title: A role for GnRH in early brain regionalization and eye development in zebrafish.
abstract: Gonadotropin-releasing hormone (GnRH) is a highly conserved peptide that is expressed early in brain development in vertebrates. In zebrafish, we detected GnRH mRNA within 2h post fertilization by RT-PCR. To determine if GnRH is involved in development, we used gene knockdown techniques to block translation of gnrh2 or gnrh3 mRNA after which the expression patterns for gene markers were examined at 24h post fertilization with in situ hybridization. First, loss of either GnRH2 or GnRH3 affected regionalization of the brain as shown by a change in expression of fgf8 or pax2.1 genes in the midbrain-hindbrain boundary or diencephalon-midbrain boundary. Second, lack of GnRH2 and/or GnRH3 altered gene markers expressed in the formation of the eye cup (pax2.1, pax6.1, mab21l2 and meis1.1) or eye stalk (fgf8 and pax2.1). Third, knockdown of GnRH2 affected the size and shape of the midbrain and expression of gene markers therein. Results from assays with the TUNEL method and caspase-3 and -9 activity showed the brain and eye changes were unlikely to result from secondary apoptotic cell death before 24h post fertilization. These experiments suggest that GnRH loss-of-function affects early brain and eye formation during development.
authors.affiliation: Department of Biology, University of Victoria, Victoria, BC, Canada.
authors.forename: Sheng
authors.initials: S
authors.lastname: Wu
authors.forename: Louise
authors.initials: L
authors.lastname: Page
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Sherwood
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001483:Base Sequence; D019521:Body Patterning; D001921:Brain / Q000196:embryology* / Q000378:metabolism; D004027:Diencephalon / Q000196:embryology / Q000378:metabolism; D004625:Embryo, Nonmammalian; D005123:Eye / Q000196:embryology* / Q000378:metabolism; D005136:Eye Proteins / Q000378:metabolism; D051524:Fibroblast Growth Factor 8 / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018398:Homeodomain Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D008636:Mesencephalon / Q000196:embryology / Q000378:metabolism; D008969:Molecular Sequence Data; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D038081:Organogenesis / Q000502:physiology; D051762:PAX2 Transcription Factor / Q000378:metabolism; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D034622:RNA Interference; D036122:Receptor, EphA4 / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D012249:Rhombencephalon / Q000196:embryology / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000378:metabolism / Q000502:physiology
chemical_list: D005136:Eye Proteins; D018398:Homeodomain Proteins; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D016376:Oligonucleotides, Antisense; D009842:Oligopeptides; D051762:PAX2 Transcription Factor; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; C448022:gonadotropin-releasing hormone-III; C499233:mab21l2 protein, zebrafish; C508763:meis1b protein, zebrafish; D051524:Fibroblast Growth Factor 8; D007987:Gonadotropin-Releasing Hormone; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-; D036122:Receptor, EphA4; D011761:Pyrrolidonecarboxylic Acid