Barth syndrome: Evaluating cardiolipin mediated tissue specific oxidative phosphorylation dysfunction

巴特综合征：评估心磷脂介导的组织特异性氧化磷酸化功能障碍

• 批准号: 9759571
• 负责人: Arianna Lee Franca Anzmann
• 金额: $ 4.5万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2021-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9759571
• 关键词: 3-Methylglutaconic aciduria type 2; Address; Affect; Apoptotic; Basic Science; Biological Assay; Brain; Cardiac; Cardiac Myocytes; Cardiolipins; Cardiomyopathies; Cell model; Cells; Complex; Crista ampullaris; Diagnostic; Disease; Enzyme Stability; Enzymes; Functional disorder; Gene Expression; Genes; Genetic Diseases; Genetic Transcription; Hereditary Disease; Individual; Inner mitochondrial membrane; Knowledge; Laboratory Research; Leigh Disease; Link; Mediating; Metabolic; Mitochondria; Mitochondrial Diseases; Monitor; Myocardium; Myopathy; NADH; NADH dehydrogenase (ubiquinone); Neurologic; Neurons; Neutropenia; Outcome; Oxidative Phosphorylation; Patients; Phospholipid Metabolism; Phospholipids; Play; Proteins; Rare Diseases; Research; Respiratory Chain; Role; Site; Skeletal Muscle; Specificity; Testing; Therapeutic; Time; Tissues; Transacylase; Translating; Variant; Work; base; career; clinically relevant; induced pluripotent stem cell; insight; lymphoblastoid cell line; mRNA Expression; mitochondrial dysfunction; monolysocardiolipin; novel; protein expression; screening; skeletal; skills; therapeutic target; translational approach

Project Summary Barth Syndrome (BTHS), is an X-linked inborn error of mitochondrial phospholipid metabolism, caused by variants in the gene tafazzin (TAZ). TAZ encodes for a transacylase involved in the final remodeling step of cardiolipin (CL), a phospholipid localized to the inner mitochondrial membrane with key roles in cristae formation, organization of the mitochondrial respiratory chain, and in the apoptotic cascade. Both TAZ and CL are ubiquitously expressed in all tissues, however the CL content is tissue specific; brain CL is characterized by a diversified array of acyl chains including polyunsaturated chains, whereas in the cardiac and skeletal muscle CL is predominantly characterized by the tetralinoleoyl form. As is typical of most primary mitochondrial diseases, BTHS is a multisystem disorder, characterized by cardiomyopathy, skeletal myopathy, and neutropenia among other features. However, in sharp contrast to many mitochondrial diseases, BTHS has minimal neurological burden. Thus, understanding the mechanisms of tissue specificity in BTHS has the potential to provide great insight into the role of specific CL content on mitochondrial function, as well as to offer novel treatment targets for BTHS. In my preliminary work with a novel TAZ deficient cellular model, I found that complex I of the respiratory chain is dysregulated at the protein and metabolic level. Based on this, I hypothesize that complex I is a major site of oxidative phosphorylation (OXPHOS) dysfunction in tissues affected in BTHS. Dysregulation of complex I in BTHS is a particularly interesting finding, because other complex I disorders, including Leigh Disease, have a significant neurological impact. Therefore, I further hypothesize that the tissue specific CL content of neurologic tissue spares it from this dysfunction. To address this hypothesis, I propose two specific aims. Aim 1: To determine the impact of TAZ deficiency, and therefore abnormal CL content, on complex I function. I will first investigate the effect of the reduced expression of Complex I proteins on enzyme stability and function. Then I will determine whether the assembly factor NDUFAF1 plays a prominent role in the reduced expression of complex I proteins, and if the reduced NDUFAF1 expression is due to dysregulation at the transcriptional level. Aim 2: To understand the role of tissue specificity of CL content on the pathophysiology of BTHS. I will first differentiate TAZ deficient iPSCs, iPSC TAZ∆50, into cardiomyocytes and neurons in order to characterize and compare complex I dysregulation by assessing NDUFAF1 protein expression, NADH/NAD+ ratio, and complex I enzyme stability/function. Then, I will determine if TAZ deficient neurons display altered CL as compared to WT neurons, and if the lack of altered CL content in TAZ deficient neurons reflects a smaller role for TAZ in neuronal CL remodeling. This project proposal combines basic science and translational approaches to unravel cellular pathophysiology and identify potential therapeutic targets for a rare disease. The skills I will acquire as I complete this research will prepare me for a career in therapeutic discovery for rare genetic conditions.

项目概要 巴特综合征 (BTHS) 是一种 X 连锁的线粒体磷脂代谢缺陷，由以下原因引起： tafazzin (TAZ) 基因的变体编码参与最终重构步骤的转酰基酶。 心磷脂 (CL)，一种定位于线粒体内膜的磷脂，在嵴中发挥关键作用 线粒体呼吸链的形成、组织以及细胞凋亡级联反应中的 TAZ 和 CL。 在所有组织中普遍表达，但 CL 含量具有组织特异性； 由包括多不饱和链在内的多种酰基链组成，而在心脏和骨骼中 肌肉 CL 主要以四亚油酰形式为特征，这是大多数初级线粒体的典型特征。 BTHS 是一种多系统疾病，其特征为心肌病、骨骼肌病和 然而，与许多线粒体疾病形成鲜明对比的是，BTHS 具有中性粒细胞减少症等特征。 因此，了解 BTHS 的组织特异性机制具有重要意义。 具有深入了解特定 CL 含量对线粒体功能的作用的潜力，以及 在我对新型 TAZ 缺陷细胞模型的初步研究中，我为 BTHS 提供了新的治疗靶点。 发现呼吸链复合物 I 在蛋白质和代谢水平上失调。 我发现复合物 I 是氧化磷酸化 (OXPHOS) 功能障碍的主要位点 BTHS 中复合物 I 的失调是一个特别有趣的发现，因为 其他复杂的 I 型疾病，包括 Leigh 病，具有显着的神经系统影响，因此，I 进一步。 研究发现，神经组织中的组织特异性 CL 含量使其免受这种功能障碍的影响。 针对这一假设，我提出了两个具体目标：确定 TAZ 缺乏的影响，以及 因此，异常的CL含量，对复合物I功能的影响我将首先研究降低。 然后我将确定复合物 I 蛋白的表达对酶稳定性和功能的影响。 NDUFAF1 因子在复合物 I 蛋白表达减少中起着重要作用，如果减少 NDUFAF1 表达是由于转录水平的失调所致。 目标 2：了解 NDUFAF1 的作用。 CL 含量对 BTHS 病理生理学的组织特异性 我将首先区分 TAZ 缺陷的 iPSC， iPSC TAZΔ50，进入心肌细胞和神经元，以表征和比较复合物 I 失调 然后，通过评估 NDUFAF1 蛋白表达、NADH/NAD+ 比率和复合物 I 酶稳定性/功能。 我将确定与 WT 神经元相比，TAZ 缺陷神经元是否表现出改变的 CL，以及是否缺乏 TAZ TAZ 缺陷神经元中 CL 含量的改变反映了 TAZ 在神经元 CL 重塑中的作用较小。 项目提案结合了基础科学和转化方法来阐明细胞病理生理学和 确定罕见疾病的潜在治疗靶点 当我完成这项研究时，我将获得技能。 为我从事罕见遗传疾病治疗发现的职业做好准备。