The Role of Fgf Signaling in Vertebrate Development

该项目的长期目标是了解称为成纤维细胞生长因子(FGFs)的重要信号配体家族如何控制广泛的细胞生物学行为，如增殖、细胞死亡、迁移、干细胞维持和基因表达。特别是，我们使用复杂的小鼠遗传学来了解成纤维细胞生长因子信号在中胚层谱系中的作用，特别强调体轴的延伸和体节的形成(节段性中胚层片段是脊椎动物肌肉、真皮和椎体的基石)。我们的工作表明，遗传冗余是这一生物学的一个重要方面；因此，这个项目的所有工作都是为了全面表征中胚层谱系中成纤维细胞生长因子信号的遗传冗余。这项工作与许多癌症病例有关，在这些病例中，可能有不止一个成纤维细胞生长因子基因受损。为了实现这一点，我们需要培育和鉴定重要的Cre小鼠品系，这些品系是允许控制早期胚胎基因表达的工具。这些基因包括TCre(在早期出现的新生中胚层中表达)，TCre-ERT2(在所有胚胎阶段的新生中胚层中可激活)和Tbx4-Cre(在包括尿囊、后肢和外生殖器的后中胚层区域表达)。动态，2011年出版，)。特别是TCRE在该领域产生了重大影响，在大约20份出版物中发挥了重要作用，今年出版了3份(Dev.生物，2011 349：395，Dev.生物，2011 351：254，(美国国家科学院院刊，2011 108：4018)和两份印刷品。2011财年，作为我们对早期发育的普遍兴趣的一部分，在合作研究中，我们帮助确定了Pitx2在眼外肌发生中的作用(Dev。生物，2011 349：395)和迪格尔在体细胞发生(Dev.生物，2011 351：254)。在2011财年，我们还发表了一项重大发现，定义了哪些成纤维细胞生长因子配体控制将形成体节的细胞的分化(PNAS，2011 108：4018)。2005年，我们发表了令人惊讶的见解，即FGF8在这个过程中并不是必需的，尽管一系列备受瞩目的工作已将其置于当前模型的中心位置。我们发现，Fgf8和Fgf4一起是体细胞发生所必需的：振荡基因结构域、WNT途径基因和未分化的分裂前中胚层的标记的表达。重要的是，我们证明了整个分裂前中胚层的过早分化。通过研究我们在基因上恢复WNT信号的类似突变体，我们证明了在这一过程中，成纤维细胞生长因子信号独立于WNT信号工作。我们发现的这种功能冗余与癌症有关，因为这两种FGFs在睾丸肿瘤中都被发现异常活跃。此外，这种冗余对进化有影响，因为相同的FGFs在肢体发育中起着补偿作用。在2011财年，在一项合作研究中，我们还发表了(Dev Dyn，正在出版中)对先前产生的但未完全描述的小鼠品系的广泛表征，该品系携带Tbx4等位基因，其中CRE已被敲入基因3的非翻译区。最值得注意的是，我们确定，尽管尿囊血管生成需要Tbx4，但假定的尿囊内皮细胞不表达Tbx4，通过激活Cre报告基因进行的Tbx4-Cre追踪显示，脐带血管谱系从未表达过Tbx4。这些结果表明，内皮细胞系在血管生成开始之前是分离的，并证明了血管周围组织在血管生成中的作用。

The long term goal of this project is to understand how a the important family of signaling ligands, called Fibroblast Growth Factors (FGFs), control a wide spectrum of cell biological behaviors such as proliferation, cell death, migration, stem cell maintenance and gene expression. In particular we use complex mouse genetics to understand the role of FGF signaling in mesodermal lineages with a special emphasis on extension of the body axis and formation of somites (segmented mesodermal segments that are the building blocks of vertebrate muscle, dermis and vertebral bodies). Our work has made clear that genetic redundancy is an important aspect of this biology; therefore all work in this project emerges from an effort to comprehensively characterize the genetic redundancy of FGF signaling in the mesodermal lineage. Such work is relevant to many cases of cancer where more than one FGF gene may be damaged. To achieve this, we needed to generate and characterized important Cre mouse lines, which are tools that allow the control of gene expression in the early embryo. These include TCre (expressed in the early emerging nascent mesoderm), TCre-Ert2 (activatable in emerging nascent mesoderm at all embryonic stages) and Tbx4-Cre (expressed in a posterior mesodermal domain that includes the allantois, hindlimb, and external genitalia(Dev. Dyn., 2011 in press,). TCre in particular has had a major impact on the field, being essential in about 20 publications, with three published this year(Dev. Biol., 2011 349:395, Dev. Biol., 2011 351:254, (PNAS, 2011 108:4018) and two publications in press. In FY 2011, as part of our general interest in early development, in collaborative studies we have helped to define the role of Pitx2 in extraocular myogenesis (Dev. Biol., 2011 349:395) and Dicer in somitogenesis (Dev. Biol., 2011 351:254). In FY 2011 we also published a major finding that defined which FGF ligands control the differentiation of cells that will form somites (PNAS, 2011 108:4018). In 2005 we had published the surprising insight that Fgf8 not required for this process, although a body of high profile work had placed it in a central position in current models. We showed that Fgf8, together with Fgf4, are required for essential aspects of somitogenesis: expression of oscillating gene domains, WNT pathway genes and markers of undifferentiated presomitic mesoderm. Importantly, we demonstrated the premature differentiation of the entire presomitic mesoderm. By examining similar mutants in which we genetically restored WNT signaling, we demonstrated that FGF signaling operates independently of WNT signaling in this process. This functional redundancy that we uncovered has implications for cancer as both FGFs have been found to be aberrantly active in testicular tumors. Furthermore this redundancy has implications for evolution as the same FGFs play compensatory roles in limb development. In FY2011, in a collaborative study, we also published (Dev Dyn, in press) the extensive characterization of a mouse line previously generated, but incompletely described, that carries an allele of Tbx4 in which Cre had been knocked in into the genes 3 untranslated region. Most notably, we determined that, despite the requirement for Tbx4 in allantoic vasculogenesis, the presumptive endothelial cells of the allantois do not express Tbx4 and Tbx4-Cre tracing, via activation of Cre reporters, revealed that the umbilical vasculature lineage never expressed Tbx4. These results imply that endothelial lineages are segregated prior to the onset of vasculogenesis, and demonstrate a role for the peri-vascular tissue in vasculogenesis.