Studies of the functions of TGFBI in bone homeostasis and cancer development

细胞外基质(ECM)是人体结缔组织的主要组成部分，如骨和软骨。因此，几种影响细胞外基质蛋白质的突变与人类疾病有关。例如，成骨不全的特点是骨密度降低和生物力学不稳定。此外，ECM在不同类型的癌症中具有关键作用，因为癌细胞与ECM的相互作用影响癌细胞的迁移、增殖、存活和凋亡。我计划分析细胞外基质蛋白TGFBI(或βIg-h3)的功能，它是AP-1转录因子fos在成骨细胞和肌细胞中可能的靶基因。通过对成骨细胞特异性Tgfbi功能丧失的小鼠和成骨细胞诱导过表达Tgfbi的小鼠的表型特征的研究，将探讨Tgfbi在骨稳态中的生理作用。在H2启动子的控制下，FOS的过表达导致了小鼠骨肉瘤的发生。因此，Tgfbi作为Fos靶基因的作用将在这一背景下得到遗传上的重视。我们将利用人类OS细胞株和人类肿瘤活检组织来阐明Fos和TGFBI的功能，并验证在小鼠模型中获得的数据。由于Fos在特定的细胞环境中也可以作为肿瘤抑制基因发挥作用，该项目的第二个目标是研究Tgfbi作为潜在的肿瘤抑制基因在依赖Fos的横纹肌肉瘤(RMS)小鼠模型中的功能。我们的目标将首先是通过删除肌肉细胞中特异的Fos和P53来建立一种改进的小鼠RMS模型，并研究TGFBI在这一背景下与人类RMS的相关性。我计划在稳定下调或过表达FOS和TGFBI后，对人RMS细胞进行体外分析。人类患者的材料也将被分析。

The extracellular matrix (ECM) is a major part of the body’s connective tissues like bone and cartilage. Thus several mutations affecting proteins of the ECM are linked to human diseases. For example Osteogenesis imperfecta is characterized by a reduced bone mineral density and biomechanical instability. Additionally the ECM has pivotal functions in diverse types of cancer, since interactions of cancer cells with the ECM influence migration, proliferation, survival and apoptosis of cancer cells. I plan to analyze the functions of the ECM protein TGFBI (or βIg-h3), a putative target gene of the AP- 1 transcription factor FOS in bone-forming osteoblasts and myocytes. By characterizing the phenotype of mice with osteoblast-specific loss of function of Tgfbi and mice that inducibly overexpress Tgfbi in osteoblasts, the physiological role of TGFBI in bone homeostasis will be investigated. Fos overexpression under the control of the H2 promoter results in the development of osteosarcoma (OS) in mice. Therefore the role of Tgfbi as a target gene of Fos will be genetically adressed in this context. Human OS cell lines and human tumor biopsies will be used to elucidate the function of FOS and TGFBI and to validate the data obtained in mouse models.Since Fos can also function as a tumor suppressor in specific cellular contexts, the second aim of the project is to investigate the function of Tgfbi as a potential tumor suppressor gene in a Fos-dependent mouse model of Rhabdomyosarcoma (RMS). The goal will be first to establish an improved model of RMS in mice by deleting Fos and p53 specifically in muscle cells and to investigate the relevance of TGFBI in this setting and in human RMS. I plan to perform in vitro analyses of human RMS cells after stable knock-down or over-expression of FOS and TGFBI. Human patient material will also be analyzed.