Genetic Studies of Diabetes

除了广泛研究的1型和2型糖尿病，还有一些单基因遗传形式 这种疾病，包括年轻人的成熟期发病糖尿病（MODY）。第一个MODY的遗传基础 HNF 4A亚型是20年前通过与HNF 4A核受体突变相关而发现的。 这种与转录因子的联系集中在确定Hnf4A在关键组织中的中心作用上。 控制新陈代谢的器官：肝脏，肠和胰腺然而，在小鼠模型中的遗传研究， 没有概括与MODY1相关的全部症状-特别是，持续的 低胰岛素血症高血糖症临床观察。我们发现HNF4A的表达模式是： 从果蝇到哺乳动物，Hnf4A在进化过程中是保守的，而果蝇的Hnf4A直系同源物突变体 （dHNF4）显示一系列类似于MODY1患者的表型。其中包括成人发病 高血糖症、葡萄糖刺激的胰岛素分泌受损、葡萄糖耐受不良和外周血胰岛素水平降低。 胰岛素信号此外，我们的RNA-seq转录谱鉴定了几个功能组， dHNF4调节基因，在果蝇和人类中表达受体的组织中起作用。这 包括对炎症反应途径的广泛影响，类似于Hnf4A在哺乳动物中的作用。 肠，以及参与葡萄糖刺激胰岛素分泌的关键基因。没想到，我们也 发现在突变体中，dHNF4编码的基因表达显著减少， 蛋白定位于线粒体并特异性结合线粒体基因组的控制区。 dHNF4还直接调节编码线粒体蛋白的核基因，显示出核心作用 在线粒体生理学中。鉴于在哺乳动物中仅鉴定了少数核转录因子， 线粒体，他们的作用知之甚少，我们建议进行详细的分析， dHNF4的线粒体功能，并将其与受体的关键下游作用联系起来。此外，我们将 利用果蝇遗传学来阐明线粒体功能障碍、炎症和 糖尿病背景下的代谢缺陷虽然这些途径通常与代谢有关， 综合征，其因果关系尚不清楚。我们的总体假设是，dHNF 4的行为， 多个组织，以维持线粒体功能，并抑制炎症和糖尿病。我们提出 三个具体的目的是（1）确定dHNF 4的组织特异性功能，（2）确定生理 dHNF4调节途径和靶基因的功能，以及（3）表征进化保守性 dHNF4的功能，从苍蝇到哺乳动物。综合起来，这项研究将提供一个简单的遗传系统 来剖析线粒体功能障碍、炎症和糖尿病之间的相互作用， MODY1的模型。我们的结果，反过来，可以用来指导未来的研究，在小鼠模型，以及设计 预防和治疗人类糖尿病的新的潜在治疗方法。

In addition to the widely studied type 1 and type 2 diabetes, there are a number of monogenic inherited forms of this disorder, including Maturity-Onset Diabetes of the Young (MODY). The genetic basis for the first MODY subtype was discovered 20 years ago through its association with mutations in the HNF4A nuclear receptor. This link with a transcription factor focused efforts on defining the central roles of Hnf4A in the key tissues where it controls metabolism: the liver, intestine, and pancreas. Genetic studies in mouse models, however, did not recapitulate the full range of symptoms associated with MODY1 – in particular, the sustained hypoinsulinemic hyperglycemia seen in the clinic. We discovered that the expression pattern of HNF4A is conserved through evolution, from flies to mammals, and that mutants for the Drosophila ortholog of Hnf4A (dHNF4) display a range of phenotypes that resemble those of MODY1 patients. These include adult-onset hyperglycemia, impaired glucose-stimulated insulin secretion, glucose intolerance, and reduced peripheral insulin signaling. In addition, our RNA-seq transcriptional profiling identified several functional groups of dHNF4-regulated genes that act in the tissues where the receptor is expressed in flies and humans. This includes widespread effects on inflammatory response pathways, similar to the role of Hnf4A in the mammalian intestine, as well as key genes involved in glucose-stimulated insulin secretion. Unexpectedly, we also discovered that mitochondrial-encoded gene expression is significantly reduced in the mutant, and that dHNF4 protein localizes to mitochondria and binds specifically to the control region of the mitochondrial genome. dHNF4 also directly regulates nuclear genes that encode mitochondrial proteins, demonstrating a central role in mitochondrial physiology. Given that only a few nuclear transcription factors have been identified in mitochondria, and their roles are poorly understood, we propose to undertake a detailed analysis of the mitochondrial functions of dHNF4 and link these to key downstream roles of the receptor. In addition, we will use Drosophila genetics to elucidate the interactions between mitochondrial dysfunction, inflammation, and metabolic defects in the context of diabetes. Although these pathways are often associated in metabolic syndrome, their cause and effect relationships remain unclear. Our overall hypothesis is that dHNF4 acts in multiple tissues to maintain mitochondrial function and to suppress inflammation and diabetes. We propose three specific aims to (1) determine the tissue-specific functions of dHNF4, (2) determine the physiological functions of dHNF4-regulated pathways and target genes, and (3) characterize the evolutionary conservation of dHNF4 functions, from flies to mammals. Taken together, this research will provide a simple genetic system to dissect the interplay between mitochondrial dysfunction, inflammation, and diabetes, as well as an animal model for MODY1. Our results, in turn, can be used to guide future studies in mouse models as well as devise new potential therapeutic approaches for preventing and treating diabetes in humans.