Canonical Wnt signaling is required for the maintenance of dorsal retinal identity.
Accurate retinotectal axon pathfinding depends upon the correct establishment of dorsal-ventral retinal polarity. We show that dorsal retinal gene expression is regulated by Wnt signaling in the dorsal retinal pigment epithelium (RPE). We find that a Wnt reporter transgene and Wnt pathway components are expressed in the dorsal RPE beginning at 14-16 hours post-fertilization. In the absence of Wnt signaling, tbx5 and Bmp genes initiate normal dorsal retinal expression but are not maintained. The expression of these genes is rescued by the downstream activation of Wnt signaling, and tbx5 is rescued by Bmp signaling. Furthermore, activation of Wnt signaling cannot rescue tbx5 in the absence of Bmp signaling, suggesting that Wnt signaling maintains dorsal retinal gene expression by regulating Bmp signaling. We present a model in which dorsal RPE-derived Wnt activity maintains the expression of Bmp ligands in the dorsal retina, thus coordinating the patterning of these two ocular tissues.
Veien
Eric S
ES
Department of Neurobiology and Anatomy, University of Utah, 401 MREB, 20 N. 1900 E., Salt Lake City, UT 84132, USA.
Rosenthal
Judith S
JS
Kruse-Bend
Renee C
RC
Chien
Chi-Bin
CB
Dorsky
Richard I
RI
D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics / Q000502:physiology; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D012160:Retina / Q000196:embryology*; D055213:Retinal Pigment Epithelium / Q000196:embryology; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000235:genetics / Q000502:physiology; D051153:Wnt Proteins / Q000235:genetics / Q000502:physiology*; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics / Q000502:physiology; D029961:Zebrafish Proteins / Q000235:genetics / Q000502:physiology*
D019485:Bone Morphogenetic Proteins; D036341:Intercellular Signaling Peptides and Proteins; D020825:T-Box Domain Proteins; C103172:T-box transcription factor 5; D051153:Wnt Proteins; D029961:Zebrafish Proteins; C501128:dkk1b protein, zebrafish