Zhao C, Xu Z, Chen J, Yu Z, Tong K-L, Lo W-S, Pun F W, Ng S-K, Tsang S-Y, Xue H
Bioengineering Graduate Program, Hong Kong University of Science & Technology, Clear Water Bay, Hong Kong, China.
Mol Psychiatry. 2006 Dec;11(12):1092-105. doi: 10.1038/sj.mp.4001899. Epub 2006 Sep 19.
Single nucleotide polymorphisms in type A gamma-aminobutyric acid (GABA(A)) receptor beta2 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 beta(2L), 13.4% in the short isoform beta(2S) and 15.8% in the sum of the two isoforms beta(2T) 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 beta(2L), beta(2S) and beta(2T), and the heterozygous of rs2546620 (A/G) and homozygous-minor of rs1876071 (C/C) and rs1876072 (G/G) were correlated with reduced expression of beta(2T). Significant correlations of expression levels with different alleles and haplotypes were also indicated by quantitative trait analysis. Recombinant GABA(A) receptors expressed in HEK293 human cells containing beta(2L) underwent a steeper current rundown upon repetitive GABA activation than receptors containing beta(2S). The results thus revealed genotype-dependent expression of the alternatively spliced isoforms of GABA(A) receptor beta2 subunit, giving rise to electrophysiological consequences that could play an important role in the pathogenesis mechanism of schizophrenia.
在中国、德国、日本和葡萄牙人群中，已发现A型γ-氨基丁酸（GABA(A)）受体β2亚基基因（GABRB2）中的单核苷酸多态性与精神分裂症相关。为探究这些DNA序列多态性的潜在功能后果，本研究检测了GABRB2两种可变剪接产物的表达及电生理特性，并进行了基因分型疾病关联分析。对31名美国精神分裂症患者和31名对照人群进行实时定量聚合酶链反应，结果显示，在死后的精神分裂症患者大脑中，长亚型β(2L)的表达降低了21.7%，短亚型β(2S)降低了13.4%，两种亚型之和β(2T)降低了15.8%。此外，两种独立的mRNA定量方法显示，在精神分裂症中，长亚型与短亚型的相对表达显著降低，提示发生了剪接改变。在男性精神分裂症患者中，rs1876071（T/C）和rs1876072（A/G）的杂合基因型与β(2L)、β(2S)和β(2T)的表达降低相关，rs2546620（A/G）的杂合子以及rs1876071（C/C）和rs1876072（G/G）的纯合次要等位基因与β(2T)的表达降低相关。定量性状分析也表明表达水平与不同等位基因和单倍型存在显著相关性。在HEK293人细胞中表达的含β(2L)的重组GABA(A)受体在重复GABA激活后比含β(2S)的受体经历更陡的电流衰减。因此，结果揭示了GABA(A)受体β2亚基可变剪接异构体的基因型依赖性表达，产生了可能在精神分裂症发病机制中起重要作用的电生理后果。
