Morphological analysis of the early development of telencephalic and diencephalic gonadotropin-releasing hormone neuronal systems in enhanced green fluorescent protein-expressing transgenic medaka lines.
Teleosts possess two or three paralogs of gonadotropin-releasing hormone (GnRH) genes: gnrh1, gnrh2, and gnrh3. Some species have lost the gnrh1 and/or gnrh3 genes, whereas gnrh2 has been completely conserved in the teleost species analyzed to date. In most teleosts that possess gnrh1, GnRH1 peptide is the authentic GnRH that stimulates gonadotropin release, whereas GnRH2 and GnRH3, if present, are neuromodulatory. Progenitors of GnRH1 and GnRH3 neurons originate from olfactory placodes and migrate to their destination during early development. However, because of the relatively low affinity/specificity of generally available antibodies that recognize GnRH1 or GnRH3, labeling of these neurons has only been possible using genetic manipulation. We used a model teleost, medaka, which possesses all three paralogous gnrh genes, to analyze development of forebrain GnRH neurons composed of GnRH1 and GnRH3 neurons. Here, we newly generated transgenic medaka lines that express enhanced green fluorescent protein under the control of promoters for gnrh1 or gnrh3, to detect GnRH neurons and facilitate immunohistochemical analysis of the neuronal morphology. We used a combination of immunohistochemistry and three-dimensional confocal microscopy image reconstructions to improve identification of neurites from GnRH1 or GnRH3 neuronal populations with greater precision. This led us to clearly identify the hypophysiotropic innervation of GnRH1 neurons residing in the ventral preoptic area (vPOA) from as early as 10 days post hatching. Furthermore, these analyses also revealed retinopetal projections of nonhypophysiotropic GnRH1 neurons in vPOA, prominent during early developmental stages, and multiple populations of GnRH3 neurons with different origins and migratory pathways.
Department of Biological Science, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Akiko
A
Takahashi
Department of Biological Science, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
M Sadiqul
MS
Islam
Department of Biological Science, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Hideki
H
Abe
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Kataaki
K
Okubo
Department of Biological Science, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Yasuhisa
Y
Akazome
Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Takeshi
T
Kaneko
Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Hiroyuki
H
Hioki
Department of Biological Science, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Yoshitaka
Y
Oka
D000818:Animals; D030801:Animals, Genetically Modified; D002465:Cell Movement / Q000502:physiology; D004027:Diencephalon / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D021621:Imaging, Three-Dimensional / Q000379:methods; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D018613:Microscopy, Confocal / Q000379:methods; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D009990:Oryzias / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D013687:Telencephalon / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism
D029941:Fish Proteins; D012333:RNA, Messenger; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D007987:Gonadotropin-Releasing Hormone
GnRH; GnRH neuronal ontogeny; GnRH1; GnRH3; development; medaka; pituitary; transgenics