Studies on Role and Regulation of the Ventral Nervous SystemDefective Homeobox Gene During Drosophila Neurogenesis

PI：Mellerick-Dressler IBN：9604413脊椎动物和苍蝇的中枢神经系统都由数以千计的神经细胞或神经元组成，每个神经细胞都有独特的位置，表达神经递质和离子通道的特定组合，并与其他神经元和靶细胞进行适当的接触。这项研究的目的是了解神经系统发育过程中个体细胞身份是如何被指定的。由于哺乳动物神经系统发育中固有的复杂性由细胞数量和细胞类型决定，Mellerick-Dressler博士的实验室正在果蝇黑腹果蝇身上研究中枢神经系统的特性。虽然相对简单，但果蝇已被证明是分析基因功能的一个优雅和高度相关的模型。神经系统的原基由多种调节基因表达的基因沿着背腹轴和前后轴形成图案。其中一个基因，称为腹侧神经系统缺陷(VND)或NK-2，在有限的背侧-腹侧细胞群中表达，这些细胞在苍蝇和哺乳动物胚胎中都能产生神经元，这表明这个基因家族指导着图案形成。事实上，当vnd/NK-2基因发生突变时，果蝇胚胎会死亡，中枢神经系统发育异常，这表明该基因对神经发育至关重要。为了验证vND/NK-2在神经元模式中发挥作用的假设，将检查现有的vND/NK-2突变体是否存在正常表达在vND/NK-2表达区域内的基因的表达变化。VND/NK-2基因表达的时间和空间受限模式的功能意义将通过产生和分析两种不同类型的转基因“转基因”苍蝇胚胎来解决--一种在所有细胞中表达VND/NK-2，另一种在中枢神经系统发育过程中在受限的细胞群体中过度表达该基因。最后，为了解决vnd/NK-2在胚胎发育后是否具有显著的功能意义，将在胚胎中枢神经系统发育后确定vnd/NK-2基因产物在野生型果蝇中的时空定位。支持这项研究的工作假设是，VND/NK-2功能和调控的许多方面在进化上是保守的。因此，这项工作的结果也可能有助于理解脊椎动物VND/NK-2类基因在神经发育过程中的功能。

PI: Mellerick-Dressler IBN: 9604413 The central nervous system (CNS) of both vertebrates and flies is composed of thousands of nerve cells, or neurons, each uniquely positioned, that express a specific combination of neurotransmitters and ion channels, and make appropriate contact with other neurons and target cells. The aim of this research is to understand how individual cell identities are specified during nervous system development. Because of the complexity inherent in mammalian nervous system development defined by both cell numbers and cell types, CNS specification is being studied in the fruit fly, Drosophila melanogaster, in Dr. Mellerick-Dressler's laboratory. Although relatively simple, Drosophila has proven to be an elegant and highly relevant model for analyzing gene function. The primordium of the nervous system is patterned along both the dorsal-ventral axis and the anterior-posterior axis by a variety of genes that regulate gene expression. One of these genes, called ventral nervous system defective (vnd) or NK-2, is expressed in a restricted dorsal-ventral population of cells that give rise to neurons in both fly and mammalian embryos suggesting that this gene family directs patterning. Indeed, fly embryos die and the central nervous system develops abnormally when mutations are present in the vnd/NK-2 gene, indicating that this gene is critical for neural development. To test the hypothesis that vnd/NK-2 functions in neuronal patterning, existing vnd/NK-2 mutants will be examined for altered expression of genes that are normally expressed within the vnd/NK-2 expression domain. The functional significance of the temporal and spatially restricted pattern of vnd/NK-2 gene expression will be addressed by generating and analyzing two different types of genetically altered "transgenic" fly embryos -- one that expresses vnd/NK-2 in all cells, the second that over-expresses the gene within a restricted population of cells during CNS development. Finally, with the even tual aim of addressing whether expression of vnd/NK-2 is functionally significant after embryogenesis, the temporal and spatial localization of the vnd/NK-2 gene product will be determined in wild-type flies after embryonic CNS development. The working hypothesis underlying this research is that many aspects of vnd/NK-2 function and regulation are evolutionarily conserved. Thus, the results from this work may also contribute to understanding how vertebrate vnd/NK-2 like genes function during neural development.