Cell Fate Specification in the Developing Nervous System

描述(申请人提供)：基本螺旋-环-螺旋类的神经转录因子在确定神经前体细胞群体和控制其后代的分化方面具有关键的保守作用。了解这些因子的多重、质的不同功能是发育神经科学的中心目标。本研究的长期目标是在分子遗传水平上确定线虫神经原基因Lin-32控制单个神经前体细胞产生3种不同神经细胞的机制。这3种细胞类型(称为RNA和RnB的两个神经元和一个神经胶质样结构细胞RNST)共同构成了射线感受器，这是线虫雄性尾巴中的一个模式感觉器官。我们假设射线前体细胞的后代是由依赖于LIN-32和它所在的细胞环境的转录级联来组合指定的。这里提出的研究将确定并从功能上描述建立这种背景的因素以及那些执行特定射线细胞命运的因素。在其他特征中，线虫的遗传复杂性以及在活体动物中观察发育和标记基因表达的能力使线虫成为解决这些问题的理想模式。这项提案概述了3个相关的目标，旨在通过表征协调射线发育的调控网络来检验我们的假设。(1)我们将测试在射线亚系的1个分支中调节射线细胞命运的不对称Lin-32表达模式的新模型，并探讨Wnt/MAPK信号在这一过程中的作用。(2)我们将研究LIM-HD基因LIM-7在RnB神经元亚型确定中的作用，并确定其与LIN-32的关系。(3)我们将进行一种新的正向遗传筛选，并从分子上克隆2个新的基因，这些基因控制着射线亚系中的神经模式。这些研究将确定决定原神经基因功能特异性的遗传机制，并在一个简单易处理的模型中建立神经亚型。了解这些机制对于充分认识人类神经发育疾病和设计合理的治疗方法都是至关重要的。LAY摘要：我们将使用一种小型土壤蛔虫，探索在神经系统中产生细胞复杂性的遗传机制。这对于这些过程被破坏的人类疾病具有特别的相关性。

DESCRIPTION (provided by applicant): Proneural transcription factors of the basic helix-loop-helix class have critical conserved roles in specifying populations of neural precursor cells and in controlling the differentiation of their progeny. Understanding the multiple, qualitatively different functions of these factors is a central goal in developmental neuroscience. The long-term goal of this research is to define at a molecular genetic level the mechanisms by which the C. elegans proneural gene lin-32 controls the generation of 3 distinct neural cell types from a single neural precursor cell. These 3 cell types (2 neurons called RnA and RnB and a glial-like structural cell, Rnst) together form the ray sensillum, a model sensory organ in the C. elegans male tail. We hypothesize that the progeny of the ray precursor cell are specified combinatorially by a transcriptional cascade that depends both on lin-32 and on the cellular context in which it functions. The research proposed here will identify and functionally characterize the factors that establish this context and those that act to implement specific ray cell fates. Among other characteristics, the genetic sophistication of C. elegans and the ability to observe development and marker gene expression in live animals make the nematode an ideal model for addressing these issues. This proposal outlines 3 related aims to test our hypothesis by characterizing the regulatory network that coordinates ray development. (1) We will test the novel model that regulated asymmetric lin-32 expression patterns ray cell fates in 1 branch of the ray sublineage and explore the role of Wnt/MAPK signaling in this process. (2) We will examine the role of the LIM-HD gene lim-7 in the specification of RnB neuron subtype and determine its relationship to lin-32. (3) We will carry out a novel forward genetic screen and molecularly clone 2 new genes that act to control neural patterning in the ray sublineage. These studies will define the genetic mechanisms that determine the specificity of proneural gene function and the establishment of neural subtypes in a simple and tractable model. Understanding these mechanisms is essential both for a full appreciation of human neurodevelopmental disease and for the design of rational therapies. Lay summary: Using a small soil roundworm, we will explore the genetic mechanisms that generate cellular complexity in the nervous system. This has special relevance for human diseases in which these processes are disrupted.