Fig. 5: LpR1 regulates lipid homeostasis in the larval brain.

a Lipid droplets are detected in the larval optic neuropil (LON). Nile red staining (red) and Lsd2-YFP (green) expression both label lipid droplets in the larval brain. Representative projected confocal images of the larval brain lobe (left) and the LON region (circled region, right) are shown (observed in at least 10 brains). b Lipid droplets (red) are found in the vicinity of the LNv dendrites. Representative confocal images show the 24B10 stained axonal terminals of larval photoreceptor cells (gray) making contacts with LNv dendrites (labeled by CD8::GFP, green) within LON (observed in at least 10 brains). c The density of lipid droplets in LON is quantified by 3D reconstructions. Representative projected confocal images (top: green, LNv dendrites; red, lipid droplets) and 3D reconstructions for lipid droplet quantification (bottom: gray, LNv dendrite; red, lipid droplets) are shown (observed in at least 10 brains). d Compared to controls, LpR1^−/− mutants shows decreased lipid droplet density in LON. Representative confocal images and quantifications are shown. Data are presented as mean values +/− SEM. Statistical significance was assessed by a two-tailed Student’s t-test. p < 0.0001, t = 4.879, df = 26. n = 14 for both groups. n represents individual larval brain samples. ***p < 0.001. e Representative images from MALDI mass spectrometry analysis revealed a general reduction of lipid contents in the LpR1^−/− the mutant brain. Representative H&E stained adult fly brain sections (left) and the MALDI scan images (right) are shown (observed in at least 4 biological repeats). The lipid species, their corresponding m/z spectrum, and the scale of the heatmap are as indicated. Bottom: The average fold of reduction in the LpR1^−/− mutant, as compared to wild-type controls, are shown as numbers next to the arrow.