title: Partially redundant proneural function reveals the importance of timing during zebrafish olfactory neurogenesis.
abstract: Little is known about proneural gene function during olfactory neurogenesis in zebrafish. Here, we show that the zebrafish Atonal genes neurogenin1 (neurog1) and neurod4 are redundantly required for development of both early-born olfactory neurons (EONs) and later-born olfactory sensory neurons (OSNs). We show that neurod4 expression is initially absent in neurog1 mutant embryos but recovers and is sufficient for the delayed development of OSN. By contrast, EON numbers are significantly reduced in neurog1 mutant embryos despite the recovery of neurod4 expression. Our results suggest that a shortened time window for EON development causes this reduction; the last S-phase of EON is delayed in neurog1 mutant embryos but mutant EONs are all post-mitotic at the same stage as EONs in wild-type embryos. Finally, we show that expression of certain genes, such as robo2, is never detected in neurog1 mutant EONs. Failure of robo2 expression to recover correlates with defects in the fasciculation of neurog1 mutant olfactory axonal projections and in the organisation of proto-glomeruli because projections arrive at the olfactory bulb that are reminiscent of those in robo2 mutant embryos. We conclude that the duration of proneural expression in EON progenitors is crucial for correct development of the zebrafish olfactory system.
authors.affiliation: Université de Toulouse, UPS, Centre de Biologie du Développement (CBD), 118 route de Narbonne, F-31062 Toulouse, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Madelaine
authors.forename: Laurence
authors.initials: L
authors.lastname: Garric
authors.forename: Patrick
authors.initials: P
authors.lastname: Blader
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D055495:Neurogenesis / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009833:Olfactory Pathways / Q000033:anatomy & histology / Q000502:physiology*; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism; D015027:Zebrafish / Q000033:anatomy & histology* / Q000196:embryology* / Q000235:genetics; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism; D000097905:Roundabout Proteins
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D009419:Nerve Tissue Proteins; D011971:Receptors, Immunologic; D029961:Zebrafish Proteins; C476737:neurod4 protein, zebrafish; C486337:neurog1 protein, zebrafish; C498889:robo2 protein, zebrafish; D000097905:Roundabout Proteins