title: Intraspinal serotonergic neurons consist of two, temporally distinct populations in developing zebrafish.
abstract: Zebrafish intraspinal serotonergic neuron (ISN) morphology and distribution have been examined in detail at different ages; however, some aspects of the development of these cells remain unclear. Although antibodies to serotonin (5-HT) have detected ISNs in the ventral spinal cord of embryos, larvae, and adults, the only tryptophan hydroxylase (tph) transcript that has been described in the spinal cord is tph1a. Paradoxically, spinal tph1a is only expressed transiently in embryos, which brings the source of 5-HT in the ISNs of larvae and adults into question. Because the pet1 and tph2 promoters drive transgene expression in the spinal cord, we hypothesized that tph2 is expressed in spinal cords of zebrafish larvae. We confirmed this hypothesis through in situ hybridization. Next, we used 5-HT antibody labeling and transgenic markers of tph2-expressing neurons to identify a transient population of ISNs in embryos that was distinct from ISNs that appeared later in development. The existence of separate ISN populations may not have been recognized previously due to their shared location in the ventral spinal cord. Finally, we used transgenic markers and immunohistochemical labeling to identify the transient ISN population as GABAergic Kolmer-Agduhr double-prime (KA″) neurons. Altogether, this study revealed a novel developmental paradigm in which KA″ neurons are transiently serotonergic before the appearance of a stable population of tph2-expressing ISNs.
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Jacob E
authors.initials: JE
authors.lastname: Montgomery
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Wiggin
authors.affiliation: Department of Biology, University of Puerto Rico in Ponce, Ponce, Puerto Rico.
authors.forename: Luis M
authors.initials: LM
authors.lastname: Rivera-Perez
authors.affiliation: Department of Physiological Chemistry, Biocenter, University of Würzburg, Würzburg, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Lillesaar
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Masino
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D004625:Embryo, Nonmammalian; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007814:Larva; D009474:Neurons / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology* / Q000254:growth & development; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014365:Tryptophan Hydroxylase / Q000235:genetics / Q000378:metabolism; D015027:Zebrafish / Q000033:anatomy & histology* / Q000254:growth & development*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: C521369:FEV protein, zebrafish; D014157:Transcription Factors; D029961:Zebrafish Proteins; D049452:Green Fluorescent Proteins; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; C497467:TPH1 protein, human; C494784:TPH2 protein, human; D014365:Tryptophan Hydroxylase
keywords: Kolmer-Agduhr; pet1; serotonin; spinal cord; tryptophan hydroxylase