ZFIN ID: ZDB-PUB-991216-4
Exo-rhodopsin: a novel rhodopsin expressed in the zebrafish pineal gland
Mano, H., Kojima, D., and Fukada, Y.
Date: 1999
Source: Mol. Brain Res.   73(1-2): 110-118 (Journal)
Registered Authors: Fukada, Yoshitaka, Kojima, Daisuke
Keywords: exo-rhodopsin; opsin; pineal gland; circadian rhythm; zebrafish (Danio rerio)
MeSH Terms:
  • Amino Acid Sequence
  • Animals
  • Brain/metabolism
  • Cloning, Molecular
  • DNA, Complementary/chemistry
  • DNA, Complementary/genetics
  • Gene Expression
  • Immunohistochemistry
  • In Situ Hybridization
  • Molecular Sequence Data
  • Phylogeny
  • Pineal Gland/chemistry
  • Pineal Gland/metabolism*
  • RNA, Messenger/genetics
  • RNA, Messenger/metabolism
  • Retina/metabolism
  • Rhodopsin/analysis
  • Rhodopsin/genetics*
  • Rod Opsins/genetics
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Sequence Homology, Amino Acid
  • Tissue Distribution
  • Zebrafish/genetics*
PubMed: 10581404 Full text @ Mol. Brain Res.
The zebrafish, a useful animal model for genetic studies, has a photosensitive pineal gland, which has an endogenous circadian pacemaker entrained to environmental light-dark cycles [G.M. Cahill, Brain Res. 708 (1996) 177-181]. Although pinopsin has been found in the pineal glands of birds and reptiles, the molecular identity responsible for fish pineal photosensitivity remains unclear. This study reports identification of a novel opsin gene expressed in the zebrafish pineal gland. The deduced amino acid sequence is similar to, but not identical (74% identity) with that of canonical rhodopsin in the zebrafish retina. This novel rhodopsin is expressed in the majority of pineal cells but not in retinal cells, and hence named exo-rhodopsin after extra-ocular rhodopsin. This study first shows that two different rhodopsin genes are expressed in an individual animal each within a unique location. A phylogenetic analysis indicated that the exo-rhodopsin gene was produced by a duplication of the rhodopsin gene at an early stage in the ray-finned fish lineage. As expected, the exo-rhodopsin gene was found in the medakafish and European eel genomes, suggesting strongly that exo-rhodopsin is a pineal opsin common to teleosts. Identification of exo-rhodopsin in the zebrafish provides an opportunity for studying the role of pineal photoreceptive molecules by using genetic approaches.