Elsevier

Schizophrenia Research

Volume 185, July 2017, Pages 33-40
Schizophrenia Research

Comprehensive association analysis of 27 genes from the GABAergic system in Japanese individuals affected with schizophrenia

https://doi.org/10.1016/j.schres.2017.01.003Get rights and content

Abstract

Involvement of the gamma-aminobutyric acid (GABA)-ergic system in schizophrenia pathogenesis through disrupted neurodevelopment has been highlighted in numerous studies. However, the function of common genetic variants of this system in determining schizophrenia risk is unknown. We therefore tested the association of 375 tagged SNPs in genes derived from the GABAergic system, such as GABAA receptor subunit genes, and GABA related genes (glutamate decarboxylase genes, GABAergic-marker gene, genes involved in GABA receptor trafficking and scaffolding) in Japanese schizophrenia case-control samples (nĀ =Ā 2926; 1415 cases and 1511 controls). We observed nominal association of SNPs in nine GABAA receptor subunit genes and the GPHN gene with schizophrenia, although none survived correction for study-wide multiple testing. Two SNPs located in the GABRA1 gene, rs4263535 (PalleleĀ =Ā 0.002; uncorrected) and rs1157122 (PalleleĀ =Ā 0.006; uncorrected) showed top hits, followed by rs723432 (PalleleĀ =Ā 0.007; uncorrected) in the GPHN gene. All three were significantly associated with schizophrenia and survived gene-wide multiple testing. Haplotypes containing associated variants in GABRA1 but not GPHN were significantly associated with schizophrenia. To conclude, we provided substantiating genetic evidence for the involvement of the GABAergic system in schizophrenia susceptibility. These results warrant further investigations to replicate the association of GABRA1 and GPHN with schizophrenia and to discern the precise mechanisms of disease pathophysiology.

Introduction

Schizophrenia is a complex psychiatric disorder, manifesting heterogeneous behavioral and cognitive deficits, and afflicting approximately one percent of the global population (Owen et al., 2016). Overwhelming evidence supports neurodevelopmental abnormalities caused by genetic and environmental factors, in schizophrenia pathogenesis (Hashimoto et al., 2008b, Lewis and Levitt, 2002, Schmidt and Mirnics, 2015). In addition to the progressive symptoms seen in individuals affected with schizophrenia, observations of reduced cortical thickness, enlarged ventricles, reductions in gray matter volume, whole-brain volume, white matter anisotropy and a decreased neurogenic: gliogenic competence ratio further underscore neurodevelopmental dysfunction in disease pathology (Bakhshi and Chance, 2015, Harrison, 1999, Lewis and Lieberman, 2000, Toyoshima et al., 2016). In keeping with the neurodevelopment hypothesis, changes in neurodevelopment precede the onset of disease, affecting normal maturation, which in turn influences neuroplastic processes during development (Bakhshi and Chance, 2015).

The gamma-aminobutyric acid (GABA)-ergic system plays a significant role in neurodevelopment, by regulating neural proliferation, migration, differentiation, neuronal connectivity and synaptic activity (Deidda et al., 2014). Gamma-aminobutyric acid is the major inhibitory neurotransmitter in adult brains, and is synthesized from glutamate, by glutamate decarboxylases (GAD65 and GAD67) (Soghomonian and Martin, 1998). Its inhibitory function is mediated through the GABAA receptor, a heteropentameric ligand-gated chloride channel (Jacob et al., 2008). In addition, several receptor associated proteins aid in trafficking, tethering and lateral movement of GABAA receptors on the neuronal surface, thereby regulating GABAergic activity (Luscher et al., 2011).

