SYNTHETIC LETHAL INTERACTIONS IN BARTH SYNDROME

描述(申请人提供)：Barth综合征(BTHS)是一种严重的X连锁疾病，由他法津基因突变引起。以扩张型心肌病、骨骼肌病、中性粒细胞减少、生长迟缓、线粒体异常和高心律失常为特征。BTHS细胞显示磷脂心磷脂(CL)水平降低和CL酰基异常。与此一致，他法津是一种转酰基酶，催化CL的重塑(用新的脂肪酸取代CL上的现有脂肪酸)。虽然所有BTHS患者都有异常的CL成分，但BTHS的临床表现差异很大，即使在具有相同Tafazzin突变的患者中也是如此。这表明缺陷他法津的结局受到生理调节剂的强烈影响。目前我们对他法津的功能和修饰因素的认识上的差距使BTHS的治疗复杂化。这项拟议研究的长期目标是阐明他法津的细胞作用和生理调节剂。为此，将实施一种创新的遗传方法，以确定与他法津的合成致命相互作用。识别合成致死基因，即在缺乏目标基因的情况下生存所必需的基因，是为基因分配功能和识别加剧其丢失的因素的有效方法。在这项拟议的研究中，首先将在BTHS的特征良好的酵母模型(taz1？然后，将在哺乳动物心肌细胞中测试合成致死性。这项研究将检验这一假说，即他法津的丢失对需要CL的途径中的突变体具有合成致命性。具体目标如下：1)对所有(4,815)活性酵母缺失突变体进行全基因组筛选，以确定所有对酵母taz1？变种人。2)在酵母中发现的人工致死相互作用将在哺乳动物心肌细胞中进行测试，使用RNAi方法来抑制他法津和潜在的相互作用基因的表达。成功识别与他法津的合成致死相互作用将为BTHS的病理和治疗提供新的见解。这些知识将有助于确定扩张型心肌病和其他与CL相关的线粒体功能障碍的一般机制。公共卫生相关性拟议的研究将确定影响Barth综合征严重程度的改变生理因素，Barth综合征是一种线粒体脂代谢紊乱，由于扩张型心肌病和心律失常而导致心力衰竭和猝死。这些修饰因素的识别将为Barth综合征的治疗提供新的理论依据。此外，这一知识将有助于阐明心肌病和心律失常的潜在病理机制，并将对其他与线粒体脂质代谢相关的疾病，包括缺血、衰老、帕金森病和糖尿病具有指导意义。

DESCRIPTION (provided by applicant): Barth syndrome (BTHS) is a severe, X-linked disorder resulting from mutations in the tafazzin gene. It is characterized by dilated cardiomyopathy, skeletal myopathy, neutropenia, growth retardation, abnormal mitochondria, and a high rate of cardiac arrythmia. BTHS cells exhibit decreased levels of the phospholipid cardiolipin (CL) and aberrant CL acyl species. Consistent with this, tafazzin is a transacylase that catalyzes the remodeling of CL (replacing existing fatty acids on CL with new ones). While all BTHS patients have aberrant CL composition, the clinical presentation of BTHS is highly variable, even among patients with the same tafazzin mutation. This indicates that the outcome of defective tafazzin is strongly influenced by physiological modifiers. The current gap in our understanding of the function of tafazzin and the identity of the modifying factors complicates the treatment of BTHS. The long-term goal of the proposed research is to elucidate the cellular role and physiological modifiers of tafazzin. To this end, an innovative genetic approach will be implemented to identify synthetic lethal interactions with tafazzin. The identification of synthetic lethals, i.e., genes that are essential for survival in the absence of the gene of interest, is a powerful method to assign function to a gene and to identify factors that exacerbate its loss. In the proposed study, synthetic lethals will first be identified in the well-characterized yeast model for BTHS (the taz1? mutant), and synthetic lethality will then be tested in mammalian cardiomyocytes. This study will test the hypothesis that loss of tafazzin is synthetically lethal with mutants in pathways that require CL. The specific aims are as follows: 1) A genome-wide screen of all (4,815) viable yeast deletion mutants will be carried out to identify all mutants that are synthetically lethal with the yeast taz1? mutant. 2) The synthetic lethal interactions discovered in yeast will be tested in mammalian cardiomyocytes, using RNAi methodology to knock down expression of tafazzin and potential interacting genes. The successful identification of synthetic lethal interactions with tafazzin will provide new insights into the pathology and treatment of BTHS. This knowledge will lead to the identification of general mechanisms underlying dilated cardiomyopathy and other CL-associated disorders of mitochondrial dysfunction. PUBLIC HEALTH RELEVANCE The proposed study will identify modifying physiological factors that affect the severity of Barth syndrome, a disorder of mitochondrial lipid metabolism that causes heart failure and sudden death due to dilated cardiomyopathy and cardiac arrhythmia. The identification of these modifying factors will lead to new rationales for the treatment of Barth syndrome. Furthermore, this knowledge will help to elucidate mechanisms underlying the pathology of cardiomyopathy and cardiac arrhythmia, and will also have implications for other conditions associated with mitochondrial lipid metabolism, including ischemia, aging, Parkinson's disease, and diabetes.