Fgf signals from a novel signaling center determine axial patterning of the prospective neural retina.
Axial eye patterning determines the positional code of retinal ganglion cells (RGCs), which is crucial for their topographic projection to the midbrain. Several asymmetrically expressed determinants of retinal patterning are known, but it is unclear how axial polarity is first established. We find that Fgf signals, including Fgf8, determine retinal patterning along the nasotemporal (NT) axis during early zebrafish embryogenesis: Fgf8 induces nasal and/or suppresses temporal retinal cell fates; and inhibition of all Fgf-receptor signaling leads to complete retinal temporalization and concomitant loss of all nasal fates. Misprojections of RGCs with Fgf-dependent alterations in retinal patterning to the midbrain demonstrate the importance of this early patterning process for late topographic map formation. The crucial period of Fgf-dependent patterning is at the onset of eye morphogenesis. Fgf8 expression, the restricted temporal requirement for Fgf-receptor signaling and target gene expression at this stage suggests that the telencephalic primordium is the source of Fgf8 and acts as novel signaling center for non-autonomous axial patterning of the prospective neural retina.
Picker
Alexander
A
University of Technology, Department of Genetics, c/o Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauer Strasse 108, 01307 Dresden, Germany. picker@mpi-cbg.de
Brand
Michael
M
D000818:Animals; D001369:Axons / Q000502:physiology; D019521:Body Patterning / Q000502:physiology*; D005123:Eye / Q000196:embryology; D051524:Fibroblast Growth Factor 8 / Q000502:physiology; D005346:Fibroblast Growth Factors / Q000502:physiology*; D012160:Retina / Q000196:embryology* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D019170:Somites / Q000502:physiology; D013687:Telencephalon / Q000196:embryology / Q000502:physiology; D013997:Time Factors; D015027:Zebrafish / Q000196:embryology*
D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors