title: cDNA sequences and organization of IgM heavy chain genes in two holostean fish.
abstract: Immunoglobulin M heavy chain (mu) sequences of two holostean fish, the bowfin, Amia calva, and the longnose gar, Lepisosteus osseus, were amplified from spleen mRNA by RACE-PCR, cloned, and sequenced. Each mu chain showed the conserved four constant domain structure typical of a secreted mu chain. Southern blot analyses with specific heavy chain variable (VH) and constant (CH) region probes suggest that both fish possess an IgH locus that resembles that of the teleosts, amphibians, and mammals in its organization. The overall sequence similarity of gar and bowfin mu chains was 60% and 48% at the nucleotide and amino acid levels, respectively, while similarity to the mu chains of teleosts and elasmobranchs was lower. The bowfin mu chain possesses a distinctive proline-rich sequence at the C mu 1/C mu 2 boundary; a shorter proline-rich sequence is present at this position in the gar mu chain. Both gar and bowfin show, in their C mu 4 sequences, motifs that could serve as cryptic splice donor sites for the production of mRNA encoding the membrane-bound form of the mu chains, and the bowfin also shows a potential cryptic splice donor site in the C mu 3 exon.
authors.affiliation: Department of Microbiology, University of Mississippi Medical Center, Jackson 39216-4505, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Wilson
authors.forename: E
authors.initials: E
authors.lastname: van Ravenstein
authors.forename: N W
authors.initials: NW
authors.lastname: Miller
authors.forename: L W
authors.initials: LW
authors.lastname: Clem
authors.forename: D L
authors.initials: DL
authors.lastname: Middleton
authors.forename: G W
authors.initials: GW
authors.lastname: Warr
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000302:isolation & purification*; D005399:Fishes / Q000235:genetics*; D007127:Immunoglobulin Constant Regions / Q000235:genetics; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007075:Immunoglobulin M / Q000235:genetics*; D007148:Immunoglobulin mu-Chains / Q000235:genetics; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D018076:DNA, Complementary; D007127:Immunoglobulin Constant Regions; D007143:Immunoglobulin Heavy Chains; D007075:Immunoglobulin M; D007148:Immunoglobulin mu-Chains