Sox9-mediated control of chondrogenesis

描述（由申请人提供）：软骨是发育和成人必不可少的组织。可悲的是，由于软骨畸形导致的出生缺陷的普遍性和严重性，儿童由于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，最能说明这一点。然而，目前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了解。该项目的主要目标是通过增加对软骨形成中的主要转录因子Sox9的作用和调节的了解来帮助消除这一障碍。众所周知，Sox9可以激活早期软骨细胞分化程序，我们最近的数据显示，在整个软骨细胞肥大过程中，它仍然是生长板中的主转录因子。它维持柱状软骨细胞增殖，延缓前期肥大，并确保肥大。基于这些数据，我们提出必须存在重要的机制来确定Sox9在从早期到肥大分化的每个软骨细胞发育阶段的特定活性。目的1是验证这样的假设，即冗余蛋白Sox5和Sox6通过提高Sox9与基因增强子结合的效率来增强Sox9激活早期软骨细胞分化程序的能力。目的2是验证camp依赖性蛋白激酶A的Sox9磷酸化对延迟甲状旁腺激素相关蛋白信号下游软骨细胞成熟起关键作用的假设。目的3是验证特定的转录机制允许Sox9激活肥大软骨细胞程序，尤其是Col10a1基因的假设。所有目标都将在发育中的小鼠和最先进的基因组学、细胞和分子方法中实现。我们预计，该项目的成就将导致对软骨细胞多步骤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机制提供新的见解，并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.