Fig. S2

Retinoic acid signaling within a subpopulation of red- or green-sensitive cone photoreceptors in response to prolonged retinoic acid treatment. (A to C) Embryos carrying the RARE-YFP transgene were treated with DMSO (A to C) or 0.3 μM RA from 36 to 60 hpf, and processed as 4 μm cryosections for indirect immunofluorescence with an anti-GFP antibody (green) and the antibody zpr1 which labels both red- and green-sensitive cones. (A) In control embryos red and green-sensitive cones are found widely distributed in the retina. (B) In control embryos, endogenous reporter expression is limited to cells of the ventral retina, (bracket) but found in all retinal layers in that region. (C) Merged panel from A and B showing no colocalization with YFP in the dorsal retina (inset). (D) A retina from an embryo treated with RA. (E) In experimental embryos, the RA treatment leads to widespread expression of YFP, including many cells in the ONL. (F) Merged panel from D and E, showing some cones in the dorsal retina expressing YFP (inset, arrowheads) and many that do not express YFP (inset, arrows). Bar = 50 μm.