Phenotypic analyses of a medaka mutant reveal the importance of bilaterally synchronized expression of isthmic fgf8 for bilaterally symmetric formation of the optic tectum.
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.
Takashima
Shigeo
S
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo, Japan.
Kage
Takahiro
T
Yasuda
Takako
T
Inohaya
Keiji
K
Maruyama
Kouichi
K
Araki
Kazuo
K
Takeda
Hiroyuki
H
Ishikawa
Yuji
Y
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
D051524:Fibroblast Growth Factor 8