Characterization of a non-classical MHC class II gene in the vulnerable Chinese egret (Egretta eulophotes)
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Genes of the major histocompatibility complex (MHC) are valuable makers of adaptive genetic variation in evolutionary ecology research, yet the non-classical MHC genes remain largely unstudied in wild vertebrates. In this study, we have characterized the non-classical MHC class II gene, Egeu-DAB4, in the vulnerable Chinese egret (Ciconiiformes, Ardeidae, Egretta eulophotes). Gene expression analyses showed that Egeu-DAB4 gene had a restricted tissue expression pattern, being expressed in seven examined tissues including the liver, heart, kidney, esophagus, stomach, gallbladder, and intestine, but not in muscle. With respect to polymorphism, only one allele of exon 2 was obtained from Egeu-DAB4 using asymmetric PCR, indicating that Egeu-DAB4 is genetically monomorphic in exon 2. Comparative analyses showed that Egeu-DAB4 had an unusual sequence, with amino acid differences suggesting that its function may differ from those of classical MHC genes. Egeu-DAB4 gene was only found in 30.56–36.56 % of examined Chinese egret individuals. Phylogenetic analysis showed a closer relationship between Egeu-DAB4 and the DAB2 genes in nine other ardeid species. These new findings provide a foundation for further studies to clarify the immunogenetics of non-classical MHC class II gene in the vulnerable Chinese egret and other ciconiiform birds.
KeywordsMHC Non-classical Class IIb Chinese egret Ardeidae
We thank Professor Frederic A. Troy II of the University of California (Davis) School of Medicine, for help in reviewing the manuscript. We also thank Yufei Dai who helped collect some samples for this study. This work was funded by the National Natural Science Foundation of China (Grant Nos. 41476113, 31000963, and 31272333) and by the Fujian Natural Science Foundation of China (2010Y2007).
All procedures involving collection of animal tissue in the wild were approved by the Administration Center for Wildlife Conservation in Fujian Province (FJWCA-1208) and were in accordance with its ethical standards.
Conflict of interest
We declare that we have no conflict of interests.
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