LEDER, EH; SILVERSTEIN, JT; National Center for Cool and Cold Water Aquaculture, Leetown, West Virginia: The pro-opiomelanocortin genes in rainbow trout Oncorhynchus mykiss

The pro-opiomelanocortin gene (POMC) is a precursor for several important peptide hormones involved in a variety of functions ranging from stress response to energy homeostasis. In mammals and fish, the POMC-derived peptide melanocyte stimulating hormone (MSH) is known to be involved in appetite suppression through its interaction with melanocortin-4 receptors. The details of feed intake regulation in fishes are beginning to be elucidated and many of the same pathways that have been observed in mammals are being investigated in fish. In salmonid fishes such as the rainbow trout, genome duplication has added another degree of complexity when trying to determine gene function and homology with other vertebrates. This is true of the POMC gene. Two copies of the POMC gene have been identified, A and B, presumably resulting from the salmonid duplication. However, while investigating POMC for its role in the feeding response of rainbow trout, three distinct cDNA transcripts were identified for POMC-A. One of these transcripts is likely a splice-variant, but the other two appear to be distinct enough to be separate genes. Out of 88 deduced amino acids of the cDNA sequence, 13 amino acids varied between the two cDNA fragments. Using primers specific to one copy of POMC-A, dissociation curves of quantitative PCR revealed two distinct peaks in some tissues suggesting two products were amplified, so in addition to the duplicated genes, additional splice variants or alleles may be present.