title: Conserved sensory-neurosecretory cell types in annelid and fish forebrain: insights into hypothalamus evolution.
abstract: Neurosecretory control centers form part of the forebrain in many animal phyla, including vertebrates, insects, and annelids. The evolutionary origin of these centers is largely unknown. To identify conserved, and thus phylogenetically ancient, components of neurosecretory brain centers, we characterize and compare neurons that express the prohormone vasotocin (vasopressin/oxytocin)-neurophysin in the developing forebrain of the annelid Platynereis dumerilii and of the zebrafish. These neurons express the same tissue-restricted microRNA, miR-7, and conserved, cell-type-specific combinations of transcription factors (nk2.1, rx, and otp) that specify their identity, as evidenced by the specific requirement of zebrafish rx3 for vasotocin-neurophysin expression. MiR-7 also labels another shared population of neurons containing RFamides. Since the vasotocinergic and RFamidergic neurons appear to be directly sensory in annelid and fish, we propose that cell types with dual sensory-neurosecretory properties were the starting point for the evolution of neurosecretory brain centers in Bilateria.
authors.affiliation: Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69012 Heidelberg, Germany. kristin.tessmar@embl.de
authors.forename: Kristin
authors.initials: K
authors.lastname: Tessmar-Raible
authors.forename: Florian
authors.initials: F
authors.lastname: Raible
authors.forename: Foteini
authors.initials: F
authors.lastname: Christodoulou
authors.forename: Keren
authors.initials: K
authors.lastname: Guy
authors.forename: Martina
authors.initials: M
authors.lastname: Rembold
authors.forename: Harald
authors.initials: H
authors.lastname: Hausen
authors.forename: Detlev
authors.initials: D
authors.lastname: Arendt
mesh_terms: D000818:Animals; D000845:Annelida / Q000033:anatomy & histology / Q000502:physiology*; D005075:Biological Evolution; D015415:Biomarkers / Q000378:metabolism; D017124:Conserved Sequence / Q000235:genetics; D019143:Evolution, Molecular; D007031:Hypothalamus / Q000378:metabolism* / Q000648:ultrastructure; D035683:MicroRNAs / Q000235:genetics; D046529:Microscopy, Electron, Transmission; D009475:Neurons, Afferent / Q000378:metabolism* / Q000648:ultrastructure; D009479:Neuropeptides / Q000378:metabolism; D009489:Neurosecretion / Q000502:physiology; D009490:Neurosecretory Systems / Q000378:metabolism* / Q000648:ultrastructure; D013045:Species Specificity; D014157:Transcription Factors / Q000235:genetics; D014668:Vasotocin / Q000378:metabolism; D015027:Zebrafish / Q000033:anatomy & histology / Q000502:physiology*
chemical_list: D015415:Biomarkers; D035683:MicroRNAs; D009479:Neuropeptides; D014157:Transcription Factors; C058047:arginylphenylalaninamide; D014668:Vasotocin