Methyl Donor Pathway Genetics in the Development of Orofacial Clefts

描述（由申请人提供）：该申请涉及广泛的挑战领域（08）基因组学和特定挑战主题，08- de -104：颅面、牙科和口腔疾病现有队列的基因分型。口腔面裂，特别是唇裂和腭裂，是一种常见的、昂贵的先天性异常，其病因在很大程度上仍然未知。对于导致口面部裂的原因，最有希望的线索之一是，在怀孕早期服用含有叶酸的维生素的女性患唇裂的风险要低得多。虽然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裂口。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。基于我们的观察（Proc Natl Acad Sci, 2008, 105:8055和一项正在进行的研究），我们提出了进一步定义口面裂分子遗传学机制的方法，深度测序揭示了大量低频、非同义的叶酸通路基因变异（频率< 1%），这些变异迄今为止尚未被注意到。此外，这些低频变异的很大一部分影响酶的功能，但在营养上是补救的。我们假设甲基供体代谢的遗传易感性可能是唇裂的病因，这些易感性可以由低频和常见变异以及它们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名唇腭裂婴儿和250名对照人群的23个甲基供体代谢基因的编码区域进行测序，我们还获得了母亲营养摄入和其他流行病学参数的数据。我们将基于定量互补分析测试所有酵母菌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。我们希望能更好地确定唇腭裂的因果关系，了解营养补充的治疗作用，并确定额外补充是否可以预防。这项研究计划利用了已经存在的合作，为其执行结合了独特的专业知识组合。这一建议应该揭示一些常见形式的出生缺陷被称为唇裂和/或腭裂的原因。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): 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.