title: The complete salmonid IGF-IR gene repertoire and its transcriptional response to disease.
abstract: The insulin-like growth factor (IGF) receptor (IGF-IR) is necessary for IGF signalling and has essential roles in cellular growth. In teleost fish, two distinct IGF-IR duplicates are conserved called IGF-IRa and IGF-IRb. However, while a salmonid-specific whole genome duplication (ssWGD) is known to have expanded several key genes within the IGF axis, its impact on the IGF-IR repertoire remains unresolved. Using bioinformatic and phylogenetic approaches, we establish that salmonids retain two IGF-IRa paralogues from ssWGD and a single IGF-IRb copy. We measured the tissue-specific and developmental transcriptional regulation of each IGF-IR gene, revealing tight co-expression between the IGF-IRa paralogues, but expression divergence comparing IGF-IRa and IGF-IRb genes. We also examined the regulation of each IGF-IR gene in fish challenged by bacterial and viral infections, adding to recent reports that the IGF axis has roles linking growth and immunity. While whole salmonid fry showed a small upregulation of IGF-IR expression during both types of infection, bacterial challenge caused striking downregulation of IGF-IRa1 and IGF-IRa2 in head kidney and spleen of adult fish, alongside genes coding IGF hormones, highlighting a strong repression of IGF-signalling in primary immune tissues. The reported immune-responsive regulation of IGF-IR genes adds to an emerging body of evidence that supports important cross-talk between master growth and immune pathways in vertebrates.
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, UK.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Alzaid
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, UK.
authors.forename: Samuel A M
authors.initials: SAM
authors.lastname: Martin
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, UK.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Macqueen
mesh_terms: D000818:Animals; D001424:Bacterial Infections / Q000276:immunology*; D049109:Cell Proliferation; D019295:Computational Biology; D005786:Gene Expression Regulation; D016678:Genome; D007113:Immunity, Innate / Q000235:genetics; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D010802:Phylogeny; D017451:Receptors, Somatomedin / Q000235:genetics* / Q000378:metabolism; D012487:Salmonidae / Q000235:genetics* / Q000276:immunology; D015398:Signal Transduction
chemical_list: D017451:Receptors, Somatomedin; D007335:Insulin-Like Growth Factor II