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The Impact of Vitamin B12 Deficiency on Nuclear de novo Thymidylate Biosynthesis

维生素 B12 缺乏对核胸苷酸从头生物合成的影响

基本信息

批准号：
8783490
负责人：
Ashley Melissa Palmer
金额：
$ 3.92万
依托单位：
CORNELL UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2014
资助国家：
美国
起止时间：
2014-08-15 至 2016-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8783490
关键词：
Adult Affect Anabolism Anencephaly Animal Model Area Biological Markers Birth Cell Nucleus Cell model Colon Carcinoma Complex Congenital Abnormality Controlled Clinical Trials Country DNA DNA Repair DNA biosynthesis Deoxyuridine Development Diet Dietary Supplementation Dihydrofolate Reductase Embryo Embryonic Development Enzymes Epidemiology Ethnic Origin Etiology Folate Folic Acid Folic Acid Deficiency Future Genes Genome Genome Stability Genomic DNA Glycine Hydroxymethyltransferase Health Policy Homocysteine Homocystine Human Impairment Incidence Individual Intake Laboratories Life Cycle Stages Literature Liver Measures Metabolic Methionine Mitochondria Modeling Multienzyme Complexes Mus Neural Fold Neural Tube Defects Neuraxis Nuclear Nucleosides Nucleotide Biosynthesis Nutritional status Pathology Pathway interactions Phenotype Placebo Control Plasma Play Policies Policy Making Population Pregnancy Pregnancy Complications Prevalence Prevention Public Health Pyrimidine Pyrimidine Nucleosides Recommendation Recurrence Risk Risk Factors Role S phase Scaffolding Protein Serum Site Source Spinal Dysraphism Subgroup Supplementation Testing Tetrahydrofolates Thymidylate Synthase Tissues Uncertainty Uracil Uridine Vitamin B 12 Vitamin B 12 Deficiency Work clinical practice cofactor dietary supplements feeding fetal folic acid metabolism fortification improved insight mouse model offspring population based prenatal prevent public health relevance research study thymidylate

项目摘要

DESCRIPTION (provided by applicant): In these studies, we will determine the role of vitamin B12 in regulating nuclear de novo dTMP biosynthesis, maintaining genome stability, as well as elucidate the mechanisms underlying vitamin B12 in birth defects. Impairments nuclear in de novo dTMP biosynthesis underlie folate-associated pathologies in a gene by diet manner, as Shmt1-/+ mice fed a folate-deficient diet accumulate uracil in DNA and are sensitized to developing neural tube defects (NTDs) and colon cancer. Recently, SHMT was identified as a scaffolding protein required for proper assembly of the de novo dTMP biosynthesis complex at sites of DNA replication and repair. Vitamin B12 deficiency results in elevated intracellular 5-methylTHF and uracil accumulation in DNA, and has been suggested but not proved to cause NTDs. These proposed studies will determine the impact of a vitamin B12 deficiency on de novo dTMP biosynthesis and establish whether impairments in this pathway contribute to vitamin B12-associated NTDs. Furthermore, the findings from these studies will inform future clinical practice through identification of additional periconceptional measures to further prevent occurrence of prenatal folate - and vitamin B12-associated pathologies, and inform policy-making decisions in the development of population- based approaches to improve vitamin B12 status through mandated fortification. The two related and overlapping areas to be investigated are: Aim I. a) Determine if vitamin B12 deficiency impairs de novo thymidylate (dTMP) biosynthesis in the nucleus. These studies will determine the potential mechanisms by which vitamin B12 deficiency, as modeled by MTR inhibition leading to an irreversible accumulation of 5-methylTHF, impairs nuclear de novo dTMP biosynthesis via the: 1) disruption of the multi-enzyme complex for dTMP synthesis or 2) depletion of tetrahydrofolate cofactors required for nucleotide biosynthesis. b) Determine if pyrimidine nucleosides, dU and U, are differentially incorporated as either dUTP or dTTP in nuclear DNA. These studies will establish the origin(s) of uracil in nuclear DNA in a cell model of vitamin B12 deficiency, and reconcile the current uncertainty in the literature with respect to the nucleosides that are incorporated as dUTP. Aim II. Determine if vitamin B12 deficiency increases the incidence of NTDs in mouse models of impaired de novo dTMP biosynthesis. These studies will determine if maternal vitamin B12 deficiency increases NTD incidence in offspring through a gene by diet interaction using our mouse model of impaired de novo dTMP biosynthesis. Additionally, these studies will determine if vitamin B12 deficiency compromises genome integrity in maternal and fetal genomes.

描述（由申请人提供）：在这些研究中，我们将确定维生素B12在调节核从头dTMP生物合成、维持基因组稳定性中的作用，以及阐明维生素B12在出生缺陷中的潜在机制。从头dTMP生物合成中的核损伤以饮食方式在基因中构成叶酸相关病理学的基础，因为喂食叶酸缺乏饮食的Shmt 1-/+小鼠在DNA中积累尿嘧啶，并对发展神经管缺陷（NTD）和结肠癌敏感。最近，SHMT被鉴定为在DNA复制和修复位点正确组装从头dTMP生物合成复合物所需的支架蛋白。维生素B12缺乏导致细胞内5-甲基THF和尿嘧啶在DNA中的积累增加，并且已经被提出但未被证明引起NTD。这些拟议的研究将确定维生素B12缺乏对从头dTMP生物合成的影响，并确定该途径中的损伤是否有助于维生素B12相关的NTD。此外，这些研究的结果将通过确定额外的围产期措施为未来的临床实践提供信息，以进一步预防产前叶酸和维生素B12相关疾病的发生，并为制定基于人群的方法以通过强制强化改善维生素B12状况的决策提供信息。需要研究的两个相关和重叠的领域是：a）确定维生素B12缺乏是否会损害细胞核中胸苷酸（dTMP）的重新生物合成。这些研究将确定维生素B12缺乏（通过MTR抑制导致5-甲基THF的不可逆蓄积建模）通过以下方式损害核从头dTMP生物合成的潜在机制：1）破坏dTMP合成的多酶复合物或2）消耗核苷酸生物合成所需的四氢叶酸辅因子。B）确定嘧啶核苷dU和U是否以dUTP或dTTP的形式差异性地掺入核DNA中。这些研究将在维生素B12缺乏的细胞模型中建立细胞核DNA中尿嘧啶的来源，并调和文献中关于以dUTP形式掺入的核苷的当前不确定性。Aim II.确定维生素B12缺乏是否会增加从头dTMP生物合成受损小鼠模型中NTD的发生率。这些研究将确定母体维生素B12缺乏是否通过基因与饮食的相互作用增加后代的NTD发病率，使用我们的dTMP生物合成受损的小鼠模型。此外，这些研究将确定维生素B12缺乏是否会损害母体和胎儿基因组的基因组完整性。