Role of Dlx-5 in Chondrocyte Differentiation

软骨内骨化的过程，四肢的骨骼是在软骨模型生成后形成的 依赖于一个精心调控的软骨细胞成熟程序。基因和信号分子的鉴定 控制肥大的软骨细胞成熟以及它们之间的调控相互作用对于理解 骨骼的生长和发育。这项研究的目的是调查假设，同源结构域转录 在软骨内成骨过程中，Dlx5因子是软骨细胞成熟的关键正向调节因子，并解开 Dlx5与其他参与控制过程的因素之间的关系。Dlx5在转换为 未成熟的增殖软骨细胞到有丝分裂后肥大前期的软骨细胞，这是成熟的关键步骤。逆转录病毒 Dlx5在体内鸡肢骨骼元素分化过程中的错误表达导致严重的 缩短的骨骼元素，包含过多的肥大软骨细胞、扩张和上调的结构域 肥大分化的一些分子标志物的表达，包括骨桥蛋白和X型胶原，以及 矿化软骨基质扩张。Dlx5的错误表达还显著降低了伴随着 促进肥厚性成熟。这些结果表明，Dlx5至少部分地通过促进成熟来积极地调节成熟。 未成熟的增殖软骨细胞转化为肥大的软骨细胞。Dlx5在软骨细胞中的作用 通过检测Dlx5在雏鸡肢体中的错误表达对其表达的影响，将进一步研究成熟过程。 肥大成熟的其他标志物，并确定Dlx5是否促进软骨细胞成熟 错误表达是针对转基因小鼠胚胎四肢软骨模型的。它也将是 如果成熟是由Dlx6促进的，则D_终止。Dlx6是DLX家族中一个功能冗余的成员。这一机制 Dlx5的成熟调节将通过肢体间充质细胞的功能增益法和功能损失法进行研究 和软骨细胞模型培养体系。可能的监管关系是：在Dlx5和其他积极的监管机构之间 软骨细胞的成熟包括RMPs、Cbfal/Runx2和[%catenin介导的Wnt信号将被研究。品种繁多 分子激动剂和拮抗剂将被用来开始解开Dlx5和其他因子如何相互作用和合作 在调节肥大成熟方面的作用。还将确定Dlx5是否参与了对 软骨细胞成熟过程中的骨桥蛋白、骨涎蛋白和X型胶原基因。Dlx5相互作用的可能性 并协同BMP信号通路和/或Cbfal/Runx2对One的启动子进行转录调控 或者更多的候选目标基因将被研究。

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.