The function and regulation of the novel pregnancy-specific hexokinase HKDC1

 描述(由申请人提供)：妊娠期高血糖可导致母亲和子女的急性和慢性不良后果。在最近一项关于高血糖和不良妊娠结局(HAPO)队列的遗传学研究中，PiLayden、共同调查者Reddy和共同作者报告了一个新的与母亲妊娠期血糖特征相关的基因座。相关区域的前导候选基因编码己糖激酶域包含1(HKDC1)蛋白。因此，这项建议的总体目标是了解新基因HKDC1在妊娠期血糖稳态中的作用。最近，Pi Layden和合作研究员Reddy发表了HKDC1的第一个特征，意外地揭示HKDC1是第五种脊椎动物己糖激酶(郭等人，2015自然通讯)。这项建立在这些初步发现基础上的提案的目标是检验HKDC1是一种新的己糖激酶的中心假设，它控制着怀孕期间的葡萄糖稳态。验证这一假设很重要，因为它将揭示导致全球最常见的妊娠并发症之一的新机制。这些结果也将对理解脊椎动物的新陈代谢产生广泛的影响，因为己糖激酶是糖酵解的第一步，而第五个人己糖激酶的首次表征将极大地改变我们对控制健康和疾病期间葡萄糖动态平衡的酶的基本理解。核心假设将在三个互补的水平上进行检验。首先，在初步发现HKDC1是己糖激酶之后，将对该蛋白质的酶活性进行系统的表征。这样做将揭示HKDc1更可能负责葡萄糖感应还是葡萄糖代谢，并将HKDc1与其他己糖激酶联系起来。这些见解对于理解HKDC1在孕产妇健康中的作用是至关重要的。其次，将评估HKDC1在妊娠期血糖稳态中的体内作用。组织表达模式表明，HKDc1通过其在胰腺β细胞和肝脏中的作用来调节妊娠期的葡萄糖稳态。通过全局和组织特异性消融的小鼠模型，将评估怀孕期间的葡萄糖稳态。这些发现将转化为对人类胰岛和原代人类肝细胞的体外研究。第三，将通过检验妊娠期高血糖相关基因变异改变怀孕期间HKDC1的调节的假说来研究HKDC1在怀孕期间调节血糖的作用。这一假设将通过新的高通量报告分析进行验证：(I)发现调节HKDC1表达的主要和次要激素和葡萄糖反应元件；(Ii)识别改变原始GWA群中调节元件功能的遗传变异。这项建议的结果将是全面了解HKDC1在怀孕期间的活动和转录调控。从长远来看，这些发现将支持下游预测、预防和治疗妊娠期高血糖的努力。

 DESCRIPTION (provided by applicant): Gestational hyperglycemia can result in acute and chronic adverse outcomes for mother and offspring. In a recent genetic study of the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) cohort, PI Layden, Co- investigator Reddy, and co-authors reported a novel loci associated with maternal glycemic traits specifically during pregnancy. The lead candidate gene in the associated region encodes the hexokinase-domain containing 1 (HKDC1) protein. Therefore, the overall objective of this proposal is to understand the role of the novel gene HKDC1 in gestational glucose homeostasis. Recently, PI Layden and co-Investigator Reddy published the first characterization of HKDC1, revealing unexpectedly that HKDC1 is a fifth vertebrate hexokinase (Guo et al., 2015 Nature Communications). The goal of this proposal, which builds upon those initial findings, is to test the central hypothesis that HKDC1 is a novel hexokinase that controls glucose homeostasis during pregnancy. Testing that hypothesis is important because it will reveal new mechanisms contributing to one of the most common complications of pregnancy worldwide. The results will also have broad-reaching impacts on understanding vertebrate metabolism because hexokinase is the first step in glycolysis, and the first characterization of the fifth human hexokinase will substantially revise our basic understanding of the enzymes controlling glucose homeostasis during health and disease. The central hypothesis will be tested at three complementary levels. First, following up on the initial discovery that HKDC1 is a hexokinase, the enzymatic activity of the protein will be systematically characterized. Doing so will reveal whether HKDC1 is more likely responsible for glucose sensing or glucose metabolism, and will relate HKDC1 to the other hexokinases. Those insights are essential for understanding the role of HKDC1 in maternal health. Second, the in vivo role of HKDC1 in glucose homeostasis during pregnancy will be assessed. Tissue expression patterns suggest that HKDC1 regulates glucose homeostasis during pregnancy specifically through its role in pancreatic β cells and liver. Through global and tissue-specific ablation mouse models, glucose homeostasis during pregnancy will be assessed. These findings will be translated to in vitro studies in human islets and primary human hepatocytes. Third, the role of HKDC1 in regulating glucose during human pregnancy will be investigated by testing the hypothesis that gestational hyperglycemia-associated genetic variants alter the regulation of HKDC1 during pregnancy. That hypothesis will be tested using novel high- throughput reporter assays (i) to discover the primary and secondary hormone and glucose response elements that regulate HKDC1 expression and (ii) to identify genetic variants that alter regulatory element function in the original GWAS population. The outcome of this proposal will be a comprehensive understanding of the activity and transcriptional regulation of HKDC1 during pregnancy. Long term, those findings will support downstream efforts to predict, prevent, and treat gestational hyperglycemia.