Abstract
Methylenetetrahydrofolate reductase (MTHFR) reduces 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, the major carbon donor in the remethylation of homocysteine to methionine. Mild MTHFR deficiency, due to a common variant at nucleotide 677, has been reported to influence risk for several disorders including cardiovascular disease, neural tube defects, pregnancy complications and cancer. In recent work, we characterized the complete cDNA and gene sequences in the human and mouse genes, which had previously been mapped to chromosomes 1 and 4, respectively. During the course of this work, we observed that PCR primers in exons 1 and 2 of Mthfr generated amplicons of the expected size for the normal Mthfr transcript, using both reverse-transcribed RNA and genomic DNA as templates. These findings alluded to the existence of a pseudogene in the murine genome. Here, we report the characterization of this pseudogene. The absence of intron 1, the partial retention of intron 2, the location of this gene on chromosome 5, and the presence of sequences unrelated to Mthfr at the 5′ and 3′ ends of the 1259 bp fragment are features that are indicative of a partially-processed pseudogene, that we have designated Mthfr-ps. A Mthfr-ps transcript was not detectable by sensitive RT-PCR using assays designed to simultaneously detect the authentic Mthfr transcript. The structure of this paralogous gene and the identification of a repeat sequence at the 3′ end of this pseudogene suggest that it arose by retrotransposition of a mis-spliced Mthfr transcript. Investigations of the Mthfr gene should take into account the presence of the non-functional Mthfr-ps to avoid misinterpretation of results.
References
Frosst P, Blom HJ, Milos R, Goyette P, Sheppard CA, Matthews RG, Boers GJ, Den Heijer M, Kluijtmans LA, Van Den Heuvel LP, Rozen R: A candidate genetic risk factor for vascular disease: A common mutation in methylenetetrahydrofolate reductase. Nature Genet 10: 111-113, 1995
Boushey CJ, Beresford SA, Omenn GS, Motulsky AG: A quantitative assessment of plasma homocysteine as a risk factor for vascular disease. Probable benefits of increasing folic acid intakes. J Am Med Assoc 274: 1049-1057, 1995
Schwahn B, Rozen R: Polymorphisms in the methylenetetrahydrofolate reductase gene: Clinical consequences. Am J Pharmacogenomics 1: 189-201, 2001
Jacques PF, Bostom AG, Williams RR, Curtis Ellison R, Eckfeldt JH, Rosenberg IH, Selbhub J, Rozen R: Relation between folate status, a common mutation in methylenetetrahydrofolate reductase, and plasma homocysteine concentrations. Circulation 93: 7-9, 1996
Botto LD, Yang Q: 5,10-methylenetetrahydrofolate reductase gene variants and congenital anomalies: A HuGE review. Am J Epidemiol 151: 862-877, 2000
Kupferminc MJ, Eldor A, Steinman N, Many A, Bar-Am A, Jaffa A, Fait G, Lessing JB: Increased frequency of genetic thrombophilia in women with complications of pregnancy. N Engl J Med 340: 9-13, 1999
Mills JL, Kirke PN, Molloy AM, Burke H, Conley MR, Lee YJ, Mayne PD, Weir DG, Scott JM: Methylenetetrahydrofolate reductase thermolabile variant and oral clefts. Am J Med Genet 86: 71-74, 1999
James SJ, Pogribna M, Pogribny IP, Melnyk S, Hine RJ, Gibson JB, Yi P, Tafoya DL, Swenson DH, Wilson VL, Gaylor DW: Abnormal folate metabolism and mutation in the methylenetetrahydrofolate reductase gene may be maternal risk factors for Down syndrome. Am J Clin Nutr 70: 495-501, 1999
Wenstrom KD, Johanning GL, Johnston KE, DuBard M: Association of the C677T methylenetetrahydrofolate reductase mutation and elevated homocysteine levels with congenital cardiac malformations. Am J Obstet Gynecol 184: 806-812, 2001
Ma J, Stampfer MJ, Giovannucci E, Artigas C, Hunter DJ, Fuchs C, Willet WC, Selhub J, Hennekens CH, Rozen R: Methylene-tetrahydrofolate reductase polymorphism, dietary interactions, and risk of colorectal cancer. Cancer Res 57: 1098-1102, 1997
Skibola CF, Smith MT, Kane E, Roman E, Rollinson S, Cartwright RA, Morgan G: Polymorphisms in the methylenetetrahydrofolate reductase gene are associated with susceptibility to acute leukemia in adults. Proc Natl Acad Sci USA 96: 12810-12815, 1999
Wiemels JL, Smith RN, Taylor GM, Eden OB, Alexander FE, Greaves MF: Methylenetetrahydrofolate reductase (MTHFR) polymorphisms and risk of molecularly defined subtypes of childhood acute leukemia. Proc Natl Acad Sci USA 98: 4004-4009, 2001
Goyette P, Sumner JS, Milos R, Duncan AMV, Rosenblatt DS, Matthews RG, Rozen R: Human methylenetetrahydrofolate reductase: Isolation of cDNA, mapping, and mutation identification. Nature Genet 7: 195-200, 1994
Frosst P, Zhang ZX, Pai A, Rozen R: The methylenetetrahydrofolate reductase (Mthfr) gene maps to distal mouse Chromosome 4. Mamm Genome 7: 864-865, 1996
Goyette P, Pai A, Milos R, Frosst P, Tran P, Chen Z, Chan M, Rozen R: Gene structure of human and mouse methylenetetrahydrofolate reductase (MTHFR). Mamm Genome 9: 652-656, 1998
Daubner SC, Matthews RG: Purification and properties of methylenetetrahydrofolate reductase from pig liver. J Biol Chem 257: 140-145, 1982
Tran P, Leclerc D, Chan M, Pai A, Goyette P, Hiou-Tim F, Wu Q, Milos R, Artigas C, Rozen R: Multiple transcription start sites and alternative splicing in the methylenetetrahydrofolate reductase gene result in two active enzyme isoforms. Mammalian Genome 13: 483-492, 2002
Leclerc D, Wilson A, Dumas R, Gafuik C, Song D, Watkins D, Heng HH, Rommens JM, Scherer SW, Rosenblatt DS, Gravel RA: Cloning and mapping of a cDNA for methionine synthase reductase, a flavoprotein defective in patients with homocystinuria. Proc Natl Acad Sci USA 95: 3059-3064, 1998
Mighell AJ, Smith NR, Robinson PA, Markham AF: Vertebrate pseudogenes. FEBS Letters 468: 109-114, 2000
Chen Z, Karaplis AC, Ackerman SL, Pogribny IP, Melnyk S, Lussier-Cacan S, Chen MF, Pai A, John SWM, Smith RS, Bottiglieri T, Bagley P, Selhub J, Rudnicki MA, James SJ, Rozen R: Mice deficient in methylenetetrahydrofolate reductase exhibit hyperhomocysteinemia and decreased methylation capacity, with neuropathology and aortic lipid deposition. Hum Mol Genet 10: 433-443, 2001
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Leclerc, D., Darwich-Codore, H. & Rozen, R. Characterization of a pseudogene for murine methylenetetrahydrofolate reductase. Mol Cell Biochem 252, 391–395 (2003). https://doi.org/10.1023/A:1025540304067
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DOI: https://doi.org/10.1023/A:1025540304067