title: Developmental tracing of luteinizing hormone β-subunit gene expression using green fluorescent protein transgenic medaka (Oryzias latipes) reveals a putative novel developmental function.
abstract: BACKGROUND
  Luteinizing hormone (LH) and follicle stimulating hormone (FSH), produced in gonadotrope cells in the adenohypophysis are key regulators of vertebrate reproduction. The differential regulation of these hormones, however, is poorly understood and little is known about gonadotrope embryonic development. We developed a stable transgenic line of medaka with the LH beta subunit gene (lhb) promotor driving green fluorescent protein (gfp) expression to characterize development of LH-producing gonadotropes in whole larvae and histological sections. Additionally, developmental and tissue-specific gene expression was examined.
  
  
  RESULTS
  The lhb gene is maternally expressed during early embryogenesis. Transcript levels increase by stage 21 (36 hours post fertilization [hpf]) and then decrease during continued larval development. Examination of the expression of pituitary marker genes show that LH-producing cells are initially localized outside the primordial pituitary, and they were localized to the developing gut tube by 32 hpf. At hatching, lhb-GFP is clearly detected in the gut epithelium and in the anterior digestive tract. lhb-GFP expression later consolidate in the developing pituitary by 2 weeks postfertilization.
  
  
  CONCLUSIONS
  During embryonic development, lhb is primarily expressed outside the central nervous system and pituitary. The novel expression of lhb in the embryonic gut suggests that LH has a hitherto unidentified developmental function.
authors.affiliation: Norwegian School of Veterinary Science, Department of Basic Science and Aquatic Medicine, Oslo, Norway.
authors.forename: Jon
authors.initials: J
authors.lastname: Hildahl
authors.forename: Guro K
authors.initials: GK
authors.lastname: Sandvik
authors.forename: Rikke
authors.initials: R
authors.lastname: Lifjeld
authors.forename: Kjetil
authors.initials: K
authors.lastname: Hodne
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nagahama
authors.forename: Trude M
authors.initials: TM
authors.lastname: Haug
authors.forename: Kataaki
authors.initials: K
authors.lastname: Okubo
authors.forename: Finn Arne
authors.initials: FA
authors.lastname: Weltzien
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D017403:In Situ Hybridization; D007986:Luteinizing Hormone / Q000235:genetics / Q000378:metabolism*; D009990:Oryzias / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction
chemical_list: D049452:Green Fluorescent Proteins; D007986:Luteinizing Hormone