Role of Transcription Factor ERG in Skeletogenesis

在肢体骨骼发生过程中，软骨细胞遵循两条发育路径， 终身持续存在的软骨或细胞成熟的短暂生长板软骨，肥大， 并被骨头取代。尽管这种发育分叉对骨骼发育的重要性 形成和功能被广泛认可，潜在的调节机制仍不清楚， 特别是在分子水平上。在上一个资助期，我们专注于转录因子 ERG及其变体C-1-1。鸡和人C-1-1的功能获得研究表明：（a）C-1-1是 能够在整个肢体软骨细胞群上施加稳定的和关节样的表型， 生长板形成、软骨细胞成熟和骨形成;（B）C-1-1抵消 促成熟转录因子Runx 2;和（c）关节主调节因子GDF-5快速诱导 ERG/C-1-1在滑膜关节发育中的表达。这些和其他发现导致我们的中央 对这种竞争性的继续提议的假设：（a）在GDF-5下游活动的C-1-1有助于 （B）C-1-1又抑制Runx 2功能，维持 细胞的永久状态，并防止成熟和肥大。我们的目标是：（i） 通过细胞和外植体培养以及转基因方法功能性表征鼠ERG变体;（ii） 确定在发育或出生后生活中条件性ERG基因消融的后果，使用 GDF-5-Cre和GDF-5-CreER小鼠;和（iii）确定GDF-5触发ERG的机制 通过信号传导途径和启动子作用表达，以及ERG/C-1-1如何抑制Runx 2功能。的 该项目将产生对关节软骨细胞的发生和功能的基本见解。还应当 产生退行性关节疾病的小鼠模型，可用于测试未来的基因， 骨关节炎患者和老年人常见的关节疾病的细胞疗法。

During limb skeletogenesis chondrocytes follow two developmental paths and produce permanent articular cartilage persisting through life or transient growth plate cartilage in which the cells mature, hypertrophy, and are replaced by bone. Though the critical importance of this developmental bifurcation for skeletal formation and function is widely recognized, the underlying mechanisms of regulation remain unclear, particularly at the molecular level. In the previous funding period, we focused on the transcription factor ERG and its variant C-1-1. Gain-of-function studies with chick and human C-1-1 show that: (a) C-1-1 is able to impose a stable and articular-like phenotype over the entire limb chondrocyte population, blocking growth plate formation, chondrocyte maturation and bone formation; (b) C-1-1 counteracts action of the pro-maturation transcription factor Runx2; and (c) the joint master regulator GDF-5 rapidly induces ERG/C-1-1 expression in developing synovial joints. These and other findings lead to our central hypotheses for this competitive continuation proposal: (a) C-1-1 acting down-stream of GDF-5 contributes to formation of permanent articular chondrocytes; and (b) C-1-1 in turn inhibits Runx2 function, maintains the permanent status of the cells, and prevents maturation and hypertrophy. Our aims are: (i) to functionally characterize murine ERG variants by cell and explant cultures and transgenic approaches;(ii) determine the consequences of conditional ERG gene ablation during development or postnatal life, using GDF-5-Cre and GDF-5-CreER mice; and (iii) determine the mechanisms by which GDF-5 triggers ERG expression by signaling pathways and promoter action, and how ERG/C-1-1 inhibits Runx2 function. The project will produce fundamental insights into genesis and function of articular chondrocytes. It should also generate mouse models of degenerative joint disease that could be used to test future gene- and cell-based therapies for joints conditions common to osteoarthritic patients and aging individuals.