EXPRESSION ZONES IN MAMMALIAN OLFACTORY EPITHELIUM

嗅觉系统中潜在的感知敏锐度的机制是 不是很清楚。我们已经确定了一个多基因家族，它编码 嗅觉表达的数百种不同的气味受体 鼻腔内的感觉神经元。我们最近获得了证据 这些受体以不同的空间模式表达，可能 提供传入感官信息的初始组织 嗅觉上皮在其传输到嗅球之前。 嗅觉上皮似乎被分成有限数量。 气味感受器表达区域。这些区域是双边的 在两个鼻腔中对称，在不同的 个人。每个受体基因可能只在一个区域表达。 然而，许多不同的受体基因在同一区域和 每个基因都在散布在整个区域的神经元中表达。 看来，发育中的神经元在选择哪个受体基因时 表达，可能局限于严格定义的区带基因集，但可能 通过随机机制从该集合中选择一个成员。 拟议的研究将调查高度明确的分区如何 气味受体基因表达的组织实现和检测 该组织的职能意义。一种体外试验 神经发生系统将被用来确定带状图案 是嗅觉上皮固有的或由嗅觉施加的 灯泡通过逆行信号。为了深入了解分子 机制，我们将使用染色体原位 杂交以检查区带基因组的基因组组织。 为了识别充当区域说明符的分子，我们将：L)研究 5‘侧翼是否存在区带特异性序列基序 气味受体基因的序列，如果是的话，使用这些基序 识别识别这些基序的DNA结合蛋白，2)执行聚合酶链式反应 用简并引物鉴定已知家族成员的反应 差异表达的DNA结合蛋白 不同区域，3)执行区域特定RNA的广泛搜索 差异RNA显示方法。最后，在一系列 合作研究，我们会问气味感受器 当嗅觉上皮起到功能单位的作用时，表达带起作用 暴露在气味中。总而言之，这些研究应该提供一个很好的 有关该表达式的功能意义的大量信息 区域和它们被指定的分子机制。自.以来 用于实现功能组织的机制 嗅觉系统很可能被神经衰弱的其他部位所共享 系统，这些研究可能有助于更广泛的理解 神经系统的发育和功能。

The mechanisms underlying perceptual acuity in the olfactory system are not well understood. We have identified a multigene family that codes for hundreds of diverse odorant receptors that are expressed by olfactory sensory neurons in the nasal cavity. We have recently obtained evidence that these receptors are expressed in distinct spatial patterns that may provide for an initial organization of incoming sensory information in the olfactory epithelium prior to its transmission to the olfactory bulb. It appears that the olfactory epithelium is divided into a limited number of odorant receptor expression zones. These zones are bilaterally symmetrical in the two nasal cavities and are the same in different individuals. Each receptor gene may be expressed in only one zone. However, many different receptor genes are expressed in the same zone and each gene is expressed in neurons that are scattered throughout the zone. It appears that the developing neuron, in choosing which receptor gene to express, may be confined to a strictly defined zonal gene set, but may select a member of that set via a stochastic mechanism. The proposed studies will investigate how the highly specified zonal organization of odorant receptor gene expression is achieved and examine the functional significance of this organization. An in vitro neurogenesis system will be used to determine whether zonal patterning is intrinsic to the olfactory epithelium or is imposed by the olfactory bulb via retrograde signals. In order to gain insight into the molecular mechanisms underlying zonal patterning, we will use chromosomal in situ hybridization to examine the genomic organization of the zonal gene sets. To identify molecules which act as zone specifiers, we will: l) examine whether zone specific sequence motifs are present in the 5' flanking sequences of odorant receptor genes and, if so, use these motifs to identify DNA binding proteins that recognize these motifs, 2) perform PCR reactions with degenerate primers to identify members of known families of DNA binding proteins that are differentially expressed in the different zones, 3) perform a broad search for zone specific RNAs using the differential RNA display method. Finally, in a series of collaborative studies, we will ask whether the odorant receptor expression zones behave as functional units when the olfactory epithelium is exposed to odorants. Together, these studies should provide a great deal of information about the functional significance of the expression zones and the molecular mechanisms by which they are specified. Since the mechanisms that are used to achieve the functional organization of the olfactory system are likely to be shared by other parts of the nervous system, these studies are likely to contribute to a broad understanding of nervous system development and function.