Evidence of IgY Subclass Diversification in Snakes: Evolutionary Implications.

Mammalian IgG and IgE are thought to have evolved from IgY of nonmammalian tetrapods; however, no diversification of IgY sub-classes 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 (v) genes in snakes. Two v genes were identified in the snake Elaphe taeniura, and three v genes were identified in the Burmese python (Python molurus bivittatus). Although four of the v genes displayed a conven-tional four-H chain C region exon structure, one of the v genes in the Burmese python lacked the H chain C region 2 exon, thus exhibiting a structure similar to that of the mammalian 7 genes. We developed mouse mAbs specific for the IgYl 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 (jl and 8 genes, but no a gene, in both snakes. This study provides valuable clues for our understanding of Ig gene evolution in tetrapods. [ABSTRACT FROM AUTHOR]