Regulation of Skeletal Growth by Nuclear Retinoid Receptors

核视黄醇受体对骨骼生长的调节

• 批准号: 8308674
• 负责人: MASAHIRO IWAMOTO
• 金额: $ 34.95万
• 依托单位: CHILDREN'S HOSP OF PHILADELPHIA
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-30 至 2014-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8308674
• 关键词: Affect; Area; Attention; Behavior; Binding Sites; Biochemical; Biology; Cartilage; Cell Nucleus; Chondrocytes; Collagen; DNA; DNA Binding; Data; Defect; Disease; Drops; Dwarfism; EP300 gene; Elements; Embryonic Development; Enhancers; Epiphysial cartilage; Exhibits; Extracellular Matrix; Future; Gene Expression; Gene Structure; Genes; Glare; Goals; Growth; Homeostasis; Hypertrophy; In Situ; Individual; Knockout Mice; LacZ Genes; Lead; Life; Ligands; Light; Limb structure; Measurement; Mediating; Molecular; Mus; Mutant Strains Mice; Nuclear; Nuclear Hormone Receptors; Partner in relationship; Pathology; Predisposition; Process; Proliferating; Property; Proteins; Proteoglycan; RXR; Regulation; Reporter; Repression; Research Activity; Response Elements; Retinoic Acid Receptor; Retinoid Receptor; Retinoids; Role; Site; Skeletal Development; Skeleton; Staging; Structure; Transcription Coactivator; Transcription Repressor/Corepressor; aggrecan; bone; chondrodysplasia; craniofacial; cranium; functional restoration; insight; macromolecule; postnatal; prenatal; skeletal

Growth of endochondral skeletal structures in skull, trunk and limbs is governed by the activity of the growth plates where chondrocytes proliferate, undergo maturation and hypertrophy and are replaced by bone. Functioning of the growth plates in turn depends on their unique extracellular matrix composed of aggrecan, collagen II and other macromolecules, and abnormalities in matrix gene expression or structure cause growth plate malfunction and chondrodysplasias, including dwarfism. There have been significant advances in growth plate and matrix biology and pathology in recent years, but much remains to be understood and discovered. The retinoic acid receptors ¿, ¿ and ¿ (RAR¿, RAR¿ and RAR¿) are nuclear hormone receptors that regulate numerous fundamental processes and act as ligand-less transcriptional repressors or ligand- dependent transcriptional activators. Studies conducted a decade or so ago showed that mice lacking RAR genes have skeletal defects, but detailed understanding of RAR roles has been lacking since. To study skeletal- specific RAR function, we created conditional RAR mouse mutants. We find that mice lacking RAR¿ and RAR¿ (or RAR¿/RAR¿) genes in cartilage exhibit severe growth retardation. Their growth plates are defective and, importantly, display a major drop in aggrecan expression and content. Mice lacking RAR¿ and RAR¿, however, are normal, suggesting that RAR¿ is essential. Indeed, we find that RAR¿ is the most strongly expressed RAR in mouse growth plates, and its expression characterizes the proliferative and pre-hypertrophic zones where aggrecan is strongly expressed also. Biochemical analysis shows that those zones are devoid of active endogenous ligands, signifying that the RARs operate as ligand-less factors. Studies with mouse chondrocyte cultures indicate that (a) RAR¿ over-expression enhances aggrecan expression; (b) RAR¿ exerts its function in cooperation with transcriptional co-repressor Zac1; and (c) RAR action on aggrecan expression is indirect and involves Sox proteins. Our central hypothesis is that RARs, and RAR¿ in particular, exert previously unappreciated roles in growth plate function and promote aggrecan expression and content. Ligand-less RAR repressor function would lead to stimulation of Sox expression; this, in turn, would increase aggrecan expression. Our specific goals are: (i) to determine whether RAR function in growth plates is largely, if not exclusively, due to RAR¿; (ii) to define the molecular mechanisms by which RAR¿ regulates aggrecan gene expression via Sox proteins; and (iii) to characterize the roles of co-repressor Zac1. The results of the project will produce fundamentally new insights in skeletal and growth plate biology. The RARs represent a critical but currently understudied area of skeletal biology, and the project will begin to bridge this glaring gap. Because RAR function is susceptible to experimental and pharmacologic manipulations, the project will also lead to envision future ways in which such treatments could be exploited therapeutically to rectify chondrocyte behavior and matrix homeostasis and restore function in skeletal growth deficiencies and related pathologies.

颅骨、躯干和四肢中的软骨内骨骼结构的生长受 软骨细胞增殖、成熟和肥大并被骨取代的生长板。 生长板的功能反过来取决于它们独特的细胞外基质， 胶原蛋白II和其他大分子，以及基质基因表达或结构的异常引起生长 板功能障碍和软骨发育不良，包括侏儒症。在增长方面取得了重大进展 近年来，我们在平板和基质生物学和病理学方面取得了一些进展，但仍有许多有待理解和发现。 视黄酸受体<$、<$和<$（RAR <$、RAR <$和RAR <$）是核激素受体， 调节许多基本过程，并作为无配体转录抑制因子或配体发挥作用， 依赖性转录激活因子。大约十年前进行的研究表明，缺乏RAR的小鼠 基因具有骨骼缺陷，但此后一直缺乏对RAR作用的详细了解。去研究骨骼- 为了特异性RAR功能，我们创建了条件RAR小鼠突变体。我们发现缺乏RAR和RAR的小鼠 (or RAR <$/RAR <$）基因表现出严重的生长迟缓。它们的生长板有缺陷， 重要是，显示聚集蛋白聚糖表达和含量的大幅度下降。然而，缺乏RAR和RAR的小鼠， 这是正常的，表明RAR是必不可少的。事实上，我们发现RAR是表达最强烈的RAR， 小鼠生长板，其表达表征了增殖区和前肥大区， 聚集蛋白聚糖也被强烈表达。生物化学分析表明，这些区域缺乏活性 内源性配体，表明RAR作为无配体因子起作用。小鼠软骨细胞研究 培养物表明：（a）RAR过表达增强聚集蛋白聚糖表达;（B）RAR发挥其功能， 与转录辅阻遏物Zac 1合作;和（c）RAR对聚集蛋白聚糖表达的作用是间接的， 涉及Sox蛋白质。我们的中心假设是RAR，特别是RAR， 在生长板功能和促进聚集蛋白聚糖表达中以前未被认识到的作用， 内容无配体RAR阻遏物功能将导致Sox表达的刺激;这反过来又将导致 增加聚集蛋白聚糖表达。我们的具体目标是：（i）确定生长板中RAR功能是否是 主要是，如果不是完全，由于RAR <$;（ii）定义RAR <$调节的分子机制 聚集蛋白聚糖基因表达通过Sox蛋白;和（iii）表征的作用，共阻遏物Zac 1。的结果 该项目将在骨骼和生长板生物学方面产生根本性的新见解。RAR代表一个 关键但目前研究不足的骨骼生物学领域，该项目将开始弥合这一明显的差距。 由于RAR功能易受实验和药理学操作的影响，该项目还将 这导致了对未来方法的设想，在这些方法中，可以在治疗上利用这些治疗来矫正软骨细胞 在骨骼生长缺陷和相关病理中的行为和基质稳态以及恢复功能。