Division of Histology and Embryology, Department of Anatomy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
Department of Endocrinology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430014, China.
Neurotox Res. 2018 May;33(4):693-701. doi: 10.1007/s12640-017-9803-0. Epub 2017 Oct 3.
Expanded hexanucleotide GGGGCC repeat in a noncoding region of C9ORF72 is the most common cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). However, its molecular pathogenesis remains unclear. In our previous study, the expanded GGGGCC repeats have been shown to be sufficient to cause neurodegeneration. In order to investigate the further role of expanded GGGGCC repeats in the neuron, the normal r(GGGGCC) and mutant-type expanded r(GGGGCC) expression vectors were transfected into Neuro-2a cells. Cell proliferation, dendrite development, and the proteins' levels of microtubule-associated protein-2 (MAP2) and cyclin-dependent kinase-5 (CDK5) were used to evaluate the cell toxicity of GGGGCC repeats on Neuro-2a cells. The results were shown that expression of expanded GGGGCC repeats caused neuronal cell toxicity in Neuro-2a cells, enhanced the expression of pMAP2 and pCDK5. Moreover, overexpression of Purα repaired expanded GGGGCC repeat-inducing neuronal toxicity in Neuro-2a cells and reduced the expression of pMAP2 and pCDK5. In all, our findings suggested that the expanded GGGGCC repeats might cause neurodegeneration through destroyed neuron cells. And the GGGGCC repeat-induced neuronal cell toxicity was inhibited by upregulation of Purα. We inferred that Purα inhibits expanded GGGGCC repeat-inducing neurodegeneration, which might reveal a novel mechanism of neurodegenerative diseases ALS and FTD.
非编码区 C9ORF72 中的 GGGGCC 六核苷酸重复扩展是额颞叶痴呆（FTD）和肌萎缩侧索硬化症（ALS）最常见的原因。然而，其分子发病机制尚不清楚。在我们之前的研究中，已经表明扩展的 GGGGCC 重复足以引起神经退行性变。为了进一步研究扩展的 GGGGCC 重复在神经元中的作用，将正常的 r(GGGGCC)和突变型扩展的 r(GGGGCC)表达载体转染到 Neuro-2a 细胞中。用细胞增殖、树突发育以及微管相关蛋白-2（MAP2）和细胞周期蛋白依赖性激酶-5（CDK5）的蛋白水平来评估 GGGGCC 重复对 Neuro-2a 细胞的毒性。结果表明，表达扩展的 GGGGCC 重复会导致 Neuro-2a 细胞中的神经元细胞毒性，增强 pMAP2 和 pCDK5 的表达。此外，Purα 的过表达修复了扩展的 GGGGCC 重复诱导的 Neuro-2a 细胞毒性，并降低了 pMAP2 和 pCDK5 的表达。总之，我们的研究结果表明，扩展的 GGGGCC 重复可能通过破坏神经元细胞引起神经退行性变。并且 Purα 可抑制 GGGGCC 重复诱导的神经元细胞毒性。我们推断 Purα 抑制扩展的 GGGGCC 重复诱导的神经退行性变，这可能揭示了 ALS 和 FTD 等神经退行性疾病的新机制。
