Sammendrag
Many biological processes in fish, such as growth, feeding, and maturation, are strongly dependent on environmental conditions and seasonal changes. We have recently identified several circadian genes rhythmically expressed in Atlantic cod fast muscle, which indicate the presence of a functional clock system in muscle that may influence other gene networks. We have previously observed a circadian oscillation of some transcripts in cultured myosatellite cells kept either under continuous light or constant darkness. In order to understand this preliminary observation in a global perspective, this study was designed to examine changes in the whole muscle transcriptome of Atlantic cod during a circadian cycle by next-generation sequencing technology. Whole transcriptome libraries from muscle samples (0-, 6-, 12-, 18- and 24 h) were prepared from cod reared under a 12L:12N light regime and sequenced using the Ion Torrent PGM™. There were transcriptome differences throughout the day and sequence reads of some genes showed periodicity and cyclic patterns. For example, the muscle transcription factors myoD and myoG showed higher expression at night than at daytime. The results of our study unveiled the circadian influence on the muscle transcriptome profile of cod. Further, it might be possible that this circadian rhythmicity of the transcriptome is being regulated by the genes of the proposed clock system in cod muscle.
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