title: Targeted insertion of two Mthfr promoters in mice reveals temporal- and tissue-specific regulation.
abstract: 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.
authors.affiliation: Departments of Human Genetics and Pediatrics, McGill University and Montreal Children's Hospital Research Institute, Montreal, QC, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Pickell
authors.forename: Qing
authors.initials: Q
authors.lastname: Wu
authors.forename: Xiao-Ling
authors.initials: XL
authors.lastname: Wang
authors.forename: Daniel
authors.initials: D
authors.lastname: Leclerc
authors.forename: Hana
authors.initials: H
authors.lastname: Friedman
authors.forename: Alan C
authors.initials: AC
authors.lastname: Peterson
authors.forename: Rima
authors.initials: R
authors.lastname: Rozen
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000378:metabolism; D002490:Central Nervous System / Q000378:metabolism; D004622:Embryo, Mammalian / Q000378:metabolism*; D005260:Female; D005838:Genotype; D006712:Homocystinuria / Q000378:metabolism*; D008297:Male; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009128:Muscle Spasticity / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D010920:Placenta / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D011618:Psychotic Disorders / Q000378:metabolism; D013737:Testis / Q000378:metabolism
chemical_list: D042965:Methylenetetrahydrofolate Reductase (NADPH2)