Causal biology of Chd8 haploinsufficiency in complex brain disorders

摘要 在绘制神经发育障碍(NDDS)的遗传原因图方面取得了重大进展。在……里面 自闭症谱系障碍(ASD)和智力残疾(ID)，从头突变到一个融合的网络 编码染色质重塑因子(CRF)的基因已成为 遗传风险。目前该领域面临的一个主要挑战是确定基因组机制和 与NDD相关CRF突变相关的神经发育后果。CRF基因 在ASD和ID队列中观察到的CHD8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，以及CHD8突变 携带者也经常被诊断为巨头症。我们的工作和其他人的工作证实了 小鼠CHD8种系杂合突变引起新城疫相关病理改变 基因组学、神经解剖学和行为学领域。网络分析具有CHD8和CHD8的链接功能 其他与NDD相关的CRF在发育中的大脑中，增加了理解CHD8- 神经发育过程中的相关病理机制将揭示可概括的因果路径 由CRF单倍体功能不全介导。然而，独立于大脑早期发育的作用，CHD8，AS 和其他与NDD相关的CRF一样，表达在神经元中，突变可能导致行为病理 通过神经元在出生后大脑中的特定影响。因此，解决发育与神经元之间的因果关系是 对于理解CRF相关的NDDS机制至关重要。我们将利用有条件的CHD8+/- 小鼠模型体内解剖CHD8突变导致新城疫相关的机制 病理学。我们的初步数据表明，大头症和认知缺陷是相互依赖的 CHD8+/-小鼠早期脑发育过程中的病理变化及其分子机制 通过CHD8介导的染色质相关RNA处理。我们将应用互补组学，细胞 化验，和小鼠研究来测试这个模型，具体地说，我们将：1)建立 CHD8单倍体缺陷对胚胎脑染色质和转录的影响，2)细胞类型 CHD8单倍体不足对脑发育过程中神经发生的具体影响，以及3)定义 CHD8单倍体功能不全引起的行为、脑电和突触病理 是通过发育机制与神经机制驱动的。这项研究将绘制CHD8的影响图 体内单倍体不足，阐明CHD8剂量敏感性导致NDD的机制 病理学以及将分子和细胞机制与行为和系统水平联系起来。重要的是，这些 关键研究不能使用体外模型进行，这种高兴趣的新城疫风险基因的研究是 在基因关联和机制理解之间架起桥梁所必需的。通过揭示最高风险的因果关系 对于CHD8等基因，我们将确定因果因素，并确定新的治疗方法，以改善NDDS的护理。

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.