MECHANISMS OF RNA-MEDIATED CNS PATHOGENESIS IN MYOTONIC DYSTOPHY

虽然强直性肌营养不良症（DM）被归类为肌营养不良症，但它是一种对中枢神经系统（CNS）功能有显著影响的进行性多系统疾病。这些CNS表现包括先天性DM的智力迟钝和自闭症行为，以及成年发病形式的嗜睡、执行功能障碍和皮质萎缩。对DM分子基础的研究揭示了一种新的疾病机制，即RNA介导的发病机制，其涉及两个不相关基因中微卫星C（C）TG重复序列的扩增和毒性C（C）UG扩增RNA的合成。这些致病性RNA干扰CELF和MBNL蛋白的正常选择性剪接功能，导致成人组织中胎儿同种型的持续存在或回复。为了确定这种RNA介导的疾病模型是否与DM中的CNS功能障碍相关，我们最近产生了Mbnl2敲除小鼠，其概括了DM脑的特征性病理学特征，包括异常REM睡眠倾向和空间记忆缺陷。在该提议中，我们将首先通过证明MBNL2从其正常RNA靶向C（C）UG重复的转移发生在DM脑中来测试用于DM相关CNS发病机制的MBNL2隔离假说。接下来，我们将确定Mbnl2敲除小鼠是否模拟了DM CNS特征的全部范围，并将特定的错误剪接事件与特征性疾病表现联系起来。最后，我们将测试的假设，MBNL基因之间的相互作用被破坏的先天性疾病。这些研究将为未来的疾病机制研究和针对DM脑的治疗方法的开发提供新的成人发病和先天性DM的动物模型。

While myotonic dystrophy (DM) is classified as a muscular dystrophy, it is a progressive multi-systemic disease that has significant effects on central nervous system (CNS) function. These CNS manifestations include mental retardation and autistic behaviors in congenital DM and hypersomnia, executive dysfunction and cortical atrophy in the adult-onset form. Studies on the molecular basis of DM have revealed a novel disease mechanism, RNA-mediated pathogenesis, that involves the expansion of microsatellite C(C)TG repeats in two unrelated genes and the synthesis of toxic C(C)UG expansion RNAs. These pathogenic RNAs interfere with the normal alternative splicing functions of the CELF and MBNL proteins resulting in the persistence of, or reversion to, fetal isoforms in adult tissues. To determine if this RNA-mediated disease model is relevant to CNS dysfunction in DM, we have recently generated Mbnl2 knockout mice which recapitulate characteristic pathological features of the DM brain including abnormal REM sleep propensity and spatial memory deficits. In this proposal, we will first test the MBNL2 sequestration hypothesis for DM relevant CNS pathogenesis by demonstrating that transfer of MBNL2 from its normal RNA targets to C(C)UG repeats occurs in the DM brain. Next, we will determine if Mbnl2 knockout mice model the full range of DM CNS features and link specific mis-splicing events to characteristic disease manifestations. Finally, we will test the hypothesis that interactions between MBNL genes are disrupted in the congenital disease. These studies will provide novel animal models of adult-onset and congenital DM for future disease mechanism studies and the development of therapies that target the DM brain.