Methylenetetrahydrofolate reductase (MTHFR) synthesizes 5-methyltetrahydrofolate, a methyl donor for conversion of homocysteine to methionine. A common thermolabile variant causes mild MTHFR deficiency, induces mild hyperhomocysteinemia when plasma folate levels are low and increases risk for neural tube defects (NTD) and pregnancy loss. To increase our understanding of Mthfr regulation, the 5' and 3' regions of the mouse cDNA and gene were characterized. These studies revealed two major promoters, an internal coding exon in the 5'UTR, alternative transcriptional and translational start sites and alternative splicing and polyadenylation. These data suggest that Mthfr regulation is likely to be complex. To investigate the role of Mthfr in NTD, several approaches were taken. First, folate and MTHFR co-factor, flavin adenine dinucleotide, were shown to stabilize normal and thermolabile MTHFR during heat inactivation, suggesting that folate might prevent hyperhomocysteinemia in individuals with thermolabile enzyme through protein stabilization. Next, in situ hybridization of neurulating mouse embryos showed that Mthfr is expressed in the forebrain, hindbrain, branchial arches, blood vessels, gut, and importantly, in the ventral part of the neural tube. Mthfr+/- mice were then used as a model of mild deficiency to address the effects of maternal and embryonic Mthfr deficiency on development. When combined with inadequate dietary folate, Mthfr +/- pregnant females showed a two-fold higher rate of pregnancy loss than Mthfr+/+ pregnant females. As well, a percentage of day 10.5 embryos from only the Mthfr+/- pregnant females were underdeveloped by 2 days. These effects were not apparent when dietary folate was sufficient, consistent with a genetic-nutritional interactive effect. Finally, folate metabolism was investigated in an NTD model, the curly-tail (ct) mouse, since the ct defect and Mthfr were mapped in close proximity. However, Mthfr sequence in ct mice was simila
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.38426 |
| Date | January 2002 |
| Creators | Tran, Pamela. |
| Contributors | Rozen, R. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001872794, proquestno: NQ78787, Theses scanned by UMI/ProQuest. |
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