Figure 2.

Crb2a is expressed in all types of photoreceptors and Müller cells, whereas Crb2b is predominantly expressed in green, red and blue cones. A, B. Vertical imaging of the photoreceptor layer showed that Crb2a localizes to inner segment interfaces between photoreceptors and to the apical processes of Müller cells, which were highlighted by GFP expression in the Tg(gfap:GFP) ^mi2001 background (Bernardos and Raymond, 2006). By contrast, Crb2b localizes predominately at the junctional interfaces between the green, red and blue cone inner segments but not to the Müller cell apical processes. The long and short Müller cell apical processes are indicated with arrows. The arrowheads indicate the OLM. C, D. Slightly tilted tangential imaging of the photoreceptor layer revealed broader Crb2a expression and more restricted Crb2b localization to the junctional regions between green, red, and blue cones. Lettered arrows in panels C and D indicate UV (U), green (G), red (R), and blue (B) cones. The drawings on the right illustrate the planes of imaging (solid arrows) relative to the orientations of photoreceptors. E. Unlike Crb2a, Crb2b was not detected in Müller cells (left panels, arrows) or UV cones (middle panels, arrows) in 5-dpf nok^m520 mutant retinas. However, both Crb2a and Crb2b were detected in blue cones (right panels, arrow, GFP positive and Zpr1 negative) and double cones (Zpr1 positive cells). The backgrounds of various transgenic fish used here are indicated above the panels. F. In wildtype adult rod:GFP fish, Crb2a but not Crb2b was detected at the inner segments of rods (green). Also see Figures S1 and S2.