title: Molecular characterisation and expression of parathyroid hormone-related protein in the caudal neurosecretory system of the euryhaline flounder, Platichthys flesus.
abstract: Parathyroid hormone-related protein (PTHrP) is a hypercalcemic factor in fish, but the source of circulating PTHrP remains unclear. In this study investigation of the caudal neurosecretory system (CNSS), considered one of major sources of PTHrP in fish, provided valuable insights into this regulatory system. We report pthrpa and pthrpb gene cloning, characterization, expression, and responses to low salinity and hypocalcemia challenge in flounder. The pthrpa and pthrpb precursors, isolated from a European flounder CNSS library, consist of 166 and 192 amino acid residues, respectively, with an overall homology of approximately 59.2%. Both precursors contain a signal peptide and a mature peptide with cleavage and amidation sites. The flounder PTHrPA and PTHrPB peptides share only 41% sequence identity with human PTHrPA. Quantitative PCR analysis demonstrated that the bone and bladder, are respectively major sites of pthrpa and pthrpb expression in flounder. Urophysectomy confirmed the CNSS as a likely contributor to circulating PTHrP peptides. There were no significant differences in CNSS pthrpa and pthrpb mRNA expression or plasma PTHrP levels between seawater (SW) and freshwater (FW)-adapted fish, though plasma total calcium concentrations were higher in FW animals. The intraperitonial administration of EGTA rapidly induced hypocalcemia and concomitant elevation in plasma PTHrP accompanied by increases in both pthrpa and pthrpb expression in the CNSS. Together, these findings support an evolutionary conserved role for PTHrP in the endocrine regulation of calcium.
authors.affiliation: Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai 201306, China; College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China. Electronic address: wqlv@shou.edu.cn.
authors.forename: Weiqun
authors.initials: W
authors.lastname: Lu
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Jin
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China.
authors.forename: Jinling
authors.initials: J
authors.lastname: Xu
authors.affiliation: Faculty of Life Sciences, University of Manchester, Oxford Road, M13 9PT, United Kingdom.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Greenwood
authors.affiliation: Faculty of Life Sciences, University of Manchester, Oxford Road, M13 9PT, United Kingdom.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Balment
mesh_terms: D000064:Acclimatization; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000097:blood; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004533:Egtazic Acid / Q000008:administration & dosage; D005432:Flounder / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D005618:Fresh Water; D020869:Gene Expression Profiling; D006996:Hypocalcemia / Q000097:blood; D007274:Injections, Intraperitoneal; D009490:Neurosecretory Systems / Q000378:metabolism*; D044162:Parathyroid Hormone-Related Protein / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D054712:Salinity; D012623:Seawater; D017386:Sequence Homology, Amino Acid
chemical_list: D018076:DNA, Complementary; D044162:Parathyroid Hormone-Related Protein; D012333:RNA, Messenger; D004533:Egtazic Acid; D002118:Calcium
keywords: CNSS; Expression profile; PTHrP; Urophysectomy