Functions of thyroid hormone in retinal development

甲状腺激素在视网膜发育中的作用

• 批准号: 10008663
• 负责人: Douglas Forrest
• 金额: $ 74.94万
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10008663
• 关键词: Address; Affinity Chromatography; Apoptosis; Apoptotic; Behavior; Binding Sites; Biological Models; Cell Death; Cell membrane; Cells; Chromatin; Color Visions; Cone; Data; Defect; Degenerative Disorder; Development; Endocrine system; Enzymes; Exposure to; Functional disorder; Gene Duplication; Gene Expression Regulation; Generations; Genes; Genetic; Genetic Models; Genetic Transcription; Genomic approach; Genomics; Goals; Hormonal; Human; Impairment; Investigation; Iodide Peroxidase; Knowledge; Ligands; Light; Link; Los Angeles; Mediating; Membrane Transport Proteins; Mus; Mutation; Opsin; Outcome; Pattern; Pediatric Hospitals; Photoreceptors; Population; Process; Protein Isoforms; Regulation; Retina; Retinal; Retinal Cone; Retinal Diseases; Retinoblastoma; Role; Signal Transduction; Stem cells; System; THRB gene; Techniques; Testing; Thyroid Diseases; Thyroid Function Tests; Thyroid Hormone Receptor Beta; Thyroid Hormones; Thyroid hormone receptor alpha; Time; Tissues; Vision; Visual system structure; cell type; cofactor; developmental disease; genetic approach; insight; mouse model; nervous system development; next generation sequencing; novel; precursor cell; prevent; programs; receptor; response; transcriptome; uptake

Thyroid hormone is a critical factor for the development of the nervous system. Our study of the thyroid hormone receptor b gene (Thrb) identified a key role for a thyroid hormone receptor, TRb2, in the differentiation of retinal cone photoreceptors, the light-sensitive cells that mediate color vision and also vision in bright light or daytime conditions. Our findings indicated that the retina is an unexpectedly sensitive target of thyroid hormone. Color vision depends upon cone populations that express opsin photopigments for response to different regions of the light spectrum. Most mammalian species are dichromatic and express opsins for sensitivity to medium-longer (M, green) or short (S, blue) wavelengths of light. Apart from opsins, little is known of transcriptome distinctions between cone sub-types, nor of the mechanisms that generate cone diversity. We previously showed that deletion of TRb2 results in loss of M opsin and extended expression of S opsin in all cones. This finding established that TRb2 is critical for the diversification of cone sub-populations in mice. These results suggest an intriguing link between the endocrine and visual systems. Previous studies of human thyroid disorders largely overlooked the possibility of defects in color vision or retinal function. However, emerging evidence indicates that mutations in the human THRB gene are associated with varying degrees of impairment of photoreceptor function. This project investigates how TRb2 regulates cone differentiation, function and survival in model systems: 1. Factors that cooperate with TRb2 in the differentiation of cone photoreceptors. We have shown that the type 2 and type 3 deiodinase enzymes that activate or inactivate thyroid hormone, respectively, modify cone photoreceptor development and survival. Previous studies indicated that type 3 deiodinase protects cones from excessive exposure to ligand, thus preventing loss of cones by apoptosis. Recent evidence indicates that type 2 deiodinase also modifies retinal cone survival and function in mouse models. These studies aim to ascertain the importance of mechanisms that augment as well as constrain thyroid hormone action in the differentiation of specific cell types. 2. Investigation of downstream gene networks that are regulated by TRb2 during cone differentiation. We have developed new mouse genetic models that allow marking and isolation of cones during development. Previously, such detailed analyses of cones had not been possible because of technical limitations presented by the scarcity of cones, which represent only 3% of retinal cells in mice, and beause of lack of a specific marker for isolating immature cones at early stages. Isolated cones are amenable to analysis by next generation sequencing and our approach yields high quality transcriptome data for cones. To address the fundamental question of what distinguishes cone sub-populations, our studies use single cell genomics techniques to investigate the transcriptome of cone sub-populations. 3. Elucidate a gene regulation program for cone diversity. Given the central role of TRb2 in determining opsin identities in cones, we are pursuing a genomics approach to determine how the wider cone transcriptome is altered following deletion of TRb2 with the goal of identifying the downstream gene networks that promote cone diversity. These studes employ a novel genetic model that allows high affinity purification of TRb2 with associated chromatin from retina. Next generation sequencing can identify genomic binding sites for TRb2 to allow investigation of mechanisms of gene regulation by TRb2 in cone differentiation. This study offers new insights into the genetic and hormonal controls that promote the differentiation and survival of cone photoreceptors. Further collaborative studies with Dr. David Cobrinik (Children's Hospital Los Angeles) indicate a role for TRb2 in the behavior of retinoblastoma cells, which are thought to arise from cone-like precursor cells in retina. Gaining a deeper understanding of the role of TRb2 in cone differentiation and function is expected to advance our knowledge of how dysfunction of these processes may result in developmental or degenerative diseases of the retina.

