Modeling gene regulatory mechanisms contributing to the evolution of the human cerebral cortex

项目概要 人类大脑皮层的巨大扩张使我们有别于我们的灵长类亲戚，而这种皮层 扩展是人类独特的高阶认知的基础。众多的开发创新， 例如皮质祖细胞增殖的增加，促进了皮质的生长。最终，这些 发展创新源于人类谱系的遗传变化，它改变了分子和 支持发育的细胞程序。了解具体的基因调控网络 告知人类皮质发育和皮质大小对于理解病因至关重要 神经发育障碍，通常表现为认知障碍。努力识别人类特异性 基因变化揭示了人类加速区（HAR），这是高度保守的监管区域 表现出高频率的人类特异性序列变化的元件。越来越多的证据表明 HAR 在皮质发育和进化中的作用。特别是，HAR HACNS205 具有 (i) 人为偏见 与黑猩猩相比，大脑类器官的可及性以及增强子活性的证据； (二) 必要的 在人类神经干细胞增殖中的作用； (iii) 胎儿人类皮质中已知的靶基因 BRN2， 调节皮质生成并在皮质祖细胞中具有人类偏向表达的转录因子 相对于黑猩猩。 BRN2是一种自闭症风险基因，其靶基因表现出自闭症风险基因的富集。 此外，临床工作已将 BRN2 突变与整体发育迟缓和认知障碍联系起来。 BRN2 最近也与人类皮质进化有关。过度表达研究表明 BRN2 对于指定神经祖细胞身份、神经发生的时间以及特定神经元的产生非常重要 神经元亚型。然而，HACNS205在人类皮质发育中的作用尚不清楚；此外， BRN2 在早期皮质发育中的作用尚未见报道。该提案的目标是解决这些问题 通过使用人源化小鼠模型研究HACNS205如何影响BRN2表达水平，填补了该领域的空白 和 BRN2 转录因子结合，以及这些主要分子效应如何影响基因表达， 分子网络、祖细胞行为以及皮质发育中关键事件的时间安排。具体来说， 我将采用胚胎皮质发育的全基因组表观遗传学和单细胞转录组分析。 然后将利用这些结果对这些动物中发育中的皮层进行有针对性的表型分析。 小鼠，以确定 HACNS205 驱动的祖细胞行为、神经发生和最终皮质的变化 形态学。申请人的长期目标是研究大脑进化中新型细胞类型的出现。这个 奖学金将帮助申请人发展生物信息学和进化、监管和 功能基因组学将极大地支持她在这一领域的研究取得成功，补充她目前的 神经生物学和皮质发育方面的专业知识。

Project Summary The vast expansion of the human cerebral cortex distinguishes us from our primate relatives, and this cortical expansion is the foundation of uniquely human higher-order cognition. Numerous developmental innovations, such as increased proliferation of cortical progenitor cells, contributed to this cortical growth. Ultimately, these developmental innovations arose from genetic changes in the human lineage, which altered the molecular and cellular programs underpinning development. Understanding the gene regulatory networks that specifically inform human cortical development and cortical size is crucial for understanding the etiology of neurodevelopmental disorders, which often present with cognitive impairment. Efforts to identify human-specific genetic changes have revealed Human Accelerated Regions (HARs), which are highly conserved regulatory elements that exhibit a high rate of human-specific sequence change. A growing body of evidence implicates HARs in cortical development and evolution. In particular, the HAR HACNS205 has (i) human-biased accessibility in cerebral organoids, compared to chimpanzee, and evidence of enhancer activity; (ii) an essential role in human neural stem cell proliferation; and (iii) a known target gene in the fetal human cortex, BRN2, a transcription factor that regulates corticogenesis and has human-biased expression in cortical progenitor cells relative to chimp. BRN2 is an autism risk gene, and its target genes display enrichment for autism risk genes. In addition, clinical work has linked BRN2 mutations to global developmental delay and cognitive impairment. BRN2 has also recently been implicated in human cortical evolution. Overexpression studies indicate BRN2 is important for designating neural progenitor cell identity, the timing of neurogenesis, and the production of specific neuronal subtypes. However, the role of HACNS205 in human cortical development is not clear; moreover, the role of BRN2 in early cortical development has not been reported. The goal of this proposal is to address these gaps in the field, by using a humanized mouse model to study how HACNS205 impacts BRN2 expression levels and BRN2 transcription factor binding, and how these primary molecular effects shape gene expression, molecular networks, progenitor cell behavior, and the timing of key events in cortical development. Specifically, I will employ genome-wide epigenetic and single-cell transcriptomic analyses of embryonic cortical development. These results will then be leveraged to perform targeted phenotypic analysis of the developing cortex in these mice, to identify HACNS205-driven shifts in progenitor cell behavior, neurogenesis, and ultimately cortical morphology. The applicant’s long-term goal is to study the emergence of novel cell types in brain evolution. This fellowship will aid the applicant in developing the expertise in bioinformatics and evolutionary, regulatory, and functional genomics that will greatly bolster her success in this line of research, complementing her current expertise in neurobiology and cortical development.