Role of Dlx-5 in Chondrocyte Differentiation

Dlx-5 在软骨细胞分化中的作用

• 批准号: 6835616
• 负责人: ROBERT A KOSHER
• 金额: $ 32.63万
• 依托单位: UNIVERSITY OF CONNECTICUT SCH OF MED/DNT
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6835616
• 关键词: Role; Dlx; Chondrocyte; Differentiation

EXCEED THE SPACE PROVIDED. The process of endochondral ossification in which the bones of the limb are formed after generation of cartilage models is dependent on a carefully regulated program of chondrocyte maturation. Identification of the genes and signaling molecules that control hypertrophic chondrocyte maturation and the regulatory interactions among them is crucial to understanding bone growth and development. The goal of this research is to investigate the hypothesis that the homeodomain transcription factor Dlx5 is a key positive regulator of chondrocyte maturation during endochondral ossification, and to unravel the relationships between Dlx5 and other factors involved in controlling the process. Dlx5 is expressed during the conversion of immature proliferating chondrocytes to postmitotic prehypertrophic chondrocytes, a critical step in maturation. Retroviral misexpression of Dlx5 during differentiation of the skeletal elements of the chick limb in vivo results in formation of severely shortened skeletal elements that contain excess numbers of hypertrophying chondrocytes, expanded and upregulated domains of expression of some molecular markers of hypertrophic differentiation including osteopontin and type X collagen, and expansion of mineralized cartilage matrix. Dlx5 misexpression also markedly reduces cell proliferation concomitant with promoting hypertrophic maturation. These results suggest Dlx5 positively regulates maturation at least in part by promoting conversion of immature proliferating chondrocytes to hypertrophying chondrocytes. The role of Dlx5 in chondrocyte maturation will be further investigated by examining effects of Dlx5 misexpression in the chick limb on expression of additional markers of hypertrophic maturation, and determining if chondrocyte maturation is promoted when Dlx5 misexpression is specifically targeted to the cartilage models of the limbs of transgenic mouse embryos. It will also be d_termined if maturation is promoted by Dlx6, a putative functionally redundant member of the Dlx family. The mechanism of Dlx5 regulation of maturation will be investigated using gain- and loss-of-flmction approaches in limb mesenchymal cell and chondrocyte model culture systems. The possible regulatory relationships be:ween Dlx5 and other positive regulators of chondrocyte maturation including RMPs, Cbfal/Runx2, and [%catenin-mediated Wnt signaling will be investigated. A variety of molecular agonists and antagonists will be used to begin to unravel how Dlx5 and the other factors interact and cooperate in regulating hypertrophic maturation. It will also be determined if Dlx5 participates in transcriptional regulation of the osteopontin, bone sialoprotein, and type X collagen genes during chondrocyte maturation. The possibility that Dlx5 interacts and cooperates with the BMP signaling pathway and/or Cbfal/Runx2 in the transcriptional regulation of the promoters of one or more of these candidate target genes will be investigated. PERFORMANCE SITE ========================================Section End===========================================

超出所提供的空间。软骨模型生成后形成肢体骨骼的软骨内骨化过程依赖于软骨细胞成熟的精心调节程序。识别控制肥大软骨细胞成熟的基因和信号分子以及它们之间的调节相互作用对于了解骨生长和发育至关重要。本研究的目的是研究同源域转录因子Dlx 5是软骨内骨化过程中软骨细胞成熟的关键正调节因子的假设，并解开Dlx 5和其他参与控制该过程的因素之间的关系。Dlx 5在未成熟的增殖软骨细胞向有丝分裂后前肥大软骨细胞的转化过程中表达，这是成熟的关键步骤。在鸡肢体的骨骼元件体内分化过程中Dlx 5的逆转录病毒错误表达导致严重缩短的骨骼元件的形成，所述骨骼元件含有过量的肥大软骨细胞、肥大分化的一些分子标志物（包括骨桥蛋白和X型胶原）的表达的扩大和上调的结构域以及矿化软骨基质的扩大。Dlx 5的错误表达也显著降低细胞增殖，同时促进肥大性成熟。这些结果表明Dlx 5至少部分通过促进未成熟增殖软骨细胞向肥大软骨细胞的转化来正向调节成熟。Dlx 5在软骨细胞成熟中的作用将通过检查鸡肢中Dlx 5错误表达对肥大成熟的另外标记物的表达的影响，并确定当Dlx 5错误表达特异性靶向转基因小鼠胚胎的肢的软骨模型时是否促进软骨细胞成熟来进一步研究。它也将被确定，如果成熟是由Dlx 6，Dlx家族的一个假定的功能冗余的成员。将使用肢体间充质细胞和软骨细胞模型培养系统中的功能获得和功能丧失方法来研究Dlx 5调节成熟的机制。Dlx 5与软骨细胞成熟的其他正调控因子包括RMP、Cbfal/Runx 2和[%连环蛋白介导的Wnt信号传导]之间可能的调控关系将被研究。各种分子激动剂和拮抗剂将用于开始解开Dlx 5和其他因子如何相互作用和合作，在调节肥大成熟。还将确定Dlx 5是否参与软骨细胞成熟过程中骨桥蛋白、骨唾液酸蛋白和X型胶原基因的转录调控。将研究Dlx 5在这些候选靶基因中的一个或多个的启动子的转录调节中与BMP信号传导途径和/或Cbfal/Runx 2相互作用和协作的可能性。性能现场=