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（如骨和软骨）的主要组成部分。因此，影响ECM蛋白的几种突变与人类疾病有关。例如，成骨不全的特征是骨矿物质密度降低和生物力学不稳定。此外，ECM在多种类型的癌症中具有关键功能，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ECM蛋白TGFBI（或βIg-h3）在成骨成骨细胞和肌细胞中的功能，TGFBI被认为是AP- 1转录因子FOS的靶基因。通过表征Tgfbi在成骨细胞特异性功能缺失的小鼠和诱导Tgfbi在成骨细胞中过表达的小鼠的表型，我们将研究Tgfbi在骨稳态中的生理作用。在H2启动子的控制下，Fos过表达导致小鼠骨肉瘤（OS）的发生。因此，Tgfbi作为Fos靶基因的作用将在此背景下进行遗传定位。人类OS细胞系和人类肿瘤活检将用于阐明FOS和TGFBI的功能，并在小鼠模型中验证所获得的数据。由于Fos也可以在特定的细胞环境中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在Fos依赖的横纹肌肉瘤（RMS）小鼠模型中作为潜在肿瘤抑制基因的功能。首先，我们的目标是通过在肌肉细胞中特异性地删除Fos和p53来建立小鼠RMS的改进模型，并研究TGFBI在这种情况下和在人类RMS中的相关性。我计划在稳定敲除或过表达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.