Functional characterization of neurotransmitter-mediated signaling in human neocortical development

从进化的角度来看，新皮层是哺乳动物大脑中最新的部分，也是哺乳动物复杂认知技能的来源。虽然基因组相对稳定，但在灵长类谱系中，新皮层已经显著扩大。在人类大脑的进化过程中，新皮层的细胞数量和不同类型的细胞数量都有所增加。因此，在新皮层发育过程中，细胞的增加和不同细胞类型的分化是如何实现的问题就出现了。先前的研究表明，神经祖细胞类型的增加是形成更多神经元和胶质细胞的基础，这些神经元和胶质细胞构成了成熟的新皮层。然而，这些神经祖细胞如何在人类延长的神经发生期保持其增殖潜力，以及如何产生大量不同类型的细胞仍然未知。对啮齿动物的研究表明，发育中的大脑中神经递质介导的信号传导调节神经祖细胞的增殖和新生神经元的分化。我们假设神经递质介导的细胞间信号传导在复杂的人类大脑发育中起着更重要的作用。因此，我们的目标是研究人类大脑中不同的神经祖细胞类型是如何被神经递质调节的。我们将使用细胞内钙浓度的变化作为细胞对不同神经递质的反应性的读数，因为钙是连接细胞间信号和转录变化的重要第二信使，因此可以改变细胞命运。在目标1中，我们将描述人类神经祖细胞和新生神经元对一系列不同神经递质的生理反应概况。在目标2中，我们将使用一种新的高通量方法，通过分析单细胞转录组，将生理反应谱与细胞类型和状态联系起来。在Objective 3中，我们将通过分析神经递质应用后单细胞的转录组和研究组织切片中细胞增殖的变化来研究神经递质信号传导对不同类型细胞增殖和分化的长期影响。这种系统生物学方法将使我们首次阐明发育中的人类新皮层中不同类型的细胞如何通过神经递质介导的信号传导相互调节。由于许多神经发育障碍，如自闭症谱系障碍，是由编码突触蛋白的基因突变引起的，这项研究有助于理解这些突变如何在突触形成之前影响大脑发育。

In evolutionary terms, the neocortex is the newest part of the mammalian brain and is the source of the complex cognitive skills of mammals. While the genome has been relatively stable, the neocortex has expanded significantly in the primate lineage. Both the number of cells and the number of different cell types in the neocortex has increased during the evolution of the human brain. The question therefore arises how the increased production of cells and the differentiation of different cell types is achieved during neocortical development. Previous research has shown that an enlarged repertoire of neural progenitor types underlies the generation of the larger number of neurons and glia that constitute the mature neocortex. However, how these neural progenitor cells maintain their proliferative potential throughout the extended neurogenic period in humans and how the large diversity of cell types is generated remains unknown. Studies in rodents have shown that neurotransmitter-mediated signaling in the developing brain regulates both the proliferation of neural progenitor cells and the differentiation of newborn neurons. We hypothesize that neurotransmitter-mediated intercellular signaling plays an even more important role in the development of the complex human brain. We therefore aim to study how the different neural progenitor cell types in the human brain are regulated by neurotransmitters. We will use changes in the concentration of intracellular calcium as a readout of the responsiveness of a cell to different neurotransmitters, since calcium is an important second messenger that links intercellular signaling to changes in transcription and thereby can alter cell fates. In Objective 1 we will characterize the physiological response profiles of human neural progenitor cells and newborn neurons to a range of different neurotransmitters. In Objective 2, we will use a novel high-throughput approach to link the physiological response profiles to cell types and states by analyzing single-cell transcriptomes. In Objective 3, we will study the long-term effects of neurotransmitter signaling on the proliferation and differentiation of different cell types by analyzing transcriptomes of single cells after neurotransmitter application and by studying changes in proliferation in tissue slices. This systems biology approach will allow us for the first time to elucidate how different cell types in the developing human neocortex regulate each other through neurotransmitter-mediated signaling. Since many neurodevelopmental disorders, such as autism spectrum disorders, are caused by mutations in genes that encode synaptic proteins, this research is instrumental for understanding how these mutations affect brain development even prior to the formation of synapses.