The DNA methylome-based regulation of functional beta-cell mass

基于 DNA 甲基化组的功能性 β 细胞群调节

• 批准号: 10033594
• 负责人: Guoqiang Gu
• 金额: $ 44.17万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10033594
• 关键词: Acute; Address; Affect; Age-Months; Aging; Attenuated; B Cell Proliferation; B cell differentiation; B-Lymphocyte Subsets; Beta Cell; Birth; Cell Differentiation process; Cell Lineage; Cell physiology; Cells; DNA; DNA Methylation; DNA Modification Methylases; DNA Sequence Alteration; DNMT3a; Data; Derivation procedure; Development; Diabetes Mellitus; Diet; Dioxygenases; Disease; Down-Regulation; Embryo; Embryonic Development; Endocrine; Enhancers; Enzymes; Epigenetic Process; Exposure to; Future; Gene Expression; Genes; Genetic; Genetic Polymorphism; Glucose; Goals; Human; Hyperglycemia; Hypoglycemia; Immunocompromised Host; Instruction; Insulin Resistance; Islet Cell; Link; Maintenance; Metabolic stress; Methylation; Modeling; Molecular; Mus; Non-Insulin-Dependent Diabetes Mellitus; Nutrient; Pancreas; Pattern; Physiological; Physiology; Positioning Attribute; Predisposition; Process; Production; Protein-Restricted Diet; Publishing; Regulation; Risk Factors; Role; Sentinel; Stress; Testing; Text; allotransplant; base; combinatorial; dosage; fitness; genomic locus; improved; innovation; insulin secretion; methylome; mother nutrition; offspring; postnatal; prenatal exposure; prevent; progenitor; programs; stem cells; synaptotagmin VII; transcription factor; transcriptome

Insufficient functional β-cell mass can cause type 2 diabetes (T2D). This application will elucidate how the DNA methylomes in embryonic multipotent pancreatic progenitor cells (mPPCs) pre-determine this mass. During embryogenesis, mPPCs activate pro-endocrine transcription factor (TF) Ngn3 to give rise to endocrine progenitor cells (EPCs), from which β cells are derived. DNA methylation is a relatively stable repressive mark that is laid down by several enzymes including DNA methyl-transferase 1 (Dnmt1). DNMT1 polymorphisms are associated with attenuated β-cell function and human T2D. We show that fetal exposure to maternal low-protein diet, known to compromise functional β-cell mass, enhances Dnmt1 expression in mouse mPPCs. We recently published that both mPPC and EPC pools can be split into subsets that carry different DNA methylation levels at likely instructive gene enhancers, which can bias islet-cell fate choice. Moreover, higher Dnmt1 expression in mPPCs/EPCs favors β-cell differentiation; yet EPC differentiation toward islet cells involves a rapid and substantial downregulation of Dnmt1 and concordant de-methylation in putative enhancers of genes that regulate β-cell proliferation and function (referred to as fitness). The latter includes Synaptotagmin 7 (Syt7), a gene that promotes glucose-stimulated insulin secretion. Our model is that the methylomes in mPPCs can influence the evolving methylomes in their descendant EPCs and β cells. Thus, mPPCs with distinct methylomes can give rise to β-cell subsets with different fitness by pre-setting the expression levels of genes that will be activated later for high β-cell fitness qualities. Perturbing the early-stage methylomes, by changed Dnmt1 expression and/or maternal diet manipulation, will shift the portions of β-cell subsets and consequently the functional β-cell mass and the susceptibility to T2D. Consistent with this model, we showed that a portion (~55%) of β cells derived from a subset of Ngn3+ EPCs that co-express TF Myt1 (i.e., Myt1+Ngn3+ or “M+N+”) has higher postnatal fitness than those from M-N+ cells under normal physiology. Here, we will first define the fitness of M+N+ or M-N+ progenitor-derived β-cell subsets under metabolic stresses such as aging, hyperglycemia, or insulin resistance to elucidate their physiological significance (Am 1). We will then examine the transcriptomes/methylomes of the two subsets to define the key methylated loci that can account for their distinct β-cell fitness, including testing if the differential Syt7 expression in the two β-cell subsets (observed by us) contributes to their different insulin secretion activities (Aim 2). Lastly, we will examine how maternal low-protein diet exposure impacts the derivation and fitness of M+N+ and M-N+ progenitor-derived β-cell subsets, focusing on the roles of enhanced Dnmt1 expression in mPPCs (Aim 3). We expect to impact the field by establishing direct mechanistic links between maternal factors and genetic networks that regulate functional β-cell mass and susceptibility to T2D. Our innovative combinatorial lineage marking of β-cell subsets put us in a unique position to study these issues.

功能性β细胞质量不足可导致2型糖尿病（T2 D）。本申请将阐明胚胎多能胰腺祖细胞（mPPC）中的DNA甲基化组如何预先确定此质量。在胚胎发生期间，mPPC激活促内分泌转录因子（TF）Ngn 3以产生内分泌祖细胞（EPCs），β细胞来源于EPCs。DNA甲基化是一种相对稳定的抑制性标记，由包括DNA甲基转移酶1（Dnmt 1）在内的几种酶决定。DNMT 1多态性与β细胞功能减弱和人类T2 D相关。我们发现，胎儿暴露于母体低蛋白饮食，已知损害功能性β细胞群，增强小鼠mPPC中Dnmt 1的表达。我们最近发表了mPPC和EPC池都可以分成在可能的指导性基因增强子处携带不同DNA甲基化水平的子集，这可以使胰岛细胞命运选择偏向。此外，mPPC/EPCs中较高的Dnmt 1表达有利于β细胞分化;然而，EPC向胰岛细胞的分化涉及Dnmt 1的快速和实质性下调以及调节β细胞增殖和功能的基因的推定增强子中的一致去甲基化（称为适应性）。后者包括Synaptotagmin 7（Syt 7），一种促进葡萄糖刺激胰岛素分泌的基因。我们的模型是mPPC中的甲基化组可以影响其后代EPCs和β细胞中进化的甲基化组。因此，具有不同甲基化组的mPPC可以通过预先设定稍后将被激活以获得高β细胞适应性质量的基因的表达水平来产生具有不同适应性的β细胞亚群。通过改变Dnmt 1表达和/或母体饮食操作来扰乱早期甲基化组，将改变β细胞亚群的部分，从而改变功能性β细胞质量和对T2 D的易感性。与该模型一致，我们发现一部分（~55%）β细胞来源于共表达TF Myt 1的Ngn 3 + EPC亚群（即，Myt 1 + Ngn 3+或“M+N+”）比正常生理条件下来自M-N+细胞的那些具有更高的出生后适应性。在这里，我们将首先定义M+N+或M-N+祖细胞衍生的β细胞亚群在代谢应激（如衰老、高血糖症或胰岛素抵抗）下的适应性，以阐明它们的生理意义（Am 1）。然后，我们将检查两个子集的转录组/甲基化组，以定义可以解释其不同β细胞适应性的关键甲基化基因座，包括测试两个β细胞子集中的差异Syt 7表达（我们观察到的）是否有助于其不同的胰岛素分泌活性（目的2）。最后，我们将研究母体低蛋白饮食暴露如何影响M+N+和M-N+祖细胞衍生的β细胞亚群的衍生和适应性，重点是增强的Dnmt 1表达在mPPC中的作用（目的3）。我们希望通过在母体因素和调节功能性β细胞质量和T2 D易感性的遗传网络之间建立直接的机制联系来影响该领域。我们创新的β细胞亚群组合谱系标记使我们处于研究这些问题的独特位置。