Daily Rhythmicity of Clock Gene Transcripts in Atlantic Cod Fast Skeletal Muscle

• Published in: PloS one Vol. 9; no. 6; p. e99172
• Main Authors: Lazado, Carlo C., Kumaratunga, Hiruni P. S., Nagasawa, Kazue, Babiak, Igor, Giannetto, Alessia, Fernandes, Jorge M. O.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 12.06.2014; Public Library of Science (PLoS)
• Subjects: Amino Acid Sequence; Analysis; Animals; Aquaculture; ARNTL Transcription Factors - genetics; ARNTL Transcription Factors - metabolism; Aromatic compounds; Base Sequence; Biology and Life Sciences; Circadian Clocks - genetics; Circadian rhythm; Circadian rhythms; Clock gene; CLOCK protein; Clock systems; Clocks; Cloning; Cod; Conservation; Cryptochromes; Cryptochromes - genetics; Cryptochromes - metabolism; Drosophila; Endocrine system; Evolutionary conservation; Fish; Fish Proteins - genetics; Fish Proteins - metabolism; Fishes; Gadus morhua; Gadus morhua - metabolism; Gadus morhua - physiology; Gene expression; Genes; Genetic engineering; Immune system; Insects; Light; Mammals; Molecular Sequence Data; Muscle, Skeletal - metabolism; Muscles; Musculoskeletal system; Myogenesis; NPAS2 protein; Nuclear Receptor Subfamily 1, Group F, Member 1 - genetics; Nuclear Receptor Subfamily 1, Group F, Member 1 - metabolism; Oncorhynchus mykiss; Oscillators; Period Circadian Proteins - genetics; Period Circadian Proteins - metabolism; Physiological aspects; Physiology; Proteins; Regulation; Rhythms; RNA, Messenger - genetics; RNA, Messenger - metabolism; Skeletal muscle; Synteny; Timeless protein; Tissues; Transcription; Zebrafish; Norway
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0099172

The classical notion of a centralized clock that governs circadian rhythmicity has been challenged with the discovery of peripheral oscillators that enable organisms to cope with daily changes in their environment. The present study aimed to identify the molecular clock components in Atlantic cod (Gadus morhua) and to investigate their daily gene expression in fast skeletal muscle. Atlantic cod clock genes were closely related to their orthologs in teleosts and tetrapods. Synteny was conserved to varying degrees in the majority of the 18 clock genes examined. In particular, aryl hydrocarbon receptor nuclear translocator-like 2 (arntl2), RAR-related orphan receptor A (rora) and timeless (tim) displayed high degrees of conservation. Expression profiling during the early ontogenesis revealed that some transcripts were maternally transferred, namely arntl2, cryptochrome 1b and 2 (cry1b and cry2), and period 2a and 2b (per2a and per2b). Most clock genes were ubiquitously expressed in various tissues, suggesting the possible existence of multiple peripheral clock systems in Atlantic cod. In particular, they were all detected in fast skeletal muscle, with the exception of neuronal PAS (Per-Arnt-Single-minded) domain-containing protein (npas1) and rora. Rhythmicity analysis revealed 8 clock genes with daily rhythmic expression, namely arntl2, circadian locomotor output cycles kaput (clock), npas2, cry2, cry3 per2a, nuclear receptor subfamily 1, group D, member 1 (nr1d1), and nr1d2a. Transcript levels of the myogenic genes myogenic factor 5 (myf5) and muscleblind-like 1 (mbnl1) strongly correlated with clock gene expression. This is the first study to unravel the molecular components of peripheral clocks in Atlantic cod. Taken together, our data suggest that the putative clock system in fast skeletal muscle of Atlantic cod has regulatory implications on muscle physiology, particularly in the expression of genes related to myogenesis.