Two isoforms of GABAA receptor β2 subunit with different electrophysiological properties: differential expression and genotypical correlations in schizophrenia

Single nucleotide polymorphisms in type A γ-aminobutyric acid (GABAA) receptor β2 subunit gene (GABRB2) were found to be associated with schizophrenia in Chinese, German, Japanese and Portuguese. To explore potential functional consequences of these DNA sequence polymorphisms, this study examined the expression and electrophysiological properties of two alternatively spliced products of GABRB2 along with genotypical disease association analysis. Real-time quantitative polymerase chain reaction, performed with a cohort of 31 schizophrenics and 31 controls of US population, showed 21.7% reduction in the expression of the long isoform β2L, 13.4% in the short isoform β2S and 15.8% in the sum of the two isoforms β2T in postmortem schizophrenic brain. Furthermore, two independent mRNA quantitation methods showed that the relative expression of the long over the short isoforms was significantly decreased, suggesting the occurrence of altered splicing, in schizophrenia. In male schizophrenics, the heterozygous genotypes of rs1876071 (T/C) and rs1876072 (A/G) were correlated with reduced expression of β2L, β2S and β2T, and the heterozygous of rs2546620 (A/G) and homozygous-minor of rs1876071 (C/C) and rs1876072 (G/G) were correlated with reduced expression of β2T. Significant correlations of expression levels with different alleles and haplotypes were also indicated by quantitative trait analysis. Recombinant GABAA receptors expressed in HEK293 human cells containing β2L underwent a steeper current rundown upon repetitive GABA activation than receptors containing β2S. The results thus revealed genotype-dependent expression of the alternatively spliced isoforms of GABAA receptor β2 subunit, giving rise to electrophysiological consequences that could play an important role in the pathogenesis mechanism of schizophrenia.

[1]  R Hashimoto,et al.  Expression analysis of neuregulin-1 in the dorsolateral prefrontal cortex in schizophrenia , 2004, Molecular Psychiatry.

[2]  Takashi Asada,et al.  GABAA receptor &ggr; subunits in the prefrontal cortex of patients with schizophrenia and bipolar disorder , 2004 .

[3]  B. Devlin,et al.  Association and linkage analyses of RGS4 polymorphisms in schizophrenia. , 2002, Human molecular genetics.

[4]  H. Stefánsson,et al.  Neuregulin 1 and susceptibility to schizophrenia. , 2002, American journal of human genetics.

[5]  P. Sokoloff,et al.  Dopamine D3 receptor gene variants and substance abuse in schizophrenia , 1998, Molecular Psychiatry.

[6]  F Giangaspero,et al.  Rundown of GABA type A receptors is a dysfunction associated with human drug-resistant mesial temporal lobe epilepsy. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[7]  Takashi Asada,et al.  GABAA receptor gamma subunits in the prefrontal cortex of patients with schizophrenia and bipolar disorder. , 2004, Neuroreport.

[8]  F. Speleman,et al.  Accurate normalization of real-time quantitative RT-PCR data by geometric averaging of multiple internal control genes , 2002, Genome Biology.

[9]  R. Straub,et al.  Genetic variation in the 6p22.3 gene DTNBP1, the human ortholog of the mouse dysbindin gene, is associated with schizophrenia. , 2002, American journal of human genetics.

[10]  Daniel R Weinberger,et al.  Microarray analysis of gene expression in the prefrontal cortex in schizophrenia: a preliminary study , 2002, Schizophrenia Research.

[11]  R. Yolken,et al.  The Stanley Foundation brain collection and Neuropathology Consortium , 2000, Schizophrenia Research.

[12]  F. Dudbridge.  Pedigree disequilibrium tests for multilocus haplotypes , 2003, Genetic epidemiology.

[13]  Lin He,et al.  Positive association of the human GABA-A-receptor beta 2 subunit gene haplotype with schizophrenia in the Chinese Han population. , 2005, Biochemical and biophysical research communications.

[14]  S. Gabriel,et al.  Efficiency and power in genetic association studies , 2005, Nature Genetics.

[15]  Quantitation of mRNA levels of steroid 5α‐reductase isozymes: A method that combines one‐step reverse transcription‐polymerase chain reaction and separation by capillary electrophoresis , 2004, Electrophoresis.

[16]  Michael C O'Donovan,et al.  Haplotypes at the dystrobrevin binding protein 1 (DTNBP1) gene locus mediate risk for schizophrenia through reduced DTNBP1 expression. , 2005, Human molecular genetics.

[17]  M. Rietschel,et al.  Transmission disequilibrium and haplotype analyses of the G72/G30 locus: Suggestive linkage to schizophrenia in Palestinian Arabs living in the North of Israel , 2006, American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics.

[18]  H. Xue,et al.  GABRB2 Association with Schizophrenia: Commonalities and Differences Between Ethnic Groups and Clinical Subtypes , 2007, Biological Psychiatry.

[19]  P. Sham,et al.  Genetic and physiological data implicating the new human gene G72 and the gene for d-amino acid oxidase in schizophrenia , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[20]  Steven Lippmann,et al.  Chronic schizophrenia. , 1995, Postgraduate medicine.

[21]  Nicola Brace,et al.  SPSS for Psychologists: A Guide to Data Analysis Using Spss for Windows (Versions 12 and 13) , 2006 .

