Jab1-BMP signaling interaction in chondrocyte differentiation

 描述(申请人提供)：本项目的目标是了解Jab1和BMP信号在软骨细胞分化过程中的相互作用。BMP信号对软骨和骨形成、骨愈合以及关节和软骨修复的各个方面都很重要。含有BMP2和BMP7的成骨植入物已在全球100多万名患者中用于骨再生，用于治疗长骨不连和急性骨折以及脊柱融合。然而，BMPs的临床应用需要超生理剂量，导致高昂的成本和潜在的炎症副作用。因此，提高BMP的治疗效果对于减轻患者、他们的家人和/或卫生系统的身体痛苦和经济负担至关重要。此外，BMP信号成分的突变会导致严重的人类骨骼发育缺陷。我们最近发现转录辅助因子Jab1是BMP信号转导下游效应子Smad1/5的一个新的抑制因子。Jab1通过调节其他转录因子的功能，在不同的发育过程中发挥重要作用。Jab1在胚胎发育过程中广泛表达，包括在软骨细胞中表达。然而，Jab1在软骨形成中的作用仍不清楚。在我们的初步研究中，使用loxP/Cre系统在软骨细胞中特异性地丢失Jab1导致了新生小鼠致死性软骨发育不良，证明了Jab1对于体内正常的软骨形成是必不可少的。此外，基因表达谱和对Jab1缺陷的原代软骨细胞的体外培养实验显示，Smad1/5及其下游靶标IHH和Col10a1的表达增加。因此，我们假设Jab1通过直接抑制Smad1/5介导的BMP信号来调节软骨细胞的分化。在这项研究中，我们提出了三个具体目标来检验这一假说。目的1是用互补的细胞和分子方法描述Jab1-BMP信号相互作用在软骨细胞分化中的潜在机制。目的2通过组织学和原位分析，确定基因操作(包括功能获得和功能丧失)，特别是在软骨细胞中以诱导方式对BMP介导的胚胎软骨形成的影响。目的3是利用RNA-SEQ和CHIP-SEQ研究软骨细胞中Jab1的直接下游靶点。总之，这项研究将进一步加深我们对Jab1在BMP介导的骨骼发育中的重要作用的理解，并为骨骼发育不良研究建立新的突变小鼠模型。最终，基于控制Jab1介导的抑制BMP信号的新疗法将开启治疗急性骨折、骨关节炎和与dys调节的BMP信号相关的骨骼疾病的新纪元。

 DESCRIPTION (provided by applicant): The goal of this project is to understand the interaction of Jab1 and BMP signaling during chondrocyte differentiation. BMP signaling is important for all aspects of cartilage and bone formation, bone healings, and joint and cartilage repair. BMP2- and BMP7-containing osteogenic implants have been used for bone regeneration in over one million patients worldwide in the treatment of long-bone nonunion and acute fracture and in spinal fusion. However, the clinical use of BMPs requires super-physiological doses, resulting in high cost and potential inflammatory side effects. Thus, improving BMP treatment efficacy is critical to ease physical pain and financial burdens on patients, their families, and or health system. Furthermore, mutations in BMP signaling components lead to severe human skeletal developmental defects. We have recently identified transcriptional cofactor Jab1 as a novel inhibitor of BMP signaling downstream effector Smad1/5. Jab1 plays essential roles during various developmental processes by modulating other transcription factors' function. Jab1 is broadly expressed during embryogenesis, including in the chondrocytes. However, the role of Jab1 in cartilage formation remains mostly unknown. In our preliminary study, the loss of Jab1 specifically in chondrocytes using the loxP/Cre system led to neonatal lethal chondrodysplasia in mice, demonstrating that Jab1 is essential for proper cartilage formation in vivo. Furthermore, gene expression profiling and ex vivo culture experiments with Jab1 deficient primary chondrocytes revealed increased expression of Smad1/5 and its downstream targets Ihh and Col10a1. Thus, we hypothesize that Jab1 regulates chondrocyte differentiation by directly repressing Smad1/5-mediated BMP signaling. In this study, we propose three specific aims to test this hypothesis. Aim 1 is to use complementary cellular and molecular approaches to delineate the underlying mechanism of Jab1-BMP signaling interaction in chondrocyte differentiation. Aim 2 is to determine the effect of the genetic manipulation of Jab1 expression (both gain- and loss-of-function), specifically in chondrocytes in an inducible manner, on BMP-mediated embryonic cartilage formation using histological and in situ analysis. Aim 3 is to use RNA-seq and ChIP-seq to investigate the direct Jab1 downstream targets in chondrocytes. Overall, this study will further our understanding of the essential role of Jab1 in BMP-mediated skeletal development and generate novel mutant mouse models for skeletal dysplasia research. Ultimately, new therapies based on controlling the Jab1-mediated inhibition of BMP signaling will open a new era in treating acute fracture, osteoarthritis, and the skeletal disorders associated with dys-regulated BMP signaling.