The disruption of GABAergic function has been implicated in psychiatric diseases, like schizophrenia, for a long time (Gonzalez-Burgos et al., 2011, Nakazawa et al., 2012). Post-mortem studies have consistently showed abnormalities in parvalbumin-positive GABAergic interneurons, as well as altered expression of GABA related genes in the prefrontal cortex of individuals suffering from schizophrenia (Fung et al., 2010, Hoftman et al., 2015, Lewis et al., 2012, Lewis et al., 2005). In addition, impaired working memory, a characteristic feature of schizophrenia, has been attributed to aberrant gamma oscillations stemming from abnormal GABAergic interneuron activity in the prefrontal cortex of individuals affected with schizophrenia (Haenschel et al., 2009). Furthermore, development and maturation of the GABAergic system is also thought to be a convergent point for genetic and environmental susceptibility factors in schizophrenia (Schmidt and Mirnics, 2015).

Although post-mortem and animal studies showed GABAergic deficits in schizophrenia, human genetics data is limited to candidate gene association analysis and hampered by discrepant results (Cherlyn et al., 2010). A recent study showed for the first time that copy number variations (CNVs) are enriched for genes involved in GABAergic neurotransmission in schizophrenia cases (Pocklington et al., 2015). Moreover, results from our previous genome-wide association study (GWAS) in Japanese individuals affected with schizophrenia have shown association signals on the GABAA receptor subunit gene cluster at chromosome 5q34 (Yamada et al., 2011). In this study, we aimed to systematically investigate the role of common genetic variants from the GABAergic system in determining predisposition to schizophrenia. To this end, we performed a comprehensive case-control genetic association study of GABAA receptor subunit genes, and GABA related genes (glutamate decarboxylase genes, GABAergic-marker gene, genes involved in GABA receptor trafficking and scaffolding) in a large cohort of Japanese individuals affected with schizophrenia.

Section snippets

Subjects

The study examined 2926 unrelated Japanese case-control samples, consisting of 1415 individuals with schizophrenia (771 males, 644 females, mean ageĀ Ā±Ā SDĀ =Ā 51.19Ā Ā±Ā 13.68Ā years) and 1511 unrelated healthy controls (514 males, 997 females, mean ageĀ Ā±Ā SDĀ =Ā 44.11Ā Ā±Ā 14.04Ā years). The cohort also included samples from our previous GWAS study (120 probands from Japanese schizophrenia trio samples) (Yamada et al., 2011). Diagnosis of schizophrenia was based on Diagnosis and Statistical Manual of Mental Disorders IV

Allelic and genotypic analyses of 27 genes

A total of 375 SNPs were successfully genotyped after applying quality control (QC) criteria (SNP call rateĀ >Ā 90%, sample call rateĀ >Ā 95%) from the 406 SNPs selected from 27 GABA receptors genes and genes involved in the GABAergic signaling (Supplementary Table 1). One SNP (rs187269) was excluded due to deviation from Hardy Weinberg equilibrium (PĀ <Ā 0.001) and two SNPs in GAD2 gene (rs1330580 and rs11015010) were monomorphic, bringing the total number of SNPs studied to 372 (Supplementary Table 1).

Discussion

Accumulating evidence from post-mortem studies, imaging studies and animal experiments link the GABAergic system to schizophrenia pathogenesis, through altered neurodevelopmental events (Schmidt and Mirnics, 2015). Although several genes associated with GABAergic function are implicated in this process, the contribution of common genetic variants in the GABAergic system to schizophrenia susceptibility is still undefined. In this study, we performed genetic association analysis of common

Funding body agreements and policies

This study was supported in part by the Grant-in-Aid for Scientific Research (S.B.; 26860954, K.Y.; 26293267 and Tak. H.; 25293247) from Japan Society for the Promotion of Science (JSPS), the Grant-in-Aid for Scientific Research on Innovative Areas (Unraveling the microendophenotypes of psychiatric disorders at the molecular, cellular, and circuit levels) (Tak. H.: 15H01280 and T.Y.: 24116002), and the Strategic Research Program for Brain Sciences from Japan Agency for Medical Research and

Contributors

S.B., Ka. Y., Tak. H. and T.Y. designed the experiments. S.B., Ka. Y., C.S. and M.M. analyzed the data. S.B. and T.Y. wrote the manuscript. Y.I. performed the experiments. T.T., S.T., T.W., Y.K., D.K., Ko. Y., M.K., Tas. H. and N.K. coordinated sample recruitment and phenotype assessment. T.Y. supervised all phases of the project. All authors discussed the results and implications and approved the final manuscript.

