Causal biology of Chd8 haploinsufficiency in complex brain disorders

总结 在绘制神经发育障碍（NDD）的遗传原因方面取得了重大进展。在 自闭症谱系障碍（ASD）和智力残疾（ID），从头突变到一个收敛的网络， 编码染色质重塑因子（CRF）的基因已成为免疫系统中最强的组成部分之一。 遗传风险该领域目前面临的一个主要挑战是确定基因组机制， 与NDD相关CRF突变相关的神经发育后果CRF基因 在ASD和ID队列中观察到，CHD 8具有最高的从头功能丧失突变率， 在精神分裂症和强迫症病例中也描述了突变， 携带者也经常被诊断为大头畸形。我们的工作和其他人的工作都证实了 Chd 8种系杂合突变在小鼠中引起NDD相关的病理变化， 基因组学、神经解剖学和行为学领域。网络分析将CHD 8的功能与 其他NDD相关的CRF在发育中的大脑，提高了理解CHD 8- 神经发育过程中的相关病理机制将揭示可推广的因果通路 由CRF单倍不足介导。然而，独立于在早期大脑发育中的作用，CHD 8， 以及其他与NDD相关的CRF在神经元中表达，突变可能会导致行为病理学 通过出生后大脑中的神经元特异性影响。因此，解决发育与神经元的因果关系， 对于理解CRF相关的NDD机制至关重要。我们将利用条件Chd 8 +/- 小鼠模型，以解剖体内Chd 8突变引起NDD相关的机制， 病理我们的初步数据表明，大头畸形和认知缺陷是相互依赖的， Chd 8 +/-小鼠早期脑发育过程中的病理学，以及分子机制与 与Chd 8介导的染色质相关RNA加工有关。我们将应用互补组学，细胞 具体来说，我们将：1）建立机制，通过这些机制， Chd 8单倍不足影响胚胎脑中的染色质和转录，2）表征细胞类型 Chd 8单倍不足对脑发育过程中神经发生的具体影响，以及3）定义 行为、EEG和突触病理，并测试这种病理是否 是由发育机制和神经机制驱动的。这项研究将绘制Chd 8的影响， 体内单倍不足，阐明CHD 8剂量敏感性导致NDD的机制 病理学和连接分子和细胞机制的行为和系统水平。重要的是这些 关键的研究不能使用体外模型进行，并且这种高兴趣NDD风险基因的研究是 这是连接遗传关联和机械理解的桥梁。通过揭示最高风险的因果关系 基因，如CHD 8，我们将建立致病因素，并确定新的治疗方法，以改善护理的NDD。

SUMMARY Major gains have been in made in mapping the genetic causes of neurodevelopmental disorders (NDDs). In autism spectrum disorder (ASD) and intellectual disability (ID), de novo mutations to a convergent network of genes encoding chromatin remodeling factors (CRFs) has emerged as one of the strongest components of genetic risk. A major challenge now facing the field is identifying the genomic mechanisms and neurodevelopmental consequences associated with mutations of NDD-associated CRFs. The CRF gene CHD8 has among the highest rates of de novo loss-of-function mutations observed in ASD and ID cohorts with mutations also described in schizophrenia and obsessive compulsive disorder cases, and CHD8 mutation carriers frequently also are diagnosed with macrocephaly. Our work and the work of others have confirmed that Chd8 germline heterozygous mutation in mice causes NDD-relevant pathological changes across genomic, neuroanatomical, and behavioral domains. Network analyses have linked functionality of CHD8 and other NDD-associated CRFs in the developing brain, raising the possibility that understanding CHD8- associated pathological mechanisms during neurodevelopment will reveal generalizable causal pathways mediated by CRF haploinsufficiency. However, independent of a role in early brain development, CHD8, as well as other NDD-associated CRFs, are expressed in neurons and mutation may drive behavioral pathology via neuron-specific impacts in postnatal brain. Thus, resolving developmental versus neuronal causality is essential for understanding CRF-associated mechanisms of NDDs. We will leverage conditional Chd8+/- mice model to dissect in vivo the mechanisms by which Chd8 mutations cause NDD-associated pathology. Our preliminary data suggests that macrocephaly and cognitive deficits are interdependent on pathology during early brain development in Chd8+/- mice, and that the molecular mechanisms are associated with chromatin-associated RNA processing mediated by Chd8. We will apply complementary -omics, cellular assays, and mouse studies to test this model, specifically, we will: 1) establish the mechanisms through which Chd8 haploinsufficiency impacts chromatin and transcription in embryonic brain, 2) characterize cell-type specific impacts of Chd8 haploinsufficiency on neurogenesis during brain development, and 3) define behavioral, EEG, and synaptic pathology caused by Chd8 haploinsufficiency and test whether such pathology is driven via developmental versus neuronal mechanism. This research will map the effect of Chd8 haploinsufficiency in vivo, illuminating mechanisms via which CHD8 dosage-sensitivity contributes to NDD pathology and linking molecular and cellular mechanisms to behavioral and systems level. Importantly, these critical studies cannot be done using in vitro models and such studies of high interest NDD risk genes is necessary to bridge genetic association and mechanistic understanding. By revealing causality for top risk genes such as CHD8, we will establish causal factors and identify novel treatments to improve care of NDDs.