SIM2 Regulation of Mitochondrial Dysfunction in Down Syndrome

摘要 唐氏综合征(DS)是最常见的遗传性疾病，在中国大约每750名新生儿中就有1人受到影响 美国每年都是如此。DS是由人类染色体长臂的全部或部分额外复制引起的 21(HSA21)。DS表型高度复杂和多变，包括常见的表型，如 面部特征、智力残疾、骨骼肌无力和不同的表型包括 心脏缺陷、阿尔茨海默病、2型糖尿病和肥胖症的发病率增加。越来越明显的是， 线粒体功能障碍和氧化应激是DS相关病理的主要潜在因素。 在骨骼肌中已经描述了呼吸、三磷酸腺苷产生和线粒体结构的损害 以及DS患者和小鼠模型的中枢神经系统。然而，驱动线粒体的机制 DS的功能障碍仍不清楚。我们已经证明了单基因2(SIM2)，一个最初被克隆的基因 在HSA21上，是bHLH/PAS家族的一员，在骨骼肌细胞中表达，并调节 整个系统新陈代谢。我们使用增益和损失函数细胞系和小鼠模型的最新结果 发现SIM2不是作为一种经典的转录因子，而是通过直接相互作用来调节线粒体的功能 与线粒体和调节线粒体呼吸(MRC)的相互作用，可能通过与 线粒体呼吸链。基于这些新的结果，我们假设Sim2的表达增加 在DS中，骨骼肌促进线粒体活性，导致氧化应激和线粒体增加 功能障碍。为了解决这一假设，我们提出了三个具体目标。在目标1中，我们将确定 DS患者线粒体呼吸复合体中SIM2的表达。我们还将定义的物理基础和功能 代谢中SIM2与线粒体呼吸链复合体相互作用的结果。在AIM 2，我们将通过跨越井-2来确定Sim2在DS相关骨骼肌功能障碍中的作用 采用Sim2/-基因敲除小鼠建立DS小鼠模型DP(16)1Yey/DS。此外，我们还将 通过与mito-QC杂交，确定Sim2 Has对线粒体翻转和结构的影响 建立Sim2/-小鼠模型。在目标3中，我们将利用合成反义的最新进展。 寡核苷酸(ASO)技术在细胞培养和使用Sim2 ASO的DS小鼠模型中开发和测试 治疗DS的药物。我们期望这些研究的结果将有助于确定线粒体功能障碍的机制 在DS中。

SUMMARY Down Syndrome (DS) is the most common type of genetic disorder affecting approximately 1/750 newborns in the United States each year. DS is caused by an extra copy of all or part of the long arm of human chromosome 21 (HSA21). The DS phenotype is highly complex and variable including common phenotypes such characteristic facial features, intellectual disability, skeletal muscle weakness and variable phenotypes including heart defects, increased incidence of Alzheimer’s disease, type 2 diabetes and obesity. It is becoming clear that mitochondrial dysfunction and oxidative stress are major underlying factors in DS-related pathologies. Impairment in respiration, ATP production and mitochondria structure have been described in skeletal muscle and central nervous system in DS patients and mouse models. However, the mechanism driving mitochondrial dysfunction in DS is still not clear. We have shown that singleminded 2 (SIM2), a gene that was initially cloned on HSA21 and a member of the bHLH/PAS family of proteins, is expressed in skeletal muscle cells and regulates whole system metabolism. Our recent results using gain and loss function cell lines and mouse models have found that SIM2 regulates mitochondrial function, not as a classical transcription factor, but by interacting directly with mitochondria and modulating mitochondrial respiration (MRC), potentially through interaction with the mitochondria respiratory chain. Based on these new results, we hypothesize that increased expression of Sim2 in DS skeletal muscle promotes mitochondrial activity, resulting in increased oxidative stress and mitochondrial dysfunction. To address this hypothesis we propose three Specific Aims. In Aim 1, we will determine the role of SIM2 in the mitochondrial respiratory complex in DS. We will also define the physical basis for, and functional outcomes of, interactions between SIM2 and the mitochondria respiratory chain complex in metabolism. In Aim 2, we will determine the role of Sim2 in DS-associated skeletal muscle dysfunction by crossing the well- established DS mouse model, Dp(16)1Yey/+ DS, with whole body Sim2+/- knockout mice. In addition, we will also determine the impact loss of Sim2 has on mitochondrial turnover and structure by crossing the mito-QC mouse model with Sim2+/- mice. In Aim 3, we will take advantage of the recent advances in synthetic antisense oligonucleotide (ASO) technology to develop and test in cell culture and DS mouse models using a Sim2 ASO drug for DS. We expect results from these studies will help define the mechanism of mitochondrial dysfunction in DS.