SYNTHETIC LETHAL INTERACTIONS IN BARTH SYNDROME

描述（由申请人提供）：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。它的特点是扩张性心肌病、骨骼肌病、中性粒细胞减少、生长迟缓、线粒体异常和心律失常的高发率。BTHS细胞表现出磷脂心磷脂（CL）水平下降和CL酰基异常。与此一致的是，他他嗪是一种转酰基酶，可以催化CL的重塑（用新的脂肪酸取代CL上现有的脂肪酸）。虽然所有BTHS患者都有异常的CL组成，但BTHS的临床表现是高度可变的，即使在具有相同他法津突变的患者中也是如此。这表明他法嗪缺陷的结果受到生理调节剂的强烈影响。目前我们对他法嗪的作用和修饰因素的认识存在差距，使BTHS的治疗复杂化。该研究的长期目标是阐明他法嗪的细胞作用和生理调节剂。为此，将采用一种创新的遗传方法来确定与他法嗪的合成致命相互作用。鉴定合成致死性基因，即在缺少相关基因的情况下对生存至关重要的基因，是赋予基因功能并确定加剧其丧失的因素的有力方法。在拟议的研究中，合成致死物质将首先在具有良好特征的BTHS酵母模型(taz1？突变体)和合成致死率将在哺乳动物心肌细胞中进行测试。本研究将验证他法嗪缺失对需要CL的通路突变体具有合成致死性的假设。具体目的如下：1)对所有（4815个）酵母缺失突变体进行全基因组筛选，以鉴定所有对酵母taz1？突变体。2)在酵母中发现的合成致死相互作用将在哺乳动物心肌细胞中进行测试，使用RNAi方法敲低他法津和潜在相互作用基因的表达。成功鉴定与他法嗪的合成致死性相互作用将为BTHS的病理和治疗提供新的见解。这一知识将有助于确定扩张型心肌病和其他cl相关线粒体功能障碍的一般机制。拟议的研究将确定影响Barth综合征严重程度的调节生理因素，Barth综合征是一种线粒体脂质代谢紊乱，可导致扩张性心肌病和心律失常引起的心力衰竭和猝死。这些修饰因素的识别将为治疗巴斯综合征提供新的依据。此外，这一知识将有助于阐明心肌病和心律失常的病理机制，也将对其他与线粒体脂质代谢相关的疾病有启示，包括缺血、衰老、帕金森病和糖尿病。

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.