Institute for Virus Research, Kyoto University, Kyoto, Japan.
PLoS One. 2013;8(1):e53323. doi: 10.1371/journal.pone.0053323. Epub 2013 Jan 9.
The mouse segmentation is established from somites, which are iteratively induced every two hours from the presomitic mesoderm (PSM) by a system known as the segmentation clock. A crucial component of the segmentation clock is the gene Hes7, which is regulated by the Notch and Fgf/Mapk pathways, but its relation to other pathways is unknown. In addition, chemical alteration of the Wnt pathway changes the segmentation clock period but the mechanism is unclear.To clarify these questions, we have carried out Hes7 promoter analysis in transgenic mouse embryos and have identified an essential 400 bp region, which contains binding sites of Tbx6 and the Wnt signaling effector Lef1. We have found that the Hes7 promoter is activated by Tbx6, and normal activity of the Hes7 promoter in the mouse PSM requires Tbx6 binding sites. Our results demonstrate that Wnt pathway molecules activate the Hes7 promoter cooperatively with Tbx6 in cell culture and are necessary for its proper expression in the mouse PSM. Furthermore, it is shown that the chemical Gsk3 inhibitor LiCl lengthens the oscillatory period of Hes7 promoter activity.Our data suggest that Tbx6 and the Wnt pathway cooperatively regulate proper Hes7 expression. Furthermore, proper Hes7 promoter activity and expression is important for the normal pace of oscillation.
小鼠的分段是由体节建立的，体节是由前体节中胚层（PSM）每隔两小时通过一个称为分段时钟的系统迭代诱导产生的。分段时钟的一个关键组成部分是基因 Hes7，它受 Notch 和 Fgf/Mapk 途径的调节，但它与其他途径的关系尚不清楚。此外，Wnt 途径的化学改变会改变分段时钟周期，但机制尚不清楚。为了澄清这些问题，我们在转基因小鼠胚胎中进行了 Hes7 启动子分析，并鉴定了一个必需的 400bp 区域，该区域包含 Tbx6 和 Wnt 信号效应物 Lef1 的结合位点。我们发现 Hes7 启动子被 Tbx6 激活，并且小鼠 PSM 中 Hes7 启动子的正常活性需要 Tbx6 结合位点。我们的结果表明，Wnt 途径分子在细胞培养中与 Tbx6 协同激活 Hes7 启动子，并且在小鼠 PSM 中其正常表达是必需的。此外，表明化学 Gsk3 抑制剂 LiCl 延长 Hes7 启动子活性的振荡周期。我们的数据表明，Tbx6 和 Wnt 途径协同调节适当的 Hes7 表达。此外，适当的 Hes7 启动子活性和表达对于正常的振荡节奏很重要。
