Defining Characteristics of Cortical Progenitor Cells over Time in Mouse and Human

大脑皮层的发育是一个高度协调的过程，大脑皮质各层的神经元的产生是按从深到浅的顺序产生的，然后是神经胶质的产生。这一过程的时间在物种之间有很大的不同。例如，小鼠的皮质生成发生在大约一周的怀孕期间，而人类的这个过程需要几个月的时间，导致大脑皮质更大、更复杂。谱系研究已经从功能上定义了促进皮质生成的主要神经前体细胞类型，包括干细胞样放射状胶质细胞(RGC)和中间前体细胞(IPC)。然而，关于RGC和IPC是如何随着时间的推移而指定的，仍有许多有待发现的地方。我们发现，在不对称的RGC-IPC细胞分裂过程中，RNA结合蛋白Stau2将一系列复杂的编码和非编码RNA分离到IPC子体中。通过对不同胚胎阶段的这种货物进行RNA测序分析，揭示了控制IPC增殖和时间指定IPC命运的候选基因网络。在这里，我们建议在功能研究中测试这些候选基因，使用高通量自动延时图像分析进行体外研究，以及一种新的慢病毒体内筛选方法，以确定它们在指定IPC和计时皮质生成方面的作用。与在了解小鼠皮质祖细胞特性方面取得的进展相比，对人类皮质祖细胞的了解较少。关于人类RGC和IPC如何随着时间的推移产生不同的后代、它们的分裂模式、细胞周期时间和谱系的基本知识仍不清楚。在这里，我们将使用体外长期延时谱系分析来解决这些知识差距。此外，通过鉴定人类皮质祖细胞表达的基因，包括在单细胞水平上的表达，以及通过对Stau2 Cargo的分析，我们将揭示人类皮质祖细胞的亚型和异质性。此外，人类和小鼠皮质祖细胞数据的比较将有助于阐明关键的差异，以解决一个重大谜团：小鼠和人类皮质发育的时间差异。我们的实验室继续探索环境因素对皮质祖细胞的相互作用，这得益于使用延时分析快速量化增殖、分裂模式和分化的能力。生发壁龛中的结构如血管内皮细胞和脉络丛释放的可溶性因子作用于皮质祖细胞，调节它们产生的后代的数量和类型。我们最近的工作已经确定了一组由脉络丛分泌的候选利基分子，它们可以与神经前体细胞上表达的受体相互作用，我们建议在体外和体内，在小鼠和人类身上进行研究。确定利基因素及其具体行动，为解决涉及干细胞带退化的疾病铺平了道路，干细胞带通常在一生中都是活跃的。此外，确定作用于人类鼻咽癌的环境因素对于向再生治疗发展的转化是重要的。

Cerebral cortical development is a highly orchestrated process, with production of neurons destined for the cortical layers produced in order, deep to superficial, followed by glial generation. The timing of this process is very different between species. For example, mouse corticogenesis occurs over approximately a week of gestation, while in humans the process takes several months, resulting in a much larger and more complex cortex. Lineage studies have functionally defined the major types of neural progenitor cells (NPCs) contributing to corticogenesis, including stem cell-like radial glial cells (RGCs) and intermediate progenitor cells (IPCs). However, much remains to be discovered regarding how RGCs and IPCs are specified over time. We have discovered that during asymmetric RGC-IPC cell divisions, the RNA binding protein Stau2 segregates a complex cargo of coding and non-coding RNA specifically into the IPC daughter. Analysis of this cargo at different embryonic stages by RNA-sequencing has revealed networks of genes that are candidates for controlling proliferation and temporal specification of the IPC fate. Here we propose to test these candidates in functional studies, using high-throughput automated time-lapse image analysis for in vitro studies, as well as a novel lentiviral in vivo screening method, to define their roles in specifying IPCs and timing corticogenesis. In contrast to the progress made in understanding the characteristics of mouse cortical progenitor cells, less is understood regarding human cortical progenitors. Fundamental knowledge about how human RGCs and IPCs produce diverse progeny over time, their division mode, cell cycle times and lineages, remains unknown. Here we will address these gaps in knowledge using long-term time-lapse lineage analysis in vitro. In addition, by identifying genes expressed in human cortical progenitor cells, including at the single cell level and via analysis of the Stau2 cargo, we will reveal human cortical progenitor subtypes and heterogeneity. Further, a comparison of human and mouse cortical progenitor cell data will help illuminate key differences to address a major mystery: the difference in timing of mouse and human cortical development. Our lab continues to explore the interaction of environmental factors on cortical progenitor cells, aided by the ability to rapidly quantify changes in proliferation, division mode and differentiation using time-lapse analysis. Soluble factors released by structures in the germinal niche such as vascular endothelial cells and the choroid plexus, act on cortical progenitors to regulate the numbers and types of progeny they produce. Our recent work has identified a panel of candidate niche molecules secreted by the choroid plexus that could interact with receptors expressed on neural progenitors, which we propose to examine in vitro and in vivo, in mouse and human. Defining niche factors and their specific actions paves the way to address diseases that involve degeneration of stem cell zones which are normally active throughout life. Furthermore, defining environmental factors that act on human NPCs is important for translation towards regenerative therapy development.