title: Developmental and light-entrained expression of melatonin and its relationship to the circadian clock in the sea anemone Nematostella vectensis.
abstract: BACKGROUND
  The primary hormone of the vertebrate pineal gland, melatonin, has been identified broadly throughout the eukaryotes. While the role for melatonin in cyclic behavior via interactions with the circadian clock has only been reported in vertebrates, comparative research has shown that the transcription-translation loops of the animal circadian clock likely date to the cnidarian-bilaterian ancestor, leaving open significant questions about the evolutionary origin of melatonin signaling in circadian behavior by interacting with the molecular clock.
  
  
  RESULTS
  Expression of melatonin in adult anemones showed peak expression at the end of light period (zeitgeber time (ZT) = 12) when cultured under diel conditions, coinciding with expression of genes and enzyme activity for members of the melatonin synthesis pathway (tryptophan hydroxylase and hydroxyindol-O-methyltransferase), which also showed rhythmic expression. During embryogenesis and juvenile stages, melatonin showed cyclic oscillations in concentration, peaking in midday. Spatial (in situ hybridization) and quantitative (real-time PCR) transcription of clock genes during development of N. vectensis showed these 'clock' genes are expressed early in the development, prior to rhythmic oscillations, suggesting functions independent of a function in the circadian clock. Finally, time-course studies revealed that animals transferred from diel conditions to constant darkness lose circadian expression for most of the clock genes within 4 days, which can be reset by melatonin supplementation.
  
  
  CONCLUSIONS
  Our results support an ancient role for melatonin in the circadian behavior of animals by showing cyclic expression of this hormone under diel conditions, light-dependent oscillations in genes in the melatonin synthesis pathway, and the function of melatonin in initiating expression of circadian clock genes in the cnidarian N. vectensis. The differences in expression melatonin and the circadian clock gene network in the adult stage when compared with developmental stages of N. vectensis suggests new research directions to characterize stage-specific mechanisms of circadian clock function in animals.
authors.affiliation: Kewalo Marine Laboratory, University of Hawaii, 41 Ahui Street, 96813 Honolulu, HI, USA ; Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Av. Vital Brasil, 1500, Butantã, São Paulo SP, 05503-900, Brazil.
authors.forename: Rafael
authors.initials: R
authors.lastname: Peres
authors.affiliation: Department of Biological Sciences, University of North Carolina at Charlotte, 9201 University City Blvd, Charlotte, 28223-0001 Charlotte, North Carolina, USA.
authors.forename: Adam M
authors.initials: AM
authors.lastname: Reitzel
authors.affiliation: Kewalo Marine Laboratory, University of Hawaii, 41 Ahui Street, 96813 Honolulu, HI, USA.
authors.forename: Yale
authors.initials: Y
authors.lastname: Passamaneck
authors.affiliation: Laboratory of Pharmacology, Butantan Institute, São Paulo, Brazil.
authors.forename: Solange Castro
authors.initials: SC
authors.lastname: Afeche
authors.affiliation: Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Av. Vital Brasil, 1500, Butantã, São Paulo SP, 05503-900, Brazil.
authors.forename: José
authors.initials: J
authors.lastname: Cipolla-Neto
authors.affiliation: Department of Zoology, Biosciences Institute, University of São Paulo. Rua Matao, Trav. 14, 101, 05508-090 Sao Paulo, Brazil ; Center for Marine Biology, University of São Paulo. Rodovia Manoel Hypólito do Rego, km. 131,5 - Praia do Cabelo Gordo, São Sebastião SP, 11600-000, CEP, Brazil.
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Marques
authors.affiliation: Kewalo Marine Laboratory, University of Hawaii, 41 Ahui Street, 96813 Honolulu, HI, USA ; Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Blvd, 32080 St. Augustine, FL, USA.
authors.forename: Mark Q
authors.initials: MQ
authors.lastname: Martindale
keywords: Circadian clock; Embryogenesis; In situ hybridization; Melatonin