Project 2

项目概要/项目2摘要 杜氏肌营养不良症（DMD）是一种隐性遗传的X连锁神经肌肉疾病， 在肌营养不良蛋白基因，最终产生渐进的肌肉萎缩和萎缩。重要的是，DMD 患者发生心脏纤维化和心脏功能下降导致晚期心肌病， 这是目前DMD患者死亡率的主要原因。UT西南的使命 Wellstone中心将开发CRISPR/Cas9基因组编辑作为DMD患者的治疗方式; 然而，与DMD相关的心肌病相关的问题将继续存在。项目1建议使用 基因组编辑以靶向肌营养不良蛋白基因内的12个“热点”，从而产生截短的肌营养不良蛋白 将DMD患者转化为Becker肌营养不良（BMD）患者。因此， 项目2是开发新的治疗方法，以降低与DMD相关的发病率和死亡率。 相关性心肌病在治疗非DMD心肌病方面取得了重大进展; 然而，没有明确的疗法来有效地诱导长期逆转心脏重塑， 改善DMD患者的整体心脏功能。我们小组进行了一项心脏核磁共振研究 表明成年DMD患者具有非常低的左心室（LV）质量以及低LV同心度 与年龄、性别和体重匹配的对照患者相比。一旦DMD患者出现症状 与晚期心肌病相关，DMD心脏开始扩张和扩大，类似于心脏的结构。 晚期扩张型非缺血性心肌病这些观察结果提出了一个问题， 病理性心脏肥大的发展是DMD相关性心肌肥厚的主要机制。 心肌病观察到的低LV质量和同心度是由于长时间不动引起的，还是 独立于DMD患者的行走能力来自Mammen实验室的数据表明， 小鼠是DMD的鼠模型，其具有改变的心脏代谢，并且还具有低心脏质量，这是由于 在生命的第一周内增殖基因表达减少。因此， 项目2是DMD相关心肌病的低LV质量和同心度导致进行性 心肌病与DMD患者的行走能力无关。为了验证我们的核心假设，我们将 具体目标1：描述临床和分子表型 在非卧床和非卧床DMD患者中作为患者年龄的函数。具体目标2：定义 BMD相关性心肌病的心脏表型与患者年龄和遗传缺陷部位的关系 突变具体目标3：确定人DMD和BMD心肌细胞的分子表型。

Project Summary/Abstract for Project 2 Duchenne muscular dystrophy (DMD) is a recessive X-linked neuromuscular disorder resulting from mutations in the dystrophin gene, which ultimately produces progressive muscle wasting and atrophy. Importantly, DMD patients develop cardiac fibrosis and a decrease in cardiac function leading to advanced cardiomyopathy, which is currently the major contributor to mortality in DMD patients. The mission of the UT Southwestern Wellstone Center is to develop CRISPR/Cas9 genome editing as a therapeutic modality for DMD patients; however, issues related to DMD-associated cardiomyopathy will continue to persist. Project 1 proposes to use genome editing to target the 12 “hot spots” within the dystrophin gene making a truncated dystrophin protein and converting a DMD patient into a Becker muscular dystrophy (BMD) patient. Thus, the overall goal of Project 2 is to develop novel therapies to attenuate the morbidity and mortality associated with DMD- associated cardiomyopathy. Significant strides have been made in treating non-DMD cardiomyopathy; however, there are no definitive therapies to effectively induce long term reverse cardiac remodeling and improve overall cardiac function within DMD patients. Our group has undertaken a cardiac MRI study demonstrating that adult DMD patients have very low left ventricular (LV) mass as well as low LV concentricity as compared to age-, sex-, and weight-matched control patients. Once a DMD patient develops symptoms related to advanced cardiomyopathy, the DMD heart starts to dilate and enlarge resembling the structure of advanced dilated non-ischemic cardiomyopathy. These observations raise the question whether the development of pathological cardiac hypertrophy is the primary mechanism underlying DMD-associated cardiomyopathy. Does the observed low LV mass and concentricity arise due to prolonged immobility or are independent of a DMD patient’s ability to ambulate? Data from the Mammen Laboratory indicates that mdx mice, a murine model of DMD, have altered cardiac metabolism and also have low cardiac mass due to a decrease in proliferative gene expression during the first week of life. Therefore, the central hypothesis of Project 2 is that low LV mass and concentricity in DMD-associated cardiomyopathy leads to progressive cardiomyopathy independent of a DMD patient’s ability to ambulate. To test our central hypothesis, we will pursue the following three specific aims: Specific Aim 1: Characterize the clinical and molecular phenotypes in ambulatory and non-ambulatory DMD patients as a function of patient age. Specific Aim 2: Define the cardiac phenotype in BMD-associated cardiomyopathy as a function of patient age and site of the genetic mutation. Specific Aim 3: Determine the molecular phenotypes of human DMD and BMD cardiomyocytes.