重复基因被认为是基因功能歧化和新功能产生的源泉。鱼类特有的基因组加倍事件产生了大量的重复基因,这些重复基因为基因功能歧化和新功能产生提供了良好材料。
最近,中科院水生所由桂建芳研究员主持的鱼类发育遗传学学科组在鱼类重复基因功能歧化研究上取得了重要进展。他们首先在养殖鱼类银鲫中发现鉴定出重复基因dmrt2b,继而通过morpholino敲降策略在斑马鱼中研究该基因的功能及其作用机制。他们发现斑马鱼dmrt2b在体节发生时期表达,在dmrt2b敲降的胚胎中,体节发生出现明显畸形,且dmrt2b敲降胚胎中慢肌(slow muscle)发育受到严重影响。进一步研究发现,Hedgehog信号通路成员(ptc1,nkx2.2a等)在dmrt2b敲降的胚胎中表达下调,提示dmrt2b是通过Hedgehog信号通路参与以上体节发生过程。以上影响在dmrt2a敲降的胚胎中没有发现。同时,dmrt2b和dmrt2a敲降的胚胎都表现出躯体左右轴建立上的缺陷:内脏位置失去偏向性以及在身体左侧特异表达的基因在右侧或两侧同时表达等。
这些研究表明,鱼类特有的重复基因dmrt2b和dmrt2a虽都参与了躯体左右不对称建立的过程,但dmrt2b通过Hedgehog信号通路参与体节发生过程,而dmrt2a没有涉及Hedgehog信号通路。重复基因dmrt2b参与Hedgehog信号通路的发现为重复基因的功能歧化提供了一个典型实例,因而对进一步探讨重复基因功能歧化和基因新功能产生具有重要的启发意义。
该研究得到国家基础研究973计划等项目的资助,主要是由博士研究生刘沙等完成,研究论文9月30日在《公共科学图书馆·综合》(PLoS ONE)在线发表。(生物谷Bioon.com)
生物谷推荐原始出处:
PLoS ONE 4(9): e7261. doi:10.1371/journal.pone.0007261
Fish-Specific Duplicated dmrt2b Contributes to a Divergent Function through Hedgehog Pathway and Maintains Left-Right Asymmetry Establishment Function
Sha Liu, Zhi Li, Jian-Fang Gui*
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Wuhan, China
Gene duplication is thought to provide raw material for functional divergence and innovation. Fish-specific dmrt2b has been identified as a duplicated gene of the dmrt2a/terra in fish genomes, but its function has remained unclear. Here we reveal that Dmrt2b knockdown zebrafish embryos display a downward tail curvature and have U-shaped somites. Then, we demonstrate that Dmrt2b contributes to a divergent function in somitogenesis through Hedgehog pathway, because Dmrt2b knockdown reduces target gene expression of Hedgehog signaling, and also impairs slow muscle development and neural tube patterning through Hedgehog signaling. Moreover, the Dmrt2b morphants display defects in heart and visceral organ asymmetry, and, some lateral-plate mesoderm (LPM) markers expressed in left side are randomized. Together, these data indicate that fish-specific duplicated dmrt2b contributes to a divergent function in somitogenesis through Hedgehog pathway and maintains the common function for left-right asymmetry establishment.