Neurobiology of Autism With Macrocephaly

 描述(由申请人提供)：自闭症谱系障碍(ASD)影响全球1%-2.5%的儿童。我们认为，病因和遗传的异质性可能汇聚在一些神经生物学下游通路中。我们一直在研究ASD合并大脑体积(巨头畸形)的病理生物学，这是一种预后较差的表型。正在进行的研究表明，从ASD和巨头畸形患者的诱导多能干细胞(IPSC)体外分化出的端脑类器官可以促进细胞增殖，促进突触生长和GABA能抑制神经元的过度生产，表明早期谷氨酸/GABA神经元比例失衡。RNA干扰实验表明，GABA能细胞的过量生产至少部分归因于FOXG1表达的增加，FOXG1是一种对端脑发育至关重要的主要调控转录因子。该应用程序的主要目标是(1)将我们对ASD中失调的发育途径的分析扩展到更多的家庭，以及(2)了解我们发现的ASD伴巨头畸形的发育变化在多大程度上也适用于ASD。为此，我们将从脑大小增大的ASD患者和脑大小正常的ASD患者中获得神经生物学指标、转录组和染色质活性区域的数据。将推断改变的基因调控网络，并对这两个网络进行比较，以了解ASD两个亚组中的异同。为了开始了解这些发育变化的上游原因，我们将调查ASD患者是否在参与这一调控网络的基因组区域携带罕见基因组变异的增加负担。最后，我们将进行过表达和RNAi敲除实验，以检查我们目前最好的候选转录因子FOXG1在ASD来源的祖细胞中发现的一系列神经生物学和转录组改变中的特定作用。我们将分别通过RNA-SEQ和CHIP-SEQ评估FOXG1基因表达对神经生物学功能(细胞增殖、谷氨酸/GABA神经元命运、突触生长)、转录组和转录调节区活性的影响，以深入了解FOXG1驱动的转录程序在ASD来源的神经前体细胞异常神经元分化中的作用。综上所述，在本申请中，我们描述了用于(1)识别ASD两个亚组中表征改变发育的基因网络和生物学途径的策略；(2)测试此类网络中的一个关键节点--转录因子FOXG1的因果作用，该转录因子在患有大头畸形的ASD中过度活跃；以及(3)识别神经生物学和基因表达异常的上游的遗传和表观遗传学调节因子。这些实验的影响将是定义了一些与ASD神经生物学有关的生物学功能和分子标记。

 DESCRIPTION (provided by applicant): Autism spectrum disorders (ASDs) affect 1%-2.5% of children worldwide. We suggest that etiological and genetic heterogeneity might converge in a few neurobiological downstream pathways. We have been investigating the pathobiology of ASD with large brain volume (macrocephaly), a phenotype which confers poorer prognosis. Ongoing studies have shown that telencephalic organoids differentiated in vitro from induced pluripotent stem cells (iPSC) derived from patients with ASD and macrocephaly have increased cell proliferation, increased synaptic growth and overproduction of GABAergic inhibitory neurons, indicating an early imbalance in glutamate/GABA neuron ratio. RNA interference experiments suggested that the overproduction of GABAergic cells is attributable, at least in part, to an increase in expression of FOXG1, a master regulatory transcription factor crucial for telencephalic development. Major goals of this application are (1) to expand our analysis of the developmental pathways that are dysregulated in ASD to a larger number of families and (2) to understand to what extent developmental alterations we identified in ASD with macrocephaly also apply to ASD in general. To this end, we will obtain data on neurobiological measures, transcriptome and chromatin active regions in organoids derived from ASD patients with enlarged brain size and ASD patients with normal brain size. The altered gene regulatory network will be inferred and the two networks will be compared to understand similarities and differences in the two subgroups of ASD. To begin to understand the upstream causes of these developmental alterations, we will then investigate whether patients with ASD carry an increased burden of rare genomic variations in regions of the genome that participate in this regulatory network. Finally we will perform overexpression and RNAi knockdown experiments to examine the specific role of our current best candidate transcription factor, FOXG1, in the constellation of neurobiological and transcriptome alterations found in ASD-derived progenitors. We will assess the impact of perturbing FOXG1 gene expression on neurobiological functions (cell proliferation, glutamate/GABA neuron fate, synaptic growth), transcriptome and activity of transcription regulatory regions by RNA-seq and ChIP-seq, respectively, to gain insights into the role of a FOXG1-driven transcriptional program in the aberrant neuronal differentiation of ASD-derived neural progenitors. In summary, in this application we delineate strategies for (1) identifying gene networks and biological pathways that characterize altered development in two subgroups of ASD; (2) testing the causal role of one crucial node in such networks, the transcription factor FOXG1, which is over- active in ASD with macrocephaly; and (3) identifying regulatory factors, both genetic and epigenetic, upstream from neurobiological and gene expression abnormalities. The impact of these experiments will be the definition of a number of biological functions and molecular markers that are implicated in the neurobiology of ASD.