Activation of Plp Gene Expression in Oligodendrocytes

髓鞘蛋白脂蛋白(Plp)基因(Plp1)编码中枢神经系统髓鞘中含量最丰富的蛋白质。 它在少突胶质细胞中的表达受到严格的调控。人类基因的突变已被证明是 与X连锁髓鞘功能障碍相关的Pelizaeus-Merzbacher病(PMD)和某些类型的 痉挛性截瘫(SPG2)。髓鞘功能障碍可由Plp1基因表达水平升高或 它的缺失。因此，该基因在中的准确表达至关重要。携带Plp1基因的转基因小鼠- LacZ融合基因我们已经证明Plp1内含子1 DNA对于调节 中枢神经系统发育的髓鞘活动期少突胶质细胞中plp1基因的转录。这个 内含子约占Plp1基因的一半，包含超过8kb的DNA。我们已经确定了一个 Plp1内含子1DNA中的调控元件，命名为ASE，用于抗沉默/增强子。我们相信ASE 参与形成一种多蛋白核蛋白复合体，作为一种有效的转录因子 激活剂称为增强体。增殖体是一类新的转录调节因子，它们是 具有作为一个单位起作用的高阶核蛋白复合体的特征。准确的三个- 维度结构允许因子之间的协同作用，并且对于诱导基因激活是必需的。内含子 还包含另一个增强子，指定为wmN1，已大致本地化为1.2kb片段 关于DNA的。我们推测，少突胶质细胞中Plp1基因活性的急剧增加 发育受ASE和wmN1增强子及其相关(同源)DNA结合的控制 各种因素。阐明Plp1基因表达的控制机制将是设计中的重要一步 旨在促进再髓鞘形成的治疗方法，因为在髓鞘形成时， 少突胶质细胞由Plp1基因产生。早期存在的因素的发育差异 儿童时期与成人时期相比，可能解释了在多发性硬化症患者中观察到的相当低的再髓鞘形成水平。 结合ASE和wmN1增强子的同源因子可能提供新的治疗靶点 这些患者的再髓鞘形成。同样，ASE或wmN1增强子的关键突变，或者 编码增强子功能所必需的同源因子的基因会导致 Plp1基因，因此可能导致髓鞘功能障碍。在本研究中，缺失-转染法 使用plp1-lacz构建物的分析将用于最小限度地映射1.2 kb内的wmN1增强子 Plp1内含子1 DNA片段。还将产生转基因小鼠来测试ASE和wmN1是否 增强子独立发挥作用，或相互结合，显著提高Plp1的水平 发育过程中的基因表达。

The myelin proteolipid protein (PLP) gene (Plp1) encodes the most abundant protein present in CNS myelin. Its expression in oligodendrocytes is tightly regulated. Mutations in the human gene have been shown to be associated with the X-linked dysmyelinating disorder Pelizaeus-Merzbacher disease (PMD) and some types of spastic paraplegia (SPG2). Dysmyelination can arise from either elevated levels of Plp1 gene expression or the lack, thereof. Hence accurate expression of the gene in is critical. With transgenic mice that harbor Plp1- lacZ fusion genes we have shown that Plp1 intron 1 DNA is essential for regulating the dramatic increase in Plp1 gene transcription in oligodendrocytes during the active myelination period of CNS development. The intron accounts for roughly one-half of the Plp1 gene, encompassing over 8 kb of DNA. We have identified a regulatory element within Plp1 intron 1 DNA and named it ASE for antisilencer/enhancer. We believe the ASE participates in the formation of a multi-protein nucleoprotein complex which acts as a potent transcriptional activator called an enhanceosome. Enhanceosomes are a new class of transcriptional regulators that are characterized by a higher-order nucleoprotein complex which functions as a unit. The precise three- dimensional structure permits synergy between factors and is obligatory to elicit gene activation. The intron also contains another enhancer, designated as wmN1, which has been roughly localized to a 1.2 kb segment of DNA. We hypothesize that the dramatic increase in Plp1 gene activity in oligodendrocytes during development is governed by the ASE and wmN1 enhancers and their associated (cognate) DNA-binding factors. Elucidation of the mechanisms controlling Plp1 gene expression will be an important step in the design of therapies aimed at enhancing remyelination since at the time of myelination, 10% of the total mRNA in oligodendrocytes is generated from the Plp1 gene. Developmental differences in factors present early in childhood versus those in adults may explain the rather poor levels of remyelination observed in MS patients. Cognate factors which bind the ASE and wmN1 enhancers may provide new therapeutic targets to enhance remyelination in these patients. As well, critical mutations in the ASE or wmN1 enhancer, or a mutation in a gene which encodes a cognate factor obligatory for enhancer function, would lead to under-expression of the Plp1 gene and consequently may result in a dysmyelinating disorder. In this study, deletion-transfection analysis with Plp1-lacZ constructs will be used to minimally map the wmN1 enhancer within the 1.2 kb segment of Plp1 intron 1 DNA. Transgenic mice will also be generated to test whether the ASE and wmN1 enhancer work independently, or in combination with one another, to significantly increase the levels of Plp1 gene expression during development.