O'Connor L T, Lauterborn J C, Gall C M, Smith M A
Department of Anatomy and Neurobiology, University of California at Irvine 92717.
J Neurosci. 1994 Mar;14(3 Pt 1):1141-52. doi: 10.1523/JNEUROSCI.14-03-01141.1994.
Agrin is a protein implicated in the formation and maintenance of the neuromuscular junction. In addition to motor neurons, agrin mRNA has been detected in the brains of embryonic rat and chick and adult marine ray, suggesting that this molecule may also be involved in the formation of synapses between neurons. As a step toward understanding agrin's role in the CNS, we utilized Northern blot and in situ hybridization techniques to analyze the regional distribution and cellular localization of agrin mRNA in the spinal cord and brain of adult rats. The results of these studies indicate that the agrin mRNA is expressed predominantly by neurons broadly distributed throughout the adult CNS. Moreover, expression of agrin mRNA is not restricted to cholinergic structures or regions of the brain receiving cholinergic input. Recently, RNA isolated from rat embryonic spinal cord was shown to contain four alternatively spliced agrin mRNAs, referred to as agrin0, agrin8, agrin11, and agrin19, each of which encodes agrin proteins that are active in acetylcholine receptor aggregating assays (Ferns et al., 1992). Using the polymerase chain reaction we demonstrate that all four of these agrin transcripts are expressed within the adult CNS. Agrin0, agrin8, and agrin19 were present in all regions analyzed. In contrast, agrin11 was detected only in forebrain. Results of these studies indicate that both the level of expression and pattern of alternative splicing of agrin mRNA are differentially regulated in the brain. The broad and predominantly neuronal distribution of agrin mRNA in the adult brain suggests that, in addition to its role at the neuromuscular junction, agrin may play a role in formation and maintenance of synapses between neurons in the CNS.
集聚蛋白是一种与神经肌肉接头的形成和维持有关的蛋白质。除了运动神经元外，在胚胎大鼠、鸡以及成年海鳐的脑中也检测到了集聚蛋白mRNA，这表明该分子可能也参与神经元之间突触的形成。作为了解集聚蛋白在中枢神经系统中作用的第一步，我们利用Northern印迹法和原位杂交技术分析了成年大鼠脊髓和脑中集聚蛋白mRNA的区域分布和细胞定位。这些研究结果表明，集聚蛋白mRNA主要由广泛分布于成年中枢神经系统的神经元表达。此外，集聚蛋白mRNA的表达并不局限于胆碱能结构或接受胆碱能输入的脑区。最近研究表明，从大鼠胚胎脊髓中分离出的RNA含有四种选择性剪接的集聚蛋白mRNA，分别称为集聚蛋白0、集聚蛋白8、集聚蛋白11和集聚蛋白19，每一种都编码在乙酰胆碱受体聚集试验中具有活性的集聚蛋白（弗恩斯等人，1992年）。我们利用聚合酶链反应证明，这四种集聚蛋白转录本在成年中枢神经系统中均有表达。集聚蛋白0、集聚蛋白8和集聚蛋白19存在于所有分析区域。相比之下，仅在前脑检测到集聚蛋白11。这些研究结果表明，集聚蛋白mRNA的表达水平和选择性剪接模式在脑中受到不同的调控。成年脑中集聚蛋白mRNA广泛且主要在神经元中的分布表明，除了其在神经肌肉接头处的作用外，集聚蛋白可能在中枢神经系统中神经元之间突触的形成和维持中发挥作用。
