title: Gene expression profiling in melanised sites of Atlantic salmon fillets.
abstract: Black spots, which deteriorate quality of Atlantic salmon fillets represent a significant problem for commercial aquaculture. These areas are characterized with accumulation of melanomacrophages, occasional formation of granulomas and substitution of skeletal muscle with connective tissue. A number of possible causative agents have been suggested including vaccination and infection with piscine reovirus (PRV). We report transcriptome profiling of melanised foci with oligonucleotide DNA microarrays. Analyses revealed a multitude of differentially expressed genes associated with melanogenesis, metabolic changes and formation of scar. The immune profile was characterized with inflammation, preferential activation of classical complement pathway, MHCII and helper T cells combined with strong B cells responses and massive induction of immunoglobulins; innate antiviral responses were relatively weak in sharp contrast to PRV-caused heart and skeletal muscle inflammation and other viral infections. A panel of immune genes with specific activation in dark spots was found, most up-regulated were CD209-like lectin (44-fold) and prostaglandin reductase (11-fold). Further, RNA sequencing was performed on the same material to search for the presence of putative pathogens. Transcripts of prokaryotic rRNA with exclusive or preferential location in black spots were found. Results suggest mild chronic inflammation initiated with trauma, bacterial or viral infection followed by sustained immune responses to opportunistic microorganisms as a realistic scenario of dark spots formation.
authors.affiliation: Nofima AS, P.O. Box 5010, N-1432, Ås, Norway. Electronic address: Aleksei.Krasnov@nofima.no.
authors.forename: Aleksei
authors.initials: A
authors.lastname: Krasnov
authors.affiliation: Nofima AS, P.O. Box 5010, N-1432, Ås, Norway.
authors.forename: Hooman
authors.initials: H
authors.lastname: Moghadam
authors.affiliation: Nofima AS, P.O. Box 5010, N-1432, Ås, Norway.
authors.forename: Thomas
authors.initials: T
authors.lastname: Larsson
authors.affiliation: Nofima AS, P.O. Box 5010, N-1432, Ås, Norway; Sechenov Institute of Evolutionary Physiology and Biochemistry, M. Toreza av. 44, Saint Petersburg, 194223, Russia.
authors.forename: Sergey
authors.initials: S
authors.lastname: Afanasyev
authors.affiliation: Nofima AS, P.O. Box 5010, N-1432, Ås, Norway.
authors.forename: Turid
authors.initials: T
authors.lastname: Mørkøre
mesh_terms: D000818:Animals; D005393:Fish Diseases / Q000276:immunology* / Q000473:pathology / Q000821:virology; D020869:Gene Expression Profiling / Q000662:veterinary; D005786:Gene Expression Regulation / Q000276:immunology*; D007249:Inflammation / Q000276:immunology* / Q000473:pathology / Q000821:virology; D018482:Muscle, Skeletal / Q000276:immunology / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis / Q000662:veterinary; D012087:Reoviridae / Q000502:physiology*; D012088:Reoviridae Infections / Q000276:immunology / Q000473:pathology / Q000662:veterinary* / Q000821:virology; D020317:Salmo salar / Q000235:genetics* / Q000276:immunology*; D017747:Seafood / Q000032:analysis / Q000821:virology; D017423:Sequence Analysis, RNA / Q000662:veterinary
keywords: Atlantic salmon; Inflammation; Melanin; Microarray; NGS; Skeletal muscle