Fig. 4

Dark adaptation increases the number of vesicular structures in nrc^a14 photoreceptor inner segments.

TEM images of cone photoreceptors in light (A, B) or dark-adapted (C, D) WT and nrc^a14 retinas. At 4 dpf, larvae were phenotyped by OKR and placed at 28°C either on a normal light/dark cycle, or in complete darkness. 24 hours later, at 5 dpf, larvae were fixed for TEM. Dark adaptation exaggerated the vesicular structure phenotype in nrc^a14 cone photoreceptor inner segments (B vs. D). Cells were scored as “normal”, “vesiculated” or “severely vesiculated” and the quantification is shown in E. Cells with at least 3 vesicular structures >125 nm were scored as “vesiculated” and examples are shown by arrow heads in B and D, cells that contained at least 20 vesicular structures were scored as “severely vesiculated” and an example is shown by an arrow in D. OS = outer segment, N = nuclei. Scale bar = 2 μm in A–D. Graph shows mean, error bars are STDEV for three independent light/dark experiments. In total at least 400–500 cells from 5 larvae were counted per light condition and genotype.