Depletion of SREBP alters the cellular lipid spectrum and causes loss of mono-unsaturated fatty acids. (A) Lipid analysis of cells depleted of SREBP1 (siBP1) or SREBP2 (siBP2) either alone or in combination (siBP1 + 2) and treated with 100 nM 4-OHT or solvent (ethanol) for 24 hours in medium containing 1% LPDS. Heat map represents log 2 fold changes in concentrations of the different lipid species relative to control-transfected cells (siCtr) treated with solvent (ethanol) (see Additional file 6: Table S2 for complete dataset). (B) Heat map representing changes in free fatty acid species. The percentage of each fatty acid in the control sample is also indicated (% of total). Arrows indicate palmitoleic and oleic acid (see Additional file 7: Table S3 for complete dataset). (C) Diagram showing the synthetic pathway for the generation of unsaturated fatty acids. Desaturation of C:16 and C:18 fatty acids by stearoyl-CoA desaturase (SCD) is the rate-limiting step. (D) Graphs showing the changes in the two major mono-unsaturated fatty acids, oleic and palmitoleic acid, following SREBP depletion represented as percentage of total free fatty acids (FFA). Graphs show mean and range of two independent experiments. (E) Changes in the two major saturated fatty acids, stearic and palmitic acid, following SREBP depletion represented as percentage of total free fatty acids (% of FFA). Graphs show mean and range of two independent experiments. ELOVL, long-chain fatty-acyl elongase; FADS, fatty acid desaturase.