FGF Signaling Pathways and Craniofacial Development

描述(由申请人提供)：本提案的主要目的是确定由FGFs启动的信号机制，这些信号机制是腭部和面中部正常发育的基础。FGFR1和FGFR2两个受体的条件性缺失会导致多发性颅面缺损。尽管包括我们自己在内的许多实验室已经从生化的角度对成纤维细胞生长因子信号进行了广泛的研究，但对这些信号通路如何调控颅面发育中的形态发生过程知之甚少。在这一应用中，我们建议：1.研究成纤维细胞生长因子信号在腭部上皮细胞中的调控途径。上皮细胞中FGFR2的缺失会导致腭裂。为了建立这种缺陷的信号转导机制，我们将在FGFR2基因座上产生并分析一系列条件信号转导小鼠突变，以防止单个或多个效应蛋白的结合。我们将进一步确定FGFR2信号在腭部上皮中的转录靶点，并确定它们是否可以调节底层间充质的后续增殖。2.探讨成纤维细胞生长因子信号在神经棘中的调控途径。神经脊中FGFR1的缺失会导致多个头面部缺陷，包括腭部闭合。为了确定潜在的信号转导机制，我们将在FGFR1基因座上产生并鉴定一系列条件信号转导小鼠突变体，以防止单个或多个效应蛋白的结合，靶向与FGFR2相同的途径。由于腭部和其他头面部器官是从背侧神经外胚层迁移而来的神经脊细胞，我们还将进行基于CRE的谱系分析，以表征突变表型背后的神经脊细胞迁移缺陷。3.鉴定和鉴定成纤维细胞生长因子调控额鼻发育的途径。神经脊细胞中FGFR1和FGFR2的共同缺失会导致面部裂隙延伸到中线。建立 为了揭示这种表型的机制基础，我们将用携带相同效应子的点突变的复合FGFR1和FGFR2条件突变体在神经脊细胞中进行条件突变，并将其与双零突变体进行比较。我们将通过有条件的突变，特别是在额鼻突起，进一步确定成纤维细胞生长因子信号在面中部发育中的作用。这些研究有望对颅面生物学产生重大影响，因为它们将建立成纤维细胞生长因子发挥作用的信号机制，并通过可能应用于关键的成纤维细胞生长因子细胞内效应物的药物靶点，为预防头面部出生缺陷开辟新的方向。

DESCRIPTION (provided by applicant): The major aims of this proposal are to identify signaling mechanisms initiated by FGFs that underlie normal development of the palate and the midface. Conditional deletion of the two receptors Fgfr1 and Fgfr2 lead to multiple craniofacial defects. Although FGF signaling has been extensively studied from a biochemical standpoint in many laboratories, including our own, remarkably little is known about how these signaling pathways regulate morphogenetic processes in craniofacial development. In this application, we propose: 1. To investigate the pathways regulated by FGF signaling in the palatal epithelium. Loss of Fgfr2 in the epithelium leads to a cleft palate. To establish the signaling mechanisms underlying this defect, we will generate and analyze an allelic series of conditional signaling mouse mutants at the Fgfr2 locus that prevent the binding of single or multiple effector proteins. We will further characterize transcriptional targets of Fgfr2 signaling in the palatal epithelium and determine if they can regulate subsequent proliferation of the underlying mesenchyme. 2. To investigate the pathways regulated by FGF signaling in the neural crest. Loss of Fgfr1 in the neural crest leads to multiple craniofacial defects, including in palate closure. To identify the underlying signaling mechanisms, we will generate and characterize an allelic series of conditional signaling mouse mutants at the Fgfr1 locus that prevent the binding of single or multiple effectors proteins, targeting the same pathways as for Fgfr2. Since the palate and other craniofacial organs are derived from neural crest cells migrated from dorsal neural ectoderm, we will also conduct Cre based lineage analysis to characterize defects in neural crest cell migration that underlie the mutant phenotypes. 3. To identify and characterize the FGF regulated pathways that control frontonasal development. Combined loss of both Fgfr1 and Fgfr2 in neural crest cells leads to facial clefting that extends through the midline. To establish the mechanistic basis for this phenotype, we will perform conditional mutagenesis in neural crest cells with compound Fgfr1 and Fgfr2 conditional mutants carrying point mutations for identical effectors, and compare these to the double null mutants. We will further establish the role of FGF signaling in midface development by conditional mutagenesis specifically in the frontonasal process. The proposed studies are anticipated to have a significant impact in craniofacial biology because they will establish the signaling mechanisms by which FGFs exert their action and open new directions for the prevention of craniofacial birth defects by the possible application of drug targets for critical FGF intracellular effectors.