title: Temperature during early development has long-term effects on microRNA expression in Atlantic cod.
abstract: BACKGROUND
  Environmental temperature has serious implications in life cycle of aquatic ectotherms. Understanding the molecular mechanisms of temperature acclimation and adaptation of marine organisms is of the uttermost importance for ecology, fisheries, and aquaculture, as it allows modeling the effects of global warming on population dynamics. Regulatory molecules are major modulators of acclimation and adaptation; among them, microRNAs (miRNAs) are versatile and substantial contributors to regulatory networks of development and adaptive plasticity. However, their role in thermal plasticity is poorly known. We have asked whether the temperature and its shift during the early ontogeny (embryonic and larval development) affect the miRNA repertoire of Atlantic cod (Gadus morhua), and if thermal experience has long-term consequences in the miRNA profile.
  
  
  RESULTS
  We characterized miRNA during different developmental stages and in juvenile tissues using next generation sequencing. We identified 389 putative miRNA precursor loci, 120 novel precursor miRNAs, and 281 mature miRNAs. Some miRNAs showed stage- or tissue-enriched expression and miRNAs, such as the miR-17 ~ 92 cluster, myomiRs (miR-206), neuromiRs (miR-9, miR-124), miR-130b, and miR-430 showed differential expression in different temperature regimes. Long-term effect of embryonic incubation temperature was revealed on expression of some miRNAs in juvenile pituitary (miR-449), gonad (miR-27c, miR-30c, and miR-200a), and liver (let-7 h, miR-7a, miR-22, miR-34c, miR-132a, miR-192, miR-221, miR-451, miR-2188, and miR-7550), but not in brain. Some of differentially expressed miRNAs in the liver were confirmed using LNA-based rt-qPCR. The effect of temperature on methylation status of selected miRNA promoter regions was mostly inconclusive.
  
  
  CONCLUSIONS
  Temperature elevation by several degrees during embryonic and larval developmental stages significantly alters the miRNA profile, both short-term and long-term. Our results suggest that a further rise in seas temperature might affect life history of Atlantic cod.
authors.affiliation: University of Nordland, Faculty of Biosciences and Aquaculture, Post Box 1490, 8049, Bodø, Norway. ttb@uin.no.
authors.forename: Teshome Tilahun
authors.initials: TT
authors.lastname: Bizuayehu
authors.affiliation: University of Nordland, Faculty of Biosciences and Aquaculture, Post Box 1490, 8049, Bodø, Norway. steinar.johansen@uit.no.|Arctic University of Norway, FHS, RNA Lab, Dept Med Biol, N-9037, Tromsø, Norway. steinar.johansen@uit.no.
authors.forename: Steinar D
authors.initials: SD
authors.lastname: Johansen
authors.affiliation: Nofima AS, Muninbakken 9-13, P.O. box 6122, NO, 9291, Tromsø, Norway. Velmurugu.Puvanendran@nofima.no.
authors.forename: Velmurugu
authors.initials: V
authors.lastname: Puvanendran
authors.affiliation: Nofima AS, Muninbakken 9-13, P.O. box 6122, NO, 9291, Tromsø, Norway. Hilde.Toften@nofima.no.
authors.forename: Hilde
authors.initials: H
authors.lastname: Toften
authors.affiliation: University of Nordland, Faculty of Biosciences and Aquaculture, Post Box 1490, 8049, Bodø, Norway. igor.babiak@uin.no.
authors.forename: Igor
authors.initials: I
authors.lastname: Babiak
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian; D047108:Embryonic Development / Q000235:genetics; D048389:Gadus morhua / Q000235:genetics* / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks; D059014:High-Throughput Nucleotide Sequencing; D035683:MicroRNAs / Q000096:biosynthesis* / Q000235:genetics; D013696:Temperature
chemical_list: D035683:MicroRNAs