Hox transcription factors play an essential role in patterning the anteroposterior axis during embryogenesis and exhibit a complex array of spatial and temporal patterns of expression. Their earliest onset of expression in vertebrates is during gastrulation in a temporally collinear sequence in the presomitic/ventrolateral mesoderm, and it is not clear which upstream signal transduction events initiate this expression. Using Xenopus, we present evidence that Xwnt8 is necessary for initiation of this collinear sequence by activating Hox-1 expression in three Hox clusters: hoxd, hoxa, and hoxb. All three labial genes appear to be direct targets of canonical Wnt signaling through Tcf/Lef. In addition, Xwnt8 loss- and gain-of-function leads to indirect regulation of other Hox genes: Hoxb4, Hoxd4, Hoxa7, Hoxc6, and Hoxc8. These findings shed new light on the early role of Wnt8 as well as of a proposed WNT gradient in patterning the Xenopus central nervous system (Kiecker and Niehrs [2001] Development 128:4189-4201).
展开▼
机译：Hox转录因子在胚胎发生过程中在前后轴的模式中起着至关重要的作用，并表现出复杂的时空表达模式。它们最早在脊椎动物中表达的发生是在早熟/腹侧中胚层的时间共线序列的胃泌乳过程中，尚不清楚哪些上游信号转导事件启动了该表达。使用非洲爪蟾，我们提供证据表明Xwnt8对于通过激活三个Hox簇：hoxd，hoxa和hoxb中的Hox-1表达来启动该共线序列是必要的。所有三个唇基因似乎都是通过Tcf / Lef进行经典Wnt信号传导的直接靶标。另外，Xwnt8的功能丧失和获得导致间接调节其他Hox基因：Hoxb4，Hoxd4，Hoxa7，Hoxc6和Hoxc8。这些发现为Wnt8的早期作用以及拟议的WNT梯度在非洲爪蟾中枢神经系统模式中的应用提供了新的启示（Kiecker和Niehrs [2001] Development 128：4189-4201）。
展开▼