甲状腺激素是神经系统发展的关键因素。 我们对甲状腺激素受体B基因（THRB）的研究确定了甲状腺激素受体TRB2在视网膜锥光感受器的分化中的关键作用，介导色觉的光敏感细胞及其在明亮光或白天条件下的视觉介导的光敏细胞。我们的发现表明，视网膜是甲状腺激素的意外敏感靶标。 彩色视觉取决于表达对光谱不同区域的响应的锥体种群。大多数哺乳动物物种都是二分和表达蛋白，以敏感到中等长度（M，绿色）或短（S，蓝色）光的光长度。除Opsins外，几乎不知道锥形子类型之间的转录组区别，也不知道产生锥体多样性的机制。我们先前表明，TRB2的缺失会导致MOPSIN的丧失和所有锥体中S Opsin的扩展表达。这一发现表明，TRB2对于小鼠锥亚群的多样化至关重要。 这些结果表明内分泌和视觉系统之间有着有趣的联系。先前对人甲状腺疾病的研究在很大程度上忽略了色觉或视网膜功能缺陷的可能性。然而，新兴的证据表明，人类THR基因中的突变与受感受器功能的损害不同程度有关。该项目研究了TRB2如何调节模型系统中的锥体分化，功能和生存： 1。与TRB2合作在锥形感受器分化中合作的因素。 我们已经表明，分别激活或灭活甲状腺激素的2型和3型去二十二酶酶可以修改锥形光感受器的发育和存活。先前的研究表明，3型脱碘酶可保护锥体免受配体的过度暴露，从而防止凋亡因凋亡而失去锥体。最近的证据表明，2型脱碘酶还修饰了小鼠模型中的视网膜锥存活和功能。这些研究旨在确定增强和限制甲状腺激素在特定细胞类型的分化中的重要性。 2。研究锥体分化过程中受TRB2调控的下游基因网络的研究。 我们开发了新的小鼠遗传模型，可以在发育过程中标记和隔离锥体。 以前，由于锥形稀缺性的技术局限性（仅代表小鼠中仅3％的视网膜细胞），并且缺乏特定标记以在早期阶段隔离未成熟锥体的特定标记。孤立的锥体可以通过下一代测序进行分析，我们的方法可为锥体提供高质量的转录组数据。为了解决什么区别锥子群的基本问题，我们的研究使用单细胞基因组学技术来研究锥子群的转录组。 3。阐明锥体多样性的基因调节程序。鉴于TRB2在确定锥体中的Opsin身份中的核心作用，我们正在采用一种基因组学方法来确定TRB2缺失后如何改变较宽的锥转录组，以确定促进锥体多样性的下游基因网络。这些研究采用了一种新型的遗传模型，该模型允许TRB2与视网膜相关的染色质的高亲和力纯化。 下一代测序可以鉴定TRB2的基因组结合位点，以允许研究锥体分化中TRB2基因调节的机理。 这项研究为促进锥形感光体的分化和存活的遗传和激素对照提供了新的见解。与David Cobrinik博士（洛杉矶儿童医院）的进一步合作研究表明，TRB2在视网膜细胞细胞的行为中起作用，这被认为是由视网膜中的锥形前体细胞引起的。 预计对TRB2在锥体分化和功能中的作用有更深入的了解，可以促进我们对这些过程功能障碍如何导致视网膜发育或退化性疾病的了解。