Conflict of interest

All authors declare that they have no conflict of interest.

Acknowledgments

We thank all the participants of this study. We also thank Professors Mori, Minabe and Iyo, and Dr. Hattori, for their help in recruiting individuals with schizophrenia.

References (50)

  • B. Luscher et al.

    GABAA receptor trafficking-mediated plasticity of inhibitory synapses

    Neuron

    (2011)
  • K. Nakazawa et al.

    GABAergic interneuron origin of schizophrenia pathophysiology

    Neuropharmacology

    (2012)
  • M.J. Owen et al.

    Schizophrenia

    Lancet

    (2016)
  • A.J. Pocklington et al.

    Novel findings from CNVs implicate inhibitory and excitatory signaling complexes in schizophrenia

    Neuron

    (2015)
  • J.-J. Soghomonian et al.

    Two isoforms of glutamate decarboxylase: why?

    Trends Pharmacol. Sci.

    (1998)
  • Y. Yamaguchi-Kabata et al.

    Japanese population structure, based on SNP genotypes from 7003 individuals compared to other ethnic groups: effects on population-based association studies

    Am. J. Hum. Genet.

    (2008)
  • G. Zai et al.

    Possible association between the gamma-aminobutyric acid type B receptor 1 (GABBR1) gene and schizophrenia

    Eur. Neuropsychopharmacol.

    (2005)
  • X. Zhao et al.

    Systematic study of association of four GABAergic genes: glutamic acid decarboxylase 1 gene, glutamic acid decarboxylase 2 gene, GABA(B) receptor 1 gene and GABA(A) receptor subunit beta2 gene, with schizophrenia using a universal DNA microarray

    Schizophr. Res.

    (2007)
  • J. Arnedo et al.

    Uncovering the hidden risk architecture of the schizophrenias: confirmation in three independent genome-wide association studies

    Am. J. Psychiatr.

    (2015)
  • S. Balan et al.

    Population-specific haplotype association of the postsynaptic density gene DLG4 with schizophrenia, in family-based association studies

    PLoS One

    (2013)
  • M. Beneyto et al.

    Lamina-specific alterations in cortical GABA(A) receptor subunit expression in schizophrenia

    Cereb. Cortex

    (2011)
  • D.L. Braff et al.

    Lack of use in the literature from the last 20 years supports dropping traditional schizophrenia subtypes from DSM-5 and ICD-11

    Schizophr. Bull.

    (2013)
  • G. Deidda et al.

    Modulation of GABAergic transmission in development and neurodevelopmental disorders: investigating physiology and pathology to gain therapeutic perspectives

    Front. Cell. Neurosci.

    (2014)
  • J.M. Fritschy et al.

    Switch in the expression of rat GABAA-receptor subtypes during postnatal development: an immunohistochemical study

    J. Neurosci.

    (1994)
  • S.J. Fung et al.

    Expression of interneuron markers in the dorsolateral prefrontal cortex of the developing human and in schizophrenia

    Am. J. Psychiatr.

    (2010)
  • Cited by (10)

    • Investigation of betaine as a novel psychotherapeutic for schizophrenia

      2019, EBioMedicine
      Citation Excerpt :

      These variants were further pruned for linkage disequilibrium (LD) status (r2 < 0.4), yielding variants from independent LD blocks. The shortlisted variants (4 in BHMT, 3 in CHDH and 3 in GLO1) were genotyped in schizophrenia postmortem brain tissues (BA17) (n = 50) by TaqMan SNP genotyping Assays [23]. Gene expression was measured by real-time quantitative RT-PCR using TaqMan assays.

    View all citing articles on Scopus
    1

    These authors contributed equally to this study.

    View full text