ZFIN ID: ZDB-PUB-060412-12
Zebrafish arylalkylamine-N-acetyltransferase genes - targets for regulation of the circadian clock
Appelbaum, L., Vallone, D., Anzulovich, A., Ziv, L., Tom, M., Foulkes, N.S., and Gothilf, Y.
Date: 2006
Source: Journal of molecular endocrinology   36(2): 337-347 (Journal)
Registered Authors: Foulkes, Nicholas-Simon, Gothilf, Yoav, Vallone, Daniela
Keywords: none
MeSH Terms:
  • Animals
  • Arylalkylamine N-Acetyltransferase/genetics*
  • Arylalkylamine N-Acetyltransferase/metabolism*
  • Basic Helix-Loop-Helix Transcription Factors/genetics
  • Basic Helix-Loop-Helix Transcription Factors/metabolism
  • CLOCK Proteins
  • Cell Line
  • Circadian Rhythm/physiology*
  • Dimerization
  • Gene Expression Regulation, Enzymologic
  • Isoenzymes/genetics
  • Isoenzymes/metabolism
  • Otx Transcription Factors/genetics
  • Otx Transcription Factors/metabolism
  • Promoter Regions, Genetic/genetics
  • Protein Binding
  • RNA, Messenger/genetics
  • Rats
  • Regulatory Elements, Transcriptional/genetics
  • Retina/enzymology
  • Trans-Activators/genetics
  • Trans-Activators/metabolism
  • Transcription Factors/metabolism
  • Zebrafish/genetics*
  • Zebrafish/physiology*
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism
PubMed: 16595704 Full text @ J. Mol. Endocrinol.
Daily rhythms of melatonin production are controlled by changes in the activity of arylalkylamine-N-acetyltransferase (AANAT). Zebrafish possess two aanats, aanat1 and aanat2; the former is expressed only in the retina and the latter is expressed in both the retina and the pineal gland. Here, their differential expression and regulation were studied using transcript quantification and transient and stable in vivo and in vitro transfection assays. In the pineal gland, the aanat2 promoter exhibited circadian clock-controlled activity, as indicated by circadian rhythms of Enhanced green fluorescent protein (EGFP) mRNA in AANAT2:EGFP transgenic fish. In vivo transient expression analyses of the aanat2 promoter indicated that E-box and photoreceptor conserved elements (PCE) are required for expression in the pineal gland. In the retina, the expression of both genes was characterized by a robust circadian rhythm of their transcript levels. In constant darkness, the rhythmic expression of retinal aanat2 persisted while the aanat1 rhythm disappeared; indicating that the former is controlled by a circadian clock and the latter is also light driven. In the light-entrainable clock-containing PAC-2 zebrafish cell line, both stably transfected aanat1 and aanat2 promoters exhibited a clock-controlled circadian rhythm, characteristic for an E-box-driven expression. Transient co-transfection experiments in NIH-3T3 cells revealed that the two, E-box- and PCE-containing, promoters are driven by the synergistic action of BMAL/CLOCK and orthehodenticle homeobox 5. This study has revealed a shared mechanism for the regulation of two related genes, yet describes their differential phases and photic responses which may be driven by other gene-specific regulatory mechanisms and tissue-specific transcription factor profiles.