MOLECULAR ANALYSIS OF AXON FASCICLE SPECIFIC GLYCOPROTEI

理解大脑发育的一个中心问题是获得 洞察细胞识别的分子基础以及如何 精确的神经元连接被建立起来。在早期开发期间 轴突必须在未知的胚胎景观中开创新的道路 无论是在中枢神经系统内部还是从外围往返都是如此。这些路径依次为 可作为以后分化神经元的指南，其轴突 已经被证明可以做出高度特定的路径选择，并显示出 选择性分束征。这一过程可能会在 神经系统的正确布线。关于分子的大多数假说 选择性颤动的机制涉及特定的粘连或 表面介导的轴突和/或生长锥之间的识别事件 大分子。然而，挑战一直是检验这一假设，并 为了识别和表征这种分子，因为更具体和 限制它们的表达和分布，它们的丰度就越低。 因此，分离出的分子数量非常有限。 建议的粘连和识别功能，其中只有几个是 仅限于轴突的子集，而不仅仅涉及普通神经细胞 粘附力。 本建议的目的是增加我们对这种情况的了解 通过确定抗原的分子结构和功能来确定分子 由单抗LAN3-2和LAN4-2以及 定义形成特定轴突的小部分轴突的其他抗原 水蚤里的一簇簇。从抗原的氨基酸序列来看，它 是一种膜表面糖蛋白，我们将对其进行功能分析 其结构的含义。具体地说，我们想要检验这一假设 这些抗原介导了选择性轴突丛生，因此 可能代表参与神经元识别和轴突引导的分子。 我们还将通过以下方式对基因座进行分子表征 探讨其精细结构、表现形式和作用方式。 发展。在水蚤中克隆这些抗原的前景是 它们是针对非常小且定义明确的轴突群体的。 因此，不太可能只是调解普遍的粘连。 我们在分析LAN3-2/4-2抗原和其他水蚤方面的长期目标 轴突和轴突亚群特有的抗原是为了获得基本的见解 这些分子的功能意义，它们可能 层级组织、功能决定因素和发展 对表达的调节。因为已经确定了许多重要的 结构蛋白序列基序在功能上是保守的 在整个进化过程中，这些研究应该会增强我们的基础 对神经元识别和选择性颤动的理解 提供对异常神经连接的根本原因的见解 以及大脑发育异常。

A central problem in understanding the development of the brain is to gain insight into the molecular basis for cellular recognition and for how precise neuronal connections are established. During early development axons must pioneer novel pathways through uncharted embryonic landscapes both within the CNS and to and from the periphery. These pathways in turn may serve as a guide for later differentiating neurons, the axons of which have been shown to make highly specific pathway choices and to show selective fasciculation. This process may play a crucial role in the correct wiring of the nervous system. Most hypotheses about the molecular mechanism for selective fasciculation involve specific adhesion or recognition events between axons and/or growth cones mediated by surface macromolecules. However, the challenge has been to test this hypothesis and to identify and characterize such molecules, since the more specific and restricted their expression and distribution is, the lower their abundance. Consequently, a very limited number of molecules has been isolated with proposed adhesion and recognition functions and only a handful of these are confined to subsets of axons and not just involved in general neural cell adhesion. The object of the present proposal is to increase our knowledge of such molecules by determining the molecular structure and function of an antigen recognized by the monoclonal antibodies lan 3-2 and lan 4-2 as well as other antigens which define small subsets of axons forming specific fascicles in the leech. From the amino acid sequence of the antigen, which is a membrane surface glycoprotein, we will analyze the functional implications of its structure. Specifically, we want to test the hypothesis that these antigens are mediating the selective axon fasciculation and thus may represent molecules involved in neuronal recognition and axon guidance. We will also carry out a molecular characterization of the gene locus by exploring its fine structure, its expression and mode of action during development. The promise of cloning these antigens in the leech is that they are specific for a very small and well defined populations of axons and therefore are not likely to be just mediating general adhesion. Our long range goal in analyzing the lan 3-2/4-2 antigen and other leech antigens specific for axons and axonal subsets is to gain basic insights into the functional significance of such molecules, their possible hierarchial organization, functional determinants, and developmental regulation of expression. Since it has been established that many important structural protein sequence motifs have been functionally conserved throughout evolution these investigations should enhance our basic understanding of neuronal recognition and selective fasciculation and provide insights into the underlying causes of aberrant neural connections and abnormal brain development.