title: De novo assembly and transcriptome analysis of Atlantic salmon macrophage/dendritic-like TO cells following type I IFN treatment and Salmonid alphavirus subtype-3 infection.
abstract: BACKGROUND
  Interferons (IFN) are cytokines secreted by vertebrate cells involved in activation of signaling pathways that direct the synthesis of antiviral genes. To gain a global understanding of antiviral genes induced by type I IFNs in salmonids, we used RNA-seq to characterize the transcriptomic changes induced by type I IFN treatment and salmon alphavirus subtype 3 (SAV-3) infection in TO-cells, a macrophage/dendritic like cell-line derived from Atlantic salmon (Salmo salar L) head kidney leukocytes.
  
  
  RESULTS
  More than 23 million reads generated by RNA-seq were de novo assembled into 58098 unigenes used to generate a total of 3149 and 23289 differentially expressed genes (DEGs) from TO-cells exposed to type I IFN treatment and SAV-3 infection, respectively. Although the DEGs were classified into genes associated with biological processes, cellular components and molecular function based on gene ontology classification, transcriptomic changes reported here show upregulation of genes belonging to the canonical type I IFN signaling pathways together with a broad spectrum of antiviral genes that block virus replication in host cells. In addition, the transcriptome shows a profile of genes associated with apoptosis as well as genes that activate adaptive immunity. Further, our findings show that the profile of genes expressed by TO-cells is comparable to orthologous genes expressed by mammalian macrophages and dendritic cells in response to type I IFNs. Twenty DEGs randomly selected for qRT-PCR confirmed the validity of the transcriptomic changes detected by RNA-seq by showing that the genes upregulated by RNA-seq were also upregulated by qRT-PCR and that genes downregulated by RNA-seq were also downregulated by qRT-PCR.
  
  
  CONCLUSIONS
  The de novo assembled transcriptome presented here provides a global description of genes induced by type I IFNs in TO-cells that could serve as a repository for future studies in fish cells. Transcriptome analysis shows that a large proportion of IFN genes expressed in this study are comparable to IFNs genes expressed in mammalia. In addition, the study shows that SAV-3 is a potent inducer of type I IFNs and that the responses it induces in TO-cells could serve as a model for studying IFN responses in salmonids.
authors.affiliation: Faculty of Veterinary Medicine and Biosciences, Department of Basic Sciences and Aquatic Medicine, Section of Aquatic Medicine and Nutrition, Norwegian University of Life Sciences, P.O. Box 8146, Dep. NO-0033, Oslo, Norway. cheng.xu@nmbu.no.
authors.forename: Cheng
authors.initials: C
authors.lastname: Xu
authors.affiliation: Faculty of Veterinary Medicine and Biosciences, Department of Basic Sciences and Aquatic Medicine, Section of Aquatic Medicine and Nutrition, Norwegian University of Life Sciences, P.O. Box 8146, Dep. NO-0033, Oslo, Norway. oystein.evensen@nmbu.no.
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Evensen
authors.affiliation: Faculty of Veterinary Medicine and Biosciences, Department of Basic Sciences and Aquatic Medicine, Section of Aquatic Medicine and Nutrition, Norwegian University of Life Sciences, P.O. Box 8146, Dep. NO-0033, Oslo, Norway. hetroney.mweemba.munangandu@nmbu.no.
authors.forename: Hetron Mweemba
authors.initials: HM
authors.lastname: Munang'andu
mesh_terms: D018354:Alphavirus Infections / Q000188:drug therapy / Q000235:genetics / Q000662:veterinary; D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology / Q000627:therapeutic use; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D005393:Fish Diseases / Q000188:drug therapy / Q000235:genetics; D007370:Interferon Type I / Q000494:pharmacology* / Q000627:therapeutic use; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012313:RNA / Q000737:chemistry / Q000302:isolation & purification; D060888:Real-Time Polymerase Chain Reaction; D020317:Salmo salar / Q000378:metabolism*; D017423:Sequence Analysis, RNA; D015398:Signal Transduction / Q000187:drug effects; D059467:Transcriptome / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000998:Antiviral Agents; D007370:Interferon Type I; D012313:RNA