Adaptation to long chain fatty acid oxidation deficiency

描述(申请人提供)：超长链acyI-CoA脱氢酶(VLCAD)催化哺乳动物线粒体脂肪酸氧化(FAO)螺旋的第一步，该螺旋在心脏和其他高度氧化的组织中产生能量。人类隐性VLCAD缺陷会导致早期致死性心肌病和心律失常、婴儿期低酮症和肝功能衰竭、婴儿期猝死(SID)和晚期发作性骨骼肌病的表型。我们的第一个假设是VLCAD缺陷与基因-表型的相关性，我们将通过与临床表型相关的分子遗传学和研究一些VLCAD突变的致病机制来调查(目标1)，特别是在新生儿筛查中发现的患者中存在的V243A。我们的第二个假设是，VLCAD对心脏功能是必不可少的，这既是因为它的酶作用，也是因为VLCAD是多个基因转录调控所必需的。我们将通过鉴定我们分离的20个碱基长的VLCAD增强子(目标2)和鉴定VLCAD缺陷小鼠及其杂合子后代来研究这一点，这些小鼠和它们的杂合子后代表现出猝死、迟发性肥胖、肿瘤发展和诱导性心律失常以及因禁食和寒冷而死亡的表型。这一特征包括使用转基因小鼠和细胞转染来检查VLCAD转录调控(AIM 2)和VLCAD-/-和/-动物的遥测、侵入性电生理学、微阵列分析、运动测试和饮食操作(AIM 3)。我们还将创建组织特异性(心脏、棕色脂肪、肝脏、肌肉)基因敲除(目标4)，以确定这些器官对表型的相对贡献。我们知道，VLCAD-/-动物在一天内表现出组织基因表达的显著变化，这是一种围产期的“适应性反应”。我们假设，这种救命的适应性反应造成基因表达的差异，这是猝死、心律失常、肥胖和肿瘤发生等后续病理的基础。因此，这是一个模型，说明了一个基因的多态或突变如何在以后的生活中改变另一个基因的表达，从而导致病理。在这种遗传反应中，一个高度诱导的基因是一种新的蛋白质，命名为心脏内皮素相关物质(HERS)，根据同源性和表达数据，我们假设在心脏发育和钙代谢中具有功能。我们将通过在最后一个特定目标中产生她的击倒来研究它的作用。

DESCRIPTION (provided by applicant): Very-long-chain acyI-CoA dehydrogenase (VLCAD) catalyzes the first step of the mammalian mitochondrial fatty acid oxidation (FAO) spiral that generates energy in the heart and other highly oxidative tissues. Human recessive VLCAD deficiency produces phenotypes of early fatal cardiomyopathy and arrhythmias, infantile hypoketotic hypoglycemia and liver failure, sudden death in infancy (SIDS), and later episodic skeletal myopathy. Our first hypothesis is that VLCAD deficiency has a genotype-phenotype correlation that we will investigate (Aim 1) through molecular genetics, correlating with clinical phenotypes, and by studying the pathogenetics of some VLCAD mutations, particularly V243A that exists in patients discovered by newborn screening. Our second hypothesis is that VLCAD is essential for cardiac function both because of its enzymatic role, but also because VLCAD is required for transcriptional regulation of multiple genes. This will be investigated by characterizing the 20 bp long VLCAD enhancer we have isolated (Aim 2) and by characterizing VLCAD-deficient mice and their heterozygote littermates that exhibit the phenotypes of sudden death, late-onset obesity, development of tumors, and inducible arrhythmias and that die in response to fasting and exposure to cold. This characterization includes use of transgenic mice and cell transfections to examine VLCAD transcriptional regulation (Aim 2) and telemetry, invasive electrophysiology, microarray analysis, exercise testing, and dietary manipulation of VLCAD -/- and +/- animals (Aim 3). We will also create tissue-specific (heart, brown fat, liver, muscle) knockouts (Aim 4) to ascertain the relative contributions of these organs to phenotypes. We know that VLCAD -/- animals exhibit marked alterations in tissue gene expression by one day, a perinatal "adaptive response". We hypothesize that this live-saving adaptive response creates differences in gene expression that are the substrate for the later pathologies of sudden death, arrhythmias, obesity, and tumorigenesis. This is, thus, a model of how polymorphisms or mutations in one gene modify expression of other later in life, leading to pathology. One highly induced gene in this genetic response is a novel protein, designated heart endothelin-related substance (HERS) that, based upon homology and expression data, we postulate functions in cardiac development and calcium metabolism. We will investigate its role by generating a HERS knockout in the last specific aim.