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

大脑皮层发育是一个高度协调的过程，其中预定用于皮层层的神经元的产生按从深到浅的顺序产生，然后是胶质细胞的产生。这个过程的时间在物种之间是非常不同的。例如，小鼠的皮质生成大约在妊娠一周内发生，而人类的这一过程需要几个月，导致更大更复杂的皮质。谱系研究已经在功能上定义了有助于皮质生成的主要类型的神经祖细胞（NPC），包括干细胞样放射状胶质细胞（RGC）和中间祖细胞（IPC）。然而，关于RGC和IPC如何随着时间的推移而被指定，仍有很多东西有待发现。我们已经发现，在不对称RGC-IPC细胞分裂期间，RNA结合蛋白Stau 2将编码和非编码RNA的复杂货物特异性地分离到IPC子代中。通过RNA测序分析不同胚胎阶段的这种货物揭示了作为控制IPC命运的增殖和时间特异性的候选基因的网络。在这里，我们建议测试这些候选人在功能研究中，使用高通量自动延时图像分析的体外研究，以及一种新的慢病毒在体内筛选方法，以确定他们的作用，指定IPC和定时皮质生成。与在理解小鼠皮质祖细胞特性方面取得的进展相反，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，其分裂模式，细胞周期时间和谱系的基本知识仍然未知。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，通过鉴定在人皮质祖细胞中表达的基因，包括在单细胞水平和通过分析Stau 2货物，我们将揭示人皮质祖细胞亚型和异质性。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差异，以解决一个主要的谜团：小鼠和人类皮质发育时间的差异。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，并利用延时分析快速量化增殖，分裂模式和分化变化的能力。由生发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以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候选的小生境分子分泌的脉络丛，可以与神经祖细胞，我们建议在体外和体内，在小鼠和人类的表达受体相互作用。定义生态位因子及其特定作用为解决涉及干细胞区域退化的疾病铺平了道路，这些干细胞区域通常在整个生命中都是活跃的。此外，定义作用于人类NPC的环境因素对于再生疗法的发展非常重要。

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.