Analyses of the cellular clock gene expression in peripheral tissue, caudal fin, in the Japanese flounder, Paralichthys olivaceus

Mogi, M., Yokoi, H., Suzuki, T.
General and comparative endocrinology   248: 97-105 (Journal)
Registered Authors
Suzuki, Tohru, Yokoi, Hayato
Circadian rhythm, Clock genes, Flounder, period2
MeSH Terms
  • Animal Fins/metabolism*
  • Animals
  • Biological Clocks/genetics*
  • Biological Clocks/radiation effects
  • CLOCK Proteins/genetics*
  • CLOCK Proteins/metabolism
  • Circadian Rhythm/drug effects
  • Circadian Rhythm/genetics
  • Circadian Rhythm/physiology
  • Circadian Rhythm/radiation effects
  • Dexamethasone/pharmacology
  • Flounder/genetics*
  • Flounder/physiology*
  • Gene Expression Profiling
  • Gene Expression Regulation*/drug effects
  • Gene Expression Regulation*/radiation effects
  • Light
  • Melatonin/pharmacology
28249777 Full text @ Gen. Comp. Endocrinol.
Understanding the systems for maintaining the circadian rhythms that give organisms the flexibility to adapt to environmental changes is important in both aquaculture and fish chronobiology, because nursery lighting conditions can affect the survival and growth rates of larvae. We previously demonstrated that in flounder, the suprachiasmatic nucleus (SCN) exhibits daily rhythm in per2 expression, in sharp contrast to zebrafish, in which the SCN does not exhibit clear per2 expression rhythm. To examine whether a hierarchy exists in systems that maintain the expression rhythm of peripheral clock genes in flounder, in the present study we analyzed the in vivo and in vitro expression of three clock genes, per2, per1, and cry1, in the caudal fin and the effects of cortisol and melatonin administration on the expression of each clock gene. In vivo, the fin maintained a daily expression rhythm of all three genes, even in 24-h darkness (DD) when shifted from 12-h light:12-h dark (LD) conditions, but fin explants lost the expression rhythm after a short time of tissue culture, even under LD conditions. Cortisol, but not melatonin, significantly upregulated the expression of the three clock genes in fin both in vitro and in vivo. Therefore, we hypothesize that the SCN-pituitary-adrenal cortex pathway plays a role in the oscillation of the peripheral clock in flounder. However, in vivo, peak expression of per2 and cry1 was shifted 2-4 h earlier under DD conditions, and their expression was upregulated in response to short exposures to light when larvae were kept under DD conditions. Therefore, we also hypothesize that in addition to the SCN, a light-responsive coordinating factor also functions in photo-entrainment of the peripheral clock in flounder.
Genes / Markers
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes