Regulation and function of the MEG3 locus in human beta-cells

描述（由申请人提供）：维持葡萄糖稳态对我们的健康至关重要，其失败会导致严重的衰弱性疾病，包括糖尿病和家族性高胰岛素血症。糖尿病是一种代谢紊乱，影响全球超过2.85亿人，是许多国家的主要死因。该疾病的特征是由于胰腺产生胰岛素的β细胞的自身免疫性破坏而导致的绝对胰岛素缺乏[1型糖尿病（T1DM）]，或由于胰岛素分泌缺陷或胰岛素敏感性而导致的相对胰岛素缺乏[2型糖尿病（T2DM）]。所得 升高的血糖水平最终导致微脉管系统受损，随后是肾衰竭、失明、神经病和心脏病。因此，糖尿病目前是美国第六大死亡原因（CDC）。在过去的资助周期中，我们已经取得了令人兴奋的发现，印记MEG3基因座在2型糖尿病患者的胰岛中强烈下调。MEG3基因座是特别感兴趣的，因为它编码一个簇 我们发现54种microRNA靶向抗凋亡基因，这表明该位点的失调导致2型糖尿病中β细胞衰竭。在这里，我们建议研究小鼠和人类β细胞中该位点的表观遗传调控和生物学功能。在目标1中，我们将研究导致糖尿病中MEG3位点失调的分子机制。具体而言，我们将检验MEG3基因启动子附近差异甲基化区域（DMR）的超甲基化导致MEG3基因增强子中β细胞特异性转录因子结合丧失的假设。在目标2中，我们将使用小鼠遗传和创新的人类表观遗传失活来确定MEG3基因座在β细胞生理学和存活中的特定功能。将对MEG3缺陷β细胞进行多种生化和分子测定。总之，这些实验将为2型糖尿病β细胞衰竭的分子病因学提供重要的新见解。

DESCRIPTION (provided by applicant): Maintenance of glucose homeostasis is central to our health, and its failure results in severe debilitating diseases including diabetes and familial hyperinsulinism. Diabetes mellitus is a metabolic disorder that affects over 285 million people worldwide and is a leading cause of death in many countries. The disease is characterized by either absolute insulin deficiency due to the autoimmune destruction of pancreatic insulin-producing β-cells [Type 1 diabetes mellitus (T1DM)], or relative insulin deficiency due to defective insulin secretion or insulin sensitivity [Type 2 diabetes mellitus (T2DM)]. The resulting elevated blood glucose levels eventually lead to an impairment of the microvasculature followed by kidney failure, blindness, neuropathy and heart disease. Consequently, diabetes is currently the sixth leading cause of death in the United States (CDC). During the past grant cycle, we have made the exciting discovery that the imprinted MEG3 locus is strongly down-regulated in islets from type 2 diabetics. The MEG3 locus is of particular interest in that it encodes a cluster of 54 microRNAs, which we have found to target anti-apoptotic genes, suggesting that dysregulation of this locus contributes to β-cell failure in type 2 diabetes. Here, we propose to investigate both epigenetic regulation and biological function of this locus in mouse and human β-cells. In Aim 1, we will investigate the molecular mechanism that causes dysregulation of the MEG3 locus in diabetes. Specifically, we will test the hypothesis that hyper-methylation of a differentially methylated region (DMR) near the promoter of the MEG3 gene causes loss of binding of β-cell specific transcription factors in an enhancer in the MEG3 gene. In Aim 2, we will determine the specific function of the MEG3 locus in β-cell physiology and survival using both mouse genetic and innovative human epigenetic inactivation. Multiple biochemical and molecular assays will be performed on MEG3 deficient β-cells. Together, these experiments will provide important new insights into the molecular etiology of β-cell failure in type 2 diabetes.