Methyl Donor Pathway Genetics in the Development of Orofacial Clefts

描述(由申请人提供)：本申请涉及广泛的挑战领域(08)基因组学和特定的挑战主题，08-DE-104：颅面、牙齿和口腔条件下现有队列的基因分型。口腔面裂，特别是唇裂和腭裂，是常见且代价高昂的先天性畸形，其病因仍未完全清楚。关于口腔裂隙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裂隙妊娠的风险要低得多。尽管叶酸有助于降低风险的潜在机制尚不清楚，但有证据表明，叶酸摄入通过补偿甲基供体代谢的易感性来预防唇裂。然而，通过关联研究明确识别这些途径中的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口裂背后的分子遗传学机制的方法是基于我们的观察(Proc Natl Acad Sci，2008,105：8055和一项正在进行的研究)，深度测序揭示了大量低频的、非同义的叶酸途径基因变异(频率和1%)，到目前为止还没有被注意到。此外，这些低频变异中有相当一部分会影响酶的功能，但在营养上是补救的。我们假设甲基供体代谢中的遗传易感性可以是裂隙的病因，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所赋予。为了验证这一假设，我们将对来自250名受唇裂影响的婴儿和250名对照婴儿的23个甲基供体代谢基因的编码区进行排序，我们还拥有关于母亲营养摄入量和其他流行病学参数的数据。我们将基于定量互补分析在酿酒酵母中测试所有酶变体的功能影响和营养修复，并将等位基因分布和功能研究与临床表型和营养数据相关联。我们希望更好地确定口腔裂隙的因果关系，了解营养补充的补救作用，并确定额外的补充是否可以预防。这项研究计划充分利用了现有的合作，将独特的专业知识结合在一起进行执行。这项提议应该揭示一种常见的出生缺陷--唇裂和/或腭裂--的一些原因。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): This application addresses broad Challenge Area (08) Genomics and specific Challenge Topic, 08-DE-104: Genotyping of Existing Cohorts in Craniofacial, Dental and Oral Conditions. Orofacial clefts, specifically cleft lip and cleft palate, are common and costly congenital anomalies whose etiologies remain largely unknown. One of the most promising clues to the causes of orofacial clefts is that women who use vitamins containing folic acid in early pregnancy are at much lower risk for cleft-affected pregnancies. Although the underlying mechanisms by which folic acid contributes to these reduced risks are unknown, evidence suggests that folate intake prevents clefts by compensating for susceptibilities in methyl donor metabolism. However, clear identification of genetic determinants in these pathways through association studies has proven elusive. The approach we propose to further define the molecular genetics mechanisms behind orofacial clefts is based on our observations (Proc Natl Acad Sci, 2008, 105:8055 and an ongoing study) 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, a significant fraction of these low-frequency variants affect enzyme function, yet are nutritionally remedial. We hypothesize that genetic susceptibilities in methyl donor metabolism can be etiological for clefts 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 sequence the coding regions in 23 methyl donor metabolic genes from a population of 250 cleft-affected infants and 250 controls, for which we also have data on maternal nutritional intake and other epidemiological parameters. We will test all enzyme variants for functional impact and nutritional remediation based on quantitative complementation assays in the yeast S. cerevisiae, and correlate allele distribution and functional studies with clinical phenotype and nutritional data. We hope to better define the causality of orofacial clefts, understand the remedial role of nutritional supplementation, and determine whether additional supplementation may be preventative. This research plan capitalizes on an already existing collaboration that unites a unique combination of expertise for its execution. This proposal should reveal some of the causes of a common form of birth defect known as cleft lip and/or cleft palate. Ultimately, this research may lead to better diagnostic and preventive strategies.