Diverse splicing pathways of the membrane IgHM pre-mRNA in a Chondrostean, the Siberian sturgeon.
Teleosts and tetrapods have evolved different splice patterns to generate their membrane-bound IgM. In the tetrapod lineage, the first transmembrane exon is spliced to an internal cryptic site located close to the end of the fourth constant exon. Because teleosts lack this site they use the regular 3'-splice site of the CH3 exon instead. We characterized the mum splicing patterns in a Chondrostean, the Siberian sturgeon. We observed a surprising diversity of splice patterns, the TM1 exon being spliced to a cryptic site at the end of CH4, to a cryptic site in CH3 or to the 3'-end of CH1. These different pathways lead to mIGHM transcripts encoding four, two or one complete C-domain(s), respectively. The short variant CH1-TM1 was found only in VH2 positive transcripts, while the two other variants were observed for IgHM transcripts expressing all VH families. These results shed light on the evolution of IgM splicing pathways.
Lundqvist
Mats
M
Immunology Programme, Department of Cell and Molecular Biology, BMC, Uppsala University, Box 596, S-751 24 Uppsala, Sweden.
Strömberg
Siv
S
Bouchenot
Catherine
C
Pilström
Lars
L
Boudinot
Pierre
P
D017398:Alternative Splicing / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002462:Cell Membrane / Q000276:immunology; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics; D005399:Fishes / Q000235:genetics / Q000276:immunology*; D007143:Immunoglobulin Heavy Chains / Q000145:classification / Q000235:genetics* / Q000276:immunology; D007075:Immunoglobulin M / Q000145:classification / Q000235:genetics* / Q000276:immunology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012322:RNA Precursors / Q000235:genetics*; D016415:Sequence Alignment
D007143:Immunoglobulin Heavy Chains; D007075:Immunoglobulin M; D012322:RNA Precursors