The Role of Fgf Signaling in Vertebrate Development

该项目的长期目标是了解一个重要的信号配体家族，称为成纤维细胞生长因子（FGFs），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理解FGF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（分割的中胚层节段是脊椎动物肌肉、真皮和椎体的基石）。我们的工作已经清楚地表明，基因冗余是这种生物学的一个重要方面；因此，本项目的所有工作都是为了全面表征中胚层谱系中FGF信号的遗传冗余。这项工作与许多可能有一个以上FGF基因受损的癌症病例有关。为了实现这一目标，我们需要生成和表征重要的Cre小鼠系，这是允许控制早期胚胎基因表达的工具。这些基因包括tcree（表达于早期新生中胚层）、tcree - ert2（可在所有胚胎阶段的新生中胚层中激活）和Tbx4-Cre（表达于后胚层区域，包括尿囊、后肢和外生殖器）。Dyn.， 2011年出版)。特别是tgre对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，其中今年出版了三份(Dev。医学杂志。[j] .生物医学工程学报，2011(3):391 - 391。（PNAS, 2011, 108:4018）并发表了两篇论文。在2011财年，作为我们对早期发育的总体兴趣的一部分，在合作研究中，我们帮助确定了Pitx2在眼外肌发生中的作用。生物工程学报，2011,39(3):395)。中文信息学报，2011,351:254)。在2011财年，我们还发表了一项重要发现，确定了哪些FGF配体控制将形成some的细胞的分化（PNAS, 2011 108:4018）。在2005年，我们发表了令人惊讶的见解，Fgf8不需要这个过程，虽然高调的工作机构已将其置于当前模型的中心位置。我们发现Fgf8和Fgf4在体细胞发生的一些基本方面是必需的：振荡基因结构域、WNT通路基因和未分化的体细胞前中胚层的标记物的表达。重要的是，我们证明了整个体前中胚层的过早分化。通过研究类似的突变体，我们从基因上恢复了WNT信号，我们证明了FGF信号在这一过程中独立于WNT信号。我们发现的这种功能冗余对癌症有影响，因为两种fgf在睾丸肿瘤中都异常活跃。此外，这种冗余对进化有影响，因为相同的FGFs在肢体发育中起补偿作用。在2011财年，在一项合作研究中，我们还发表了（Dev Dyn，出版中）对先前生成的一种小鼠品系的广泛表征，但描述不完整，该品系携带Tbx4等位基因，其中Cre被敲入基因3非翻译区。最值得注意的是，我们确定，尽管尿囊血管形成需要Tbx4，但尿囊推定的内皮细胞不表达Tbx4，通过激活Cre报告基因，Tbx4-Cre追踪显示脐带血管谱系从未表达Tbx4。这些结果表明内皮细胞系在血管发生之前就已经分离，并证明了血管周围组织在血管发生中的作用。

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.