Thyroid hormone-dependent DNA methylation in the developing brain

发育中大脑中甲状腺激素依赖性 DNA 甲基化

• 批准号: 8203223
• 负责人: Yasuhiro Kyono
• 金额: $ 3.15万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8203223
• 关键词: Amphibia; Binding; Biological Assay; Biological Metamorphosis; Biological Models; Brain; Cell Cycle; Cell Cycle Progression; Cell Cycle Regulation; Cell Differentiation process; Cell Line; Cell Lineage; Cell Proliferation; Cells; Comparative Genomic Analysis; Cretinism; Cyclin D1; DNA; DNA Methylation; DNA Methyltransferase; DNA Modification Methylases; DNMT3a; DNase-I Footprinting; Data Reporting; Defect; Development; Diagnosis; EMSA; Electroporation; Enhancers; Enzymes; Gene Expression; Gene Transfer; Genes; Goals; Growth; Human; Human Development; Introns; Lead; Literature; Mammals; Mediating; Mental Retardation; Messenger RNA; Methylation; Morphology; Mus; Neuroglia; Neurologic; Neuronal Differentiation; Neurons; Play; Prevention; Production; Protein Biosynthesis; Psyche structure; RXR; Rana; Regulation; Reporter; Repression; Research; Response Elements; Role; Schizophrenia; Tadpoles; Testing; Thyroid Hormone Receptor; Thyroid Hormones; Transactivation; Up-Regulation; Work; Xenopus; autism spectrum disorder; base; critical period; hormone deficiency; hormone response element; in vivo; migration; mouse genome; nerve stem cell; neuroblastoma cell; neurogenesis; overexpression; postnatal; promoter; receptor; subventricular zone

DESCRIPTION (provided by applicant): Postembryonic brain development is dependent on thyroid hormone (TH). Thyroid hormone deficiency during critical periods of human development leads to a condition of severe mental and growth retardation known as cretinism. Thyroid hormone has pleiotropic actions in the developing brain, including regulating cell proliferation, cell cycle exit and differentiation (neurogenesis). The goal of this research is to investigate the mechanisms by which TH promotes cell cycle exit and neurogenesis through its regulation of the de novo DNA methyltransferase DNMT3a. Amphibian development (metamorphosis) is dependent on TH, and we propose to use Xenopus tadpoles for our studies. We found that expression of the dnmt3a gene is strongly upregulated in subventricular zones (neurogenic zones) of the tadpole brain during spontaneous metamorphosis, or following treatment with TH. The frog dnmt3a gene has a putative TH response element (TRE) located in the intron, supporting direct TH receptor (TR) regulation. Comparative genomic analysis identified a similar, putative TRE in the mouse genome, supporting evolutionarily conservation of dnmt3a regulation by TR. Furthermore, TH induced dnmt3a mRNA in the mouse neuroblastoma cell line N2a[TR21]. Thyroid hormone is essential for neurogenesis during the early postnatal period. Recent findings showed that dnmt3a is required for neurogenesis. Gene expression analysis of neural stem cells (NSCs) from dnmt3a- deficient mice showed upregulation of genes involved in cell cycle control, supporting a defect in cell cycle exit and differentiation into the neuronal lineage. Several lines of evidence support that cyclin D1 is directly regulated by DNMT3a-mediated DNA methylation. Based on our preliminary findings and data reported in the scientific literature, we hypothesize that TH influences cell cycle exit in neural stem cells and neurogenesis through induction of Dnmt3a. To test this hypothesis we will investigate: 1) the functionality of the evolutionarily conserved TREs in frog and mouse dnmt3a genes; 2) a role for DNMT3a in repression of cyclin D1 through methylation of its promoter; and 3) the effects of altering DNMT3a expression in vivo on cell cycle exit and lineage specification of NSCs. Successful completion of the proposed research will lead to advances in our understanding of the mechanisms by which TH controls neurological development through its influence on DNA methylation. Such understanding can contribute to the prevention, diagnosis and treatment of human neurological conditions such as mental retardation, autism spectrum disorder and schizophrenia. PUBLIC HEALTH RELEVANCE: Thyroid hormone (TH) plays a critical role in early brain development. An important action of TH on the developing brain is to promote neurogenesis, or the production of neurons. Our preliminary work showed that an enzyme that methylates DNA is regulated by TH and plays an important role in neurogenesis. The proposed research will help us to understand how TH controls early brain development through DNA methylation. Such findings can contribute to the prevention, diagnosis and treatment of human neurological conditions.

描述（由申请人提供）：胚胎后大脑发育依赖于甲状腺激素（TH）。人类发育关键时期的甲状腺激素缺乏会导致严重的智力和生长迟缓，称为克汀病。甲状腺激素在发育中的大脑中具有多效性作用，包括调节细胞增殖、细胞周期退出和分化（神经发生）。本研究的目的是研究 TH 通过调节 DNA 甲基转移酶 DNMT3a 促进细胞周期退出和神经发生的机制。两栖动物的发育（变态）依赖于 TH，我们建议使用非洲爪蟾蝌蚪进行我们的研究。我们发现，在自发变态期间或 TH 治疗后，蝌蚪脑的室下区（神经源区）的 dnmt3a 基因表达强烈上调。青蛙 dnmt3a 基因在内含子中具有假定的 TH 反应元件 (TRE)，支持直接 TH 受体 (TR) 调节。比较基因组分析在小鼠基因组中发现了一个类似的推定 TRE，支持 TR 调节 dnmt3a 的进化保守性。此外，TH 在小鼠神经母细胞瘤细胞系 N2a[TR21] 中诱导 dnmt3a mRNA。甲状腺激素对于产后早期的神经发生至关重要。最近的研究结果表明 dnmt3a 是神经发生所必需的。对 dnmt3a 缺陷小鼠的神经干细胞 (NSC) 进行基因表达分析显示，参与细胞周期控制的基因上调，支持细胞周期退出和分化为神经元谱系的缺陷。多项证据支持细胞周期蛋白 D1 直接受 DNMT3a 介导的 DNA 甲基化调节。根据我们的初步发现和科学文献中报道的数据，我们假设 TH 通过诱导 Dnmt3a 影响神经干细胞的细胞周期退出和神经发生。为了验证这一假设，我们将研究：1）青蛙和小鼠 dnmt3a 基因中进化保守的 TRE 的功能； 2) DNMT3a 通过启动子甲基化抑制细胞周期蛋白 D1 的作用； 3) 改变体内 DNMT3a 表达对细胞周期退出和 NSC 谱系规范的影响。成功完成拟议的研究将有助于我们进一步了解 TH 通过影响 DNA 甲基化来控制神经发育的机制。这种认识有助于预防、诊断和治疗人类神经系统疾病，如智力低下、自闭症谱系障碍和精神分裂症。 公共卫生相关性：甲状腺激素 (TH) 在早期大脑发育中发挥着关键作用。 TH 对发育中的大脑的一个重要作用是促进神经发生或神经元的产生。我们的初步工作表明，甲基化 DNA 的酶受 TH 调节，在神经发生中发挥重要作用。拟议的研究将帮助我们了解 TH 如何通过 DNA 甲基化控制早期大脑发育。这些发现有助于人类神经系统疾病的预防、诊断和治疗。