Shimai Kotaro, Kitaura Yuki, Tamari Yoshihiro, Nishikata Takahito
Graduate School of Natural Science, Konan University, Kobe 658-8501, Japan.
Zoolog Sci. 2010 Feb;27(2):76-83. doi: 10.2108/zsj.27.76.
The relatively simple structure of ascidians and the number of associated molecular resources that are available make ascidians an excellent experimental system for Investigating the molecular mechanisms underlying neural tube formation. The ascidian neural tube demonstrates the same basic morphology as that of vertebrates. We have described the expression of the neural tubespecific gene CiNut1, which is expressed within neural tube precursor cells from the gastrula stage, and along the entire length of the neural tube during its formation. In this study, we focused on the transcriptional mechanisms that regulate CiNut1 expression. We found that an approximately 1.0 kb upstream sequence was able to recapitulate endogenous CiNut1 expression. A deletion analysis showed that the 119 bp upstream fragment containing two ZicL-binding consensus sequences and one Fox core sequence could also drive the neural tube-specific expression. When mutations were Introduced into the distal ZicL binding site (ZicL1), the neural tube-specific expression almost disappeared. Although the Importance of the proximal ZicL site (ZicL2) and the Fox core sequence have yet to be elucidated, we hypothesize that ZicL regulates gene transcription in the entire neural tube of the ascidian.
海鞘相对简单的结构以及现有的相关分子资源数量，使海鞘成为研究神经管形成背后分子机制的绝佳实验系统。海鞘的神经管展示出与脊椎动物相同的基本形态。我们已经描述了神经管特异性基因CiNut1的表达情况，该基因从原肠胚阶段开始在神经管前体细胞中表达，并在神经管形成过程中沿其全长表达。在本研究中，我们聚焦于调节CiNut1表达的转录机制。我们发现一个约1.0 kb的上游序列能够重现内源性CiNut1的表达。缺失分析表明，包含两个ZicL结合共有序列和一个Fox核心序列的119 bp上游片段也能驱动神经管特异性表达。当在远端ZicL结合位点（ZicL1）引入突变时，神经管特异性表达几乎消失。尽管近端ZicL位点（ZicL2）和Fox核心序列的重要性尚未阐明，但我们推测ZicL调节海鞘整个神经管中的基因转录。
