title: Lipid droplets as ubiquitous fat storage organelles in C. elegans.
abstract: BACKGROUND
  Lipid droplets are a class of eukaryotic cell organelles for storage of neutral fat such as triacylglycerol (TAG) and cholesterol ester (CE). We and others have recently reported that lysosome-related organelles (LROs) are not fat storage structures in the nematode C. elegans. We also reported the formation of enlarged lipid droplets in a class of peroxisomal fatty acid β-oxidation mutants. In the present study, we seek to provide further evidence on the organelle nature and biophysical properties of fat storage structures in wild-type and mutant C. elegans.
  
  
  RESULTS
  In this study, we provide biochemical, histological and ultrastructural evidence of lipid droplets in wild-type and mutant C. elegans that lack lysosome related organelles (LROs). The formation of lipid droplets and the targeting of BODIPY fatty acid analogs to lipid droplets in live animals are not dependent on lysosomal trafficking or peroxisome dysfunction. However, the targeting of Nile Red to lipid droplets in live animals occurs only in mutants with defective peroxisomes. Nile Red labelled-lipid droplets are characterized by a fluorescence emission spectrum distinct from that of Nile Red labelled-LROs. Moreover, we show that the recently developed post-fix Nile Red staining method labels lipid droplets exclusively.
  
  
  CONCLUSIONS
  Our results demonstrate lipid droplets as ubiquitous fat storage organelles and provide a unified explanation for previous studies on fat labelling methods in C. elegans. These results have important applications to the studies of fat storage and lipid droplet regulation in the powerful genetic system, C. elegans.
authors.affiliation: Stowers Institute for Medical Research, 1000 E, 50th Street, Kansas City, MO 64110, USA.
authors.forename: Shaobing O
authors.initials: SO
authors.lastname: Zhang
authors.forename: Rhonda
authors.initials: R
authors.lastname: Trimble
authors.forename: Fengli
authors.initials: F
authors.lastname: Guo
authors.forename: Ho Yi
authors.initials: HY
authors.lastname: Mak
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism* / Q000648:ultrastructure; D002788:Cholesterol Esters / Q000378:metabolism; D005456:Fluorescent Dyes / Q000737:chemistry; D050356:Lipid Metabolism / Q000502:physiology*; D008247:Lysosomes / Q000378:metabolism; D010078:Oxazines / Q000737:chemistry; D020675:Peroxisomes / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism
chemical_list: D002788:Cholesterol Esters; D005456:Fluorescent Dyes; D010078:Oxazines; D014280:Triglycerides; C044808:nile red