Wnt/beta-catenin Signaling in Endochondral Ossification

描述（由申请人提供）：本申请是对NOT-OD-09-058的回应，NIH宣布为竞争性修订申请提供恢复法案资金。控制骨骼发育、生长和功能的机制继续吸引着大量的研究努力，但还远不清楚。在当前的Parent Grant中，我们研究了Wnt/b-catenin信号在生长板功能中的作用，当时我们的新假设是“Wnt/b-catenin信号的激活是软骨细胞肥大和功能以及软骨内骨化的进展和完成所必需的。“我们从那时起获得的数据和在几篇出版物中报道的数据充分证实了我们假设的有效性，并揭示了Wnt/b-连环蛋白信号在软骨细胞肥大，基质重塑和凋亡以及在软骨内骨化期间从软骨到骨的无缝过渡中的核心重要性。我们的研究和其他人的研究对目前公众认识到Wnt/b-连环蛋白信号在骨骼发育中的重要性做出了重大贡献。随着我们的研究进展，我们获得了关于Wnt/β-连环蛋白信号传导和内质网（ER）应激之间可能联系的相关、有趣和相当新颖的数据。内质网应激和未折叠蛋白反应（UPR）由于其生理和病理作用在许多研究领域非常受欢迎，但在骨骼生物学中受到的关注相对较少。我们使用转基因小鼠的初步数据显示，Wnt/β-catenin信号刺激ER应激/UPR和体内生长板的凋亡。使用原代软骨细胞培养物，我们发现Wnt/b-连环蛋白信号传导的急性激活增强CHOP和Bip（其是关键的UPR应答基因）的表达，并导致ER应激条件下的细胞凋亡。我们对这一修订申请的中心假设是，Wnt/β-连环蛋白信号与ER应激/UPR信号相互作用，以调节和地形学限制生长板软骨细胞的凋亡。我们的目标是：（1）确定CHOP和Bip表达如何通过Wnt/b-连环蛋白信号传导的激活来调节;和（2）检查CHOP和Bip在Wnt/b-连环蛋白信号传导激活期间ER应激诱导的细胞凋亡中的作用。这个修订申请补助金将使我们开始，以填补目前的信息明显的差距，并将增加新的目标，我们的父母补助金。它将揭示Wnt/β-catenin信号传导和ER应激/UPR在生长板功能中的调节相互联系，并建立以前未被怀疑的软骨内骨化范例。这些调节性串扰和电路可能是生长板稳态和功能所必需的，并且可能被扰乱，并导致许多先天性和获得性骨骼疾病。 公共卫生相关性：项目叙述Carbohydrate在骨骼的形成和生长中起着重要作用。由于先天性或后天性条件引起的软骨功能障碍可导致身体结构缺陷、生长迟缓和退行性软骨疾病。该项目将提供有关软骨细胞行为和功能调节机制的新信息，并为揭示骨骼疾病的原因铺平道路。

DESCRIPTION (provided by applicant): This application is in response to NOT-OD-09-058, NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications. The mechanisms controlling skeletal development, growth and function continue to attract much research effort, but are far from clear. In the current Parent Grant, we studied the roles of Wnt/b-catenin signaling in growth plate function, and our novel hypothesis at the time was that 'Activation of Wnt/b-catenin signaling is required for chondrocyte hypertrophy and function and for progression and completion of endochondral ossification.' The data we obtained since and reported in several publications fully affirmed the validity of our hypothesis and did uncover the central importance of Wnt/b-catenin signaling in chondrocyte hypertrophy, matrix remodeling and apoptosis and in the seamless transition from cartilage to bone during endochondral ossification. Our studies and those by others have contributed significantly to the current public recognition of the importance of Wnt/b-catenin signaling in skeletal development. As our Parent Grant was progressing, we obtained related, intriguing and rather novel data on possible connections between Wnt/b-catenin signaling and endoplasmic reticulum (ER) stress. ER stress and unfolded protein response (UPR) are extremely popular in many fields of research because of their physiologic and pathologic roles, but have received relatively little attention in skeletal biology. Our preliminary data using transgenic mice now reveal that Wnt/b-catenin signaling stimulates ER stress/UPR and apoptosis in growth plates in vivo. Using primary chondrocyte cultures, we have found that acute activation of Wnt/b-catenin signaling enhances expression of CHOP and Bip (that are key UPR response genes) and leads to apoptosis under ER stress conditions. Our central hypothesis for this Revision Application is that that Wnt/b-catenin signaling interacts with ER stress/UPR signaling to regulate and topographically restrict apoptosis in growth plate chondrocytes. Our aims are: (1) to determine how CHOP and Bip expression is regulated by activation of Wnt/b-catenin signaling; and (2) to examine CHOP and Bip roles in ER-stress-induced apoptosis during Wnt/b-catenin signaling activation. This Revision Application grant will allow us to begin to fill glaring gaps in current information and will add novel goals to our Parent Grant. It will uncover regulatory interconnections between Wnt/b-catenin signaling and ER stress/UPR in growth plate function and establish a previously unsuspected paradigm in endochondral ossification. These regulatory cross-talk and circuitry are likely to be essential for growth plate homeostasis and function and may be deranged, and cause, a number of congenital and acquired skeletal diseases. PUBLIC HEALTH RELEVANCE: Project Narrative Cartilage plays essential roles in formation and growth of the skeleton. Dysfunction in cartilage due to congenital or acquired conditions can lead to defects in body structures, growth retardation and degenerative cartilage diseases. This project will provide novel information on mechanisms regulating behavior and function of cartilage cells and will pave the way to uncover the causes of skeletal diseases.