Role of Transcription Factor ERG in Skeletogenesis

在肢体骨骼发育过程中，软骨细胞遵循两条发育路径，形成永久性关节 存活的软骨或短暂的生长板软骨，在其中细胞成熟、肥大、 并被骨头取代。尽管这种发育分叉对骨骼的关键重要性 形成和功能得到广泛认可，潜在的调控机制仍不清楚， 尤其是在分子水平上。在之前的资助期，我们专注于转录因子 ERG及其变异体C-1-1。对鸡和人类C-1-1的功能增益研究表明：(A)C-1-1是 能够在整个肢体软骨细胞群上施加稳定的关节样表型，阻断 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Runx2；和(C)联合主控调控因子GDF-5快速诱导 ERG/C-1-1在滑膜关节发育过程中的表达这些和其他发现导致了我们的中央 这一竞争性延续提议的假设：(A)在GDF-5下游行动的C-1-1对 和(B)C-1-1进而抑制Runx2功能，维持 保持细胞的永久状态，防止成熟和肥大。我们的目标是：(I) 通过细胞和外植体培养及转基因方法确定小鼠视网膜色素变性变异体的功能特征； 确定在发育期间或出生后生活中有条件地去除ERG基因的后果，使用 GDF-5-CRE和GDF-5-Creer小鼠；以及(Iii)确定GDF-5触发ERG的机制 以及ERG/C-1-1如何抑制Runx2功能。这个 该项目将对关节软骨细胞的起源和功能产生基本的见解。它还应该 产生可用于测试未来基因的退行性关节疾病的小鼠模型--以及 骨关节炎患者和老年人常见的关节疾病的基于细胞的治疗。

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.