Next Generation Rare Variant Discovery in Multiplex AD Families

 描述(由申请人提供)：尽管人们认识到遗传因素在酒精依赖(AD)易感性中起着重要作用，但到目前为止，在研究中复制的基因很少。由于酒精依赖是一种常见的疾病，影响着五分之一的男性和十二分之一的女性，人们普遍认为常见的遗传变异(人群中微小等位基因频率超过3%的那些)将是寻找易感变异的合适地点。共同疾病/共同变异假说为大量全基因组关联研究提供了动力，在这些研究中，已经评估了大量共同变异。虽然一些研究报告了符合全基因组意义的发现，但AD的发现通常不能在其他研究中复制。此外，在各种各样的疾病中，人们现在认识到，这些常见的变异只解释了疾病结局中2-4%的差异。最近的证据表明，更罕见的变异可能更具渗透性，可能解释更大比例的疾病结果。有多个AD病例的家庭成员最有可能携带罕见和高渗透性风险变异的负担。利用从高密度AD家系成员收集的现有DNA，我们将使用下一代外显子组测序和新的生物信息学工具来识别这些高危个体中的罕见变异，并检查与杜克大学人类遗传变异中心合作的家族中变异的分布。AIM 1提供了一个发现阶段，并通过使用一个家系子集来促进这一过程，在这些家系中，父母和受影响的后代可以获得DNA。目标2使用一组更大的家系来确认已发现的变异，其中变异的存在及其在整个家系中的分布将被确定。通过关注具有多代参与的强烈遗传负担的个体，并包括整个外显子组，我们预计会发现罕见的高渗透性变异，这是其他方法无法检测到的。对阿尔茨海默病易感性的早期发育指标的研究揭示了临床(例如，儿童品行障碍的存在)和生物内表型(例如，事件相关电位的P300成分的幅度降低)。在目标3中，我们将在第三代个体样本中检验我们新发现的罕见变异，这些个体从童年到年轻成年，并且可以获得P300波幅的发展轨迹。该样本既包括AD家族多重基因的高风险后代，也包括低风险对照，这为寻找与P300轨迹相关的变异提供了机会，P300轨迹是一种与AD高度相关的内表型。

 DESCRIPTION (provided by applicant): Despite the recognition that genetic factors play an important role in susceptibility to alcohol dependence (AD), few genes have been identified to date that have been replicated across studies. Because alcohol dependence is a common disorder affecting one in five men and one in twelve women, the prevailing thought has been that common genetic variants (those with minor allele frequency over 3% in the population) would be the appropriate place to look for susceptibility variants. The common disease/common variant hypothesis has provided the impetus for a large number of genome-wide association studies (GWAS) where a large number of common variants have been assessed. While some studies have reported findings meeting genome-wide significance, often the findings for AD cannot be replicated in other studies. Also, across a wide variety of diseases, it is now recognized that only 2-4% of the variance in disease outcome is explained by these common variants. Recent evidence suggests that variants that are rarer may be more penetrant and potentially explain a greater proportion of disease outcome. Members of families in which multiple cases of AD are seen are most likely to carry a burden of rare and highly penetrant risk variants. Using existing DNA collected from members of high density AD pedigrees, we will use next generation exome sequencing and novel bioinformatics tools to identify rare variation in these high risk individuals and examine the distribution of variants in the families in collaboratin with the Center for Human Genetic Variation at Duke. Aim 1 provides a discovery stage and is facilitated by the use of a subset of pedigrees in which DNA is available for parents and affected offspring. Aim 2 provides confirmation of the discovered variation using a larger set of pedigrees in which the existence of the variants and their distribution within the full pedigree will be determined. By focusing on individuals with a strong genetic burden with multigenerational involvement and including the entire exome, we expect to find rare highly penetrant variants that would be undetectable with other approaches. A search for early developmental indicators of AD susceptibility has revealed both clinical (e.g., presence of childhood conduct disorder) and biological endophenotypes (e.g., reduced amplitude of the P300 component of the event-related potential). In Aim 3,we will examine our newly discovered rare variants in a third generation sample of individuals followed from childhood through young adulthood and for whom developmental trajectories of P300 amplitude are available. This sample includes both high-risk offspring from multiplex for AD families and low-risk controls providing an opportunity to find variants associated with P300 trajectories, an endophenotype that is highly associated with AD.