<i>hFATP1</i> overexpression in mouse RPCs increases neutral lipid accumulation and mitochondrial respiration.

(A, B) Nile Red staining of neutral lipids (red) in mRPCs of a flat-mounted eye cup from wild-type (C57BL/6J) mice (A) and hFATP1 transgenic mice (B). Nuclei are stained with DAPI (blue). Scale bars, 10 μm. (C) Quantification of Nile Red staining in wild-type (WT) and hFATP1 transgenic (hFP1) mRPCs (as shown in A and B). Mean ± SD of n = 19 and 20 animals, respectively. (D) Quantification of sterol esters (SE) and triacylglycerides (TAG) in mRPCs from WT and hFATP1 transgenic mice. Mean ± SD of n = 5 and 7 animals, respectively. (E–E”) mRPCs in whole-mount retinas from WT mice double-stained with Nile Red (E) and anti-perilipin (green, E’). The merged image (E”) shows extensive overlap between Nile Red and perilipin stainings. Scale bars, 5 μm. (F, G) TEM images of mRPCs from wild-type (C57BL/6J) mice (F) and hFATP1 transgenic mice (G). am: apical membrane, Bruch mb: Bruch membrane, me: melanosome, mi: mitochondria, p: phagosome. (H–I’) mRPCs in whole-mount retinas of WT (H) and hFATP1 transgenic (I, I’) mice double-stained with Nile Red and anti-ATP synthase antibody (green, localized to mitochondria). (I’) Magnification of the box in (I) shows the juxtaposition of mitochondria and neutral lipid stores. Scale bars, 5 μm (H, I’), 10 μm (I). (J) Quantification of mitochondrial respiratory function (O2 consumption) in RPCs isolated from WT and hFATP1 transgenic mice. EIImo, basal respiratory rate; EIIImo, β-oxidation, EIIIMPGSO, global respiratory chain function of mitochondrial complexes I and II. The boxes represent the median and lower and upper quartiles, and the whiskers represent the 1.5 interquartile range. N = 21 and 10 WT and transgenic animals, respectively. (K–N) Activities of the TCA cycle enzymes, citrate synthase (K), isocitrate dehydrogenase (DH) (L), oxoglutarate dehydrogenase (OGDH) (M), and fumarase (N) in RPCs isolated from WT and hFATP1 transgenic mice. Mean ± SD of n > 10 mice for each condition. *p<0.05, **p<0.01, ***p<0.001 for WT vs transgenic groups by two-sample t-test.