Molecular mechanisms of neurodegeneration

迄今为止，包括齿状核红核-苍白球路易氏体萎缩（DRPLA）在内的9种多聚谷氨酰胺疾病已被确定是由编码多聚谷氨酰胺片段的CAG重复序列异常扩增引起的。为了阐明多聚谷氨酰胺疾病中神经退行性变的分子机制，我们首先尝试创建密切复制人脑病理生理过程的小鼠模型。为了实现这一目标，我们试图创建转基因小鼠携带全长突变的人DRPLA基因作为一个单拷贝基因。携带大量扩增CAG重复序列（129）的Q129小鼠显示出强烈的神经学表型，包括共济失调、肌阵挛和癫痫。基于详细的神经病理学分析，我们发现，神经元的损失没有检测到，尽管强大的表型，这表明神经元死亡不是神经变性的基本过程。我们进一步发现，突变DRPLA蛋白的核内积累是重要的神经病理学发现。这条鱼 ...更多信息 这增加了核功能障碍是多聚谷氨酰胺疾病中神经变性的基础的可能性。基于细胞培养系统，我们证明，CREB依赖的转录激活严重抑制采用报告系统。我们进一步证明了内源性c-fos转录的激活也被扩展的多聚谷氨酰胺片段强烈抑制。为了进一步阐明多聚谷氨酰胺疾病中转录失调的机制，我们使用Q76、Q113和Q129进行了详细的表达谱分析，Q76、Q113和Q129携带全长突变的人DRPLA基因作为具有不同长度的扩增CAG重复单元（76、113和129个重复单元）的单拷贝基因。我们发现，大量的基因被抑制的时间依赖性和重复长度依赖的方式。在下调的基因中，包括许多cAMP应答基因（c-fos和EGR 1）。总之，我们已经证明，CREB依赖性转录激活的抑制被扩展的多聚谷氨酰胺片段强烈抑制，并且恢复这种抑制是开发多聚谷氨酰胺疾病治疗方法的目标。少

To date, 9 polyglutamine diseases including dentatorubral-pallidoluysian atrophy (DRPLA) have been identified to be caused by abnormal expansion of CAG repeats coding for polyglutamine stretches. To elucidate the molecular mechanisms of neurodegeneration in polyglutamine diseases, we first attempted to create mouse models that closely replicate pathophysiologic processes in human brains. To accomplish this aim, we tried to create transgenic mice carrying a full-length mutant human DRPLA gene as a single copy gene. The Q129 mouse carrying a largely expanded CAG repeats (129) showed strong neurological phenotypes including ataxia, myoclonus and epilepsy. Based on detailed neuropathological analyses, we found that neuronal loss was not detected despite the strong phenotypes, suggesting that neuronal death is not the essential processes in neurodegeneration. We furthermore found that intranuclear accumulation of mutant DRPLA proteins is the essential neuropathological findings. This observ … More ation raises the possibility that nuclear dysfunction underlies the neurodegeneration in polyglutamine diseases. Based on cell culture systems, we demonstrated that CREB-dependent transcriptional activation is severely suppressed employing a reporter system. We further demonstrated activation of endogenous c-fos transcription is also strongly suppressed by expanded polyglutamine stretches. To further elucidate the mechanisms of transcriptional dysregulation in polyglutamine diseases, we have conducted detailed expression profiling analyses using Q76, Q113 and Q129, carrying a full-length mutant human DRPLA gene as a single copy gene with various lengths of expanded CAG repeats (76, 113 and 129 repeat units). We found that substantial number of genes were suppressed in time-dependent and repeat length-dependent manners. Among the down-regulated genes, many cAMP-responsive genes (c-fos and EGR1) are included Taken together, we have demonstrated that suppression of CREB-dependent transcriptional activation is strongly suppressed by expanded polyglutamine stretches and restoration of such suppression is the target for developing therapeutic approaches for polyglutamine diseases. Less