Segregation of telencephalic and eye-field identities inside the zebrafish forebrain territory is controlled by Rx3.
Anteroposterior patterning of the vertebrate forebrain during gastrulation involves graded Wnt signaling, which segregates anterior fields (telencephalon and eye) from the diencephalon. How the telencephalic and retinal primordia are subsequently subdivided remains largely unknown. We demonstrate that at late gastrulation the Paired-like homeodomain transcription factor Rx3 biases cell specification choices towards the retinal fate within a population of bipotential precursors of the anterior forebrain: direct cell tracing demonstrates that retinal precursors acquire a telencephalic fate in embryos homozygous for the rx3-null allele ckh(ne2611), characterized by an enlarged telencephalon and a lack of eyes. Chimera analyses further indicate that this function of Rx3 is cell autonomous. Transfating of the eye field in the absence of Rx3 function correlates with a substantial posterior expansion of expression of the Wnt antagonist Tlc and the winged-helix transcription factor Foxg1. These results suggest that the process segregating the telencephalic and eye fields is isolated from diencephalic patterning, and is mediated by Rx3.
Stigloher
Christian
C
Zebrafish Neurogenetics Junior Research Group, Institute of Virology, Technical University-Munich, Trogerstrasse 4b, D-81675, Munich, Germany.
Ninkovic
Jovica
J
Laplante
Mary
M
Geling
Andrea
A
Tannhäuser
Birgit
B
Topp
Stefanie
S
Kikuta
Hiroshi
H
Becker
Thomas S
TS
Houart
Corinne
C
Bally-Cuif
Laure
L
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D005038:Ethylnitrosourea / Q000494:pharmacology; D005123:Eye / Q000196:embryology*; D005775:Gastrula / Q000502:physiology; D017353:Gene Deletion; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D006706:Homeostasis; D016133:Polymerase Chain Reaction; D016548:Prosencephalon / Q000196:embryology*; D013687:Telencephalon / Q000196:embryology*; D014794:Visual Fields / Q000502:physiology*; D015027:Zebrafish / Q000196:embryology*
D017931:DNA Primers; D018398:Homeodomain Proteins; C488383:Rx3 protein, zebrafish; D005038:Ethylnitrosourea