Impact of Genetic Variation on Folate Metabolsim: Etiology of Neural Tube Defects

描述(申请人提供)：神经管缺陷(NTD)是常见的，昂贵的，致命的人类先天畸形，其病因仍然很大程度上未知。关于NTDS病因的最有希望的线索之一是，在怀孕早期使用含有叶酸的维生素的妇女患NTD的风险要低得多。然而，叶酸有助于降低风险的潜在机制尚不清楚。最普遍的假说是，叶酸摄入通过补偿个体的遗传易感性来预防NTDS，尽管通过关联研究明确确定遗传决定因素已被证明是难以捉摸的。我们提出的进一步确定神经管缺陷和叶酸预防治疗背后的分子遗传学机制的方法植根于一项初步研究的结果，该研究旨在确定维生素依赖酶中的非同义替代，这些酶损害功能，但可以通过提高维生素浓度来增强。这位飞行员已经证明，深度测序揭示了大量叶酸途径基因(频率=1%)的低频率、非同义变异，到目前为止还没有被注意到。此外，在酿酒酵母中，利用一个基于互补的强大的分析平台，我们已经证明了大约一半的这些低频变异影响酶功能，并发现了新的叶酸补救等位基因。我们假设叶酸代谢的遗传易感性可能是NTDS的病因，并且这些易感性可以由低频率和常见的变异以及它们之间可能的协同作用而被赋予。为了验证这一假设，我们将对来自250名受NTD影响的婴儿和250名对照婴儿的19个叶酸代谢基因的编码区进行重新排序，我们也有关于母亲营养摄入量的信息。我们将测试所有酶变体的功能影响和叶酸修复，并将功能研究与临床表型和营养数据相关联。我们希望更好地定义NTDS的因果关系，了解叶酸补充的治疗作用，并确定额外的叶酸补充是否可能具有预防作用。我们集合了一组独特的科学专业知识来执行这项研究计划。 相关性：这项提议应该揭示一种常见形式的出生缺陷，即神经管缺陷的原因。最终，这项研究可能会带来更好的诊断和预防策略。

DESCRIPTION (provided by applicant): Neural tube defects (NTDs) are common, costly, and deadly human congenital anomalies whose etiologies remain largely unknown. One of the most promising clues to the causes of NTDs is that women who use vitamins containing folic acid in early pregnancy are at much lower risk for NTD-affected pregnancies. However, the underlying mechanisms by which folic acid contributes to these reduced risks are unknown. The most commonly held hypothesis is that folate intake prevents NTDs by compensating for individual genetic susceptibilities, although clear identification of genetic determinants through association studies has proven elusive. The approach we propose to further define the molecular genetic mechanisms behind neural tube defects and folate-prevention therapy is rooted in the results of a pilot study to identify nonsynonymous substitutions in vitamin-dependent enzymes that impair function, yet are augmentable by elevated vitamin concentration. This pilot has demonstrated that deep sequencing reveals a substantial amount of low frequency, nonsynonymous variation in folate pathway genes (frequencies <=1%) that has gone unnoticed thus far. Furthermore, using a robust assay platform based on complementation in S. cerevisiae, we have demonstrated that approximately one-half of these low frequency variants affect enzyme function and have identified novel folate-remedial alleles. We hypothesize that genetic susceptibilities in folate metabolism can be etiological for NTDs and that these susceptibilities can be conferred by both low-frequency and common variants and by the possible synergy between these. To test this hypothesis, we will resequence the coding regions in 19 folate metabolic genes from a population of 250 NTD-affected infants and 250 controls, for which we also have information on maternal nutritional intake. We will test all enzyme variants for functional impact and folate remediation, and correlate functional studies with clinical phenotype and nutritional data. We hope to better define the causality of NTDs, understand the remedial role of folate supplementation, and determine whether additional folate supplementation may be preventative. We have assembled a unique combination of scientific expertise to execute this research plan. Relevance: This proposal should reveal the causes of a common form of birth defect known as neural tube defects. Ultimately, this research may lead to better diagnostic and preventive strategies.