FIT2-interacting proteins in LD biogenesis. (A) LipidTOX staining of LDs and quantification of LDs per cell, as well as LD size, in control and tubule-forming protein-depleted HepG2 cells without OA treatment. 3D pictures of LDs were acquired under a confocal microscope by serial layer scanning along the z axis. Colorized pictures were acquired using Imaris software. Different colors indicate different LD diameters, as labeled. n = 86–200 cells/group. All graphs are representative of three repetitions, total LDs numbers >2,000. Mann–Whitney test; ***, P < 0.001. Scale bar, 10 µm. (B) As in A, except each group of cells was treated with 0.2 mM OA for 6 h before LipidTOX staining. n = 82–143 cells/group, total LDs numbers >2,000. Mann–Whitney test; ***, P < 0.001. Scale bar, 10 µm. (C and D) As in A and B, LDs were stained in WT (SEPT2-WT) and septin 2 KO (SEPT2-KO) HepG2 cells with (C) or without (D) OA treatment. The numbers and sizes (diameter) of LDs were measured. For groups without OA treatment, n = 46–76 cells/group; for groups with OA treatment, n = 53–78 cells/group, total LD numbers >2,000. Mann–Whitney test; **, P < 0.01; ***, P < 0.001. Scale bar, 10 µm. siControl, small interfering Control; siFIT2, small interfering FIT2; siREEP5, small interfering siREEP5; siRtn4, small interfering Rtn4. Error bars represent SEM.