ALTERNATE SPLICING PATHWAYS OF THE IMMUNOGLOBULIN HEAVY-CHAIN TRANSCRIPT OF A TELEOST FISH, ICTALURUS-PUNCTATUS

Previously we sequenced a partial cDNA clone encoding the 3' region of the message for the membrane receptor form of the heavy (mu) chain of the channel catfish which indicated that the first transmembrane (TM1) exon is spliced directly to the C-mu-3 exon and not into a cryptic site within the CH4 exon, as occurs in other vertebrates. Studies utilizing polymerase chain reaction analysis of mRNA and further analysis of cDNA clones now confirm that the only detectable splicing pattern used in mu-m production by the channel catfish utilizes this C-mu-3 --> TM1 pathway of pre-mRNA splicing.