Fig. 6

Outer segment development is rescued by constitutively active Rab8a. (A–A”) Cryosections of 4 dpf wt larvae with transient expression of WT mCherry-tagged Rab8a in cone PRs (tacp:mCherry-Rab8aWT) counterstained with DiO to mark OSs (green) and DAPI for nuclei. Note the punctate expression pattern of Rab8a concentrated in the inner segment space (arrow). (B–B”) A similar expression pattern is observed when expressing this transgene in ta3−/− PRs (arrow). (C–C”) Expression of a constitutively active form of mCherry-tagged Rab8a (tacp:mCherry-Rab8aCA) in wt cone PRs. (D–D”) ta3−/− PRs expressing constitutively active Rab8a develop OSs (arrowhead in D”). (E) Quantification of the proportion of 4 dpf ta3 mutant PRs expressing constitutively active Rab8a with OSs (red circles), ta3 mutant PRs expressing wild-type Rab8a with OSs (green squares) or ta3 mutant PRs without transgenic Rab8a expression with OSs (black triangles). Only the constitutively active form of Rab8a rescues OS formation in ta3 mutants (****p < 0.0001, NS not significant, Student’s t-test, n > 20 larvae expressing either transgene and 13 non-transgenic larvae). Each datapoint represents one individual larva. Bars are standard deviation. ONL outer nuclear layer, OS outer segment, S synapse. Scale bars: 3 µm in all panels.