Transcriptional regulation of tendon differentiation and matrix formation

描述（由申请人提供）：肌腱将肌肉收缩产生的力传递到骨骼，通过坚固且高度组织化的胶原纤维束建立肌腱的生物力学特性。在肌腱中，细胞延伸吞没成束的胶原纤维，并产生纤维生长的微环境。肌腱中胶原原纤维的生长是决定肌腱生物力学性能和拉伸强度的最重要因素。胶原原纤维生长发生在两个阶段，在胚胎阶段缓慢的原纤维组装和更快的原纤维生长的步伐，可能发生在出生后阶段通过原纤维融合。然而，我们对调控这些过程的基因程序一无所知。我们以前已经表明，bHLH转录因子Scleraxis是必不可少的早期肌腱分化，它可能也发挥了重要作用，在胶原纤维形成。在突变体的第二肌腱转录因子，莫霍克，我们现在发现一个失败的后期出生后阶段的胶原纤维生长。本项目的重点是巩膜和莫霍克在胶原纤维形成和肌腱成熟中的作用。第一个具体目标集中在胚胎肌腱的肌腱组装，第二个目标着眼于在出生后阶段的肌腱成熟和快速胶原纤维生长的调节。在这两个阶段，将采用类似的办法处理这些进程。正常肌腱生长和肌腱表型最初将用一组增强的结构参数进行评估，并检查Scx或Mkx过表达对肌腱生长的影响。将通过微阵列分析鉴定硬化和莫霍克功能的分子介导物，并通过Scx或Mkx表型的转基因拯救（将单个或多个靶基因的表达重新引入突变体背景）确定少量靶基因的调节作用。我们最近确定了ZFP 185，一种锌指转录因子，作为我们计划进行转基因拯救的第一个有希望的候选者。确定控制纤维生长的调节途径可能有助于在临床环境中增强和调节这些过程的能力。

DESCRIPTION (provided by applicant): Tendons transmit the force generated by muscle contraction to the skeleton, through robust and highly organized bundles of collagen fibrils that establish the biomechanical properties of tendons. In the tendons, cellular extensions engulf bundles of collagen fibrils and generate the microenvironment for fibril growth. Growth of the collagen fibrils in tendons is the single most significant factor that determines biomechanical properties and tensile strength of tendons. Collagen fibril growth occurs in two phases, slow fibril assembly in embryonic stages and a much faster pace of fibril growth that likely occurs through fibril fusion in postnatal stages. Nothing, however, is known about the genetic program that regulates these processes. We have previously shown that the bHLH transcription factor Scleraxis is essential for early tendon differentiation and that it likely also plays an important role in collagen fibrillogenesis. In mutants of a second tendon transcription factor, Mohawk, we now find a failure of the later postnatal phase of collagen fibril growth. This project focuses on the role of Scleraxis and Mohawk in collagen fibrillogenesis and tendon maturation. The first specific aim focuses on tendon assembly in embryonic tendons and the second aim looks at the regulation of tendon maturation and rapid collagen fibril growth in postnatal stages. These processes will be addressed following a similar approach in both stages. Normal tendon growth and tendon phenotypes will initially be evaluated with an enhanced set of structural parameters and the effects of overexpression of Scx or Mkx on tendon growth will be examined. Molecular mediators of Scleraxis and Mohawk functions will be identified by microarray profiling and the regulatory roles of a small number of target genes will be determined by a transgenic rescue of the Scx or Mkx phenotypes reintroducing the expression of a single or multiple target genes into the mutant background. We recently identified ZFP185, a Zinc Finger Transcription factor as the first promising candidate for which we plan to proceed with a transgenic rescue. Identifying regulatory pathways that control fibril growth will likely contribute to the ability to enhance and regulate these processes in clinical settings.