GENETIC AND MOLECULAR STUDIES OF NEUROGENESIS

果蝇中枢神经系统（CNS）由数百个神经元组成。 神经元，每一个都表达一种独特的神经递质组合， 通道、受体和细胞表面分子--每个神经元 与其他神经元或肌肉形成许多固定的联系。 如何 这种壮观的神经元多样性产生了吗？ 我们的长期目标 是为了确定用于产生 果蝇中枢神经系统的神经元多样性，并确定这些 在更复杂的生物体中是保守的。 果蝇是一种 研究中枢神经系统发育的理想生物体：神经发生是 相对简单，在两个步骤中产生蜂窝分集。 首先，神经外胚层中的位置线索控制25 独特的神经元前体细胞（神经母细胞）;第二，每个神经母细胞 经过一个不变的细胞谱系， 神经节母细胞（GMC），其各自产生一对神经元。 每个 这两个步骤的结合有助于CNS中细胞命运的多样性， 每个步骤都可以独立研究。 拟议的研究使用了几种最新的技术先进， 研究成神经细胞和神经元测定。 了解 位置线索如何控制成神经细胞的决定，我们将利用 最近开发的分子标记，使每个神经母细胞， 进行唯一鉴定，并测定改变 这些标记。 特别是，我们将侧重于该部分的作用 极性基因wingless在非自主决定的 NB4-2（Specific Aim I）。 我们还将重点讨论 5953基因，该基因在已鉴定的NB 4 -2中表达，以响应 wg的位置线索，显然需要NB 4 -2的测定。 为了表征控制基于谱系的神经元决定的基因， 我们将使用 一种新的细胞标记技术，用于标记单个已鉴定的神经母细胞， 所有的神经元后代。 特别是，我们将研究 在细胞命运的规范中， 在所鉴定的NB 1 -1、NB 4 -2和NB 7 -4的谱系中（特异性目的 II）。 此外，我们将使用特定神经母细胞的分子标记物 “亚系”和细胞周期控制基因的突变进行调查 通过细胞周期的转换和 在鉴定成神经细胞期间GMC命运的顺序特化 具体目标III（Specific Aim III） 我们预计在识别和表征基因方面会取得快速进展 控制果蝇中枢神经系统神经元多样性的产生 由于神经系统分子标记物相对简单 对于单个前体细胞， 并克隆CNS表达基因，以及新开发的细胞谱系 一种允许野生型和突变型NB谱系直接 在每个神经元的轴突投射水平上进行比较， linage。

The Drosophila central nervous system (CNS) is composed of hundreds of neurons, each expressing a unique combination of neurotransmitters, ion channels, receptors, and cell surface molecule -- with each neuron forming numerous stereotyped contacts with other neurons or muscles. How is this spectacular neuronal diversity generated? Our long term goals are to identify the cellular and molecular mechanisms used to generate neuronal diversity in the Drosophila CNS, and determine whether these mechanisms are conserved in more complex organisms. Drosophila is an ideal organism for investigating CNS development: neurogenesis is relatively simple, with cellular diversity being generated in two steps. First, positional cues in the neuroectoderm control the formation of 25 unique neuronal precursor cells (neuroblasts); second, each neuroblast goes through an invariant cell lineage to generate an average of five ganglion mother cells (GMCs) which each produce a pair of neurons. Each of these two steps contributes to the diversity of cell fate in the CNS, and each step can be studied independently. The proposed research uses several recent technical advanced to investigate both neuroblast and neuronal determination. To understand how positional cues control neuroblast determination, we will make use of recently developed molecular markers that allow each neuroblasts to be uniquely identified, and assay for mutations that alter expression of these markers. In particular, we will focus on the role of the segment polarity gene wingless in the non-autonomous determination of the identified NB4-2 (Specific Aim I). We will also focus on the role of the 5953 gene, which is expressed in the identified NB4-2 in response to the wg positional cue, and is apparently required for NB4-2 determination. To characterize genes controlling lineage-based neuronal determination, we will look for specific alterations in neuroblast cell lineages using a novel cell marking technique to label single identified neuroblast and all of its neuronal progeny. In particular, we will investigate the role of ming, seven-up and prospero genes in the specification of cell fate during the lineage of the identified NB1-1, NB4-2 and NB7-4 (Specific Aim II). In addition, we will use molecular markers for specific neuroblast "sublineages" and mutations in cell cycle control genes to investigate the relationship between transition through the cell cycle and the sequential specification of GMC fate during identified neuroblast lineages (Specific Aim III). We anticipate rapid progress in identifying and characterizing genes controlling the generation of neuronal diversity in the Drosophila CNS due to the relative simplicity of the nervous system molecular markers for individual precursor cells, powerful new techniques for identifying and cloning CNS-expressed genes, and a newly developed cell lineage method that allows wild-type and mutant NB lineages to be directly compared at the level of the axonal projections of every neuron in the linage.