Submitted to: Animal Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/7/2007
Publication Date: 10/1/2007
Citation: Hoghadam, H., Ferguson, M.M., Rexroad III, C.E., Coulibaly, I., Danzmann, R.G. 2007. Genomic Organization of the igf1, igf2, myf5, myf6 and grf/pacap Genes across Salmoninae Genera. Animal Genetics. 38(5):527-532. Interpretive Summary: Genome duplications events have occurred throughout the evolutionary histories of many organisms, sometimes on multiple occasions. In such an event, through some biological phenomenon the size of the genome doubles from diploid to a tetraploid state, and then over time evolves into a new diploid genome. Throughout the evolutionary history of salmonids there have been two whole genome duplication events, one common to bony fishes and another specific to the genera including rainbow trout, Atlantic salmon, and Arctic Charr. As a result, it is likely that salmonid genomes contain multiple copies of genes compared to some other bony fishes. In this report, we utilized genetic mapping to determine the gene complements of insulin-like growth factor, myogenic regulatory factor, and growth hormone-releasing factor/pituitary adenylate cyclase-activating polypeptide in the genomes of these species. These genes are likely to affect important production traits and having gene complement information is crucial to understanding how they impact biological processes.
Technical Abstract: The whole genome duplication in the ancient ray finned fish and the subsequent tetraploidization in the salmonids’ ancestor has complicated the genomic and the candidate gene studies in these organisms as many genes are present with multiple copies throughout their genomes. In an attempt to identify genes with a potential influence on growth and development, we investigated the genomic position of insulin like growth factors 1 and 2 (igf1, igf2), myogenic factors 5 and 6 (myf5, myf6) and the growth hormone-releasing factor/pituitary adenylate cyclase-activating polypeptide (grf/pacap) in three salmonid species, rainbow trout (Oncorhynchus mykiss), Atlantic salmon (Salmo salar) and Arctic charr (Salvelinus alpinus). Our results suggest a tight association between the igf1, myf5 and myf6 in all species investigated. We further localized the duplicated copies of the igf1 to the homeologous linkage groups RT-7/15 in rainbow trout, AC-3/24 in Arctic charr, and the two copies of the myf6 to linkage groups AS-22/24 in Atlantic salmon. Also the homology identified based on the localization of the grf/pacap to RT-7, AS-31, AC-27 and the igf2 to RT-27, AS-2 and AC-4, is consistent with the previously reported homologies identified among these chromosomal segments using other genetic markers. However, localization of the second copy of the grf/pacap to RT-19 and AC-14 and also the duplicated copy of the igf2 to AC-19, suggest a possible new homology/homeology between these chromosomes. Alternatively, these results might be an indication of a more ancient polyploidization event that occurred deep in the ray finned fish lineage.