title: Cloning and structural analysis of IgM (mu chain) and the heavy chain V region repertoire in the marsupial Monodelphis domestica.
abstract: To address the question of the Ig isotype repertoire of non placental mammals, we have examined the Ig expression in the marsupial Monodelphis domestica (grey short tailed opossum). Screening of an opossum spleen cDNA library has previously led to the isolation of full length clones for opossum IgG (gamma chain), IgE (epsilon chain) and IgA (alpha chain). We now present the isolation of several cDNA clones encoding the entire constant regions of the opossum IgM (mu chain). A comparative analysis of the amino acid sequences for IgM from various animal species showed that opossum IgM, within the various animals studied, is the most divergent member of its Ig class. However, it still conforms to the general structure of IgM in other vertebrates. Four Ig classes have now been identified in opossum and only one isotype is apparently present within each Ig class, IgM, IgG, IgA and IgE. Opossum has previously been shown to have a limited VH region diversity, with only two V gene families. Both of these belong to the group III of mammalian VH sequences. This limitation in variability is to some extent compensated for by a large variation in D, P and N regions, both in size and in sequence. However, evidence for the expression of only two functional J segments has so far been detected, which indicates a rather limited diversity also of the J segments in the opossum.
authors.affiliation: Department of Cell and Molecular Biology, University of Uppsala, Biomedical Center, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Aveskogh
authors.forename: L
authors.initials: L
authors.lastname: Pilström
authors.forename: L
authors.initials: L
authors.lastname: Hellman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D006801:Humans; D007075:Immunoglobulin M / Q000145:classification / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000145:classification / Q000235:genetics*; D007148:Immunoglobulin mu-Chains / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D009893:Opossums / Q000235:genetics / Q000276:immunology*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D018076:DNA, Complementary; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D007148:Immunoglobulin mu-Chains