Mutations affecting retinotectal axonal pathfinding in Medaka, Oryzias latipes.
We screened for mutations affecting retinotectal axonal projection in Medaka, Oryzias latipes. In wild-type Medaka embryos, all the axons of retinal ganglion cells (RGCs) project to the contralateral tectum, such that the topological relationship of the retinal field is maintained. We labeled RGC axons using DiI/DiO at the nasodorsal and temporoventral positions of the retina, and screened for mutations affecting the pattern of stereotypic projections to the tectum. By screening 184 mutagenized haploid genomes, seven mutations in five genes causing defects in axonal pathfinding were identified, whereas mutations affecting the topographic projection of RGC axons were not found. The mutants were grouped into two classes according to their phenotypes. In mutants of Class I, a subpopulation of the RGC axons branched out either immediately after leaving the eye or after reaching the midline, and this axonal subpopulation projected to the ipsilateral tectum. In mutants of Class II, subpopulations of RGC axons branched out after crossing the midline and projected aberrantly. These mutants will provide clues to understanding the functions of genes essential for axonal pathfinding, which may be conserved or partly divergent among vertebrates.
Yoda
Hiroki
H
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
Hirose
Yukihiro
Y
Yasuoka
Akihito
A
Sasado
Takao
T
Morinaga
Chikako
C
Deguchi
Tomonori
T
Henrich
Thorsten
T
Iwanami
Norimasa
N
Watanabe
Tomomi
T
Osakada
Masakazu
M
Kunimatsu
Sanae
S
Wittbrodt
Joachim
J
Suwa
Hiroshi
H
Niwa
Katsutoshi
K
Okamoto
Yasuko
Y
Yamanaka
Toshiyuki
T
Kondoh
Hisato
H
Furutani-Seiki
Makoto
M
D000818:Animals; D001369:Axons; D005123:Eye / Q000196:embryology; D009154:Mutation; D009897:Optic Chiasm / Q000196:embryology; D009900:Optic Nerve / Q000002:abnormalities / Q000196:embryology; D009990:Oryzias / Q000196:embryology* / Q000235:genetics*; D013477:Superior Colliculi / Q000196:embryology; D015027:Zebrafish / Q000196:embryology / Q000235:genetics