Transduction mechanisms and CNS targets of GC-D neurons

描述(申请人提供)：嗅觉是了解挥发性化学物质丰富而复杂的世界的主要窗口。哺乳动物的主要和辅助嗅觉系统用来检测和分析气味和信息素。然而，越来越明显的是，将鼻部化学感觉神经元划分为这两组是过于简单化的，并且不能反映鼻部受体细胞类型的功能多样性。在主嗅球的几个区域中发现了一组新的化学感觉神经元，它们针对一种独特的肾小球--位于后嗅球的“项链”肾小球。这些神经元还表现出不同于其他化学感觉神经元的基因表达谱。然而，目前尚不清楚这些感受器神经元和肾小球是否作为一个独特的化学感觉系统发挥作用。我们已经创造了一种基因靶向的小鼠，它在功能上扰乱了鸟苷酸环化酶的编码基因GC-D，这是一种对这些细胞的功能至关重要的蛋白质。打靶后，这个基因位点还编码一种组织化学报告基因--tau-β-半乳糖苷酶，它允许对表达GC-D的神经元进行可视化。我们建议使用这个小鼠模型对这一鲜为人知的化学感觉神经元群体的组织和功能特征进行第一次系统分析，并表征这些细胞在化学感觉行为中的功能作用。我们将对这些神经元和项链肾小球进行系统的解剖学描述，并确定GC-D在嗅觉系统中的发育和解剖表达模式。我们还将通过对成年动物和新生动物的行为和生化分析来确定这些神经元的化学感觉作用。最后，我们将描述这些细胞中特定化学感觉刺激(包括气味和信息素)的转导所涉及的生化级联。这些研究结果将为这些神经元和肾小球检测和分析感觉刺激的机制以及cGMP信号在这些过程中的作用提供重要的见解，并将确定这一独特神经元群体的感觉作用。

DESCRIPTION (provided by applicant): The sense of smell is the principal window on the rich and complex world of volatile chemicals. The main and accessory olfactory systems of mammals serve to detect and analyze odors and pheromones. However, it is becoming clear that the division of nasal chemosensory neurons into only these two groups is simplistic and does not reflect the functional diversity of receptor cell types in the nose. A novel group of chemosensory neurons, which target a unique population of glomeruli, the "necklace" glomeruli, in the posterior olfactory bulb, are found in several regions of the main olfactory epithelium. These neurons also exhibit a gene expression profile distinct from that of other chemosensory neurons. However, it is unclear if these receptor neurons and glomeruli function as a distinct chemosensory system. We have created a gene-targeted mouse that functionally disrupts the gene encoding the guanylyl cyclase, GC-D, a protein critical for the function of these cells. After targeting, this gene locus also encodes a histochemical reporter, tau-beta-galactosidase that permits the visualization of the neurons that express GC-D. We propose to use this mouse model to perform the first systematic analysis of the organization and functional characteristics of this poorly understood population of chemosensory neurons, as well as to characterize the functional role of these cells in chemosensory behavior. We will provide a systematic anatomical description of these neurons and the necklace glomeruli and determine the developmental and anatomical expression patterns of GC-D in the olfactory system. We will also determine the chemosensory role of these neurons through behavioral and biochemical analyses of adult and neonatal animals. Finally, we will characterize the biochemical cascade involved in the transduction of specific chemosensory stimuli, including both odors and pheromones, in these cells. These results obtained in these studies will provide important insights into the mechanism by which these neurons and glomeruli detect and analyze sensory stimuli, the role of cGMP signaling in these processes, and will define the sensory role of this unique neuronal population.