Chung Yu-Chu Ella, Chen Shao-Chien, Chuang Li-Chung, Shih Wei-Liang, Chiu Yi-Hang, Lu Mong-Liang, Chen Hsi-Chung, Kuo Po-Hsiu
Department of Public Health & Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei 100, Taiwan.
Department of Psychology and Language Sciences, College of Brain Sciences, University College London, London WC1E 6BT, United Kingdom; Child Study Center, Yale School of Medicine, New Haven, CT, USA.
J Affect Disord. 2017 Dec 1;223:1-7. doi: 10.1016/j.jad.2017.07.024. Epub 2017 Jul 10.
Glutamic acid dehydrogenase 1 (GAD1) serves as the rate-limiting enzyme for synthesizing GABA, and is reported to be associated with several psychiatric disorders. The present study examined the effects of GAD1 genetic variants on bipolar disorder (BD) and its subtypes. Moreover, we investigated functional interactions between genetic variants and miRNAs via algorithm prediction and experimental validation.
A case-control study was conducted with 280 BD patients and 200 healthy controls. Eight tag SNPs in GAD1 were genotyped. For associated markers, we performed in silico prediction for their potential functions through SNP-miRNA interactions by establishing a scoring system to combine information from several miRNA predictive algorithms. We then tested allelic expression differences using Dual-Glo luciferase reporter assays for the selected SNP-miRNA pair. Lastly, we examined the associations of the GAD1 gene and BD in two additional independent datasets with a few thousand samples for replication.
Marker rs3749034 was associated with BD, in particular the BD-II subtype. According to our scoring system, several candidate miRNAs were predicted to interact with rs3749034, and hsa-miR-504 had the highest score. Findings from an in vitro experiment revealed a non-statistically significant trend for lower gene expression level with the A allele of rs3749034 compared with the G allele. The association between rs3749034 and BD was not replicated in either of the independent datasets. Instead, other rarer genetic variants in GAD1 showed suggestive signals (e.g. rs575441409, p-value = 3.8*10, D' = 1 with rs3749034) with BD in the Taiwanese dataset.
The present study considered common genetic variants only. In addition, we only used a 293T cell-line in conducting luciferase reporter assays, as no primary cell-lines from patient samples were available to differentiate the effects between BD subtypes.
Our results demonstrate a weak effect of the GAD1 gene on the risk of bipolar illness, and the associated marker might represent a proxy for real signals of rare variants.
谷氨酸脱氢酶1（GAD1）是合成γ-氨基丁酸（GABA）的限速酶，据报道与多种精神疾病有关。本研究考察了GAD1基因变异对双相情感障碍（BD）及其亚型的影响。此外，我们通过算法预测和实验验证研究了基因变异与微小RNA（miRNA）之间的功能相互作用。
对280例BD患者和200名健康对照进行病例对照研究。对GAD1中的8个标签单核苷酸多态性（SNP）进行基因分型。对于相关标记，我们通过建立一个评分系统来整合来自几种miRNA预测算法的信息，通过SNP-miRNA相互作用对其潜在功能进行计算机模拟预测。然后，我们使用双荧光素酶报告基因检测法对选定的SNP-miRNA对进行等位基因表达差异测试。最后，我们在另外两个包含数千个样本的独立数据集中检验GAD1基因与BD的关联以进行重复验证。
标记rs3749034与BD相关，尤其是BD-II亚型。根据我们的评分系统，预测有几种候选miRNA与rs3749034相互作用，其中hsa-miR-504得分最高。体外实验结果显示，与G等位基因相比，rs3749034的A等位基因的基因表达水平有降低的趋势，但无统计学意义。rs3749034与BD之间的关联在两个独立数据集中均未得到重复验证。相反，在台湾的数据集中，GAD1中的其他罕见基因变异显示出与BD的潜在关联信号（例如rs575441409，p值 = 3.8×10，与rs3749034的连锁不平衡系数D' = 1）。
本研究仅考虑了常见基因变异。此外，我们在进行荧光素酶报告基因检测时仅使用了293T细胞系，因为没有患者样本的原代细胞系可用于区分BD亚型之间的影响。
我们的结果表明GAD1基因对双相情感障碍风险的影响较弱，且相关标记可能代表罕见变异真实信号的替代指标。
