Fig. 5.

Overexpression of bmp4 requires radar to alter dorsal–ventral patterning. (A--F) Expression patterns visualized by whole-mount in situ hybridization of eyes from 26-somite embryos. Neural retina is outlined with dashed line; green bracket identifies optic fissure location and size; red bracket indicates location of ectopic fissures in mutants. (Scale bars, 50 μm.) radar expression is mildly expanded (A), tbx5 expression dramatically increases (B), and vax2 expression is eliminated (C) in WT; hsp70:gal4; UAS:bmp4 embryos. radar expression remains absent (D), tbx5 is expressed at low levels in ectopic locations (E), and vax2 expression is dorsally expanded (F) in radar^s327 mutant; hsp70:gal4; UAS:bmp4 embryos. (G) Summary model for retinal patterning, synthesizing roles for Radar with known dorsal–ventral patterning genes. Radar is the critical determinant of dorsal identity and is required for normal expression of Bmp4, Tbx transcription factors, and ephrin-B. Blue letters indicate which panels in this figure and in Fig. 4 and Fig. S3F provide evidence for the relationships shown.