title: Phenotypic analyses of a medaka mutant reveal the importance of bilaterally synchronized expression of isthmic fgf8 for bilaterally symmetric formation of the optic tectum.
abstract: Developing neural tubes are bilaterally symmetric in all vertebrate embryos, irrespective of the presence of gene networks that generate left-right asymmetry. To explore the mechanisms that underlie the bilaterally symmetric formation of the neural tube, we examined a medaka (Oryzias latipes) dominant mutant, Oot, the neural tube of which transiently lacks normal symmetry in the optic tectum. We found that spatial changes in isthmic fgf8 expression do not occur on one side of the mutant, resulting in a transient desynchronized expression that correlates with tectal asymmetry. The application of exogenous FGF8 on one side of a wild-type embryo mimics the Oot phenotype, indicating that the bilaterally equivalent expression of isthmic fgf8 is crucial for the bilaterally symmetric development of the tectum. These results suggest that tectal symmetry is not a "default" state, but rather is maintained actively by a bilaterally coupled and synchronized regulation of isthmic fgf8 expression.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Takashima
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kage
authors.forename: Takako
authors.initials: T
authors.lastname: Yasuda
authors.forename: Keiji
authors.initials: K
authors.lastname: Inohaya
authors.forename: Kouichi
authors.initials: K
authors.lastname: Maruyama
authors.forename: Kazuo
authors.initials: K
authors.lastname: Araki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takeda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ishikawa
mesh_terms: D000818:Animals; D005260:Female; D051524:Fibroblast Growth Factor 8 / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D008297:Male; D009154:Mutation / Q000235:genetics; D009990:Oryzias / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D013477:Superior Colliculi / Q000002:abnormalities / Q000196:embryology* / Q000378:metabolism
chemical_list: D051524:Fibroblast Growth Factor 8