Myotonic Dystrophy: Molecular Pathophysiology and CNS Effects

强直性肌营养不良：分子病理生理学和中枢神经系统影响

• 批准号: 7869582
• 负责人: Laura P.W Ranum
• 金额: $ 9.4万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-15 至 2010-11-14
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7869582
• 关键词: Myotonic; Dystrophy; Molecular; Pathophysiology; CNS

Description (provided by applicant): We demonstrated previously that myotonic dystrophy type 2 (DM2) is caused by a CCTG expansion in intron 1 of the ZA/F9gene. Parallels between the DM1 and DM2 expansion mutations and the characterization of RNA binding proteins that interact with expanded CUG and CCUG repeats have uncovered a novel type of mechanism involving RNA gain-of-function effects. In this model, the accumulation of CUG or CCUG expansion transcripts results in the dysregulation of RNA binding proteins normally involved in controlling developmental changes in alternative splicing of a specific set of pre-mRNA transcripts. The failure of this set of normal developmental splicing changes is thought to occur, at least in part, because the accumulation of CUG and CCUG expansion transcripts in DM1 and DM2 leads to sequestration and depletion of nuclear MBNL1. Remarkably, recent studies performed by Dr. Swanson's group now show that AAV injection of constructs overexpressing Mbnll can rescue the muscle phenotype and reverse the splicing alterations in a skeletal muscle poly(CUG) model of DM1. Although significant progress has been made in understanding the pathology and the molecular mechanisms of RNA pathogenesis in skeletal and cardiac muscle, little is known about the molecular changes underlying a clinically important, but poorly understood, set of CNS effects in DM1 and DM2. Patients with adult onset DM1 and DM2 have strikingly similar multisystemic diseases, with preliminary data suggesting similar cerebral and cerebellar white matter abnormalities as well as executive function deficits. Congenially affected DM1 patients have more severe CNS abnormalities including mental retardation. A possible mechanism for congenital DM1 is that methylation at the DM1 locus in congenital cases is associated with increased expression of DMPK, resulting in higher levels of CUG containing transcripts and a more severe congenital phenotype. The focus of this proposal is to use transgenic models to test the hypothesis that CUG and CCUG repeat toxicity is comparable at the cellular and organismal levels, that alterations in temporal and spatial expression of RNA expansion transcripts cause phenotypic similarities and differences in DM1 and DM2, including CNS effects, and that many of the multisystemic features of the disease are reversible. Our specific aims are: 1) Clinical similarities and differences between DM1 and DM2 result from variations in temporal and spatial expression patterns of the CUG/CCUG expansion transcripts and are independent of both the repeat motif and flanking sequence. 2) CNS specific molecular changes found in myotonic dystrophy are caused by RNA gain of function effects and that molecular and phenotypic similarities and differences between DM1 and DM2 result from variations in temporal and spatial expression patterns of the CUG/CCUG expansions in the brain. 3) To evaluate the effects of increased Mbnll expression in skeletal muscle and the CNS by generating an inducible transgenic mouse model of Mbnll over-expression.

描述(由申请人提供)：我们之前证明了强直性肌营养不良2型(DM2)是由ZA/F9基因内含子1中的CCTG扩展引起的。DM1和DM2扩展突变之间的相似之处，以及与扩展的CUG和CCUG重复相互作用的RNA结合蛋白的特征，揭示了一种涉及RNA功能增益效应的新型机制。在这个模型中，CUG或CCUG扩展转录本的积累导致RNA结合蛋白的失调，这些RNA结合蛋白通常参与控制一组特定前mRNA转录本的选择性剪接的发育变化。这一组正常发育剪接变化的失败被认为至少部分是因为CUG和CCUG扩展转录在DM1和DM2中的积累导致了核MBNL1的隔离和耗尽。值得注意的是，斯旺森博士的团队最近进行的研究表明，AAV注射高表达Mbn11的构建体可以挽救DM1的骨骼肌多聚(CUG)模型的肌肉表型并逆转剪接变化。虽然在理解骨骼肌和心肌中RNA致病的病理学和分子机制方面已经取得了重大进展，但对DM1和DM2中一系列临床上重要但知之甚少的CNS效应背后的分子变化知之甚少。成人起病的DM1和DM2患者有惊人的相似的多系统疾病，初步数据显示类似的大脑和小脑白质异常以及执行功能缺陷。先天受累的DM1患者有更严重的中枢神经系统异常，包括智力低下。先天性DM1的一个可能机制是，先天性病例中DM1基因的甲基化与DMPK的表达增加有关，导致含有CUG的转录本水平更高，先天性表型更严重。这一建议的重点是使用转基因模型来检验这样的假设，即CUG和CCUG重复毒性在细胞和生物水平上是可比较的，RNA扩展转录本的时间和空间表达的变化导致DM1和DM2的表型相似和不同，包括中枢神经系统的影响，以及疾病的许多多系统特征是可逆的。我们的具体目的是：1)DM1和DM2的临床异同源于CUG/CCUG扩展转录本的时间和空间表达模式的差异，并且与重复基序和侧翼序列无关。2)强直性肌营养不良患者中枢神经系统特异性分子改变是由功能效应的RNA获得引起的，而DM1和DM2在分子和表型上的相似性和差异性是由于脑内CUG/CCUG扩展的时空表达模式的差异所致。3)建立可诱导的Mbn11过表达转基因小鼠模型，评价Mbn11在骨骼肌和中枢神经系统中高表达的效果。