Myotonic Dystrophy Type 2

描述（由申请人提供）：2型肌强直性营养不良症（DM2）是临床上与1型肌强直性营养不良症（DM1）相关的常见肌肉疾病。DM2是由位于染色体3q上的锌指因子编码基因ZNF9内含子1上CCTG重复序列扩增引起的。虽然DM1和DM2患者的一些症状相似，但其他症状仅针对一种疾病。DM2的具体特征包括没有先天性疾病，没有发育性脑异常，没有发育迟缓，骨骼肌症状明显较轻。我实验室的主要研究重点是DM1和DM2的分子碱基的研究。在DM1的研究过程中，我们发现DMPK基因中CTG三联体重复序列的扩增是通过未翻译的RNA CUG重复序列引起DM1病理的。CUG重复扩增影响两种rna结合蛋白CUGBP1和MNBL。DM2也由未翻译的CCTG重复序列的扩增引起，这表明DM1和DM2具有相似的rna依赖机制。然而，DM2表型的特定特征表明，DM2的分子机制与DM1不同。我们发现DM2中的RNA CCUG重复序列与不同的RNA结合蛋白和大型蛋白复合物相互作用，称为Mega protein-protein complexes （MPPC）。这些复合物与CUG重复序列特异性结合，但不与CUG重复序列结合。在DM2细胞的细胞质和细胞核中观察到MPPC。DM2型成肌细胞胞浆MPPC水平升高，而DM2型成肌细胞核MPPC水平降低。该应用的主要假设是CCUG重复通过改变大蛋白-蛋白复合物的生物学功能引起DM2病理。三个具体目标旨在验证这一假设。我们发现细胞质MPPC含有9个蛋白，包括CUGBP1、eJF-2a和eIF-2p，这3个蛋白都参与mrna翻译的调控。特异性目的1将鉴定细胞质MPPC的其他蛋白质成分，并检查细胞质MPPC在mRNA翻译中的作用。特异性Aim 2将确定核MPPC内蛋白质的身份，检查该复合体是否在剪接中起作用，并研究核MPPC的改变是否导致DM2剪接异常。特异性目标3将研究CCUG重复序列的扩增增加DM2细胞细胞质中MPPC的数量并减少细胞核中MPPC的数量的机制。

DESCRIPTION (provided by applicant): Myotonic Dystrophy 2 (DM2) is a common muscular disease clinically related to Myotonic Dystrophy 1 (DM1). DM2 is caused by expansion of CCTG repeats in intron 1 of the zinc finger factor encoding gene, ZNF9, located on chromosome 3q. While some symptoms in the patients with DM1 and DM2 are similar, others are specific just for one type of disease. DM2 specific features include a lack of congenital form of disease, lack of developmental brain abnormalities, lack of retardation and significantly milder symptoms in skeletal muscle. The main focus of research in my laboratory is the investigation of molecular bases for DM1 and DM2. In the course of our studies on DM1, we found that expansion of CTG triplet repeats in DMPK gene causes DM1 pathology through un-translated RNA CUG repeats. CUG repeat expansion affects two RNA-binding proteins, CUGBP1 and MNBL. DM2 is also caused by expansion of untranslated CCTG repeats suggesting similar RNA-dependent mechanisms for DM1 and DM2. However, specific features of DM2 phenotype suggest that molecular mechanisms of DM2 are not identical to those of DM1. We found that RNA CCUG repeats in DM2 interact with distinct RNA-binding proteins and with large protein-protein complexes, designated as Mega Protein-Protein Complexes (MPPC). These complexes bind specifically to CCUG repeats but not to CUG repeats. MPPC are observed in cytoplasm and in nuclei of DM2 cells. The amounts of cytoplasmic MPPC are increased in DM2 myoblasts, while the levels of nuclear MPPC are reduced in DM2 patients. The major hypothesis of this application is that CCUG repeats cause DM2 pathology via changes of biological functions of large protein-protein complexes. Three Specific Aims are designed to test this hypothesis. We have found that cytoplasmic MPPC contains 9 proteins including CUGBP1, eJF-2a and eIF-2p, all three proteins are involved in the regulation of translation of mRNAs. Specific Aim 1 will identify other protein components of cytoplasmic MPPC and examine the role of cytoplasmic MPPC in mRNA translation. Specific Aim 2 will determine identity of proteins within nuclear MPPC, examine if this complex plays a role in splicing and investigate if the alterations in nuclear MPPC cause abnormal splicing in DM2. Specific Aim 3 will study the mechanisms by which expansion of CCUG repeats increases amounts of MPPC in cytoplasm of DM2 cells and reduces amounts of MPPC in nuclei.