MOLECULAR BIOLOGY OF RETINA-SPECIFIC GABA RECEPTORS

γ-氨基丁酸(GABA)是一种主要的视网膜神经递质 可以在多种视网膜受体上发挥作用。这些受体中的一些 是配体门控离子通道，可能类似于GABA/A受体 在大脑中显著表达。互补DNA编码14 不同的GABA/A受体亚基排列在4个主要类别(α， 贝塔、伽马和德尔塔)已经从大脑中克隆出来。我们有 最近描述了通过cDNA发现的一个GABA Rho亚单位类 克隆。视网膜中GABA-RON1的表达至少是 它在任何其他组织中的表达。这种视网膜特异性受体 亚基具有独特的结构特征，并渴望与 高寡聚受体显示独特的药理和生理作用 特点。从视网膜cDNA中分离出第二个Rho亚基 文库在视网膜RNA中的表达水平较低，但显示 结构和功能特征与Rho1亚基相似。这 应用程序建议研究这一分子生物学 视网膜GABA受体亚基的不同类别及其相互关系 通过追求以下目标，可能在视网膜病理学中发挥作用： 1)分析Rho的基因组结构和相对定位 基因，包括对假定的启动子区域的详细检查 每一个基因。 2)确定GABARO1或ROG2突变是否导致常染色体 黄斑营养不良的主要形式，最近被映射到 与Rho基因相同的染色体区域(6q13-q21)。 3)确定交替拼接形式的附加构件是否 通过聚合酶链式反应在视网膜表达GABA Rho亚单位家族的 利用Rho基因设计的引物扩增视网膜cDNAs 序列。 4)执行结构/功能分析，以确定 GABA Rho的cDNA序列具有药理学和生理学意义 此子单元类的属性特征。 5)确定哪些视网膜细胞类型表达GABA Rho亚单位 利用Northern和PCR分析RNA，原位杂交和 免疫组织化学技术。

Gamma amino butyric acid (GABA) is a major retinal neurotransmitter than can function at a variety of retinal receptors. Some of these receptors are ligand-gated ion channels, probably similar to the GABA/A receptors prominently expressed in the brain. Complementary DNAs encoding 14 different GABA/A receptor subunits arranged in 4 major classes (alpha, beta, gamma, and delta) have been cloned from the brain. We have recently described a GABA rho subunit class discovered through cDNA cloning. GABA rho1 expression in retina is at least 20-fold greater than its expression in any other tissue. This retina-specific receptor subunit has distinctive structural features and avidly associates into homo-oligomeric receptors displaying unique pharmacologic and physiologic characteristics. A second rho subunit isolated from a retinal cDNA library is expressed at lower levels in retina RNA but displays structural and functional features similar to the rho1 subunit. This application proposes to investigate the molecular biology of this distinct class of retinal GABA receptor subunits and to explore their possible roles in retinal pathology by pursuit of the following aims: 1) Analyzing the genomic organization and relative orientation of the rho genes including detailed examination of the putative promoter regions of each gene. 2) Determining whether mutations in GABA rho1 or rho2 cause an autosomal dominant form of macular dystrophy which has recently been mapped to the same chromosomal region (6q13-q21) as the rho genes. 3) Ascertaining whether additional members of alternatively-spliced forms of the GABA rho subunit family are expressed in retina by PCR amplification of retinal cDNA using primers derived from rho cDNA sequences. 4) Performing structure/function analysis to determine which portions of the GABA rho cDNA sequences confer the pharmacologic and physiologic properties characteristic of this subunit class. 5) Ascertaining which retinal cell types express the GABA rho subunits using Northern and PCR analysis of RNA, in situ hybridization and immunohistochemical techniques.