Barx2 in limb muscle and tendon development

描述(申请人提供)：肢体形态发生需要肌肉、肌腱和软骨的协调发展，通过可溶性信号分子和转录因子的相互作用。我们的工作假设是同源结构域蛋白Barx2在这些过程中扮演多种角色。Barx2在胚胎肢体的肌肉和肌腱中表达，是体外成肌分化所必需的。此外，Barx2影响并受参与肢体形态发生的分子调控。我们提出的研究旨在了解Barx2在肌肉和肌腱发育中的表达、调节和功能。我们将确定Barx2在胚胎肢体发育过程中与肌肉和肌腱发育的特定调节因子相关的表达模式。然后，我们将研究Barx2的表达是否直接受到肌肉调节因子(MRF)和肌腱规格因子(如硬化轴)的调节。我们最近的研究表明，骨形态发生蛋白GDF5也调节Barx2的表达。由于骨形态发生蛋白也能调节肌腱硬化轴的表达，而GDF5可以诱导异位肌腱的形成，因此我们建议测试GDF5是否能调节肢芽培养中Barx2和硬化轴的表达。其他数据表明，Barx2通过调节细胞黏附和细胞骨架影响成肌细胞融合。因此，我们将研究Barx2表达的扰动是否会影响肢芽和成肌细胞培养中的细胞黏附和细胞骨架分子。我们还将测试Barx2是否通过控制I型胶原和其他细胞外基质蛋白的表达来影响肌腱发育。由于发育过程经常在成人组织的再生和修复过程中重复，因此识别Barx2在肌肉和肌腱发育中的新调控途径和靶点可能会为肌肉骨骼疾病的治疗干预开辟新的途径。

DESCRIPTION (provided by applicant): Limb morphogenesis requires the coordination of muscle, tendon, and cartilage development via the interactions of soluble signaling molecules and transcription factors. Our working hypothesis is that the homeodomain protein Barx2 plays multiple roles in these processes. Barx2 is expressed in muscles and tendons of the embryonic limb and is required for myogenic differentiation in vitro. Moreover, Barx2 influences and is regulated by molecules involved in limb morphogenesis. Our proposed studies are designed to understand the expression, regulation and functions of Barx2 in both muscle and tendon development. We will determine the pattern of expression of Barx2 during development of the embryonic limb with respect to specific regulators of muscle and tendon development. We will then examine whether Barx2 expression is directly regulated by muscle regulatory factors (MRFs) and tendon specification factors such as Scleraxis. Our recent studies suggest that the bone morphogenetic protein (BMP) GDF5 also regulates Barx2 expression. Because BMPs also, modulate Scleraxis expression, and GDF5 can induce ectopic tendon formation, we propose to test whether GDF5 regulates Barx2 and Scleraxis expression in limb bud cultures. Other data suggest that Barx2 influences myoblast fusion via modulation of cell adhesion and the cytoskeleton. Thus we will examine whether perturbation of Barx2 expression influences cell adhesion and cytoskeletal molecules in limb bud and myoblast cultures. We will also test whether Barx2 influences tendon development by controlling the expression of collagen I and other extracellular matrix proteins. Since developmental processes are frequently recapitulated during regeneration and repair of adult tissues, the identification of new regulatory pathways and targets for Barx2 in muscle and tendon development may lead to new avenues for therapeutic intervention in musculoskeletal disease.