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: 8513920
• 负责人: MASAHIRO IWAMOTO
• 金额: $ 31.59万
• 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 2016-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8513920
• 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、躯干和四肢软骨内骨骼结构的生长受 生长板，软骨细胞在这里增殖、成熟和肥大，并被骨取代。 生长板的功能反过来又取决于它们独特的细胞外基质， II型胶原和其他大分子，以及基质基因表达或结构的异常会导致生长 钢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，板层和基质的生物学和病理学研究取得了很大进展，但仍有许多有待了解和发现。 维甲酸受体(RAR、RAR和RAR)是一种核激素受体， 调节许多基本过程，并作为无配体转录抑制因子或配体- 依赖转录激活剂。大约十年前进行的研究表明，缺乏RAR的小鼠 基因有骨骼缺陷，但自那以来一直缺乏对RAR角色的详细了解。为了研究骨骼- 特定的RAR功能，我们创造了有条件的RAR小鼠突变体。我们发现缺乏RAR和RAR的小鼠 软骨中的(或RAR？/RAR？)基因表现出严重的生长迟缓。它们的生长板是有缺陷的， 重要的是，展示了aggrecan的表达和内容的大幅下降。然而，缺乏RAR？和RAR？的小鼠 是正常的，这表明RAR？是必不可少的。事实上，我们发现RAR？是在 小鼠生长板，其表达特征为增殖区和肥大前期区 Aggrecan也有强烈的表达。生化分析表明，这些区域没有活性 内源性配基，意味着RARs作为非配基因子发挥作用。小鼠软骨细胞的研究 培养表明：(A)RAR？的过度表达增强了aggrecan的表达；(B)RAR？在 与转录共抑制子Zac1的协同作用；以及(C)RAR对aggrecan表达的作用是间接的和 涉及SOX蛋白质。我们的中心假设是，RAR，特别是RAR？，发挥着 在生长板功能和促进集聚蛋白表达和 内容。缺乏配体的RAR抑制功能会导致SOX表达的刺激；这反过来又会 增加聚集素的表达。我们的具体目标是：(I)确定生长板中的RAR功能是否 很大程度上，如果不是完全由于RAR？；；(Ii)定义RAR？调节的分子机制 通过Sox蛋白表达aggrecan基因；以及(Iii)研究共抑制因子Zac1的作用。结果是 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 这是骨骼生物学的关键但目前研究不足的领域，该项目将开始弥合这一明显的差距。 由于RAR功能很容易受到实验和药物操作的影响，该项目还将 展望未来这种治疗方法可以被用于治疗矫正软骨细胞 骨骼发育缺陷和相关病理中的行为和基质动态平衡和恢复功能。