Project 2

项目2的项目摘要/摘要 Duchenne肌营养不良症(DMD)是一种由基因突变引起的隐性X连锁神经肌肉疾病 在营养不良蛋白基因中，最终导致进行性肌肉萎缩和萎缩。重要的是，DMD 患者会出现心脏纤维化和心功能下降，从而导致晚期心肌病， 这是目前导致DMD患者死亡的主要原因。德克萨斯大学西南分校的使命 韦尔斯通中心将开发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 针对dystrophin基因中的12个“热点”进行基因组编辑以生成截短的dystrophin蛋白 以及将DMD患者转变为Becker肌营养不良症(BMD)患者。因此，总的目标是 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。 伴发心肌病。在治疗非DMD心肌病方面取得了重大进展； 然而，目前还没有确切的治疗方法来有效地诱导长期逆转的心脏重塑和 改善DMD患者的整体心功能。我们小组进行了心脏核磁共振研究 显示成年DMD患者的左心室(LV)质量和左心室向心密度都很低 与年龄、性别和体重匹配的对照组患者相比。一旦DMD患者出现症状 与晚期心肌病有关，DMD心脏开始扩张和扩大，类似于 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，即 病理性心肌肥厚是DMD相关的主要机制 心肌病。观察到的低左室质量和向心性是由于长时间不动引起的，还是 与DMD患者的行走能力无关？来自哺乳动物实验室的数据表明，MDX 作为DMD的小鼠模型，小鼠的心脏代谢发生了改变，并且由于 在生命的第一周，增殖基因的表达减少。因此，核心假说是 项目2是DMD相关心肌病的低左室质量和向心性改变导致进展性 与DMD患者的行走能力无关的心肌病。为了检验我们的中心假设，我们将 追求以下三个具体目标：具体目标1：确定临床和分子表型 在动态和非动态DMD患者中，这与患者的年龄有关。具体目标2：界定 BMD相关性心肌病的心脏表型与患者年龄和遗传部位的关系 突变。具体目的3：测定人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.