Sox9-mediated control of chondrogenesis

描述(申请人提供)：软骨是发育中和成年人类的重要组织。可悲的是，软骨畸形引起的出生缺陷、儿童生长板缺陷导致的生长迟缓以及成人关节软骨退行性疾病的流行和严重程度最能说明这一点。然而，今天，这些疾病中的大多数都没有合适的治疗方法，这在很大程度上是由于对软骨形成的潜在机制的不完全了解。这个项目的主要目标是通过增加对Sox9的作用和调控的了解来帮助消除这一障碍。Sox9是软骨形成中的主要转录因子。众所周知，Sox9激活了软骨细胞的早期分化程序，我们最近的数据显示，它在软骨细胞肥大的整个生长板中仍然是一个主要的转录因子。它维持柱状软骨细胞的增殖，延缓前期肥大，并确保肥大。基于这些数据，我们认为必须存在重要的机制来确定从早期到肥大分化的每个软骨细胞发育阶段中Sox9的比活性。目的1验证冗余蛋白Sox5和Sox6通过提高Sox9与基因增强剂结合的效率来增强Sox9激活早期软骨细胞分化程序的能力的假说。目的2是为了验证一种假说，即cAMP依赖的蛋白激酶A对Sox9的磷酸化在甲状旁腺激素相关蛋白信号转导下游对延缓软骨细胞成熟起关键作用。目的3是测试特定的转录机制允许Sox9激活肥大的软骨细胞程序，最具体的是Col10a1基因的假设。所有的目标将通过在发育中的小鼠中使用遗传方法以及在体外使用最先进的基因组学、细胞和分子方法来实现。我们预计该项目的完成将使我们对控制软骨细胞多步分化途径的机制有更深入的了解。这一知识将为软骨畸形和退行性疾病的潜在机制提供新的见解，并将有助于找到合适的治疗方法。

DESCRIPTION (provided by applicant): Cartilage is an essential tissue in developing and adult humans. Sadly, this is best illustrated by the prevalence and severity of birth defects due to cartilage malformations, growth retardations due to growth plate defects in children, and articular cartilage degeneration diseases in adults. Today, however, no suitable treatments exist for most of these diseases, and this is largely due to incomplete understanding of the mechanisms underlying chondrogenesis. The main goal of this project is to help lift this barrier by increasing knowledge of the action and regulation of Sox9, a master transcription factor in chondrogenesis. Sox9 is well known to activate the early chondrocyte differentiation program, and our recent data reveal that it remains a master transcription factor in the growth plate throughout chondrocyte hypertrophy. It sustains columnar chondrocyte proliferation, delays prehypertrophy, and ensures hypertrophy. Based on these data, we propose that important mechanisms must exist to determine the specific activity of Sox9 at each chondrocyte developmental stage from early to hypertrophic differentiation. Aim 1 is to test the hypothesis that the redundant proteins Sox5 and Sox6 boost the ability of Sox9 to activate the differentiation program of early chondrocytes by increasing the efficiency of Sox9 binding to gene enhancers. Aim 2 is to test the hypothesis that Sox9 phosphorylation by the cAMP-dependent protein kinase A critically contributes to delaying chondrocyte maturation downstream of parathyroid hormone-related protein signaling. Aim 3 is to test the hypothesis that specific transcriptional mechanisms allow Sox9 to activate the hypertrophic chondrocyte program and most specifically the Col10a1 gene. All aims will be reached using genetic approaches in the developing mouse and state-of-the-art genomics, cellular and molecular approaches in vitro. We anticipate that the achievement of this project will lead to a deeper knowledge of the mechanisms that govern the multi-step differentiation pathway of chondrocytes. This knowledge will provide novel insights into mechanisms underlying cartilage malformation and degeneration diseases and will help find suitable treatments.