Mechanisms and Treatment of Cardiac and Skeletal Muscular Dysfunction in Barth Syndrome

项目总结 Barth综合征(BTHS)是一种罕见的、经常致命的线粒体疾病，由隐性功能丧失引起 编码他法津的基因TAZ发生突变。他法津是一种被贩卖的核编码的转移酶 到线粒体内膜，在那里它将单溶心磷脂(MLCL)重塑为成熟的心磷脂(CL)。 CL是一种重要的磷脂，参与维持线粒体膜流动性、渗透稳定性和 高效的呼吸链功能。在BTHS患者中，不适当的MLCL：CL比例会导致线粒体减少 能量产生和心脏骨骼肌病。尽管所有BTHS患者都存在CL重构缺陷， 在疾病进展和临床表现上有相当大的差异，其基础是 分歧仍然模糊不清。这些不同的临床结果与高变异性相结合 TAZ突变的位置和严重程度表明他法津具有未知的功能，可能 涉及与未知蛋白质的相互作用，以影响BTHS和常见的心力衰竭表现。 为了定义这些新的机制，我们建议1)评估整体蛋白质表达谱 BTHS患者诱导的多能干细胞的线粒体形态、周转和功能 (IPSCs)在两种标准培养条件下分化为心肌细胞(CMS)和骨骼肌管(SKM) 系统和仿生微环境，2)IPSC-CM和-SKM与人类临床表型的比较 骨骼肌和心脏功能、代谢和能量指数，以及3)设计人类天然和突变体 带有错义突变的他法津构建评估他法津蛋白定位和复合体的改变 绑定模式。Taz基因替换和随后的分析将证实观察到的影响是 由他法津缺乏症引起。体内BTHS小鼠模型分析将补充体外工作 以及一项正在进行的临床研究中的人体数据。这些模型结合在一起，将提供宝贵的平台 定义疾病机制并测试临床前基因治疗。我们假设泛函的求值 Tafazzin蛋白复合体结合伙伴的异常、鉴定及其对表达谱的影响 在BTHS的线粒体中，iPSCs分化为CMS和Skms，代表各种不同的TAZ 突变和BTHS小鼠模型将揭示他法津的新角色。随着TAZ表达的降低， 与各种非BTHS心脏病状态和CL异常相关的已在一系列范围内被检测到 从这项研究中获得的机械论知识对改善我们的一般情况有很大的潜力 理解并为广泛的健康问题提供新的治疗目标，这些问题延伸得很好 超越BTHS。

PROJECT SUMMARY Barth syndrome (BTHS) is a rare, frequently fatal, mitochondrial disease caused by recessive loss-of-function mutations in the gene TAZ, which encodes tafazzin. Tafazzin is a nuclear-encoded transferase that is trafficked to the inner mitochondrial membrane where it remodels monolysocardiolipin (MLCL) to mature cardiolipin (CL). A critical phospholipid, CL is involved in maintenance of mitochondrial membrane fluidity, osmotic stability, and efficient respiratory chain function. In BTHS patients, improper MLCL:CL ratios result in decreased mitochondrial energy production and cardioskeletal myopathy. Although deficient CL remodeling exists in all BTHS patients, there are considerable differences in disease progression and clinical presentation and the basis for these differences remains obscure. These differential clinical outcomes combined with the high variability in the location and severity of TAZ mutations suggest that tafazzin possesses uncharacterized functions that may involve interactions with unidentified proteins to influence BTHS and common heart failure presentation as well. In order to define these novel mechanisms, we propose to 1) evaluate overall protein expression profiles as well as mitochondrial morphology, turnover, and function in human BTHS patient induced pluripotent stem cells (iPSCs) differentiated into cardiomyocytes (CMs) and skeletal myotubes (SkMs) using both standard culture systems and biomimetic microenvironments, 2) compare iPSC-CM and -SkM phenotypes to human clinical skeletal muscle and cardiac functional, metabolic and energetic indices, and 3) design human native and mutant tafazzin constructs with missense mutations to evaluate alterations in tafazzin protein localization and complex binding patterns. TAZ gene replacement and subsequent analyses will confirm that the observed effects are caused by tafazzin deficiencies. The in vitro work will be complemented by in vivo BTHS mouse model analyses and human data from an ongoing clinical study. In combination, these models will provide valuable platforms for defining disease mechanisms and testing pre-clinical gene therapy. We hypothesize that evaluation of functional abnormalities, identification of tafazzin protein complex binding partners and their impact on expression profiles in mitochondria from BTHS iPSCs differentiated into CMs and SkMs representing a variety of distinct TAZ mutations and a BTHS mouse model will reveal novel roles for tafazzin. As decreased TAZ expression has been associated with a variety of non-BTHS heart disease states and CL abnormalities have been detected in a range of disorders, mechanistic knowledge gained from this study has great potential to improve our general understanding of and provide novel therapeutic targets for a wide range of health concerns that stretch well beyond BTHS.