The State Key Laboratory of Genetic Engineering and MOE Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, 220 Handan Road, Shanghai 200433, China.
Eur Heart J. 2014 Mar;35(11):733-42. doi: 10.1093/eurheartj/eht221. Epub 2013 Jun 24.
Elevated homocysteine levels are known to be a risk factor for congenital heart disease (CHD), but the mechanism underlying this effect is unknown. During early embryonic development, homocysteine removal is dictated exclusively by the MTR activity. To examine the role of MTR in CHD risk, we identified genetic variants in MTR and investigated the mechanisms that affect its expression levels and that increase the risk of CHD in Chinese populations.
The association between regulatory variants of the MTR gene and CHD was examined in three independent case-control studies in a total of 2340 patients with CHD and 2270 controls. The functional consequences of these variants were demonstrated using dual-luciferase assays, real-time polymerase chain reaction (PCR), electrophoretic mobility shift assays, surface plasma resonance, chromatin immunoprecipitation, and bisulfite sequencing, as well as by a group of predicted microRNAs using a gene reporter system. Two regulatory variants of MTR, -186T>G and +905G>A, were associated with an increased risk of CHD in both the separate and combined case-control studies (-186GG P = 1.32 × 10(-9); +905AA P = 6.35 × 10(-14)). Compared with the major allele, the -186G allele exhibited significantly lower promoter activity, decreased hnRNA and mRNA levels, reduced transcription factor binding affinity, and a more highly methylated promoter. The +905A allele exhibited a statistically stronger binding affinity to functional microRNAs that down regulate MTR expression at the translational level. Both of the minor alleles were correlated with elevated plasma homocysteine concentrations, indicating a genetic component for hyperhomocysteinaemia.
Regulatory variants of the MTR gene increase CHD risk by reducing MTR expression and inducing the homocysteine accumulation and elevation.
已知高同型半胱氨酸水平是先天性心脏病 (CHD) 的一个风险因素，但这种影响的机制尚不清楚。在胚胎早期发育过程中，同型半胱氨酸的清除完全由 MTR 活性决定。为了研究 MTR 在 CHD 风险中的作用，我们鉴定了 MTR 的遗传变异，并研究了影响其表达水平并增加中国人群 CHD 风险的机制。
在总共 2340 例 CHD 患者和 2270 例对照的 3 项独立病例对照研究中，研究了 MTR 基因调节变异与 CHD 的关联。使用双荧光素酶测定、实时聚合酶链反应 (PCR)、电泳迁移率变动分析、表面等离子体共振、染色质免疫沉淀和亚硫酸氢盐测序，以及使用基因报告系统的一组预测的 microRNAs，证明了这些变异的功能后果。MTR 的两个调节变异，-186T>G 和 +905G>A，在单独和联合病例对照研究中均与 CHD 风险增加相关（-186GG P = 1.32×10(-9)；+905AA P = 6.35×10(-14)）。与主要等位基因相比，-186G 等位基因表现出明显较低的启动子活性、减少的 hnRNA 和 mRNA 水平、降低的转录因子结合亲和力和更高甲基化的启动子。+905A 等位基因与功能 microRNAs 的结合亲和力更强，在翻译水平下调 MTR 表达。两个次要等位基因均与血浆同型半胱氨酸浓度升高相关，表明高同型半胱氨酸血症具有遗传成分。
MTR 基因的调节变异通过降低 MTR 表达并诱导同型半胱氨酸积累和升高来增加 CHD 风险。
