Evidence of IgY subclass diversification in snakes: evolutionary implications

• Published in: The Journal of immunology (1950) 2012-10, Vol.189 (7), p.3557-3565
• Main Authors: Wang, Tao, Sun, Yi, Shao, Wenwei, Cheng, Gang, Li, Lingxiao, Cao, Zubing, Yang, Zhi, Zou, Huiying, Zhang, Wei, Han, Binyue, Hu, Yang, Ren, Liming, Hu, Xiaoxiang, Guo, Ying, Fei, Jing, Hammarström, Lennart, Li, Ning, Zhao, Yaofeng
• Format: Article
• Language: English
• Subjects: Animals; Antibody Diversity - immunology; Boidae - immunology; Elaphe; Evolution, Molecular; Immunoglobulins - biosynthesis; Immunoglobulins - classification; Medicin och hälsovetenskap; Mice; Mice, Inbred BALB C; Molecular Sequence Data; Phylogeny; Python molurus; Taeniura
• ISSN: 0022-1767; 1550-6606; 1550-6606
• DOI: 10.4049/jimmunol.1200212

Mammalian IgG and IgE are thought to have evolved from IgY of nonmammalian tetrapods; however, no diversification of IgY subclasses has been reported in reptiles or birds, which are phylogenetically close to mammals. To our knowledge, we report the first evidence of the presence of multiple IgY-encoding (υ) genes in snakes. Two υ genes were identified in the snake Elaphe taeniura, and three υ genes were identified in the Burmese python (Python molurus bivittatus). Although four of the υ genes displayed a conventional four-H chain C region exon structure, one of the υ genes in the Burmese python lacked the H chain C region 2 exon, thus exhibiting a structure similar to that of the mammalian γ genes. We developed mouse mAbs specific for the IgY1 and IgY2 of E. taeniura and showed that both were expressed in serum; each had two isoforms: one full-length and one truncated at the C terminus. The truncation was not caused by alternative splicing or transcriptional termination. We also identified the μ and δ genes, but no α gene, in both snakes. This study provides valuable clues for our understanding of Ig gene evolution in tetrapods.