Molecular Mechanisms of Myotonic Dystrophy

描述（由申请人提供）：肌强直性营养不良（DM）是由营养不良性肌强直蛋白激酶基因（DMPK）和锌指9基因（ZNF9）非编码区CUG和CCUG的核苷酸扩增引起的。CUG扩张的患者为I型肌强直性营养不良（DM1），而CUG扩张的患者为II型肌强直性营养不良（DM2）。DM1和DM2患者表现出相同的症状，提示CUG和CCUG扩张通过相同的机制导致DM。这些非编码扩展如何导致糖尿病的假设是通过RNA功能获得机制；扩增的CUG和CCUG重复RNA隔离了MBNL RNA结合蛋白，也间接增加了另一种RNA结合蛋白（CUG- bp）的蛋白水平，从而破坏了MBNL和CUG- bp的正常细胞功能。MBNL和ug - bp是mrna前剪接因子，似乎具有拮抗作用。改变它们的“活性”浓度会导致多个转录本的选择性剪接的错误调节，最终导致CUG和CCUG扩增患者的DM。本提案的重点是确定MBNL在疾病状态（DM）和正常细胞中的作用。为了实现这些目标，我们正在使用生物信息学，生化，生物物理和结构方法的组合。目的1。确定MBNL的细胞靶点，并确定MBNL调节mRNA前剪接的机制。目标2。单独和与MBNL复合的CUG和CCUG重复序列的生化和结构表征。我们的目标是了解导致糖尿病的分子机制。这种理解将有助于开发治疗方法，帮助许多患有这种最常见的成人发病肌肉萎缩症的人（8000人中有1人）。

DESCRIPTION (provided by applicant): Myotonic dystrophy (DM) is caused by nucleotide expansions of CUG and CCUG in the non-coding regions of the dystrophia myotonia protein kinase gene (DMPK) and the Zn finger 9 gene (ZNF9) respectively. Patients with the CUG expansions have type I myotonic dystrophy (DM1) and patients with the CCUG expansions have type II myotonic dystrophy (DM2). Patients with DM1 and DM2 display the same symptoms, suggesting both CUG and CCUG expansions cause DM through the same mechanism. The hypothesis for how these non-coding expansions cause DM is through an RNA gain-of-function mechanism; the expanded CUG and CCUG repeat RNAs sequester the MBNL RNA binding protein and also indirectly increase the protein levels of another RNA binding protein (CUG-BP), which disrupts the normal cellular function of MBNL and CUG-BP. MBNL and CUG-BP are pre-mRNA splicing factors that appear to function antagonistically. Changing their "active" concentration results in the mis-regulation of alternative splicing of multiple transcripts with a final outcome of DM for people with CUG and CCUG expansions. The focus of this proposal is to determine the role of MBNL in the disease state (DM) as well as in normal cells. To accomplish these goals we are using a combination of bioinformatics, biochemical, biophysical and structural methods. Aim 1. Identify cellular targets of MBNL and determine the mechanisms through which MBNL regulates pre- mRNA splicing. Aim 2. Biochemical and structural characterization of CUG and CCUG repeats alone and in complex with MBNL. Our goal is to understand the molecular mechanisms that cause DM. This understanding will help lead to the development of therapies to help the many people (1 in 8000) that have this most common form of adult onset muscular dystrophy.