FAM92A1 depletion resulted in abnormal mitochondrial morphology and inner membrane ultrastructure (A) Immunofluorescence images of mitochondrial morphology after treatment with siRNA for 72 h. Bars: 10 µm (main images); 2 µm (insets). (B) Quantification of cells with fragmented mitochondria after FAM92A1 was depleted for 72 h. At least 250 cells each from the control and FAM92A1-knockdown cells were analyzed. (C) Transmission EM images of mitochondria in U2OS cells treated with siRNA for 72 h. Bars, 200 nm. (D) ET of mitochondria in control and FAM92A1-knockdown cells. The outer membrane (purple), inner membrane (yellow), and cristae (green) were superimposed on a tomographic slice and viewed from the top and side. Bars, 200 nm. (E–H) Quantification of the MIM ultrastructural profile including mitochondrial diameter (E), percentage of mitochondria with lamellar cristae (F), number of lamellar cristae per mitochondrial length (G), and length of cristae (H). At least 200 mitochondria were used for mitochondrial morphology analysis (E and F). At least 100 mitochondria was used for analyzing the number of lamellar cristae per mitochondrial length (G). 214 and 236 cristae were used for analyzing the cristae length in control and FAM92A1 siRNA–treated cells, respectively (H). Error bars indicate mean ± SEM. ***, P ≤ 0.001, Student's t test.