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

描述（由申请人提供）：神经管缺陷（NTD）是常见的，昂贵的，致命的人类先天性异常，其病因在很大程度上仍然未知。NTD原因最有希望的线索之一是，在怀孕早期使用含叶酸维生素的妇女患NTD的风险要低得多。然而，叶酸有助于降低这些风险的潜在机制尚不清楚。最常见的假设是叶酸摄入量通过补偿个体遗传易感性来预防NTD，尽管通过关联研究明确识别遗传决定因素已被证明是难以捉摸的。我们提出的进一步定义神经管缺陷和叶酸预防治疗背后的分子遗传机制的方法植根于一项初步研究的结果，以确定损害功能的维生素依赖性酶的非同义取代，但可通过提高维生素浓度来增强。该试验表明，深度测序揭示了叶酸途径基因中大量的低频非同义变异（频率<=1%），迄今为止尚未被注意到。此外，使用基于S.在酿酒酵母中，我们已经证明了这些低频变体中的大约一半影响酶功能，并且已经鉴定了新的叶酸补救等位基因。我们假设叶酸代谢中的遗传易感性可能是NTD的病因，并且这些易感性可以由低频和常见变异以及这些变异之间可能的协同作用赋予。为了验证这一假设，我们将对来自250名NTD受影响婴儿和250名对照的19个叶酸代谢基因的编码区进行重新测序，我们也有关于母亲营养摄入的信息。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NTD的因果关系，了解叶酸补充剂的治疗作用，并确定额外的叶酸补充剂是否可以预防。我们汇集了一个独特的科学专业知识组合来执行这个研究计划。 相关性：这项提案应该揭示一种常见的出生缺陷形式，即神经管缺陷的原因。最终，这项研究可能会导致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.