 316] but one point worthy of note is that receptors incorporating the γ2 subunit (except when associated with α5) cluster at the postsynaptic membrane (but may distribute dynamically between synaptic and extrasynaptic locations), whereas as those incorporating the δ subunit appear to be exclusively extrasynaptic. NC-IUPHAR [16, 235, 3, 2] class the GABA_A receptors according to their subunit structure, pharmacology and receptor function. Currently, eleven native GABA_A receptors are classed as conclusively identified (i.e., α1β2γ2, α1βγ2, α3βγ2, α4βγ2, α4β2δ, α4β3δ, α5βγ2, α6βγ2, α6β2δ, α6β3δ and ρ) with further receptor isoforms occurring with high probability, or only tentatively [235, 236]. It is beyond the scope of this Guide to discuss the pharmacology of individual GABA_A receptor isoforms in detail; such information can be gleaned in the reviews [16, 95, 168, 173, 143, 278, 216, 235, 236] and [9, 10]. Agents that discriminate between α-subunit isoforms are noted in the table and additional agents that demonstrate selectivity between receptor isoforms, for example via β-subunit selectivity, are indicated in the text below. The distinctive agonist and antagonist pharmacology of ρ receptors is summarised in the table and additional aspects are reviewed in [359, 50, 145, 223]. Several high-resolution cryo-electron microscopy structures have been described in which the full-length human α1β3γ2L GABA_A receptor in lipid nanodiscs is bound to the channel-blocker picrotoxin, the competitive antagonist bicuculline, the agonist GABA (γ-aminobutyric acid), and the classical benzodiazepines alprazolam and diazepam [198].

SeXX Matters in Multiple Sclerosis

Multiple sclerosis (MS) is the most common chronic inflammatory and neurodegenerative disease of the central nervous system (CNS). An interesting feature that this debilitating disease shares with many other inflammatory disorders is that susceptibility is higher in females than in males, with the risk of MS being three times higher in women compared to men. Nonetheless, while men have a decreased risk of developing MS, many studies suggest that males have a worse clinical outcome. MS exhibits an apparent sexual dimorphism in both the immune response and the pathophysiology of the CNS damage, ultimately affecting disease susceptibility and progression differently. Overall, women are predisposed to higher rates of inflammatory relapses than men, but men are more likely to manifest signs of disease progression and worse CNS damage. The observed sexual dimorphism in MS may be due to sex hormones and sex chromosomes, acting in parallel or combination. In this review, we outline current knowledge on the sexual dimorphism in MS and discuss the interplay of sex chromosomes, sex hormones, and the immune system in driving MS disease susceptibility and progression.

Canine distemper virus induces downregulation of GABAA,GABAB, and GAT1 expression in brain tissue of dogs

The aim of the study was to determine the expression profiles of GABA_A, GABA_B, and GAT1 using RT-PCR and the immunoreactivity of GAT1 via immunohistochemical and immunofluorescence assays in CDV-infected brain tissue of dogs. For this purpose, dogs with CDV and dogs without CDV were selected. The mRNA transcript levels of GABA_A, GABA_B, and GAT1 were significantly downregulated in brain tissue in the CDV-infected group as compared with that in non-CDV-infected brain tissue in the control group (p < 0.01, p < 0.001). In addition, the immunoreactivity of GAT1 in CDV-infected brain tissue was significantly lower than in the uninfected group (p < 0.05). We conclude that one of the main causes of myoclonus in CDV infections may be the blockage of postsynaptic inhibition in neurons or a lack of metabolism of GABA. In addition, a GABA neurotransmission imbalance could play a role in demyelination in CDV infections.

Adrenergic and dopaminergic modulation of immunity in multiple sclerosis: teaching old drugs new tricks?

Multiple sclerosis (MS) is an autoimmune disorder of the CNS characterized by inflammation, demyelination and axonal loss. Classical evidence in experimental allergic encephalomyelitis, the animal model of MS, support the relevance of sympatoadrenergic as well as of dopaminergic mechanisms. In MS patients, dysregulation of adrenergic and dopaminergic pathways contribute to the disease in immune system cells as well as in glial cells. Available evidence is summarized and discussed also in the light of the novel role of dopamine, noradrenaline and adrenaline as transmitters in immune cells, providing a conceptual frame to exploit the potential of several dopaminergic and adrenergic agents, already in clinical use for non-immune indications and with a usually favourable risk-benefit profile, as add-on drugs to conventional immunomodulating therapies in MS.

Role of gender in multiple sclerosis: clinical effects and potential molecular mechanisms

Multiple sclerosis (MS) is more prevalent in females than males, and this female predominance is increasing as time goes by. Additionally, gender appears to play critical roles in development, progression and treatment of MS, and is therefore an aspect that should always be considered in the design and interpretation of research and clinical trials for MS. In this review, factors that could potentially explain the gender-biased observations in MS are discussed. These include sex-specific differences between the male and female immune systems and nervous systems, genetic and epigenetic or environmental-related effects, the effects of gonadal hormones, and materno-fetal interactions.

