Goyette P, Pai A, Milos R, Frosst P, Tran P, Chen Z, Chan M, Rozen R
Department of Human Genetics, McGill University Health Center, Montreal, Quebec, Canada H3H 1P3.
Mamm Genome. 1998 Aug;9(8):652-6. doi: 10.1007/s003359900838.
Methylenetetrahydrofolate reductase (MTHFR) catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a co-substrate for homocysteine remethylation to methionine. A human cDNA for MTHFR, 2.2 kb in length, has been expressed and shown to result in a catalytically active enzyme of approximately 70 kDa. Fifteen mutations have been identified in the MTHFR gene: 14 rare mutations associated with severe enzymatic deficiency and 1 common variant associated with a milder deficiency. The common polymorphism has been implicated in three multifactorial diseases: occlusive vascular disease, neural tube defects, and colon cancer. The human gene has been mapped to chromosomal region 1p36.3 while the mouse gene has been localized to distal Chromosome (Chr) 4. Here we report the isolation and characterization of the human and mouse genes for MTHFR. A human genomic clone (17 kb) was found to contain the entire cDNA sequence of 2.2 kb; there were 11 exons ranging in size from 102 bp to 432 bp. Intron sizes ranged from 250 bp to 1.5 kb with one exception of 4.2 kb. The mouse genomic clones (19 kb) start 7 kb 5' exon 1 and extend to the end of the coding sequence. The mouse amino acid sequence is approximately 90% identical to the corresponding human sequence. The exon sizes, locations of intronic boundaries, and intron sizes are also quite similar between the two species. The availability of human genomic clones has been useful in designing primers for exon amplification and mutation detection. The mouse genomic clones will be helpful in designing constructs for gene targeting and generation of mouse models for MTHFR deficiency.
亚甲基四氢叶酸还原酶（MTHFR）催化5,10 - 亚甲基四氢叶酸转化为5 - 甲基四氢叶酸，后者是同型半胱氨酸再甲基化生成甲硫氨酸的辅助底物。一个长度为2.2 kb的人类MTHFR cDNA已被表达，并显示产生一种催化活性约为70 kDa的酶。在MTHFR基因中已鉴定出15种突变：14种罕见突变与严重酶缺乏相关，1种常见变异与较轻的缺乏相关。这种常见的多态性与三种多因素疾病有关：闭塞性血管疾病、神经管缺陷和结肠癌。人类基因已定位到染色体区域1p36.3，而小鼠基因已定位到远端染色体（Chr）4。在此，我们报告人类和小鼠MTHFR基因的分离与鉴定。发现一个人类基因组克隆（17 kb）包含2.2 kb的完整cDNA序列；有11个外显子，大小从102 bp到432 bp不等。内含子大小从250 bp到1.5 kb，有一个例外为4.2 kb。小鼠基因组克隆（19 kb）从外显子1上游7 kb处开始，延伸至编码序列末端。小鼠氨基酸序列与相应的人类序列约90%相同。两种物种之间的外显子大小、内含子边界位置和内含子大小也非常相似。人类基因组克隆的可用性有助于设计用于外显子扩增和突变检测的引物。小鼠基因组克隆将有助于设计用于基因靶向的构建体以及生成MTHFR缺乏的小鼠模型。
