Autism genetics: homozygosity mapping and functional validation

描述(由申请人提供)： 自闭症谱系障碍(ASD)影响1%或更多的美国儿童。自闭症是以社交行为缺陷为特征的，包括语言迟缓、不正常的社交互动、重复或刻板印象的兴趣或行为。自闭症表现出很大的遗传成分，估计遗传率高达60%-90%。然而，ASD的极端异质性是基因发现的持久障碍，已知的遗传原因只占诊断的不到15%。虽然高通量测序(HTS)方法可以对整个外显子组甚至整个基因组的遗传变异进行系统分析，但对这些数据的解释面临着尚未解决的分析挑战。利用父母共有祖先的血缘关系谱系，可以识别候选基因，然后在非血缘关系的家庭中进行更广泛的分析。有血缘关系的家系1]减少了ASD的异质性，2)简化了HTS分析和验证，3)提供了遗传连锁证据，支持单个家系中特定突变的有效性。初步数据证实，这些家系中的HTS可以以公正的方式有效地识别与血缘和非血缘队列患者相关的ASD的隐性遗传原因。这项研究将寻求登记被诊断为ASD的近亲家庭，进行纯合性图谱以定位基因组中可能包含导致他们ASD的突变的区域，并对受影响的个体进行全基因组测序(WGS)以确定候选变异。此外，将继续分析以前研究中产生的关于近亲家庭的连锁和整个外显子组测序数据。这项研究将在以前工作的基础上进行扩展，具体内容包括：1)生成关于正常对照的WGS数据以确定中东人群中的常见等位基因，从而能够在本研究和许多其他中东WGS研究中进行更快速、更敏感和最终成本更低的分析；2)使用酵母模型、转化的体细胞系和其他模型系统从功能上验证通过WGS发现的强大候选基因的方法；3)使用RNAi生成本研究中发现的候选基因的小鼠模型，以及正在进行的神经元活性依赖基因研究，以检测移除这些基因对树突和树突形态和突触活性的影响。最近的研究表明，尽管存在高度的异质性，但存在与ASD相关的常见生化途径。这项研究的发现将有助于识别组成这些途径的基因，并为ASD的治疗提供潜在的药物靶点。

DESCRIPTION (provided by applicant): Autism spectrum disorders (ASDs) affect 1% or more of American children. ASDs are characterized by defects in social behavior, including language delay, abnormal social interactions, and repetitive or stereotyped interests or behaviors. ASDs show a large genetic component, with estimates of heritability as high as 60- 90%. However, the extreme heterogeneity of ASD is a persistent hurdle to gene discovery, and known genetic causes account for less than 15% of diagnoses. Although high throughput sequencing (HTS) methods allow systematic analysis of genetic variation across the entire exome, or even the entire genome, the interpretation of this data faces analytical challenges that have by no means been solved. The use of consanguineous pedigrees, in which parents share ancestry, allows the identification of candidate genes that can then be analyzed more broadly in nonconsanguineous families. Consanguineous families 1] reduce the heterogeneity of ASD, 2] simplify HTS analysis and validation, and 3] provide genetic linkage evidence to support the validity of specific mutations in a single family. Preliminary data confirms that HTS in such pedigrees can efficiently identify, in an unbiased fashion, recessive genetic causes of ASD relevant to both consanguineous and nonconsanguineous cohorts of patients. This study will seek to enroll consanguineous families diagnosed with ASD, perform homozygosity mapping to locate regions of the genome likely to harbor the mutation that causes their ASD, and perform whole genome sequencing (WGS) on the affected individuals to identify candidate variants. Further, linkage and whole exome sequencing data that was generated on consanguineous families from previous studies will continue to be analyzed. This study will expand on the previous work by 1] Generating WGS data on normal controls to identify common alleles within Middle Eastern populations thus allowing swifter, more sensitive and ultimately cheaper analysis in this and many other Middle Eastern WGS studies; 2] Generating relatively high throughput methods of functionally validating strong candidate genes discovered through WGS using yeast models, transformed somatic cell lines, and other model systems; and 3] Using RNAi to generate mouse models of candidate genes discovered in this study, and an ongoing neuronal activity-dependent gene study, to examine the effects of removing the genes on dendrite and dendritic spine morphology and synaptic activity. Recent studies suggest that, despite the high level of heterogeneity, there are common biochemical pathways associated with ASD. The findings from this study will be instrumental in the identification of the genes that make up these pathways, and provide potential pharmaceutical targets for the treatment of ASD.