Regulation of mammalian odorant receptor gene expression

描述(申请人提供)：嗅觉系统是一种实验上易于处理的神经元多样性系统，它利用1000个(OR)基因谱系，每个基因在嗅觉感觉神经元(OSN)的一个子集中表达。给定的OSN只表达一个等位基因中的一个OR基因。OSN投射一个单独的轴突，支配嗅球中的特定肾小球，这种选择部分取决于所表达的OR的特异性。因此，嗅觉系统功能的中心是OR基因表达的过程。然而，在发现OR基因12年后，OR表达的调控仍然是一个谜；发表的文献很少，而且相互矛盾。 在初步研究中，已经开发了模型系统。短的转基因赋予了OR基因表达的许多复杂特征。这表现在两个位于不同染色体上的OR基因(MOR23和M71)，它们的序列同源性很低。MOR23转基因表达需要395个碱基区。没有LHX2同源结构域蛋白，OSN不会在末端分化，M71也不会表达。 需要检验的假设是，OR基因的表达(以及类似地，犁鼻受体基因和另外两种类型的化学感觉受体基因的表达)由短启动子控制，这些短启动子包含正常表达模式所必需的基序，并可能受到DNA重排的影响。方法是对小鼠进行遗传操作：转基因和定向突变。 其具体目的是：1：检测同源结构域基序在MOR23内源基因表达中的作用，并确定M71的表达是否可以挽救LHX2缺乏症。2：将短启动子的概念推广到其他气味受体基因。3.确定犁鼻受体基因的短转基因是否表达。4：寻找气味受体基因的DNA重排。 试验数据、工具、试剂、技术、专业知识和人员都已在实验室建立起来。由于哺乳动物的脑功能依赖于多种神经细胞类型，因此本研究将有助于我们对神经发育和功能的理解。

DESCRIPTION (provided by applicant): An experimentally tractable system for neuronal diversity is the olfactory system, which utilizes a repertoire of 1000 (OR) genes each expressed in a subset of olfactory sensory neurons (OSNs). A given OSN expresses a single OR gene, from one allele. An OSN projects a single axon that innervates a specific glomerulus in the olfactory bulb, and this choice is determined in part by the specificity of the expressed OR. Thus, central to the function of the olfactory system is the process of OR gene expression. However, twelve years after the discovery of OR genes, regulation of OR expression remains enigmatic; publications are far and few between, and are contradictory. In preliminary studies, model systems have been developed. Short transgenes impart many of the intricate features of OR gene expression. This was shown for two OR genes (MOR23 and M71) that have little sequence homology to each other and are located on different chromosomes. A 395 basepair region is required for MOR23 transgene expression. Without the Lhx2 homeodomain protein, OSNs do not differentiate terminally and M71 is not expressed. The hypothesis to be tested is that OR gene expression (and similarly, expression of vomeronasal receptor genes, two other types of chemosensory receptor genes) is controlled by short promoters that contain motifs essential for normal patterns of expression, and that are possibly altered by DNA rearrangements. The approach is genetic manipulation of the mouse: transgenesis and targeted mutagenesis. The Specific Aims are: 1: To test the function of the homeodomain motif in expression of the MOR23 endogenous gene, and to determine if Lhx2 deficiency can be rescued by M71 expression. 2: To generalize the concept of short promoters to other odorant receptor genes. 3: To determine if short transgenes of vomeronasal receptor genes are expressed. 4: To search for DNA rearrangements in odorant receptor genes. Pilot data, tools, reagents, techniques, expertise and personnel are well established in the laboratory. As mammalian brain function relies on a great many neuronal cell types, this research will contribute to our understanding of neural development and function.