Elucidating transcriptional mechanisms of motor neuron subtype specification

项目总结 每一个动作都需要对肌肉收缩的强度和速度进行精细的控制。紧张的人 系统通过招募不同功能的运动神经元(MN)亚型来实现肌肉的分级控制 特性，如靶肌肉纤维类型、电生理学或在行为中的作用。的功能多样性 MNS对于运动是至关重要的，但我们仍然缺乏对它是如何产生的基本了解。在开发过程中， MN亚型的同一性由转录密码决定。我们知道很多关于解剖MN如何 由靶肌肉定义的亚型是特定的，但功能性MN亚型的分子逻辑 开发几乎是未知的。 尽管解剖MN亚型在四足动物中被很好地分离，但功能亚型在很大程度上 混杂在一起使他们的研究复杂化。一个模型系统，其中MN的功能子类型是分离的，并且 像斑马鱼这样容易识别的物种，为剖析它们的分子决定因素提供了一个独特的机会。 斑马鱼有三种主要的MN功能亚型，分别负责慢、中和快 游泳。这些功能亚型可以根据它们的胞体位置、肌肉纤维类型、 出生日期，游泳时的招募顺序，以及内在属性。 通过初步分析，我发现了两个转录因子Evi1和Prdm16，它们分别是 在斑马鱼脊髓中有丝分裂后轴性MN的聚集性亚群中表达。Evi1和Prdm16 已知在其他细胞类型中对细胞命运和亚型指定很重要，但还没有 在脊髓中进行研究。根据它们的表达模式和突变体的初步行为数据 动物，我假设Evi1和Prdm16指定了MN的一个功能亚型，负责中间 速泳。在目标1中，我将用组织学方法确定MN亚型Evi1和Prdm16标记 方法和分子分析。在目标2中，我将确定Evi1和Prdm16是否指定子类型标识 使用功能损失法和功能增益法。本项目将阐明Evi1和Prdm16在 MN规范，可以揭示功能的确定的分子机制 属性。

PROJECT SUMMARY Every movement requires fine control of the strength and speed of muscle contractions. The nervous system achieves graded control of muscle by recruiting motor neuron (MN) subtypes with diverse functional properties, such as target muscle fiber type, electrophysiology, or role in behavior. The functional diversity of MNs is vital to locomotion, but we still lack a basic understanding of how it is created. During development, the identity of MN subtypes is determined by transcriptional codes. We know much about how anatomical MN subtypes defined by target muscle are specified, but the molecular logic by which functional MN subtypes develop is practically unknown. Though anatomical MN subtypes are well segregated in tetrapods, functional subtypes are heavily intermingled complicating their study. A model system where functional subtypes of MNs are segregated and easily identifiable, like in the zebrafish, provides a unique opportunity to dissect their molecular determinants. The zebrafish has three main functional subtypes of MNs responsible for slow, intermediate, and fast swimming. These functional subtypes can be identified based on their soma position, muscle fiber type, birthdate, recruitment order during swimming, and intrinsic properties. Through preliminary analysis, I have found two transcription factors, Evi1 and Prdm16, that are expressed in clustered subpopulations of post-mitotic axial MNs in the zebrafish spinal cord. Evi1 and Prdm16 are known to be important for cell fate and subtype specification in other cell types, but have not yet been studied in the spinal cord. Based on their expression pattern and preliminary behavioral data of mutant animals, I hypothesize Evi1 and Prdm16 specify a functional subtype of MNs responsible for intermediate speed swimming. In Aim 1, I will determine the MN subtype Evi1 and Prdm16 mark using histological approaches and molecular analyses. In Aim 2, I will determine if Evi1 and Prdm16 specify subtype identity using loss-of-function and gain-of-function methods. This project will elucidate the roles of Evi1 and Prdm16 in MN specification and could reveal molecular mechanisms responsible for the determination of functional properties.