title: Comparative study of pineal clock gene and AANAT2 expression in relation to melatonin synthesis in Atlantic salmon (Salmo salar) and European seabass (Dicentrarchus labrax).
abstract: The photoreceptive teleost pineal is considered to be essential to the generation, synchronisation and maintenance of biological rhythms, primarily via melatonin release. The role of internal (circadian clock) and external (light) signals controlling melatonin production in the fish pineal differs between species, yet the reasons underpinning this remain largely unknown. Whilst in salmonids, pineal melatonin is apparently regulated directly by light, in all other studied teleosts, rhythmic melatonin production persists endogenously under the regulation of clock gene expression. To better understand the role of clocks in teleost pineals, this study aimed to characterise the expression of selected clock genes in vitro under different photoperiodic conditions in comparison to in vivo in both Atlantic salmon (Salmo salar) and in European seabass (Dicentrarchus labrax) (in vitro 12L:12D), a species known to display endogenous rhythmic melatonin synthesis. Results revealed no rhythmic clock gene (Clock, Period 1 &2) expression in Atlantic salmon or European seabass (Clock and Period 1) pineal in vitro. However rhythmic expression of Cryptochrome 2 and Period 1 in the Atlantic salmon pineal was observed in vivo, which infers extra-pineal regulation of clocks in this species. No rhythmic arylalkylamine N-acetyltransferase 2 (Aanat2) expression was observed in the Atlantic salmon yet in the European seabass, circadian Aanat2 expression was observed. Subsequent in silico analysis of available Aanat2 genomic sequences reveals that Atlantic salmon Aanat2 promoter sequences do not contain similar regulatory architecture as present in European seabass, and previously described in other teleosts which alludes to a loss in functional connection in the pathway.
authors.affiliation: Institute of Aquaculture, University of Stirling, Stirling, Scotland FK9 4LA, UK.
authors.forename: Elsbeth
authors.initials: E
authors.lastname: McStay
authors.affiliation: Institute of Aquaculture, University of Stirling, Stirling, Scotland FK9 4LA, UK.
authors.forename: Herve
authors.initials: H
authors.lastname: Migaud
authors.affiliation: University of Murcia, Department of Physiology, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia 30100, Spain.
authors.forename: Luisa Maria
authors.initials: LM
authors.lastname: Vera
authors.affiliation: University of Murcia, Department of Physiology, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia 30100, Spain.
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Sánchez-Vázquez
authors.affiliation: Institute of Aquaculture, University of Stirling, Stirling, Scotland FK9 4LA, UK. Electronic address: andrew.davie@stir.ac.uk.
authors.forename: Andrew
authors.initials: A
authors.lastname: Davie
mesh_terms: D000818:Animals; D047068:Arylalkylamine N-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D001492:Bass / Q000235:genetics / Q000378:metabolism*; D056926:CLOCK Proteins / Q000235:genetics* / Q000378:metabolism; D057906:Circadian Clocks; D005260:Female; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D015971:Gene Expression Regulation, Enzymologic; D008297:Male; D008550:Melatonin / Q000096:biosynthesis*; D017440:Photoperiod; D010870:Pineal Gland / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020317:Salmo salar / Q000235:genetics / Q000378:metabolism*; D046509:Tissue Culture Techniques; D014158:Transcription, Genetic
chemical_list: D029941:Fish Proteins; D056926:CLOCK Proteins; D047068:Arylalkylamine N-Acetyltransferase; D008550:Melatonin
keywords: Aanat2; Atlantic salmon; Clock genes; European seabass; Melatonin; Pineal gland