Identifying pathogenic mechanisms underlying PACS1 Syndrome: implications for neural development

项目摘要 神经发育障碍(NDDS)是异质性的，通常具有复杂的病因。个人 在这些情况下，认知障碍伴随着终生缺陷；但令人惊讶的是，很少有 知道他们的神经学基础。患者和他们的家人迫切需要修改疾病 治疗。然而，为了开发有效的治疗方法，了解分子的失调是必不可少的。 以及导致这些情况的细胞过程。PACS1综合征是由单个R203W引起的NDD 200多名患者中磷酸尿苷酸性簇排序1(PACS1)蛋白的替换。此外， 全基因组关联研究发现人类PACS1基因座是重型肝炎的易感基因。 早发性肥胖症、发育迟缓和双相情感障碍，表明在大脑发育中有更广泛的作用。 PACS1编码一种多功能蛋白，其在分泌途径中的典型胞浆功能是指导 它的货物到达了跨高尔基网络。然而，PACS1还包含一个核定位信号(NLS)，航天飞机 在S期，至少在高增殖的癌细胞中，它调节染色质的稳定性 通过与HDAC蛋白相互作用。尽管之前的研究揭示了PACS1的关键功能，但 PACS1在核内的作用以及PACS1 R203W变异体在神经系统中的作用 待定。因此，我们已经产生了患者诱导的多潜能干细胞(IPSCs)来源的大脑 有机化合物来研究一个发育中的有模式的三维神经结构的转录组 病人的遗传背景。通过在发育早期在有机体中进行单细胞RNA测序， 我们生成了一个初步数据集，强烈表明调节一个重要的基因表达程序 谷氨酸/γ-氨基丁酸能命运规范。总之，关于PACS1核定位的证据， 除了我们的初步数据，还表明PACS1具有一种未被探索的核功能，可能是通过 调节神经前体细胞的基因表达。因此，我们假设PACS1调节 谷氨酸/γ-氨基丁酸能平衡通过随着神经发生而降低的非标准核功能 收益。因此，PACS1缺陷导致GABA能命运的转变，产生异位的GABA能神经元， 随后的谷氨酸/氨基丁酸能失衡，最后是NDD表型。我们将通过以下方式验证这一假设 解决PACS1是否具有因神经分化而不同的上下文特定功能(AIM1)， PACS1核功能缺陷改变谷氨酸/GABA能特性平衡(AIM2)。结果来自 这项建议将大大提高我们对PACS1缺陷如何影响发育中的神经症的理解。 系统，通过揭示目前被忽视的核功能。此外，我们的工作将扩大我们的知识 谷氨酸/氨基丁酸能失衡的分子基础和后果 一再被描述为许多NDD的先驱，指向了一种可能的共同机制 遗传来源不同，最终可能揭示出趋同的治疗靶点。

Project Summary Neurodevelopmental disorders (NDDs) are heterogenous and usually present with complex etiology. Individuals with these conditions present with cognitive impairment accompanied by lifelong deficits; yet remarkably little is known about their neurological basis. Patients and their families are in desperate need for disease-modifying therapies. However, to develop effective treatments, it is imperative to understand the dysregulation of molecular and cellular processes leading to these conditions. PACS1 Syndrome is a NDD caused by a single R203W substitution in the Phosphofurin Acidic Cluster Sorting 1 (PACS1) protein in over 200 patients. Moreover, genome-wide association studies (GWAS) identified the human PACS1 locus as a susceptibility gene in severe early-onset obesity, developmental delay, and bipolar disorder, suggesting a broader role in brain development. PACS1 encodes a multifunctional protein which canonical cytosolic function in the secretory pathway is to direct its cargo to the trans-Golgi Network.However, PACS1 also contains a nuclear localization signal (NLS), shuttles to the nucleus during S phase, and, at least in highly proliferative cancer cells, regulates chromatin stability through interaction with HDAC proteins. Despite previous studies have revealed critical PACS1 functions, the role of PACS1 within the nucleus as well as the effect of the PACS1 R203W variant in the nervous system yet to be determined. Thus, we have generated patient induced pluripotent stem cells (iPSCs)-derived cerebral organoids to investigate the transcriptome of a developing patterned, three-dimensional neural structure with the patient genetic background. By performing single cell RNA Sequencing in organoids during early development, we generated a preliminary dataset that strongly indicate that regulates a gene expression program important for Glutamatergic/GABAergic fate specification. Altogether, evidence regarding nuclear localization of PACS1, in addition to our preliminary data, suggests that PACS1 has an unexplored nuclear function, possibly by regulating gene expression in neural progenitors. Therefore, we hypothesize that PACS1 regulates Glutamatergic/GABAergic balance through a non-canonical nuclear function that decreases as neurogenesis proceeds. Thus, PACS1 deficits result in a shift towards GABAergic fate, generating ectopic GABAergic neurons, subsequent Glutamatergic/GABAergic imbalance, and finally NDD phenotypes. We will test this hypothesis by addressing whether PACS1 possesses context specific functions that differ across neural differentiation (aim1), and deficits in PACS1 nuclear function alter Glutamatergic/GABAergic specification balance (aim2). Results from this proposal will greatly enhance our understanding of how the PACS1 deficits affect the developing nervous system, by uncovering a currently disregarded nuclear function. Moreover, our work will expand our knowledge of the molecular underpinnings and consequences of the Glutamatergic/GABAergic imbalance, that has repeatedly been described as a precursor of many NDDs, pointing towards a possible common mechanism from genetically heterogeneous origins and may ultimately reveal convergent therapy targets.