Gene duplication is thought to provide raw material for functional divergence and innovation. Since fish experiences an additional whole-genome duplication event, numerous duplicated genes have been identified, and the functional divergence has been revealed in some duplicated genes. Therefore, fish duplicated genes provide appropriate materials for functional divergence and innovation.  

Recently, researchers from the Research Group of Fish Developmental Genetics and Cell Engineering (Head: Prof. Jianfang GUI) have achieved new progress on divergent function of duplicated genes. First, they identified a duplicated gene dmrt2b in Gibel Carp, and then they studied its function and mechanism by using mopholino knockdown in zebrafish. They found zebrafish dmrt2b expressed during somitogenesis, and dmrt2b knockdown leads to defects in somitogenesis and impairs slow muscle development.  

Further study found that, the expression of members of Hedgehog signaling pathway (ptc1, nkx2.2a, etc.) were down-regulated, suggesting that dmrt2b contributes to this function in somitogenesis through Hedgehog pathway. However, these defects were not observed in dmrt2a knockdown embryos. At the same time, both dmrt2b and dmrt2a knockdown embryos display defects in the establishment of left-right asymmetry of the body plan: defects in heart and visceral organ asymmetry and some lateral-plate mesoderm (LPM) markers expressed in left side are randomized.  

These data indicate that fish-specific duplicated gene dmrt2b and dmrt2a play common overlapping functions in the establishment of left-right asymmetry of the body plan, and dmrt2b contributes to a divergent function in somitogenesis through Hedgehog pathway, but dmrt2a does not contribute to Hedgehog pathway. Clarifying divergent function of the fish-specific duplicated gene dmrt2b, which through Hedgehog pathway, provides a significant and interesting case for functional divergence of duplicate genes and enlightens further study in functional divergence and innovation of duplicate genes. 

This work was supported by grants from the National Major Basic Research Program (973 Program) and the like, and mainly accomplished by IHB graduate student Sha LIU. The paper was published online in PLoS ONE on September 30, 2009.  

Related link: 

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0007261 

A schematic diagram illustrating the divergent function of dmrt2b