Investigation of gamma-aminobutyric acid (GABA) A receptors genes and migraine susceptibility

BACKGROUND

Migraine is a neurological disorder characterized by recurrent attacks of severe headache, affecting around 12% of Caucasian populations. It is well known that migraine has a strong genetic component, although the number and type of genes involved is still unclear. Prior linkage studies have reported mapping of a migraine gene to chromosome Xq 24-28, a region containing a cluster of genes for GABA A receptors (GABRE, GABRA3, GABRQ), which are potential candidate genes for migraine. The GABA neurotransmitter has been implicated in migraine pathophysiology previously; however its exact role has not yet been established, although GABA receptors agonists have been the target of therapeutic developments. The aim of the present research is to investigate the role of the potential candidate genes reported on chromosome Xq 24-28 region in migraine susceptibility. In this study, we have focused on the subunit GABA A receptors type epsilon (GABRE) and type theta (GABRQ) genes and their involvement in migraine.

METHODS

We have performed an association analysis in a large population of case-controls (275 unrelated Caucasian migraineurs versus 275 controls) examining a set of 3 single nucleotide polymorphisms (SNPs) in the coding region (exons 3, 5 and 9) of the GABRE gene and also the I478F coding variant of the GABRQ gene.

RESULTS

Our study did not show any association between the examined SNPs in our test population (P>0.05).

CONCLUSION

Although these particular GABA receptor genes did not show positive association, further studies are necessary to consider the role of other GABA receptor genes in migraine susceptibility.

Multiple sclerosis susceptibility and the X chromosome

Multiple sclerosis (MS) is a chronic autoimmune complex trait with strong evidence for a genetic component. A female gender bias is clear but unexplained and a maternal parent-of-origin effect has been described. X-linked transmission of susceptibility has been previously proposed, based on pedigree, association and linkage studies. We genotyped 726 relative pairs including 552 affected sib-pairs for 22 X-chromosome microsatellite markers and a novel dataset of 195 aunt-uncle/niece-nephew (AUNN) affected pairs for 18 markers. Parent-of-origin effects were explored by dividing AUNN families into likely maternal and paternal trait transmission. For the sib-pair dataset we were able to establish exclusion at a lambda s = 1.9 for all markers using an exclusion threshold of LOD < or = -2. Similarly for the AUNN dataset, we established exclusion at lambdaAV = 1.9. For the combined dataset we estimate exclusion of lambda = 1.6. We did not identify significant linkage in either the sib-pairs or the AUNN dataset nor when datasets were stratified for the presence/absence of the HLA-DRB1*15 allele or for paternal or maternal transmission. This comprehensive scrutiny of the X-chromosome suggests that it is unlikely to harbour an independent susceptibility locus or one which interacts with the HLA. Complex interactions including epigenetic ones, and masking by balanced polymorphisms are mechanisms not excluded by the approach taken.

Mapping gene activity in complex disorders: Integration of expression and genomic scans for multiple sclerosis

Genetic predisposition contributes to the pathogenesis of most common diseases. Genetic studies have been extremely successful in the identification of genes responsible for a number of Mendelian disorders. However, with a few exceptions, genes predisposing to diseases with complex inheritance remain unknown despite multiple efforts. In this article we collected detailed information for all genome-wide genetic screens performed to date in multiple sclerosis (MS) and in its animal model experimental autoimmune encephalomyelitis (EAE), and integrated these results with those from all high throughput gene expression studies in humans and mice. We analyzed a total of 55 studies. We found that differentially expressed genes (DEG) are not uniformly distributed in the genome, but rather appear in clusters. Furthermore, these clusters significantly differ from the known heterogeneous organization characteristic of eukaryotic gene distributions. We also identified regions of susceptibility that overlapped with clusters of DEG leading to the prioritization of candidate genes. Integration of genomic and transcriptional information is a powerful tool to dissect genetic susceptibility in complex multifactorial disorders like MS.

Association of CCR5 delta32 deletion with early death in multiple sclerosis

PURPOSE

The interaction between chemokines and their receptors is extremely important in controlling T cell migration into sites of CNS inflammation. Because trafficking of inflammatory T cells into the central nervous system (CNS) is a key player in the pathogenesis of multiple sclerosis (MS), we investigated the possible association of CCR5 delta32 deletion in this disorder.

METHODS

DNA isolated from postmortem brain tissue samples of 132 patients with MS and from blood tissue samples of 163 gender and ethnicity-matched healthy controls was used to screen for the CCR5 delta32 deletion allele.

