Genetische Kontrolle der Notochordentwicklung: Analyse der truncate Mutation der Maus

在之前的资助期间，我们确定小鼠同源框基因诺托是早期胚胎形成的关键。诺托在节点和新生脊索中表达，并且如我们产生的对节点发育、正常9+0纤毛的发生和左右不对称的建立至关重要的无效等位基因所证明的。我们已经确定Foxjl，一种在结和其他组织的纤毛细胞中表达的转录因子，作为诺托的潜在靶点。Foxjl是形成9+2纤毛、呼吸道上皮细胞骨架的极化组织以及建立左右不对称性所必需的，尽管Foxjl突变节点具有纤毛。细胞表型的相似性表明，诺托至少部分通过诺托启动子中的FoxjL TCF/LEF和Smad结合位点起作用，表明Wnt和TGF β信号调节诺托表达。在本提案中，我们将检验以下假设：i）Foxjl是诺托下游所必需的，以介导小鼠胚胎中结节和纤毛发育的主要方面，和ii）Wnt和TGF β信号调节诺托表达。此外，我们将进一步表征诺托突变体中的细胞缺陷，并描绘指导诺托的节点和脊索特异性表达的基因组区域。总之，这个提议的结果将阐明诺托如何指导重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.