title: RNAseq analysis of fast skeletal muscle in restriction-fed transgenic coho salmon (Oncorhynchus kisutch): an experimental model uncoupling the growth hormone and nutritional signals regulating growth.
abstract: BACKGROUND
  Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (Gh) express Gh in multiple tissues which results in increased appetite and continuous high growth with satiation feeding. Restricting Gh-transgenics to the same lower ration (TR) as wild-type fish (WT) results in similar growth, but with the recruitment of fewer, larger diameter, muscle skeletal fibres to reach a given body size. In order to better understand the genetic mechanisms behind these different patterns of muscle growth and to investigate how the decoupling of Gh and nutritional signals affects gene regulation we used RNA-seq to compare the fast skeletal muscle transcriptome in TR and WT coho salmon.
  
  
  RESULTS
  Illumina sequencing of individually barcoded libraries from 6 WT and 6 TR coho salmon yielded 704,550,985 paired end reads which were used to construct 323,115 contigs containing 19,093 unique genes of which >10,000 contained >90 % of the coding sequence. Transcripts coding for 31 genes required for myoblast fusion were identified with 22 significantly downregulated in TR relative to WT fish, including 10 (vaspa, cdh15, graf1, crk, crkl, dock1, trio, plekho1a, cdc42a and dock5) associated with signaling through the cell surface protein cadherin. Nineteen out of 44 (43 %) translation initiation factors and 14 of 47 (30 %) protein chaperones were upregulated in TR relative to WT fish.
  
  
  CONCLUSIONS
  TR coho salmon showed increased growth hormone transcripts and gene expression associated with protein synthesis and folding than WT fish even though net rates of protein accretion were similar. The uncoupling of Gh and amino acid signals likely results in additional costs of transcription associated with protein turnover in TR fish. The predicted reduction in the ionic costs of homeostasis in TR fish associated with increased fibre size were shown to involve multiple pathways regulating myotube fusion, particularly cadherin signaling.
authors.affiliation: Scottish Oceans Institute, School of Biology, University of St Andrews, KY16 8LB, St Andrews, Scotland, UK. dgdlsc@st-andrews.ac.uk.
authors.forename: Daniel
authors.initials: D
authors.lastname: Garcia de la Serrana
authors.affiliation: Department of Fisheries and Oceans, Centre for Aquaculture and Environmental Research, 4160 Marine Drive, West Vancouver, BC, V7V 1N6, Canada. Robert.Devlin@dfo-mpo.gc.ca.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Devlin
authors.affiliation: Scottish Oceans Institute, School of Biology, University of St Andrews, KY16 8LB, St Andrews, Scotland, UK. iaj@st-andrews.ac.uk.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Johnston
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics* / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D013006:Growth Hormone / Q000096:biosynthesis / Q000235:genetics*; D059014:High-Throughput Nucleotide Sequencing; D006706:Homeostasis / Q000235:genetics; D006801:Humans; D008099:Liver / Q000254:growth & development / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000378:metabolism; D017684:Oncorhynchus kisutch / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D013006:Growth Hormone