Cardiac Channel Mutations in Sudden Infant Death Syndrome (SIDS)

描述（由申请人提供）：美国每年有超过2000例死亡，婴儿猝死综合症（SIDS）仍然是1个月至1岁婴儿死亡的主要原因。对小岛屿发展中国家的根本原因仍然知之甚少。根据小岛屿发展中国家的三重风险假说，目前对小岛屿发展中国家的病因学研究主要集中在中枢/自主神经系统、先天代谢错误和遗传性心脏通道病变作为“易感婴儿”的可能底物。我们之前对SIDS的心脏通道突变（HD42569）的研究已经确定，大约10%的SIDS的致病机制可能源于最常见的心脏通道病变，即长QT间期综合征（LOTS）。最近，我们的猝死基因组学实验室发现并功能表征了两个新的lqts易感基因：CAV3 （LQT9）和SCN4B (LQT10)，涉及心脏钠通道大分子复合物的通道相互作用蛋白（ChlPs）突变，产生lqts表型。最近，对编码钙释放通道有限区域的突变扫描显示，大约2%的白人婴儿中存在致病性突变。功能研究表明心律失常发生机制与1型儿茶酚胺能多态性室性心动过速（CPVT1）一致。此外，在自主神经系统（ANS）的各种信号通路中已经发现了可能使婴儿在危急情况下容易猝死的多态性。然而，这些来自小岛屿发展中国家小群体的初步观察结果尚未得到证实。鉴于QT间期延长与ANS失调之间的关系，本提案将寻求确认小岛屿发展中国家与ANS关键组分遗传变异之间的联系。这些发现为本更新中概述的实验提供了框架，并支持了申请人的假设，即额外的5 - 10%的小岛屿发展中国家可能源于包含钠通道大分子复合物和钙释放通道大分子复合物的chlp的突变。如果正确，这一建议将提供分子和功能证据，表明心脏通道孔隙形成亚基或chlp的突变可能是20% SIDS（估计每年400例）的原因。此外，它将探索编码ANS相关的血清素能信号通路关键蛋白的基因变异在该疾病发病机制中的作用。具体来说，利用聚合酶链反应、变性高效液相色谱和DNA测序，对世界上最大的SIDS病例之一（N = 600）进行测序，申请人拟i)对编码钠通道和钙释放通道大分子复合物内关键chlp的12个基因进行全面的开放阅读框/剪接位点突变分析，作为小岛屿发展中国家的候选基因；ii)进行涉及ANS多态性/遗传变异的确认性病例对照关联研究，以及对编码ANS相关血清素能信号关键决定因素的VMAT2基因进行新的候选基因突变分析。

DESCRIPTION (provided by applicant): With over 2000 deaths each year in the United States, Sudden Infant Death Syndrome (SIDS) remains the leading cause of death in infants 1 month to 1 year of age. The fundamental causes of SIDS remain poorly understood. Current etiologic studies for SIDS have focused on the central/autonomic nervous system, inborn errors of metabolism, and genetic cardiac channelopathies as possible substrates for the "vulnerable infant" in accordance with the SIDS triple risk hypothesis. Our prior work investigating Cardiac Channel Mutations in SIDS (HD42569) has established that the pathogenic mechanism for approximately 10% of SIDS may stem from the most common cardiac channelopathy known as long QT syndrome (LOTS). Recently, our Sudden Death Genomics Laboratory has discovered and functionally characterized two novel LQTS-susceptibility genes: CAV3 (LQT9) and SCN4B (LQT10) involving mutations in Channel Interacting Proteins (ChlPs) of the cardiac sodium channel macromolecular complex yielding LQTS-phenotypes. Most recently, mutation scanning of a limited region of the encoded calcium release channel revealed pathogenic mutations in approximately 2% of white infants. Functional studies indicate an arrhythmogenic mechanism consistent with type 1 catecholaminergic polymorphic ventricular tachycardia (CPVT1). In addition, polymorphisms that might predispose infants to sudden death in critical situations have been identified in various signaling pathways of the autonomic nervous system (ANS). However, these initial observations, derived from small cohorts of SIDS, have not been confirmed. Given the relationship between prolongation of the QT interval and dysregulation of the ANS, this proposal will seek to confirm the associations between SIDS and genetic variation in critical components of the ANS. These discoveries frame the experiments outlined in this renewal and support the applicant's hypothesis that an additional 5 - 10% of SIDS may stem from mutations in the ChlPs that comprise the sodium channel macromolecular complex and the calcium release channel macromolecular complex. If correct, this proposal will provide molecular and functional evidence implicating mutations in either the cardiac channel pore-forming subunits or ChlPs as the probable cause for 20% of SIDS (an estimated 400 cases each year). Furthermore, it will explore the involvement of genetic variations in genes encoding key proteins of the ANS- related serotonergic signaling pathways in the pathogenesis of this disease. Specifically, using polymerase chain reaction, denaturing high performance liquid chromatography, and DNA sequencing on one of the world's largest DNA cohorts of SIDS cases (N = 600), the applicant proposes to i) conduct comprehensive open reading frame/splice site mutational analysis of 12 genes that encode key ChlPs within the sodium channel and calcium release channel macromolecular complexes as candidate genes for SIDS and ii) conduct confirmatory case-control association studies involving polymorphisms/genetic variations in the ANS as well as novel candidate gene mutation analysis of VMAT2, a gene that encodes a key determinant of ANS-related serotonergic signaling.