Lipid droplets as fat storage organelles in Caenorhabditis elegans: Thematic Review Series: Lipid Droplet Synthesis and Metabolism: from Yeast to Man

Abstract

Lipid droplets are evolutionarily conserved organelles where cellular fat storage and mobilization are exquisitely regulated. Recent studies have defined lipid droplets in C. elegans and explored how they are regulated by genetic and dietary factors. C. elegans offers unique opportunities to visualize lipid droplets at single-cell resolution in live animals. The development of novel microscopy techniques and protein markers for lipid droplets will accelerate studies on how nutritional states and subcellular organization are linked in vivo. Together with powerful tools for genetic and biochemical analysis of metabolic pathways, alteration in lipid droplet abundance, size, and distribution in C. elegans can be readily connected to whole-animal energy homeostasis, behavior, and life span. Therefore, further studies on lipid droplets in C. elegans promise to yield valuable insights that complement our knowledge gained from yeast, Drosophila, and mammalian systems on cellular and organismal fat storage.

Fig. 1.

Lipid droplets in C. elegans intestinal cells. A: A wild-type larval stage L4 animal. The first intestinal segment is boxed in red. Scale bar, 100 µm. B, C: Electron micrographs showing cross-sections of the first intestinal segment in wild-type (B) and daf-22(−) (C) mutant animals. Red asterisks indicate enlarged lipid droplets. Scale bar, 5 µm. (D) Electron micrograph showing a phospholipid monolayer (red arrowhead) that surrounds an expanded lipid droplet (boxed area in inset) in contrast to phospholipid bilayers (red arrows) of nearby organelles. The lumen of the intestine is at the bottom of the inset. B–D: Reprint from Ref. .

Fig. 2.

ATGL-1::GFP as a marker for lipid droplets in C. elegans intestinal cells. Confocal microscopy and linear unmixing distinguishes lipid droplets that are marked by ATGL-1::GFP fusion protein (in green) and autofluorescent LROs (in red). Scale bar, 10 µm.