Islet transcription factor activation: FoxPs are required for postnatal endocrine cell proliferation while Pdx1 recruited chromatin remodeling enzymes impact pancreas size

胰岛转录因子激活：FoxPs 是出生后内分泌细胞增殖所必需的，而 Pdx1 招募的染色质重塑酶会影响胰腺大小

• 批准号: 8907572
• 负责人: Jason M Spaeth
• 金额: $ 4.65万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8907572
• 关键词: ATP phosphohydrolase; Acinar Cell; Address; Adult; Age; Alleles; Alpha Cell; Apoptosis; Beta Cell; Biochemical; Biological Assay; Blood Glucose; Cell Count; Cell Proliferation; Cell physiology; Cells; Chad; Chromatin Remodeling Factor; Collaborations; Complex; Data; Development; Diabetes Mellitus; Disease Progression; Doctor of Philosophy; Ductal Epithelial Cell; Endocrine; Enzymes; Epithelial Cells; Excision; Exhibits; Family; Fasting; Genes; Glucagon; Glucose; Hyperglycemia; Hypoglycemia; In Vitro; Insulin; Insulin Resistance; Intestines; Islet Cell; Knock-out; Knockout Mice; Light; London; Mass Spectrum Analysis; Mediating; Metabolic; Modeling; Molecular; Multipotent Stem Cells; Mus; Onset of illness; Organ Size; Pancreas; Pennsylvania; Peripheral; Phenotype; Physiological; Population; Postabsorptive Hypoglycemia; Postdoctoral Fellow; Production; Property; RNA Interference; Recruitment Activity; Reporting; Role; Serum; Staging; Stem cells; T-Cell Development; Techniques; Testing; Therapeutic; Tissues; Transcription Repressor/Corepressor; Transgenic Mice; United States National Institutes of Health; Universities; Work; base; blood glucose regulation; cell type; chromatin remodeling; cohort; college; endocrine pancreas development; in vivo; insight; interest; islet; member; mouse model; mutant; pancreas development; postnatal; public health relevance; research study; response; transcription factor

 DESCRIPTION (provided by applicant): Diabetes mellitus is metabolic condition that is characterized by impaired function and/or mass of the pancreatic β-cell population that results in severe hyperglycemia. Efforts supported by the NIH are aimed at β-cell replacement or reprogramming other islet cell types into functional β-cells (e.g. islet α-cells). Thus, the discovery of mechanisms which control α- and β-cell proliferation will provide significant insigh into developing therapeutics to treat diabetes. The Stein lab has a direct interest in characterizing the transcription factors and their obligatory coregulators that govern pancreas size and islet development. In this regard, we have discovered that FoxP1, FoxP2 and FoxP4 are essential for α-cell proliferation and will investigate the molecular impact of Pdx1 recruited Swi/Snf chromatin remodeling complex on regulating pancreas size. The role of the FoxP class of transcription factors have yet to be characterized in the islet. In aim 1 of this proposal I hav generated, along with Dr. Chad Hunter, transgenic mice with an endocrine specific knockout of FoxP1/2/4. Our data reveals that this cohort of mice clear glucose normally, but have hypoglycemia and decreased serum glucagon levels under fasting conditions at 4 weeks of age. All endocrine cell types (α-, -, β-) have reduced proliferative capability; however, the α-cel population is the most profoundly impacted (~90% reduction in cell number). Previous reports show that only 3% of the α-cell population is required for euglycemia and normoglucagonemia, which suggests the remaining 10% of α-cells in the FoxP1/2/4 conditional knockout mice are dysfunctional. This question will be addressed using glucagon secretion assays from isolated islets and immunohistochemical techniques in pancreata from 4 week old experimental groups. Pdx1 is one of the first transcription factors expressed during pancreatogenesis and its transcriptional activity is required in both pancreas development and postnatal β-cell functions. To address how the activity of Pdx1 is modulated, our lab has shown that the Swi/Snf chromatin remodeling complex interacts with (both in vivo and in vitro) and regulates Pdx1 transcriptional activity. Preliminary results have shown that RNAi- mediated knockdown of Brg1, an ATPase essential for Swi/Snf chromatin remodeling activity, negatively impacts the expression of glucose homeostasis genes. Conditional knockout of Brg1 during the early stages of pancreatogenesis results in mice with a hypoplastic pancreas, approximately 50% the size of control littermates. This conditional knockout model will be used in Aim 2 to examine how Brg1 impacts pancreas size. I will examine whether the population of cells in the Brg1 mutant that are designated to become all pancreatic cell types, known as the multipotent progenitor cells (MPCs), are decreased in number, exhibit decreased proliferation or increased apoptosis that could explain the hypoplastic pancreas. Collectively, this proposal will be of major interest to th diabetes field as it will shed light on how the Swi/Snf chromatin remodeling complex impacts pancreas mass and the FoxP1/2/4 regulators influence proper α-cell development and function.

 描述（由申请人提供）：糖尿病是一种代谢性疾病，其特征是胰腺 β 细胞群的功能和/或质量受损，导致 NIH 支持的努力旨在替代 β 细胞或将其他胰岛细胞类型重新编程为功能性 β 细胞（例如胰岛 α 细胞）。斯坦因实验室对表征控制胰腺大小和胰岛发育的转录因子及其必需的共同调节因子具有直接的兴趣。我们发现 FoxP1、FoxP2 和 FoxP4 对于 α 细胞增殖至关重要，并将研究招募的 Pdx1 的分子影响 Swi/Snf 染色质重塑复合物对调节胰腺大小的作用 FoxP 类转录因子在胰岛中的作用尚未得到表征。在本提案的目标 1 中，我与 Chad Hunter 博士一起培育了具有胰岛功能的转基因小鼠。 FoxP1/2/4 的内分泌特异性敲除显示，这组小鼠正常清除葡萄糖，但在 4 周龄禁食条件下出现低血糖和血清胰高血糖素水平降低。所有内分泌细胞类型（α-、-、β-）的增殖能力均下降；然而，α-cel 群体受到的影响最为严重（之前的报告显示，只有 3% 的细胞数量减少了约 90%）。正常血糖和正常高血糖素血症需要 α 细胞群，这表明 FoxP1/2/4 条件敲除小鼠中剩余 10% 的 α 细胞功能失调。对 4 周龄实验组的胰岛进行胰高血糖素分泌测定和免疫组织化学技术 Pdx1 是胰腺发生过程中最早表达的转录因子之一，其转录活性是胰腺发育和出生后 β 细胞功能所必需的。 Pdx1 的活性受到调节，我们的实验室已证明 Swi/Snf 染色质重塑复合物与（体内和体外）相互作用并调节 Pdx1初步结果表明，RNAi 介导的 Brg1（一种 Swi/Snf 染色质重塑活性所必需的 ATP 酶）的敲除会对葡萄糖稳态基因的表达产生负面影响。发育不良的胰腺，大小约为对照同窝小鼠的 50%。该条件性敲除模型将用于目标 2，以检查其如何发挥作用。 Brg1 会影响胰腺大小。总的来说，该提案将引起糖尿病领域的重大兴趣，因为它将阐明 Swi/Snf 染色质重塑复合物如何影响胰腺质量和胰腺功能。 FoxP1/2/4 调节因子影响 α 细胞的正常发育和功能。