title: Daily rhythmicity of clock gene transcripts in atlantic cod fast skeletal muscle.
abstract: 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.
authors.affiliation: Faculty of Biosciences and Aquaculture, University of Nordland, Bodø, Norway.
authors.forename: Carlo C
authors.initials: CC
authors.lastname: Lazado
authors.affiliation: Faculty of Biosciences and Aquaculture, University of Nordland, Bodø, Norway.
authors.forename: Hiruni P S
authors.initials: HP
authors.lastname: Kumaratunga
authors.affiliation: Faculty of Biosciences and Aquaculture, University of Nordland, Bodø, Norway.
authors.forename: Kazue
authors.initials: K
authors.lastname: Nagasawa
authors.affiliation: Faculty of Biosciences and Aquaculture, University of Nordland, Bodø, Norway.
authors.forename: Igor
authors.initials: I
authors.lastname: Babiak
authors.affiliation: Faculty of Biosciences and Aquaculture, University of Nordland, Bodø, Norway; Department of Biological and Environmental Sciences, University of Messina, Messina, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Giannetto
authors.affiliation: Faculty of Biosciences and Aquaculture, University of Nordland, Bodø, Norway.
authors.forename: Jorge M O
authors.initials: JM
authors.lastname: Fernandes
mesh_terms: D056930:ARNTL Transcription Factors / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D057906:Circadian Clocks / Q000235:genetics*; D056931:Cryptochromes / Q000235:genetics / Q000378:metabolism; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D048389:Gadus morhua / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism*; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1 / Q000235:genetics / Q000378:metabolism; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism
chemical_list: D056930:ARNTL Transcription Factors; D056931:Cryptochromes; D029941:Fish Proteins; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D056950:Period Circadian Proteins; D012333:RNA, Messenger