title: Melatonin receptor genes in vertebrates.
abstract: Melatonin receptors are members of the G protein-coupled receptor (GPCR) family. Three genes for melatonin receptors have been cloned. The MT1 (or Mel1a or MTNR1A) and MT2 (or Mel1b or MTNR1B) receptor subtypes are present in humans and other mammals, while an additional melatonin receptor subtype, Mel1c (or MTNR1C), has been identified in fish, amphibians and birds. Another melatonin related orphan receptor, GPR50, which does not bind melatonin, is found exclusively in mammals. The hormone melatonin is secreted primarily by the pineal gland, with highest levels occurring during the dark period of a circadian cycle. This hormone acts systemically in numerous organs. In the brain, it is involved in the regulation of various neural and endocrine processes, and it readjusts the circadian pacemaker, the suprachiasmatic nucleus. This article reviews recent studies of gene organization, expression, evolution and mutations of melatonin receptor genes of vertebrates. Gene polymorphisms reveal that numerous mutations are associated with diseases and disorders. The phylogenetic analysis of receptor genes indicates that GPR50 is an outgroup to all other melatonin receptor sequences. GPR50 may have separated from a melatonin receptor ancestor before the split between MTNR1C and the MTNR1A/B ancestor.
authors.affiliation: College of Animal Science and Technology, Sichuan Agricultural University, Ya'an 625014, China. zhuqing5959@163.com.
authors.forename: Di Yan
authors.initials: DY
authors.lastname: Li
authors.forename: David Glenn
authors.initials: DG
authors.lastname: Smith
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Hardeland
authors.forename: Ming Yao
authors.initials: MY
authors.lastname: Yang
authors.forename: Huai Liang
authors.initials: HL
authors.lastname: Xu
authors.forename: Long
authors.initials: L
authors.lastname: Zhang
authors.forename: Hua Dong
authors.initials: HD
authors.lastname: Yin
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D011110:Polymorphism, Genetic; D044094:Receptors, Melatonin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014714:Vertebrates / Q000235:genetics*
chemical_list: D009419:Nerve Tissue Proteins; D044094:Receptors, Melatonin