RUI: Molecular Genetic Analysis of Drosophila Neuroglian

果蝇神经胶质细胞是免疫球蛋白样细胞粘附分子（Ig-CAM）的L1亚家族的成员，其成员包括神经胶质细胞同系物人L1。 这些分子被认为参与胚胎神经系统发育的关键过程，如细胞粘附、神经突生长、轴突成束和细胞间信号传导。 有证据表明，神经胶质细胞和人类L1之间的功能相当保守，因为果蝇神经胶质细胞和人类L1的突变导致运动神经元轴突寻路缺陷。 我们对这些分子的功能的了解大部分都是从细胞培养研究中推断出来的。 培养物中转染细胞表面神经胶质细胞的表达导致细胞聚集，表明嗜同性细胞粘附。 目前的证据表明，位于细胞外部的分子部分中的某些区域（结构域）对于培养条件下的细胞聚集是必需的。 本提案中描述的实验将把这些发现从培养的细胞扩展到活的有机体。 一种称为P-元件介导的生殖系转化的技术将被用来检查活果蝇中神经胶质细胞的蛋白变体的功能。 这些研究将确定哪些参与培养中细胞粘附的神经胶质细胞胞外结构域也参与产生突变胚胎中发生的感觉细胞图案缺陷和运动神经元寻路缺陷。 这些研究也将探讨神经胶质细胞在神经元中的过度表达对神经系统发育的影响。 将评价神经胶质细胞突变形式对轴突成束的影响，以确定物理粘附是否是神经胶质细胞的主要功能，如果是，则确定培养细胞中参与细胞粘附的结构域是否是活体动物中粘附的决定因素。

Drosophila neuroglian is a member of the L1 subfamily of immunoglobulin-like cell adhesion molecules (Ig-CAMs) whose members include the neuroglian homolog human L1. These molecules are thought to be involved in critical processes of embryonic nervous system development such as cell adhesion, neurite growth, axon fasciculation and intercellular signaling. There is evidence of considerable conservation of function between neuroglian and human L1 since mutations in both Drosophila neuroglian and human L1 lead to motor neuron axonal pathfinding defects. Much of what we know about the function of these molecules has been inferred from cell culture studies. Expression of neuroglian on the surfaces of transfected cells in culture causes the cells to aggregate, demonstrating homophilic cell adhesion. Current evidence suggests that certain regions (domains) in the portion of the molecule located on the exterior of the cell are necessary for cell aggregation in culture conditions. The experiments described in this proposal will extend these findings from cultured cells to the living organism. A technique termed P-element mediated germ-line transformation will be used to examine the function of protein variants of neuroglian in living Drosophila. These studies will determine which of the extracellular domains of neuroglian that are involved in cell adhesion in culture also are involved in producing the sensory cell patterning defects and motor neuron pathfinding defects that occur in mutant embryos. These studies also will investigate the effects on nervous system development of the overexpression of neuroglian in neurons. Effects of the mutant forms of neuroglian on axon fasciculation will be evaluated to determine whether physical adhesion is a major function of neuroglian, and if it is, to determine whether or not the domains involved in cell adhesion in cultured cells are the determinants of adhesion in the living animal.