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: 10205058
• 负责人: Guoqiang Gu
• 金额: $ 44.31万
• 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/10205058
• 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; islet stem cells; 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细胞团不足可导致2型糖尿病(T2D)。这一应用将阐明胚胎多潜能胰腺前体细胞(MPPC)中的DNA甲基体如何预先确定这一质量。在胚胎发育过程中，mPPC激活前内分泌转录因子(TF)NGN3产生内分泌祖细胞(EPC)，β细胞由此衍生而来。DNA甲基化是一种相对稳定的抑制标记，它由包括DNA甲基转移酶1(DNMT1)在内的几种酶决定。DNMT1基因多态性与β细胞功能减弱和人类T2D相关。我们发现，胎儿暴露在母体低蛋白饮食中，已知会损害功能性β细胞团，增强小鼠mPPC中DNMT1的表达。我们最近发表了mPPC和EPC池可以被分成不同的子集，这些子集在可能具有启发性的基因增强子上携带不同的DNA甲基化水平，这可能会倾向于胰岛细胞的命运选择。此外，在mPPC/EPC中较高的DNMT1表达有利于β细胞的分化；然而，EPC向胰岛细胞的分化涉及DNMT1的快速和实质性的下调，以及调控β细胞增殖和功能的基因的相应去甲基化(称为适合性)。后者包括突触素7(Syt7)，这是一种促进葡萄糖刺激的胰岛素分泌的基因。我们的模型是，mPPC中的甲基体可以影响其后代内皮祖细胞和β细胞中进化的甲基体。因此，具有不同甲基组的mPPC可以通过预先设定稍后将被激活的基因的表达水平来产生具有不同适合性的β细胞亚群，以获得高β细胞适合性质量。通过改变DNMT1的表达和/或母亲的饮食操作来扰乱早期的甲基体会改变β细胞亚群的部分，从而改变功能性β细胞质量和对T2D的易感性。与这一模型一致，我们发现，在正常生理条件下，部分(~55%)来源于共同表达TFMyt1(即Myt1+Ngn3+或“M+N+”)的β细胞比来自M-N+细胞的细胞具有更高的出生后适合性。在这里，我们将首先定义M+N+或M-N+祖细胞亚群在代谢应激(如衰老、高血糖或胰岛素抵抗)下的适合性，以阐明它们的生理意义(AM1)。然后，我们将检查这两个亚组的转录本/甲基组，以确定能够解释它们不同的β细胞适应性的关键甲基化基因座，包括测试(我们观察到的)两个β细胞亚组中不同的Syt7表达是否有助于它们不同的胰岛素分泌活动(目标2)。最后，我们将研究母亲低蛋白饮食暴露如何影响M+N+和M-N+祖细胞亚群的来源和适合性，重点是mPPC中增强的DNMT1表达的作用(目标3)。我们希望通过在母体因素和基因网络之间建立直接的机械联系来影响这一领域，这些基因网络调节功能性β细胞质量和对T2D的易感性。我们对β细胞亚群的创新组合谱系标记使我们处于研究这些问题的独特位置。