Transcriptional regulation of Sox9 in chondrogenesis

描述（由申请人提供）：软骨形成或成人维持中的遗传和获得性缺陷导致多种类型的骨骼发育不良和关节退行性疾病，即骨关节炎。Sox9编码软骨形成所必需的转录因子。然而，软骨细胞中Sox9转录的机制在很大程度上仍然未知。Sox 9增强子已被鉴定用于发育性腺、神经嵴和脊髓，但尚未发现用于软骨细胞。该研究项目的总体目标是确定软骨细胞中Sox9表达的机制。我们已经确定了一个高度保守的增强子位于上游的Sox9启动子。在转基因小鼠中的初步结果表明，这种增强剂在软骨原基和生长板中的增殖软骨细胞中具有活性。我认为这种增强剂结合的蛋白质在确保这些细胞中Sox 9表达方面具有关键作用，因此需要维持软骨细胞分化并确保骨骼生长和及时骨化。本项目的主要目的是通过以下三个具体目标来验证这一假设：（1）确定增强子在体内的活性域，（2）测试增强子是否是Sox 9在体内表达所必需的，以及（3）鉴定结合并激活Sox 9增强子的转录因子，并确定它们在软骨形成中的重要性。了解软骨形成中Sox9表达的分子基础将确定潜在的药理学治疗靶点，这可能对治疗骨骼发育不良和退行性软骨疾病如骨关节炎具有临床意义。 公共卫生相关性：软骨成分和调节因子的缺陷导致许多类型的骨骼畸形疾病（骨骼发育不良）和流行的关节变性疾病，如骨关节炎。这项新的研究旨在确定Sox9表达所需的机制，Sox9是软骨发育所需的基因。从这项研究中获得的知识将使产生功能性软骨的治疗策略取得重大进展。

DESCRIPTION (provided by applicant): Inherited and acquired defects in the formation or adult maintenance of cartilage cause many types of skeletal dysplasias and joint degeneration diseases, namely osteoarthritis. Sox9 encodes a transcription factor that is absolutely required for cartilage formation. The mechanisms underlying Sox9 transcription in chondrocytes, however, remain largely unknown. Sox9 enhancers have been identified for developing gonad, neural crest, and spinal cord, but none have been discovered for chondrocytes. The overarching goal of the research project is to identify the mechanisms underlying Sox9 expression in chondrocytes. We have identified a highly conserved enhancer located far upstream of the Sox9 promoter. Preliminary results in transgenic mice indicate that this enhancer is active in proliferative chondrocytes in cartilage primordia and growth plates. I propose that this enhancer binds proteins that have a key role in ensuring Sox9 expression in these cells and are thereby required to maintain chondrocyte differentiation and ensure skeletal growth and timely ossification. The main goal of this project is to test this hypothesis by pursuing the following three specific aims: (1) define the domain of activity of the enhancer in vivo, (2) test whether th enhancer is required for Sox9 expression in vivo, and (3) identify the transcription factors that bind to and activate the Sox9 enhancer, and to determine their importance in chondrogenesis. Understanding the molecular basis of Sox9 expression in chondrogenesis will identify potential pharmacological therapeutic targets, which may have clinical implications for the treatment of skeletal dysplasias and degenerative cartilage diseases such as osteoarthritis. PUBLIC HEALTH RELEVANCE: Defects in cartilage components and regulatory factors cause many types of skeletal malformation diseases (skeletal dysplasias) and prevalent joint degeneration diseases, such as osteoarthritis. This novel study aims to identify the mechanisms that are required for Sox9 expression, a gene that is required for cartilage development. Knowledge obtained from this study will allow major progress to be made to generate functional cartilage for therapeutic strategies.