RESULTS

An increased frequency of 32-bp deletion allele was found to be associated with early death (P = 0.00005) and with a progressive reduction in the years of survival (onset to death). The death hazard ratio of CCR5 with deletion versus no deletion was 2.12, suggesting that MS patients with the 32-bp deletion have twice the mortality rate of patients with the normal genotype. This effect was more significant in females (hazard ratio 3.58).

CONCLUSION

A strong association of the CCR5delta32 deletion with early death could serve as a prognostic marker for MS.

Endophyte-infected tall fescue diet alters gene expression in heifer luteal tissue as revealed by interspecies microarray analysis

Cattle consuming endophyte-infected tall fescue grass have an associated reduction in circulating progesterone and reduced reproductive rates. In this study, commercially available rat microarrays were used to analyze the gene expression in luteal tissues from heifers fed endophyte-free fescue, endophyte-infected fescue, or endophyte-infected fescue supplemented with the dopamine (DA) antagonist, domperidone. The number of hybridized spots represented approximately 40% of the total 10,000 rat genes/ESTs evaluated. Each luteal sample was analyzed in triplicate, resulting in within treatment correlation coefficients of >/=0.98. Median values of mRNA abundance from luteal tissue taken from the endophyte-infected fed heifers revealed 598 genes and ESTs that were down regulated and 56 genes and ESTs that were upregulated compared with luteal mRNA values from the endophyte-free treatment. There were fewer comparative differences between median values from luteal mRNA from the endophyte-free versus feeding endophyte-infected plus domperidone treated heifers. Only 19 genes and ESTs were upregulated and two were down-regulated.

Genetics of multiple sclerosis: linkage and association studies

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system caused by an interplay of environmental and genetic factors. The only genetic region that has been clearly demonstrated by linkage and association studies to contribute to MS genetic susceptibility is the human leukocyte antigen (HLA) system. The majority of HLA population studies in MS have focused on Caucasians of Northern European descent, where the predisposition to disease has been consistently associated with the class II DRB1*1501-DQA1*0102-DQB1*0602 haplotype. A positive association with DR4 was detected in Sardinians and in other Mediterranean populations. Moreover DR1, DR7, DR11 have been found to be protective in several populations. Systematic searches aimed at identifying non-HLA susceptibility genes were undertaken in several populations by means of linkage studies with microsatellite markers distributed across the whole genome. The conclusion of these studies was that there is no major MS locus, and genetic susceptibility to the disease is most likely explained by the presence of different genes each conferring a small contribution to the overall familial aggregation. The involvement of several candidate genes was tested by association studies, utilizing either a population-based (case control) or a family-based (transmission disequilibrium test) approach. Candidate genes were selected mainly on the basis of their involvement in the autoimmune pathogenesis and include immunorelevant molecules such as cytokines, cytokine receptors, immunoglobulin, T cell receptor subunits and myelin antigens. With the notable exception of HLA, association studies met only modest success. This failure may result from the small size of the tested samples and the small number of markers considered for each gene. New tools for large scale screening are needed to identify genetic determinants with a low phenotypic effect. Large collaborative studies are planned to screen several thousands of patients with MS with several thousands of genetic markers. The tests are increasingly based on the DNA pooling procedure.

The mouse GABA(A) receptor alpha3 subunit gene and promoter

Gamma-aminobutyric acid (GABA) type A receptors are multisubunit ligand-gated ion channels which mediate inhibition in the brain. The GABA(A) receptor alpha3 subunit gene exhibits extensive variation in its developmental and regional expression, but the detailed mechanisms governing the expression patterns of this gene remain unknown. We have cloned and begun to characterize the murine alpha3 subunit gene Gabra3. All but one of the 10 exons and the intron-exon boundaries have been sequenced; the first intron is in the 5' untranslated region (5'UTR) of the alpha3 mRNA. Rapid amplification of the cDNA 5'-end (5'-RACE) and RNase protection indicated many transcription start sites, with the major site (=+1) corresponding to a 5'UTR of 178 bases. Most sites were in or just downstream of a region of 55 (mouse) and 25 (human) GA repeats in the proximal promoter, as revealed by genome walking of Gabra3 and the human gene GABRA3. No canonical TATA or CAAT boxes or initiator (Inr) sites were found in either promoter, but both contained conserved consensus sites for several transcription factors. Progressive deletion of the mouse promoter produced positive or negative effects on expression of reporter (luciferase) constructs, with the highest observed activity in several types of transiently transfected cells for a construct containing bases -320 to +35. The GA repeats and a much shorter nearby series of four GC repeats, the first three of which are part of a consensus E2F site, appear to contribute significantly to mouse promoter activity. Upstream GA repeats enhanced activity of the SV40 promoter, and the GA repeat sequence bound nuclear proteins from several tissues.