[22]  E. Korpi,et al.  GABA(A) receptor subtypes as targets for neuropsychiatric drug development. , 2006, Pharmacology & therapeutics.

[23]  S Purcell,et al.  Genetic investigation of chromosome 5q GABAA receptor subunit genes in schizophrenia , 2005, Molecular Psychiatry.

[24]  Daniel R. Weinberger,et al.  Prefrontal neurons and the genetics of schizophrenia , 2001, Biological Psychiatry.

[25]  Hidehiro Iida,et al.  The association between the Val158Met polymorphism of the catechol-O-methyl transferase gene and morphological abnormalities of the brain in chronic schizophrenia. , 2006, Brain : a journal of neurology.

[26]  D. Nickerson,et al.  PolyPhred: automating the detection and genotyping of single nucleotide substitutions using fluorescence-based resequencing. , 1997, Nucleic acids research.

[27]  T. Asada,et al.  Immunohistochemical and immunoblot study of GABAA α1 and β2/3 subunits in the prefrontal cortex of subjects with schizophrenia and bipolar disorder , 2004, Neuroscience Research.

[28]  S. Akbarian,et al.  GABAA receptor subunit gene expression in human prefrontal cortex: comparison of schizophrenics and controls. , 1995, Cerebral cortex.

[29]  Mark Daly,et al.  Haploview: analysis and visualization of LD and haplotype maps , 2005, Bioinform..

[30]  C. Crombie,et al.  Association analysis of the RGS4 gene in Han Chinese and Scottish populations with schizophrenia , 2005, Genes, brain, and behavior.

[31]  Paul J. Harrison,et al.  Schizophrenia genes, gene expression, and neuropathology: on the matter of their convergence , 2005, Molecular Psychiatry.

[32]  H. Xue,et al.  Association of SNPs and haplotypes in GABAA receptor β2 gene with schizophrenia , 2004, Molecular Psychiatry.

[33]  Molly M. Huntsman,et al.  Altered ratios of alternatively spliced long and short γ2 subunit mRNAs of the γ-amino butyrate type A receptor in prefrontal cortex of schizophrenics , 1998 .

[34]  T. Shinkai,et al.  Untranslated region haplotype in dysbindin gene: analysis in schizophrenia , 2005, Journal of Neural Transmission.

[35]  Daniel R Weinberger,et al.  Expression of DISC1 binding partners is reduced in schizophrenia and associated with DISC1 SNPs. , 2006, Human molecular genetics.

[36]  R. Macdonald,et al.  Mutation of the GABAA receptor M1 transmembrane proline increases GABA affinity and reduces barbiturate enhancement , 2002, Neuropharmacology.

[37]  R. Wong,et al.  GABAA receptor function is regulated by phosphorylation in acutely dissociated guinea‐pig hippocampal neurones. , 1990, The Journal of physiology.

[38]  J. Beckmann,et al.  A highly significant association between a COMT haplotype and schizophrenia. , 2002, American journal of human genetics.

[39]  D. Weinberger,et al.  Evidence of dysfunction of a prefrontal-limbic network in schizophrenia: a magnetic resonance imaging and regional cerebral blood flow study of discordant monozygotic twins. , 1992, The American journal of psychiatry.

[40]  G. Kirov,et al.  Evidence that interaction between neuregulin 1 and its receptor erbB4 increases susceptibility to schizophrenia , 2006, American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics.

[41]  B. Dean,et al.  Changes in serotonin2A and GABA(A) receptors in schizophrenia: studies on the human dorsolateral prefrontal cortex. , 1999, Journal of neurochemistry.

[42]  Stephen J. Moss,et al.  Modulation of GABAA receptors by tyrosine phosphorylation , 1995, Nature.

[43]  W H Wong,et al.  Genome-wide expression analysis reveals dysregulation of myelination-related genes in chronic schizophrenia , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[44]  K. Davis,et al.  Expression of the ionotropic glutamate receptor subunits and NMDA receptor-associated intracellular proteins in the substantia nigra in schizophrenia. , 2004, Brain research. Molecular brain research.

[45]  G. Dillon,et al.  Maintenance of recombinant type A gamma-aminobutyric acid receptor function: role of protein tyrosine phosphorylation and calcineurin. , 1998, The Journal of pharmacology and experimental therapeutics.

[46]  P. Whiting.  The GABA-A receptor gene family: new targets for therapeutic intervention , 1999, Neurochemistry International.

[47]  R. Miledi,et al.  Phosphatase inhibitors remove the run-down of gamma-aminobutyric acid type A receptors in the human epileptic brain. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[48]  Hong Xue,et al.  Analysis of GABRB2 association with schizophrenia in German population with DNA sequencing and one-label extension method for SNP genotyping. , 2006, Clinical biochemistry.

[49]  R. Mckernan,et al.  Molecular and Functional Diversity of the Expanding GABA‐A Receptor Gene Family , 1999, Annals of the New York Academy of Sciences.

[50]  D. D. McKinley,et al.  Cloning, sequence analysis and expression of two forms of mRNA coding for the human beta 2 subunit of the GABAA receptor. , 1995, Brain research. Molecular brain research.

[51]  J. Felsenstein.  Evolutionary trees from DNA sequences: A maximum likelihood approach , 2005, Journal of Molecular Evolution.