Identification of Epha4 enhancer required for segmental expression and the regulation by Mesp2
Identification of Epha4 enhancer required for segmental expression and the regulation by Mesp2
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DOI：
10.1242/dev.02422
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发表时间：
2006-07-01
期刊：
影响因子：
4.6
通讯作者：
Saga, Yumiko
中科院分区：
文献类型：
--
作者：
Nakajima, Yoshiro;Morimoto, Mitsuru;Saga, Yumiko
体节是脊椎动物轴向结构的基础，通过前体节中胚层基因的表达来确定节段特征。节段边界形成的关键蛋白是bHLH转录因子Mesp 2，其表达仅限于前PSM。被Mesp 2激活的候选基因是Epha 4，因为它的表达模式类似于Mesp 2，并且在Mesp 2缺失的胚胎中不存在。我们已经分析了Epha 4的增强子区域，该区域负责其在前PSM中的表达，并鉴定了包含E-box的区域。随后的转基因和瞬时荧光素酶分析成功地确定了重复的E-box序列的存在是在前PSM中表达的最低基本要求。我们还表明，Mesp 2直接结合到Epha 4的增强子序列。此外，Mesp 2在体节细胞中的强制表达导致Epha 4的激活和尾部基因Uncx4.1的抑制，这可能触发导致异常体节和喙状椎骨形成的事件。此外，异位Mesp 2表达诱导异常上皮化结构，这支持了Mesp 2通过激活在细胞上皮化中起作用的基因诱导节段性边界形成的观点。
Somites provide the basic body plan for metameric axial structures in vertebrates, and establish the segmental features through the sequential gene expression in the presomitic mesoderm (PSM). A crucial protein for segment border formation is the bHLH transcription factor Mesp2, the expression of which is restricted to the anterior PSM. A gene candidate that is activated by Mesp2 is Epha4, as its expression pattern resembles Mesp2 and is absent in Mesp2- null embryos. We have analyzed the enhancer region of Epha4, which is responsible for its expression in the anterior PSM, and identified an E-box containing region. Subsequent transgenic and transient luciferase analyses successfully determined that the presence of repeated E-box sequences is a minimum essential requirement for the expression in the anterior PSM. We also show that Mesp2 directly binds to the enhancer sequence of Epha4. Furthermore, the forced expression of Mesp2 in somitic cells results in the activation of Epha4 and repression of the caudal gene Uncx4.1, which may trigger the events leading to the formation of abnormal somites and rostralized vertebra. In addition, ectopic Mesp2 expression induces abnormally epithelialized structures, which support to the idea that Mesp2 induces the formation of segmental borders by activating genes that play roles in cellular epithelialization.