Myotonic Dystrophy Type 2

描述（由申请方提供）：强直性肌营养不良2型（DM 2）是一种临床上与强直性肌营养不良1型（DM 1）相关的常见肌肉疾病。DM 2是由位于染色体3q上的锌指因子编码基因ZNF 9的内含子1中的CCTG重复扩增引起的。虽然DM 1和DM 2患者的一些症状是相似的，但其他症状仅针对一种疾病。DM 2的具体特征包括缺乏先天性疾病形式、缺乏发育性脑异常、缺乏发育迟缓和骨骼肌中明显较轻的症状。我实验室的主要研究重点是DM 1和DM 2的分子基础的研究。在对DM 1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通过非翻译RNA CUG重复序列引起DM 1的病理变化。CUG重复扩增影响两种RNA结合蛋白CUGBP 1和MNBL。DM 2也是由非翻译的CCTG重复序列的扩增引起的，这表明DM 1和DM 2具有相似的RNA依赖性机制。然而，DM 2表型的特定特征表明，DM 2的分子机制与DM 1的分子机制不同。我们发现DM 2中的RNA CCUG重复序列与不同的RNA结合蛋白和大的蛋白质-蛋白质复合物相互作用，称为Mega蛋白质-蛋白质复合物（MPPC）。这些复合物特异性结合CCUG重复序列，但不结合CUG重复序列。在DM 2细胞的胞质和胞核中观察到MPPC。DM 2成肌细胞胞浆MPPC的量增加，而DM 2患者细胞核MPPC的水平降低。本申请的主要假设是CCUG重复序列通过改变大蛋白质-蛋白质复合物的生物学功能引起DM 2病理学。三个具体目标是为了检验这一假设。我们发现MPPC细胞质中含有CUGBP 1、eJF-2a和eIF-2 p等9种蛋白质，这3种蛋白质都参与了mRNA翻译的调控。特异性目的1将鉴定胞质MPPC的其他蛋白组分，并检查胞质MPPC在mRNA翻译中的作用。特异性目标2将确定核MPPC内蛋白质的身份，检查该复合物是否在剪接中起作用，并研究核MPPC的改变是否导致DM 2的异常剪接。具体目标3将研究CCUG重复序列扩增增加DM 2细胞细胞质中MPPC量和减少细胞核中MPPC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.