We thank Shreyas Sinha and Elmon Meijering for their assistance during the initial phase of experiments. Microscopic images were acquired at the Center of Cellular Imaging, Faculty of Veterinary Medicine, Utrecht University. We thank Esther van’t Veld for technical assistance. Lipid analyses were performed at the Lipidomics Centre, Faculty of Veterinary Medicine, Utrecht University. We thank Jeroen Jansen for technical assistance. EM for quantification of LD size in yeast (Fig. 4) was performed at the Electron Microscopy Core Facility at the University of Texas Southwestern Medical Center. We thank Alain de Bruin, Simon de Neck, and Elsbeth van Liere at the Dutch Molecular Pathology Center (Utrecht University) for expert help and analysis of seipin KO livers.

This research was supported in part by the Intramural Research Program of the National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. H. Yang is supported by project grants from the National Health and Medical Research Council (1141938, 1141939, and 1144726).

The authors declare no competing financial interests.

Author contributions: M.R. Molenaar: Conceptualization, methodology, validation, formal analysis, investigation, writing - original, review and editing, visualization. K.K. Yadav: Formal analysis, investigation. A. Toulmay: Formal analysis, investigation. T.A. Wassenaar: Methodology, software, validation, formal analysis, investigation, writing - original, visualization. M.C. Mari:Formal analysis, investigation, writing - original, visualization. L. Caillon: Formal analysis, investigation. A. Chorlay: Formal analysis, investigation. I.E. Lukmantara: Formal analysis, investigation. M.W. Haaker: Formal analysis, investigation. R.W. Wubbolts:Formal analysis, investigation. M. Houweling: Conceptualization, writing - original. A.B. Vaandrager: Conceptualization, writing - original. X. Prieur:Investigation.F. Reggiori:Formal analysis, writing - original. V. Choudhary: Formal analysis, investigation. H. Yang: Formal analysis, writing - original. R. Schneiter: Formal analysis, writing - original. A.R. Thiam: Methodology, analysis, writing - original. W.A. Prinz:Conceptualization, methodology, formal analysis, writing - original, review and editing. J.B. Helms: Conceptualization, methodology, writing - original, review and editing, supervision.