Departments of Human Genetics and Pediatrics, McGill University and Montreal Children's Hospital Research Institute, Montreal, QC, Canada.
Mamm Genome. 2011 Dec;22(11-12):635-47. doi: 10.1007/s00335-011-9351-5. Epub 2011 Jul 19.
Methylenetetrahydrofolate reductase (MTHFR), a key enzyme in folate metabolism, synthesizes 5-methyltetrahydrofolate, the main circulatory form of folate which is required for maintaining nontoxic levels of homocysteine and providing one-carbon units for methylation. A common 677C → T variant in MTHFR confers mild MTHFR deficiency and has been associated with a number of human disorders, including neural tube defects and vascular disease. Two promoters of Mthfr, designated as upstream and downstream promoters, are located upstream of a transcription start site cluster and have previously demonstrated cell-specific activities. In this study we used a unique approach for targeted, single-copy transgene insertion to generate transgenic mice carrying a Mthfr upstream or Mthfr downstream promoter-reporter construct located 5' to the endogenous Hprt (hypoxanthine-guanine phosphoribosyltransferase) locus. The Mthfr downstream promoter demonstrated activity in the neural tube, neural crest cells, dorsal root ganglia, heart, and endothelial cells of blood vessels in 10.5-days post coitum embryos and placentas. Upstream promoter activity was absent at this developmental stage. Postnatally, both promoters demonstrated activity in the brain stem, hippocampus, and thalamus of 1-week-old brain that became stronger in the adult. The Mthfr upstream promoter also showed activity in the cerebellum and cerebral cortex. Both promoters were active in male reproductive tissues, including 1-week-old epididymides, and there was upstream promoter-specific activity in the adult testis. Our investigation of Mthfr regulation in an in vivo mouse model revealed temporal- and tissue-specific regulation that supports important roles for MTHFR in the developing embryo, and in postnatal brain and male reproductive tissues.
亚甲基四氢叶酸还原酶（MTHFR）是叶酸代谢中的关键酶，它合成 5-甲基四氢叶酸，这是叶酸的主要循环形式，对于维持同型半胱氨酸的无毒水平和为甲基化提供一碳单位是必需的。MTHFR 中的一个常见 677C→T 变体赋予轻度 MTHFR 缺乏，并与许多人类疾病有关，包括神经管缺陷和血管疾病。Mthfr 有两个启动子，称为上游启动子和下游启动子，位于转录起始位点簇的上游，并且先前已经表现出细胞特异性活性。在这项研究中，我们使用了一种独特的方法，即靶向、单拷贝转基因插入，以产生携带 Mthfr 上游或 Mthfr 下游启动子-报告基因构建体的转基因小鼠，该构建体位于内源性 Hprt（次黄嘌呤-鸟嘌呤磷酸核糖基转移酶）基因座的 5'端。在 10.5 天龄合子胚胎和胎盘的神经管、神经嵴细胞、背根神经节、心脏和血管内皮细胞中，Mthfr 下游启动子具有活性。在这个发育阶段，上游启动子没有活性。出生后，两个启动子在 1 周龄大脑的脑干、海马体和丘脑都有活性，在成年时变得更强。Mthfr 上游启动子也在小脑和大脑皮层中有活性。两个启动子在雄性生殖组织中都有活性，包括 1 周龄的附睾，并且在成年睾丸中有上游启动子特异性活性。我们在体内小鼠模型中对 Mthfr 调控的研究揭示了时空和组织特异性调控，支持 MTHFR 在发育中的胚胎以及出生后大脑和雄性生殖组织中的重要作用。
