Cis-regulatory organization of the Pax6 gene in the ascidian Ciona intestinalis
Cis-regulatory organization of the Pax6 gene in the ascidian Ciona intestinalis
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DOI：
10.1016/j.ydbio.2008.01.036
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发表时间：
2008-05-15
影响因子：
2.7
通讯作者：
Antony, Rajee
中科院分区：
文献类型：
--
作者：
Irvine, Steven Q.;Fonseca, Vera C.;Antony, Rajee
Pax6基因在许多动物的眼和中枢神经系统（CNS）的发育过程中起着重要作用，因此引起了广泛的研究兴趣。Pax6在比较基因组学中也很有意义，因为它在四足动物中没有重复，这使得玻璃海鞘基因CiPax6和Pax6在哺乳动物中直接同源。CiPax6已显示在前脑、尾神经索和与感光单眼相关的脑部分中表达。这一信息在这里使用原位杂交进行了扩展，并显示CiPax6转录物标记神经索的侧部区域，与小鼠中的Pax6表达非常相似。作为剖析CiPax6的顺式调节的手段，我们使用瞬时报告转基因测定测试了8kb的序列。发现三个独立的区域共同作用以驱动整体CiPax6表达模式。发现第一外显子上游2 kb的211 bp序列是驱动感觉囊泡（海鞘脑的前部）中表达的主要增强子。其他上游序列显示与感觉囊泡增强子一起工作以驱动CNS的其余部分中的表达。一个“眼增强子”定位于第一个内含子，其控制感觉囊泡（包括感光细胞）中央部分的特异性表达。第四内含子被发现抑制报告基因在胚胎大脑中部的异位表达。这一整体调控组织的各个方面与小鼠和果蝇中Pax6同系物的组织相似，特别是在眼、脑和神经索中存在驱动表达的内含子元件。(C)2008年爱思唯尔公司All rights reserved.
The Pax6 gene has attracted intense research interest due to its apparently important role in the development of eyes and the central nervous system (CNS) in many animal groups. Pax6 is also of interest for comparative genomics since it has not been duplicated in tetrapods, making for a direct orthology between the Ciona intestinalis gene CiPax6 and Pax6 in mammals. CiPax6 has been shown to be expressed in the anterior brain, caudal nerve cord, and in parts of the brain associated with the photoreceptive ocellus. This information was extended here using in-situ hybridization, and shows that CiPax6 transcripts mark the lateral regions of the nerve cord, remarkably similar to Pax6 expression in the mouse. As a means of dissecting the cis-regulation of CiPax6 we tested 8 kb of sequence using transient reporter transgene assays. Three separate regions were found that work together to drive the overall CiPax6 expression pattern. A 211 bp sequence 2 kb upstream of the first exon was found to be a major enhancer driving expression in the sensory vesicle (the anterior portion of the ascidian brain). Other upstream sequences were shown to work with the sensory vesicle enhancer to drive expression in the remainder of the CNS. An "eye enhancer" was localized to the first intron, which controls specific expression in the central portion of the sensory vesicle, including photoreceptor cells. The fourth intron was found to repress ectopic expression of the reporter gene in middle portions of the embryonic brain. Aspects of this overall regulatory organization are similar to the organization of the Pax6 homologs in mice and Drosophila, particularly the presence of intronic elements driving expression in the eye, brain and nerve cord. (C) 2008 Elsevier Inc. All rights reserved.