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Melatonin receptor of a reef fish with lunar‐related rhythmicity: cloning and daily variations
Author(s) -
Park YongJu,
Park JiGweon,
Kim SeJae,
Lee YoungDon,
Saydur Rahman Md.,
Takemura Akihiro
Publication year - 2006
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.2006.00350.x
Subject(s) - melatonin , biology , melatonin receptor , circadian rhythm , medicine , endocrinology , receptor , complementary dna , pineal gland , gene expression , gene , genetics
Melatonin receptors are expressed in neural and peripheral tissues and mediate melatonin actions on the regulation of circadian rhythms in various species. For overall understanding of ‘circa’ rhythms in the golden rabbitfish, Siganus guttatus , which exhibits restricted lunar‐related rhythms and spawns synchronously around the first quarter moon, the aim of the present study was to clone a melatonin receptor (Mel lb ) cDNA and examine daily variations of Mel lb mRNA expression in certain tissues of the rabbitfish. The full‐length Mel lb cDNA (1808 bp) contained an open reading frame to encode a protein with a length of 354 amino acids, which was highly homologous to a protein of nonmammalian species. Northern blot analysis showed transcripts of Mel lb in the brain and retina. Real‐time quantitative polymerase chain reaction analysis also revealed expression of Mel lb in all tissues tested. Significantly high expression of the gene during daytime was evident in the liver and kidney. When the expression of Mel lb was examined in the brain and retina under conditions of light/dark cycles or constant darkness, daily and circadian variations of gene expression with two increases during daytime and nighttime for the brain and a single increase during nighttime for the retina were recognized. Moreover, daily variations in the expression of Mel lb were observed in the cultured pineal gland. These results suggest that the melatonin receptor plays a role in integration of melatonin actions in various tissues and that daily variations of Mel lb in the neural tissues may be related to regulation of circadian clock.