Development and Function of the Mammalian Olfactory System

过去一年的研究重点是界定 发展的分子机制 哺乳动物的嗅觉系统特别强调 鉴定指导建立 突触连接的精确模式， 外周感觉神经元及其靶神经元 灯泡这些研究导致了新成员的鉴定， 在嗅觉器官中高度表达的脑信号蛋白基因家族 和犁鼻系统几个基因的全长cDNA克隆 分离这些基因并测序。原位杂交 实验表明，该基因家族的成员表达 在发育的早期， 初级感觉神经元和延髓二尖瓣细胞。的 编码神经纤毛蛋白1和2的基因， 受体，也被发现表达在嗅觉和 犁鼻系统发育早期。特别令人感兴趣的是， 我们发现特定的信号蛋白和它们的受体 在辅助嗅觉系统和主嗅觉系统中差异表达 或者在嗅上皮的不同区域。功能 这些分子的差异分布的重要性是 正在调查 第二个研究重点是 气味受体的表征。为探讨 包括配体的气味受体的功能特性 特异性、G蛋白偶联和选择性，以及 配体依赖性修饰，我们目前正在开发一种 异源细胞表达系统。哺乳动物载体， 几种气味受体的完整编码区被 构建了稳定和瞬时转染的细胞系， 目前正在评估更高水平的气味受体mRNA 用于产生功能性气味受体。

Research during the past year focused on defining the molecular mechanisms underlying the development of the mammalian olfactory system. Particular emphasis was placed on the identification of molecules which direct the establishment of the precise patterns of synaptic connectivity observed between peripheral sensory neurons and their target neurons in the olfactory bulb. These studies led to the identification of novel members of the semaphorin gene family that are highly expressed in the olfactory and vomeronasal systems. Full length cDNA clones for several of these genes were isolated and sequenced. In situ hybridization experiments indicate that members of this gene family are expressed early in development during the time when synaptogenesis between primary sensory neurons and bulbar mitral cells is occurring. The genes encoding neuropilin 1 and 2, the two identified semaphorin receptors, were also found to be expressed in the olfactory and vomeronasal systems early in development. Of particular interest, we found that particular semaphorins and their receptors were differentially expressed in the accessory and main olfactory systems or in different zones of the olfactory epithelium. The functional significance of the differential distribution of these molecules is being investigated. A second focus of research was the molecular characterization of odorant receptors. In order to examine the functional properties of odorant receptors including ligand specificity, G- protein coupling and selectivity, and ligand-dependent modifications, we are currently developing a heterologous cell expression system. Mammalian vectors containing the complete coding regions of several odorant receptors were constructed. Stable and transiently transfected cell lines producing high levels of odorant receptor mRNA are currently being evaluated for the production of functional odorant receptors.