Transcriptional regulation of Sox9 in chondrogenesis

描述（由申请人提供）：软骨形成或成人维持的遗传性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编码的转录因子是软骨形成所必需的。然而，软骨细胞中Sox9转录的机制在很大程度上仍然未知。已发现Sox9增强子可用于性腺、神经嵴和脊髓的发育，但尚未发现可用于软骨细胞。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Sox9启动子的上游。在转基因小鼠中的初步结果表明，该增强子在软骨原基和生长板的增殖软骨细胞中具有活性。我认为这种增强子结合了在确保Sox9在这些细胞中的表达中起关键作用的蛋白质，因此需要维持软骨细胞分化，确保骨骼生长和及时骨化。该项目的主要目标是通过以下三个具体目标来验证这一假设：(1)确定体内增强子的活性域，(2)测试体内Sox9表达是否需要增强子，以及(3)确定结合并激活Sox9增强子的转录因子，并确定其在软骨形成中的重要性。了解Sox9在软骨形成中表达的分子基础将确定潜在的药物治疗靶点，这可能对骨骼发育不良和退行性软骨疾病（如骨关节炎）的治疗具有临床意义。

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.