Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL, United States; Program in Cell and Molecular Biology, University of Chicago, Chicago, IL, United States.
Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL, United States; Program in Cell and Molecular Biology, University of Chicago, Chicago, IL, United States; Committee on Development, Regeneration, and Stem Cell Biology, University of Chicago, Chicago, IL, United States; Grossman Institute for Neuroscience, University of Chicago, Chicago, IL, United States.
Curr Top Dev Biol. 2021;142:409-442. doi: 10.1016/bs.ctdb.2020.11.010. Epub 2020 Dec 19.
In this review, we discuss motor circuit assembly starting from neuronal stem cells. Until recently, studies of neuronal stem cells focused on how a relatively small pool of stem cells could give rise to a large diversity of different neuronal identities. Historically, neuronal identity has been assayed in embryos by gene expression, gross anatomical features, neurotransmitter expression, and physiological properties. However, these definitions of identity are largely unlinked to mature functional neuronal features relevant to motor circuits. Such mature neuronal features include presynaptic and postsynaptic partnerships, dendrite morphologies, as well as neuronal firing patterns and roles in behavior. This review focuses on recent work that links the specification of neuronal molecular identity in neuronal stem cells to mature, circuit-relevant identity specification. Specifically, these studies begin to address the question: to what extent are the decisions that occur during motor circuit assembly controlled by the same genetic information that generates diverse embryonic neuronal diversity? Much of the research addressing this question has been conducted using the Drosophila larval motor system. Here, we focus largely on Drosophila motor circuits and we point out parallels to other systems. And we highlight outstanding questions in the field. The main concepts addressed in this review are: (1) the description of temporal cohorts-novel units of developmental organization that link neuronal stem cell lineages to motor circuit configuration and (2) the discovery that temporal transcription factors expressed in neuronal stem cells control aspects of circuit assembly by controlling the size of temporal cohorts and influencing synaptic partner choice.
在这篇综述中，我们从神经元干细胞开始讨论运动回路的组装。直到最近，神经元干细胞的研究还集中在相对较少的干细胞如何产生大量不同的神经元特性。从历史上看，通过基因表达、大体解剖特征、神经递质表达和生理特性来检测胚胎中的神经元特性。然而，这些身份定义在很大程度上与成熟的、与运动回路相关的功能神经元特征无关。这些成熟神经元的特征包括突触前和突触后伙伴关系、树突形态，以及神经元的放电模式和在行为中的作用。这篇综述主要关注最近将神经元干细胞中神经元分子特性的特化与成熟的、与回路相关的特性特化联系起来的工作。具体来说，这些研究开始解决以下问题：在运动回路组装过程中发生的决策在多大程度上受产生不同胚胎神经元多样性的相同遗传信息控制？解决这个问题的大部分研究都是使用果蝇幼虫运动系统进行的。在这里，我们主要关注果蝇运动回路，并指出与其他系统的相似之处。并强调该领域的悬而未决的问题。本文综述中讨论的主要概念有：（1）时相群的描述——将神经元干细胞谱系与运动回路结构联系起来的新的发育组织单元；（2）发现在神经元干细胞中表达的时相转录因子通过控制时相群的大小和影响突触伙伴选择来控制回路组装的各个方面。
