title: Migration-related phenotypic divergence is associated with epigenetic modifications in rainbow trout.
abstract: Migration is essential for the reproduction and survival of many animals, yet little is understood about its underlying molecular mechanisms. We used the salmonid Oncorhynchus mykiss to gain mechanistic insight into smoltification, which is a morphological, physiological and behavioural transition undertaken by juveniles in preparation for seaward migration. O. mykiss is experimentally tractable and displays intra- and interpopulation variation in migration propensity. Migratory individuals can produce nonmigratory progeny and vice versa, indicating a high degree of phenotypic plasticity. One potential way that phenotypic plasticity might be linked to variation in migration-related life history tactics is through epigenetic regulation of gene expression. To explore this, we quantitatively measured genome-scale DNA methylation in fin tissue using reduced representation bisulphite sequencing of F2 siblings produced from a cross between steelhead (migratory) and rainbow trout (nonmigratory) lines. We identified 57 differentially methylated regions (DMRs) between smolt and resident O. mykiss juveniles. DMRs were high in magnitude, with up to 62% differential methylation between life history types, and over half of the gene-associated DMRs were in transcriptional regulatory regions. Many of the DMRs encode proteins with activity relevant to migration-related transitions (e.g. circadian rhythm pathway, nervous system development, protein kinase activity). This study provides the first evidence of a relationship between epigenetic variation and life history divergence associated with migration-related traits in any species.
authors.affiliation: Department of Animal Science, University of California - Davis, Davis, CA, 95616.
authors.forename: Melinda R
authors.initials: MR
authors.lastname: Baerwald
authors.affiliation: Department of Animal Science, University of California - Davis, Davis, CA, 95616.
authors.forename: Mariah H
authors.initials: MH
authors.lastname: Meek
authors.affiliation: School of Natural Sciences, University of California - Merced, Merced, CA, 95343.
authors.forename: Molly R
authors.initials: MR
authors.lastname: Stephens
authors.affiliation: GlaxoSmithKline, Cancer Epigenetics Discovery Performance Unit, Collegeville, PA 19426.
authors.forename: Raman P
authors.initials: RP
authors.lastname: Nagarajan
authors.affiliation: Department of Animal Science, University of California - Davis, Davis, CA, 95616.
authors.forename: Alisha M
authors.initials: AM
authors.lastname: Goodbla
authors.affiliation: Department of Animal Science, University of California - Davis, Davis, CA, 95616.
authors.forename: Katharine M H
authors.initials: KMH
authors.lastname: Tomalty
authors.affiliation: School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164.
authors.forename: Gary H
authors.initials: GH
authors.lastname: Thorgaard
authors.affiliation: Department of Animal Science, University of California - Davis, Davis, CA, 95616.
authors.forename: Bernie
authors.initials: B
authors.lastname: May
authors.affiliation: Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd E, Seattle, WA 98112.
authors.forename: Krista M
authors.initials: KM
authors.lastname: Nichols
mesh_terms: D025041:Animal Migration; D000818:Animals; D018899:CpG Islands; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D015870:Gene Expression; D008297:Male; D017686:Oncorhynchus mykiss / Q000235:genetics*; D010641:Phenotype; D017422:Sequence Analysis, DNA
keywords: Oncorhynchus mykiss; epigenetics; life history variation; plasticity; smoltification