title: Discovery of conventional prolactin from the holocephalan elephant fish, Callorhinchus milii.
abstract: The conventional prolactin (PRL), also known as PRL1, is an adenohypophysial hormone that critically regulates various physiological events in reproduction, metabolism, growth, osmoregulation, among others. PRL1 shares its evolutionary origin with PRL2, growth hormone (GH), somatolactin and placental lactogen, which together form the GH/PRL hormone family. Previously, several bioassays implied the existence of PRL1 in elasmobranch pituitaries. However, to date, all attempts to isolate PRL1 from chondrichthyans have been unsuccessful. Here, we cloned PRL1 from the pituitary of the holocephalan elephant fish, Callorhinchus milii, as the first report of chondrichthyan PRL1. The putative mature protein of elephant fish PRL1 (cmPRL1) consists of 198 amino acids, containing two conserved disulfide bonds. The orthologous relationship of cmPRL1 to known vertebrate PRL1s was confirmed by the analyses of molecular phylogeny and gene synteny. The cmPRL1 gene was similar to teleost PRL1 genes in gene synteny, but was distinct from amniote PRL1 genes, which most likely arose in an early amphibian by duplication of the ancestral PRL1 gene. The mRNA of cmPRL1 was predominantly expressed in the pituitary, but was considerably less abundant than has been previously reported for bony fish and tetrapod PRL1s; the copy number of cmPRL1 mRNA in the pituitary was less than 1% and 0.1% of that of GH and pro-opiomelanocortin mRNAs, respectively. The cells expressing cmPRL1 mRNA were sparsely distributed in the rostral pars distalis. Our findings provide a new insight into the studies on molecular and functional evolution of PRL1 in vertebrates.
authors: Hawai'i Institute of Marine Biology, University of Hawai'i, Kaneohe, HI 96744, USA. Electronic address: yoko7@hawaii.edu.
authors: Yoko
authors: Y
authors: Yamaguchi
authors: Laboratory of Physiology, Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Chiba 277-8564, Japan. Electronic address: wtakagi@aori.u-tokyo.ac.jp.
authors: Wataru
authors: W
authors: Takagi
authors: Phyloinformatics Unit, RIKEN Center for Life Science Technologies, Kobe, Hyogo 650-0047, Japan. Electronic address: shigehiro.kuraku@riken.jp.
authors: Shigehiro
authors: S
authors: Kuraku
authors: School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan. Electronic address: morisuke@kitasato-u.ac.jp.
authors: Shunsuke
authors: S
authors: Moriyama
authors: Institute for Marine and Antarctic Studies, University of Tasmania, Taroona, TAS 7053, Australia. Electronic address: Justin.Bell@utas.edu.au.
authors: Justin D
authors: JD
authors: Bell
authors: Hawai'i Institute of Marine Biology, University of Hawai'i, Kaneohe, HI 96744, USA. Electronic address: seale@hawaii.edu.
authors: Andre P
authors: AP
authors: Seale
authors: Hawai'i Institute of Marine Biology, University of Hawai'i, Kaneohe, HI 96744, USA; Sea Grant College Program, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA. Electronic address: lerner@hawaii.edu.
authors: Darren T
authors: DT
authors: Lerner
authors: Hawai'i Institute of Marine Biology, University of Hawai'i, Kaneohe, HI 96744, USA; Sea Grant College Program, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA. Electronic address: grau@hawaii.edu.
authors: E Gordon
authors: EG
authors: Grau
authors: Laboratory of Physiology, Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Chiba 277-8564, Japan. Electronic address: hyodo@aori.u-tokyo.ac.jp.
authors: Susumu
authors: S
authors: Hyodo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D003001:Cloning, Molecular; D004555:Electric Fish / Q000254:growth & development / Q000378:metabolism*; D019143:Evolution, Molecular; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D010802:Phylogeny; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
chemical_list: D011388:Prolactin
keywords: Cartilaginous fish; GH/PRL family; Molecular evolution; Prolactin