IMMUNOGLOBULIN HEAVY-CHAIN CDNA FROM THE TELEOST ATLANTIC COD (GADUS-MORHUA L) - NUCLEOTIDE-SEQUENCES OF SECRETORY AND MEMBRANE FORM SHOW AN UNUSUAL SPLICING PATTERN

Rabbit antibodies to Atlantic cod (Gadus morhua L.) immunoglobulin were affinity purified and used to screen cDNA libraries from spleen and head kidney mRNA. cDNA clones for both the secretory and membrane-bound heavy (H) chain were isolated, the nucleotide and deduced amino acid sequences of which are reported here. Comparisons of the cod secretory H chain amino acid sequence show 24%, 27%, 30% identity to the mu-chain of Mus, Xenopus and Ictalurus, respectively. The highest degree of identity was observed in the C(H)4 domain. The cDNA encoding the transmembrane form shows a novel splicing pattern where the TM1 exon is spliced directly onto the C(H)3 domain and not to the C(H)4 domain as in other animal groups. Southern blot analyses with V(H) and C probes on genomic DNA from cod erythrocytes indicate that there is a unique C gene but several V genes in the cod immunoglobulin H chain locus.