IDENTIFICATION OF A NEW CALCITONIN-GENE IN THE SALMON ONCORHYNCHUS-GORBUSCHA

Three isoforms of calcitonin (CT) exist in salmonids. Isohormones I an d II are expressed in the pink salmon Oncorhynchus gorbuscha. We repor t here the existence in this species of a CT gene and of its transcrip ts, which encode for a fourth isohormone, the salmon CT (sCT) IV. This new CT gene was identified by PCR from genomic DNA and by sequencing the amplified DNA. The expression of this CT gene was established in u ltimobranchial body and brain, by reverse transcription-PCR, hybridiza tion and sequencing. The sCT IV gene, like the sCT I gene, is a comple x transcription unit, containing exons encoding for a CT as a calciton in gene-related peptide (CGRP) molecule. The predicted peptide, sCT IV , has a greater homology with the eel CT and the sCT II than with the sCT I. Alignment of the sCT IV with other fish and chicken CT showed a mino acid modifications in similar positions as those found during evo lution. The predicted salmon CGRP IV peptide is highly homologous to t he known CGRP molecules in other species, confirming the high conserva tion of the molecule during evolution. This identification of a nerv s almon CT gene is interesting both for the therapeutic potential repres ented by the new molecules encoded by this gene and for phylogenetic s tudies.