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Fig. 2 Mislocalized mitochondria are abnormal and reside in and outside of cone photoreceptors (A) Transmission electron micrographs taken at the optic nerve. Cones with activated mKR have many mitochondria with disturbed, swollen morphology both in and outside of the ellipsoid clusters; an inset (black box) shows a cone ellipsoid containing multiple swollen mitochondria. Black arrowhead: ellipsoid cluster with typical mitochondria morphology, white arrowhead: ellipsoid cluster with swollen mitochondria. Scale bar: 5 μm. (B) Quantification of individual cone mitochondria from slices in (A). A greater fraction of mitochondria are swollen and mislocalized in mKR+ cones. All mislocalized mitochondria had swollen morphology. n = 2 kR− fish (641 and 759 total mitochondria) and n = 3 kR+ fish (520, 613, and 566 total mitochondria). ∗p < 0.05 and ∗∗∗∗p < 0.0001 using a two-way ANOVA. (C) Imaging of Tg(gnat2:mtBFP, gnat2:GFP) fish reveals that mislocalized cone mitochondria reside inside cones (filled arrowheads) and partially or completely outside of cones (unfilled arrowheads). Hi-C, high-contrast to enhance visibility of mitochondria. Scale: 5 μm. (D) Quantification of mislocalized mitochondria by colocalization of cone GFP; cone− includes mitochondria that appear partially or completely out of cones (see C). mtKR increases cone mitochondria number both inside and outside cones. ∗p < 0.05 and ∗∗∗∗p < 0.0001 using a two-way ANOVA. n = 13 fish each condition. (E) Pooled cone-mislocalized mitochondria totals across all fish binned by retinal region. IR, inner retina; PR, photoreceptor layer. (F) Immunohistochemistry images of mislocalized mitochondria (filled arrows) colocalized with MTCO1 in PR and inner retina IR. Fraction of mislocalized cone mitochondria colocalized with mitochondrial protein, MTCO1. mKillerRed−: 74 mislocalized mitochondria from 4 eyes mtKillerRed+: 104 mislocalized mitochondria from 5 eyes. Comparisons are ns with unpaired t test. Scale: 5 μm.