FIGURE 2

Trβ2 gain-of-function induces co-expression of lws2 in non-LWS cones. The proportion of photoreceptors co-labeled lws2 and a different opsin type per unit area also increases after thyroid hormone (T3) treatment. (A) Fluorescence in situ hybridization (HCR) of 4dpf fish showing lws2 co-expression with selected opsin transcripts (sws1, sws2, rh2-1, rh2-2, and rho). In wildtype fish, no co-expression with other opsin subtypes within individual cones was observed (WT + DMSO and WT + T3 rows). However, lws2 co-expression was observed in both transgenic groups with increased proportions in the transgenic group that received T3 treatment (GOF + T3). No clear co-labeling of sws2 (cyan) or rho (green) with lws2 was observed in either transgenic group. The arrowheads indicate cells that are co-labeled for both lws2 and another opsin subtype. Insets display enlarged regions with separate channels to highlight co-expression. (B) Box and whisker plot showing the percentage of cells that are positive for both lws2 and sws1 or rh2-1, rh2-2, rho per 3500 μm² area dorsal to the optic nerve head. Statistical significance is represented as ****P < 0.0001. P-values were calculated using beta regression to compare co-expression proportions in transgenic DMSO and T3 groups. (C) Stacked bar graph of photoreceptor counts in WT and trβ2 GOF after DMSO/T3 treatment. Colors indicate opsin expression: lws1+ (green), lws2+ (magenta), sws1+ or rh2+ (yellow), sws2+ or rho+ (gray), and lws2/sws1+ or lws2/rh2+ co-expression (orange crosshatch). Scale bar = 10 μm.