The Role of Germline Mutation and Parental Age in Autism Spectrum Disorders

描述（由申请人提供）：自闭症谱系障碍（ASD）的遗传病因反映了基因组不稳定性的性质。部分基于该项目第一阶段的拷贝数变异（CNV）研究，现在人们广泛认识到生殖系中的新生或近期突变是ASD风险的重要因素。导致自闭症高风险的突变位于超变区域（ROH）内。例子包括在1q21.1、15 q11 -13和16p11.2的大于500 kb的区域，其中局部基因组结构倾向于频繁的复发性重排。总的来说，新生CNVs占病例的约5-10%。很可能是外显子和非编码区的其他类型的从头突变（DNM）导致了ASD。作为一个领域，我们对人类生殖系突变的全球模式的了解有限，并且我们对DNM如何导致疾病风险的理解不完全。基于上述知识，并基于我们在自闭症中的初步基因组测序研究中出现的关键发现，我们假设，主要由核苷酸取代热点组成的超变区（ROH）在ASD中起主要作用。在我们项目的新阶段，我们将应用基于全基因组测序的方法来确定ROH在ASD中的作用。我们将探讨内在的超变性和外在的力量，如父亲的 年龄，影响生殖细胞突变率。我们将通过以下具体目标来实现这些目标：具体目标1将通过家族中的全基因组测序来表征生殖系新生突变（DNM）。这些研究将在120个trios（60个ASD和60个对照）样本中识别和验证约8，000个从头点突变和结构变体，并确定DNM的起源亲本。具体目标2将研究ROH在ASD中的作用。我们将根据基因组中DNM的区域密度来识别ROH，并确定DNA序列特征对突变率的影响。我们将从2700例病例和2700例对照的独立样本中确定发现样本以及外显子组和CNV数据集中ROH与ASD的关联。具体目标3将描述外在因素的影响，包括父母的年龄和环境，对全基因组突变率。我们将量化父亲年龄对精子中致病性和中性等位基因的影响，并研究某些DNM是否具有种系选择优势。这项研究的结果将为自闭症风险的遗传基础和ASD中观察到的父母年龄效应的遗传机制提供基本见解。我们将确定基因，赋予自闭症的重大风险，我们将确定如何基因组的内在属性与外在力量相互作用，以确定疾病的风险在后代。

DESCRIPTION (provided by applicant): The genetic etiology of Autism Spectrum Disorders (ASDs) reflects of the nature of genome instability. Based in part on studies of copy number variation (CNV) from the first phase of this project, it is now widely recognized that de novo or recent mutations in the germline are important contributors to risk for ASDs. Mutations that confer high risk for autism are located within regions of hypermutability (ROHs). Examples include large >500 kb regions at 1q21.1, 15q11-13 and 16p11.2, where local genomic architecture predisposes to frequent recurrent rearrangements. All told, de novo CNVs contribute in approximately 5-10% of cases. It is likely that other classes of de novo mutation (DNM), in exons and in non-coding regions, contribute to ASD. As a field, we have a limited knowledge of global patterns of germline mutation in humans, and we have an incomplete understanding of how DNM contributes to risk for disease. Based on the knowledge above, and based on key findings that have emerged from our preliminary genome sequencing studies in autism, we hypothesize that, regions of hypermutability (ROHs), primarily consisting of nucleotide substitution hotspots, play a major role in ASDs. In the new phase of our project, we will apply a whole genome sequencing-based approach to determine the role of ROHs in ASD. We will investigate the nature intrinsic hypermutability and the extrinsic forces, such as paternal age, that influence rates of germline mutation. We will accomplish these goals through the following specific aims: Specific Aim 1 will characterize germline de novo mutations (DNMs) by whole genome sequencing in families. These studies will identify and validate ~8,000 de novo point mutations and structural variants in a sample of 120 trios (60 ASD and 60 controls) and determine the parent of origin of DNMs. Specific Aim 2 will investigate the role of ROHs in ASD. We will identify ROHs based on the regional density of DNMs in the genome, and determine the effects of DNA sequence features on rates of mutation. We will determine the association of ROHs with ASD in the discovery sample and in exome and CNV datasets from an independent sample of 2700 cases and 2700 controls. Specific Aim 3 will characterize the effects of extrinsic factors, including parental age and environment, on genome-wide rates of mutation. We will quantify the effect of paternal age on pathogenic and neutral alleles in sperm and investigate whether some DNMs confer a germline selective advantage. The findings of this study will provide fundamental insights into the genetic basis of autism risk and the genetic mechanism of the observed parental age effects in ASD. We will identify genes that confer significant risk for autism, and we will determine how intrinsic properties of the genome interact with extrinsic forces to determining risk for disease in offspring.