重復(fù)基因被認為是基因功能歧化和新功能產(chǎn)生的源泉,。魚類特有的基因組加倍事件產(chǎn)生了大量的重復(fù)基因,，這些重復(fù)基因為基因功能歧化和新功能產(chǎn)生提供了良好材料。
最近,，中科院水生所由桂建芳研究員主持的魚類發(fā)育遺傳學(xué)學(xué)科組在魚類重復(fù)基因功能歧化研究上取得了重要進展,。他們首先在養(yǎng)殖魚類銀鯽中發(fā)現(xiàn)鑒定出重復(fù)基因dmrt2b，繼而通過morpholino敲降策略在斑馬魚中研究該基因的功能及其作用機制,。他們發(fā)現(xiàn)斑馬魚dmrt2b在體節(jié)發(fā)生時期表達,，在dmrt2b敲降的胚胎中，體節(jié)發(fā)生出現(xiàn)明顯畸形,，且dmrt2b敲降胚胎中慢肌(slow muscle)發(fā)育受到嚴重影響,。進一步研究發(fā)現(xiàn)，Hedgehog信號通路成員（ptc1,nkx2.2a等）在dmrt2b敲降的胚胎中表達下調(diào),，提示dmrt2b是通過Hedgehog信號通路參與以上體節(jié)發(fā)生過程,。以上影響在dmrt2a敲降的胚胎中沒有發(fā)現(xiàn)。同時,，dmrt2b和dmrt2a敲降的胚胎都表現(xiàn)出軀體左右軸建立上的缺陷：內(nèi)臟位置失去偏向性以及在身體左側(cè)特異表達的基因在右側(cè)或兩側(cè)同時表達等,。
這些研究表明，魚類特有的重復(fù)基因dmrt2b和dmrt2a雖都參與了軀體左右不對稱建立的過程,，但dmrt2b通過Hedgehog信號通路參與體節(jié)發(fā)生過程,，而dmrt2a沒有涉及Hedgehog信號通路。重復(fù)基因dmrt2b參與Hedgehog信號通路的發(fā)現(xiàn)為重復(fù)基因的功能歧化提供了一個典型實例，因而對進一步探討重復(fù)基因功能歧化和基因新功能產(chǎn)生具有重要的啟發(fā)意義。
該研究得到國家基礎(chǔ)研究973計劃等項目的資助,，主要是由博士研究生劉沙等完成,，研究論文9月30日在《公共科學(xué)圖書館·綜合》（PLoS ONE）在線發(fā)表,。（生物谷Bioon.com）
生物谷推薦原始出處：
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.
