M-opsin and L-opsin expression in fetal retinas and WERI-RB-1 cells.

(A) 20 μm section of a fetal day 122 retina with expression of M-/L-opsin protein (magenta), Ki67 (cyan), and Hoechst/nuclei (white). M-/L-opsin protein is observed in the ONL. Ki67 expression indicates proliferating cells. (B) M- and L-opsin expression in control- and T3-treated WERI-Rb-1 retinoblastoma cells (N = 1 experiment). The WERI-Rb-1 retinoblastoma cell line expresses M- and L-opsin at low levels [50]. T3, the active form of thyroid hormone, induces M- and L-opsin expression in WERI-Rb-1 cells [15,51]. Values indicate total pileup count normalized to total read count. Each data point indicates 1 nucleotide difference in M- or L-opsin. Original data sets are in S5 Data. (C–I) Analysis of M- and L-opsin mRNA expression in 130-day-old human fetal retina. (C) Example of M- and L-opsin mRNA expression in 130-day-old human fetal retina section. Anterior = left, posterior = right. Dorsal/ventral orientation is unknown. Colored boxes indicate regions shown in (D–G) zoomed in regions from (C). The central region in (F) expressed opsin mRNA. The more peripheral regions in (D), (E), and (G) show no expression of opsin mRNA. (H) Quantification of cones expressing M- and L-opsin mRNA from the temporal to nasal sides of the globe. (I) Identification of retinal layers using Hoechst (light gray) in the experiment in (S2C–S2H Fig). M-opsin (blue), L-opsin (pink), and retinal pigmented epithelial (RPE, dark brown) colorimetric signals were deconvoluted to generate pseudo fluorescent images. These were overlaid with Hoechst nuclear counterstains to visualize retinal layers. ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer. Original data sets are in S5 Data.

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