Many types of antifreeze proteins evolved recently in some polar fishes， function to prevent ice growth in their freezing habitats. The independent arising of the fish antifreeze proteins provides a superior system to explore molecular and evolutionary mechanisms governing new gene evolution. A recent published study from Liangbiao Chen’s laboratory in the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and his colleague in University of Illinois showed that the type III antifreeze protein (AFPIII) of the Antarctic eelpouts evolved by neofunctionalization of an old sialic acid synthase (SAS) enzyme. A SAS gene in the ancestor of the Antarctic eelpouts was duplicated and one copy underwent N-terminal domain  deletion and reassigning of the translation start site that produced a primordial AFPIII gene. Sialic acid synthase activity and ice-inhibition analyses of the gene products showed that the gene structural change and functional improvements of the SAS copies are driven by an evolutionary force called Escape from Adaptive Conflict (EAC). It was found that a pre-existing but rudimentary ice-binding activity in the SAS C-terminal domain was naturally selected in the eelpouts when facing the Cenozoic cooling and freezing of the polar oceans. However, the selected improvement of ice-binding activity in the C-terminal domain of the ancestral SAS adversely affected the sialic acid synthase function. Duplication of the ancestral SAS gene and deletion of its N-terminal domain in the ancestral AFPIII copy permanently removed structural conflicts between the SAS function and the emerging ice-inhibition function, allowing full improvement of both functions. This study provided the first comprehensive example of neofunctionalization of gene duplicate driven by EAC. In addition, the finding that signal peptide could be generated from a hidden function by incorporating a new translation start site shed new lights on the molecular mechanisms by which signal for protein secretion could evolve. Ratification of the EAC model is important becasue it potentially provides a unified framework to explain how and why many evolutionary novelties arose. The work was published in Deng et. al. (2010). Evolution of an antifreeze protein by neofunctionalization under escape from adaptive conflict. Proc. Natl. Acad. Sci. USA. DOI:10.1073/pnas.1007883107.