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， 渠道受体和细胞表面分子，每一个都使特定的 与其他细胞接触。这种神经元多样性是如何产生的？ 神经发生开始于神经干细胞的形成， 成神经细胞从后代的链条上出芽进入胚胎：以这种方式 每个节原基中的50个神经母细胞被转化为 大约500个神经元的神经节。神经发生的三个步骤是：（1） 成神经细胞-表皮决定由细胞-细胞控制 外胚层细胞之间的相互作用。(2)成神经细胞测定：每个 神经母细胞根据其在神经元中的位置获得特定的身份。 神经上皮细胞;单个成神经细胞显示不同的基因模式 表达并产生神经元的特征家族。（三） 神经元决定。控制成神经细胞后代的测定 他们的出生顺序，或细胞谱系，从神经母细胞， 发育中的神经元之间的相互作用。我们的目标是分离基因 专门控制神经元和神经母细胞的决定。 许多分割和同源异型基因，包括enrailed（en）甚至- skipped（eve）和napedia（Antp）在特定的子集中表达 神经母细胞和神经母细胞后代的生长。 分割和同源异型基因表达因此是第一个 神经母细胞和神经元决定的表现;异常的 成神经细胞或神经元决定可以观察到的改变， 分割和同源异型基因表达。我们利用现有的 染色体缺陷和P元件诱变，以鉴定 改变en、eve和Antp的神经表达模式。的屏幕 约100个P元件诱导的致死突变与抗 en蛋白证实了该方法的可行性。几 影响神经发生的突变已经被确认， 包括一个，异常血统（ali），这似乎是专门 影响神经元测定;所有检查的非神经元组织均出现 正常我们正在对ali基因进行基因定位， 突变表型的发育分析，我们将克隆 基因通过筛选大量的P元素诱导致死系（- 1，000）与高特异性的en，eve和Antp抗体探针，我们将 鉴定控制神经元决定的其它基因， 果蝇这些基因中的一组对发育的影响 将被分析。它们的功能的分子基础将被探索 通过克隆基因并研究它们的表达模式， 其产物的结构和亚细胞定位。

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 molecules, each making specific contacts with other cells. How is this neuronal diversity generated? Neurogenesis begins with the formation of neuronal stem cells called neuroblasts which bud off chains of progeny into the embryo: in this way the 50 neuroblasts in each segment primordium are transformed into a ganglion of about 500 neurons. Three steps of neurogenesis are: (1) The neuroblast-epidermal decision which is controlled by cell-cell interactions among ectodermal cells. (2) Neuroblast determination: Each neuroblast acquires a specific identity based on its position in the neuroepithelium; individual neuroblasts show distinct patterns of gene expression and give rise to characteristic families of neurons. (3) Neuronal determination. Determination of neuroblast progeny is controlled by their birth-order, or cell lineage, from the neuroblast, and by interactions among the developing neurons. Our goal is to isolate genes that specifically control neuronal and neuroblast determination. Many segmentation and homeotic genes including engrailed (en) even- skipped (eve), and Antennapedia (Antp) are expressed in specific subsets of neuroblasts and neuroblast progeny as these cells are born. Segmentation and homeotic gene expression is thus one of the first manifestations of neuroblast and neuronal determination; aberrant neuroblast or neuronal determination can be observed as alterations in segmentation and homeotic gene expression. We are using existing chromosomal deficiencies and P element mutageneses to identify loci that alter the neural expression patterns of en, eve, and Antp. A screen of about 100 P element-induced lethal mutation with an antibody against the en protein has confirmed the feasibility of the approach. Several mutations that affect neurogenesis have already been identified, including one, aberrant lineages (ali), that appears to specifically affect neuronal determination; all non-neuronal tissues examined appear normal. We are genetically mapping the ali locus and continuing a developmental analysis of the mutant phenotype, and we will clone the gene. By screening a large number of P element-induced lethal lines (- 1,000) with the highly specific en, eve and Antp antibody probes, we will identify additional genes controlling neuronal determination in Drosophila. The developmental effects of a selected group of these genes will be analyzed. the molecular basis of their functions will be explored by cloning the genes and studying their expression patterns and the structure and subcellular localization of their products.