Genetische Kontrolle der Notochordentwicklung: Analyse der truncate Mutation der Maus

在之前的资助阶段，我们发现小鼠同源盒基因Noto在早期胚胎模式形成中起关键作用。Noto在结节和新生的脊索中表达，我们产生的零等位基因对节点发育、正常9+0纤毛的形成和左右不对称的建立是必要的。我们已经确定在结节和其他组织的纤毛细胞中表达的转录因子Foxj1是Noto的潜在靶标。尽管Foxjl突变的结节有纤毛，但Foxjl对于9+2纤毛的形成、呼吸道上皮细胞骨架的极化组织以及左右不对称的建立是必需的。细胞表型的相似性表明，Noto至少部分通过FoxjL、Tcf/Lef和Noto启动子中的Smad结合位点起作用。在这项提议中，我们将检验这样的假设：i)Foxjl需要在Noto下游调控小鼠胚胎中节点和纤毛发育的主要方面，以及ii)Wnt和转化生长因子？？信号调节Noto的表达。此外，我们还将进一步鉴定Noto突变体中的细胞缺陷，并描绘指导Noto节点和脊索特异性表达的基因组区域。综上所述，这项提议的结果将阐明Noto如何指导必要的早期图案化过程。

During the previous funding period we identified the mouse homeobox gene Noto as pivotal for early embryo patterning. Noto is expressed in the node and nascent notochord, and as demonstrated by a null allele that we generated essential for node development, genesis of normal 9+0 cilia, and establishment of left-right asymmetry. We have identified Foxjl, a transcription factor expressed in the node and in ciliated cells of other tissues, as potential target of Noto. Foxjl is required for formation of 9+2 cilia, polarized organization of the cytoskeleton in the respiratory epithelium, and for establishment of left-right asymmetry, although Foxjl mutant nodes have cilia. Similarities of cellular phenotypes suggest that Noto acts at least in part through FoxjL TCF/LEF and Smad binding sites in the Noto promoter suggest that Wnt and TGFß signals regulate Noto expression. In this proposal we will test the hypotheses that i) Foxjl is required downstream of Noto to mediate major aspects of node and cilia development in mouse embryos, and ii) Wnt and TGFß signals regulate Noto expression. In addition we will further characterize the cellular defects in Noto mutants and delineate genomic regions that direct node and notochord-specific expression of Noto. Together, the results of this proposal will elucidate how Noto directs essential early patterning processes.