Isolation and comparison of the IgM heavy chain constant regions from Australian (Trichosurus vulpecula) and American (Monodelphis domestica) marsupials

cDNAs encoding IgM heavy chain constant region (C mu) were isolated from two metatherians (marsupials) - the Australian common brushtail possum (Trichosurus vulpecula) and the South American grey short-tailed opossum (Monodelphis domestica). Analysis of the sequences suggested that they correspond to the secreted form of C mu in both species. The domain size and structure of the marsupial C mu sequences were compared with other C mu sequences acid a high degree of conservation throughout vertebrate evolution was observed. Amino acid sequence comparisons revealed a marked level of sequence similarity between the two marsupial sequences (79%), relatively high similarity between the marsupials and eutherians (63%), and lower similarities between marsupials and birds (45%), marsupials and amphibians (47%), marsupials and reptiles (45%) and marsupials and fish (37%), These data allow the incorporation of metatherians into the study of mammalian IgM evolution. (C) 1999 Elsevier Science Ltd. All rights reserved.