Role of somatic mosaicism in autism, schizophrenia, and bipolar disorder brain

 描述(申请人提供)：拟议研究的广泛、长期目标是确定自闭症谱系障碍(ASD)、精神分裂症(SZ)和双相情感障碍(BD)患者大脑区域发生的体细胞基因突变。最终，体细胞突变的发现和特征可能有助于我们理解这些疾病的病因，并最终导致改进的治疗策略和诊断标记。ASD、SZ和BD都是常见的神经精神疾病，有很大的遗传基础(估计每种情况的遗传率约为75%至80%)。然而，在病因学中具有因果作用的DNA变异相对较少。我们假设，体细胞嵌合体--受孕后特定身体区域发生突变--发生在大脑中，并与ASD、SZ和BD的病因有关。具体目标1是确定明显正常的人死后样本中跨大脑和身体区域的体细胞镶嵌突变的性质和程度。我们将评估四类体细胞变异：(1)单核苷酸变异(SNV)，(2)包括拷贝数变异的结构变异(SVS)，(3)L1逆转座子事件，(4)线粒体异质性。这些类型的变异将使用全基因组测序(第1年和第2年)、DNA纳米通道的单分子成像(第2年)和单核苷酸多态(SNP)阵列来检测。样本包括大脑区域(例如前额叶皮质和小脑)和器官(例如心脏和肾脏)。在鉴定了体细胞变异后，我们将进行严格的验证。具体目标2是确定ASD、SZ和BD患者基因组DNA中体细胞嵌合体的性质和程度。发现和验证的方法将与目标1相同。具体目标3是从功能上对体细胞变异进行分类，特别是那些被预测会扰乱先前与这些疾病有关的基因功能的变异。一种方法是单细胞RNA-seq(确定突变对转录的影响，并推断体细胞变体起源的细胞类型)。另一种方法使用来自诱导多能干细胞(IPSCs)的神经元(或神经胶质细胞)，并稳定表达野生型或突变型的体细胞变体。这些研究将有助于确定体细胞突变在神经精神障碍中的作用，包括这种变异的功能后果。

 DESCRIPTION (provided by applicant): The broad, long-term objective of the proposed research is to identify somatic genetic mutations that occur in brain regions of individuals with autism spectrum disorder (ASD), schizophrenia (SZ), and bipolar disorder (BD). Ultimately the discovery and characterization of somatic mutations may help us to understand the etiology of these disorders and eventually lead to improved therapeutic strategies and diagnostic markers. ASD, SZ, and BD are all commonly occurring neuropsychiatric disorders that have a large genetic basis (with estimated heritability of ~75% to 80% for each condition). However, relatively few DNA variants have been identified that have causal roles in the etiology. We hypothesize that somatic mosaicism--the occurrence of mutations in selected body regions after conception--occurs in brain and contributes to the etiology of ASD, SZ, and BD. Specific Aim 1 is to identify the nature and extent of somatic mosaic mutations across brain and body regions in postmortem samples from apparently normal individuals. We will assess four categories of somatic variation: (1) single nucleotide variants (SNVs), (2) structural variants (SVs) including copy number variants, (3) L1 retrotransposition events, and (4) mitochondrial heteroplasmy. These types of variation will be detected using whole genome sequencing (Years 1 and 2), single molecule imaging with DNA nanochannels (Year 2), and single nucleotide polymorphism (SNP) arrays. Samples include brain regions (e.g. prefrontal cortex and cerebellum) and organs (e.g. heart and kidney). After identifying somatic variants we will perform rigorous validation. Specific Aim 2 is to identify the nature and extent of somatic mosaicism in genomic DNA from individuals with ASD, SZ, and BD. The same approaches for discovery and validation will be applied as in Aim 1. Specific Aim 3 is to functionally categorize somatic variants, particularly those that are predicted to disrupt the functions of genes previously implicated in those disorders. One approach is single-cell RNA-seq (to determine the consequence of the mutation on transcription, and to infer the cell type of origin of the somatic variant). Another approach uses neurons (or glia) derived from induced pluripotent stem cells (iPSCs) and stably expressing the wildtype or mutant forms of the somatic variants. These studies will help to establish the role of somatic mutation in neuropsychiatric disorders, including the functional consequences of such variation.