Sox9-mediated control of chondrogenesis

描述（由申请人提供）：软骨是发育中和成年人类的重要组织。可悲的是，由于软骨畸形导致的出生缺陷、由于儿童生长板缺陷导致的生长迟缓以及成人关节软骨变性疾病的患病率和严重程度最好地说明了这一点。然而，今天，大多数这些疾病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机制的不完全理解。该项目的主要目标是通过增加对Sox 9（软骨形成中的主要转录因子）的作用和调节的了解来帮助解除这一障碍。众所周知，Sox 9可以激活早期软骨细胞分化程序，我们最近的数据显示，在软骨细胞肥大的整个过程中，它仍然是生长板中的主要转录因子。它维持柱状软骨细胞增殖，延迟肥大前期，并确保肥大。基于这些数据，我们提出，必须存在重要的机制，以确定在每个软骨细胞的发育阶段，从早期到肥大分化的Sox 9的比活性。目的1是验证冗余蛋白Sox 5和Sox 6通过增加Sox 9与基因增强子结合的效率来增强Sox 9激活早期软骨细胞分化程序的能力的假设。目的2是检验这样的假设，即cAMP依赖性蛋白激酶A的Sox 9磷酸化对延迟甲状旁腺相关蛋白信号传导下游的软骨细胞成熟有重要作用。目的3是测试特定的转录机制允许Sox 9激活肥大软骨细胞程序，特别是Col10a1基因的假设。所有的目标都将通过使用遗传学方法在发展中的小鼠和最先进的基因组学，细胞和分子方法在体外实现。我们预计，该项目的实现将导致对软骨细胞多步分化途径的机制有更深入的了解。这些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.