STRUCT/FUNCTIONAL GENOMICS OF OLFACTORY RECEPTOR GENES

我们闻到数千种不同气味的能力是由鼻子感觉神经元上表达的大量气味受体（OR）介导的。嗅觉与气味分子结合，并将信息传递给大脑。在发育过程中，Ors还引导神经元到嗅球中空间固定的中继站。它们是哺乳动物基因组中最大的基因家族之一，至少有1000个成员。OR基因以簇的形式分布在许多染色体上，这些染色体可能占据基因组的1%。该家族还包括许多假基因和OR样基因，它们可能具有其他化学感觉功能，如细胞-细胞识别或精子趋化性。这个项目的目标是了解(A)在小鼠和人类中，Ors表达曲目的多样性是如何进化以满足不同的嗅觉需求的；(B)这些基因的转录是如何被控制的，使得每个感觉神经元表达一个单一的OR，而鼻子作为一个整体显示出不同的功能；(C)配体结合和神经元靶向的特异性如何体现在OR蛋白的结构中；(D) Ors的复杂基因组组织是否基于功能考虑；(E)负责嗅觉的OR基因是如何与其他家族成员区分和组织的；(F) OR亚基因组的进化动态特性如何影响功能库；(G)不同个体或不同年龄暴露在气味中的能力如何变化。因此，我们建议对小鼠和人类的OR家族进行全面而详细的基因组分析，并将这些基因组数据与基因功能和调控分析相结合。目的1是表征在小鼠和人类嗅觉组织中活性的几乎全部的or。目标2是绘制这些活性or的位置，并在每个染色体位置对所有or样序列进行测序，包括假基因和在鼻子外起作用的序列。目的3是描述包含大约20%的活性OR基因的基因组序列，以进行基因结构和簇组织的同源和同源比较。目的4是表征OR基因的5' utr和表达模式，并在小鼠中进行功能分析，以确定配体结合和神经元靶向的关键调控基序和结构元件。目标5是开发利用cDNA阵列一次性检测100个OR基因表达谱的技术。阿克塞尔集团在转基因和嗅觉生物学方面拥有专业知识，而Trask和Hood集团在测序、基因组进化和dna阵列技术方面拥有丰富经验，这是将大规模基因组学和功能生物学联合起来的独特机会。我们相信，这种功能基因组学的合作关系代表了未来合作努力的一种模式，以表征复杂的神经生物学系统和大型基因家族。

Our ability to smell thousands of different odors is mediated by a large repertoire of odorant receptors (OR) expressed on sensory neurons in the nose. The Ors bind odorous molecules and transmit this information to the brain. During development, Ors also guide neurons to spatially fixed relay stations in the olfactory bulb. Ors form one of the largest gene families in the mammalian genome, with at least 1000 members. OR genes are distributed on many chromosomes in clusters that may occupy as much as 1 percent of the genome. The family also includes many pseudogenes and OR- like genes that may perform other chemosensory functions, such as cell-cell recognition or sperm chemotaxis. This project s goal is to learn (A) how the diversity of the expressed repertoire of Ors has evolved to meet the differing demands for olfaction in mouse and human; (B) how transcription of these genes is controlled such that each sensory neuron expresses a single OR, while a diverse repertoire is displayed in the nose as a whole; (C) how the specificity of ligand-binding and neuronal-targeting is embodied in the structure of the OR proteins; (D) whether the complex genomic organization of Ors is based on functional considerations; (E) how the OR genes responsible for the sense of smell are distinguished from and organized relative to other members of the family; (F) how the evolutionary dynamic nature of the OR subgenome impacts the functional repertoire; and (G) how the repertoire varies among individuals or with age exposure to odors. We therefore propose to conduct a comprehensive and detailed genomic analysis of the OR families in mouse and human and to integrate these genomic data with assays of gene function and regulation. Aim 1 is to characterize nearly the full repertoire of Ors active in the olfactory tissue of mouse and human. Aim 2 is to map the locations of these active Ors and to sequence all OR-like sequences, including pseudogenes and ones functioning outside the nose, at each chromosomal location. Aim 3 is to characterize genomic sequence encompassing approximately 20 percent of the active OR genes to make paralogous and orthologous comparisons of gene structure and cluster organization. Aim 4 is to characterize the 5'UTRs and expression patterns of OR genes and to perform functional assays in mice to identify regulatory motifs and structural elements key for ligand-binding and neuron-targeting. Aim 5 is to develop technology to use cDNA arrays to examine expression profiles of 100's of OR genes at once. This partnership between the Axel group, with expertise in transgenics and olfactory biology, and the Trask and Hood groups, with experience in sequencing, genomic evolution, and cDNA-array technology, represents a unique opportunity to unite the worlds of large-scale genomics and functional biology. It is our belief that this sort of partnership in functional genomics represents a model for future collaborative efforts to characterize complex neurobiological systems and large gene families.