Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8212
Title: Ontogenetic changes in embryonic and brain gene expression in progeny produced from migratory and resident Oncorhynchus mykiss
Author: Garrett McKinney, M. Hale, Giles W. Goetz, Michael Gribskov, Frank P. Thrower, Krista M. Nichols
Publication Year: 2015
Journal: Molecular Ecology
Volume: 24
Pages: 1792-1809
Keywords: genomics,RNAseq,steelhead

 Little information has been gathered regarding the ontogenetic changes that contribute to differentiation between resident and migrant individuals, particularly before gross morphological and physiological changes are evident.  The aim of this study was to explore differentiation in gene expression during early development in two populations of rainbow trout with different life histories, in a tissue known to integrate environmental signals with molecular responses to those signals for complex developmental processes and behaviors.  Using whole embryos and brain tissue, we generated a reference transcriptome, resulting in 30,177 genes that passed count thresholds.  In total, 1,984 genes showed differential expression between cross types, over four time points in the first year of development.  The greatest number of differentially expressed genes occurred in the brain transcripts between males of each cross type at eight months of age, in the spring a full year before the obvious physiological transformation from stream-dwelling parr to seawater adaptable smolts begins.  There were considerable effects of sex and age on patterns of differential gene expression between progeny from different crosses.  Within brains and whole embryos, differential expression was identified in genes that have been previously associated with migration vs. residency, as well as in previously unassociated genes that have plausible connections with life history divergence.  Notably, pathway analysis revealed coordinated differential expression in genes related to phototransduction that could modulate responsiveness to photoperiod, and play a role in modulating circadian rhythms.  The role for early differentiation in light sensitivity and biological rhythms is particularly intriguing in understanding the early brain processes involved in differentiation of migratory and resident life history types.