ZFIN ID: ZDB-PUB-191220-15
Circadian regulation of phosphodiesterase 6 genes in zebrafish differs between cones and rods: Implications for photopic and scotopic vision
Abalo, X.M., Lagman, D., Heras, G., Del Pozo, A., Eggert, J., Larhammar, D.
Date: 2019
Source: Vision Research   166: 43-51 (Journal)
Registered Authors: Abalo, Xesus, Lagman, David, Larhammar, Dan
Keywords: Circadian rhythm, Photoreceptor, Retina, Retinomotor movements, Visual sensitivity, qRT-PCR
MeSH Terms:
  • Animals
  • Circadian Rhythm/physiology*
  • Color Vision/physiology*
  • Cyclic Nucleotide Phosphodiesterases, Type 6/genetics*
  • Gene Expression Regulation, Enzymologic/physiology*
  • Night Vision/physiology*
  • Photoreceptor Cells, Vertebrate/enzymology*
  • RNA, Messenger/genetics
  • Real-Time Polymerase Chain Reaction
  • Zebrafish
  • Zebrafish Proteins/genetics*
PubMed: 31855667 Full text @ Vision Res.
A correlation is known to exist between visual sensitivity and oscillations in red opsinand rhodopsin gene expression in zebrafish, both regulated by the clock gene. This indicates that an endogenous circadian clock regulates behavioural visual sensitivity, apart from the regulation exerted by the pineal organ. However, the specific mechanisms for cones (photopic vision) and rods (scotopic vision) are poorly understood. In this work, we performed gene expression, cosinor and immunohistochemical analyses to investigate other key genes involved in light perception, encoding the different subunits of phosphodiesterase pde6 and transducin GαT, in constant lighting conditions and compared to normal light-dark conditions. We found that cones display prominent circadian oscillations in mRNA levels for the inhibitory subunit gene pde6ha that could contribute to the regulation of photopic sensitivity by preventing overstimulation in photopic conditions. In rods, the mRNA levels of the inhibitory subunit gene pde6ga oscillate under normal conditions and dampen down in constant light but continue oscillating in constant darkness. There is an increase in total relative expression for pde6gb in constant conditions. These observations, together with previous data, suggest a complex regulation of the scotopic sensitivity involving endogenous and non-endogenous components, possibly present also in other teleost species. The GαT genes do not display mRNA oscillations and therefore may not be essential for the circadian regulation of photosensitivity. In summary, our results support different regulation for the zebrafish photopic and scotopic sensitivities and suggest circadian regulation of pde6ha as a key factor regulating photopic sensitivity, while the regulatory mechanisms in rods appear to be more complex.