Fig. 4

Alteration of mitochondria by adenylate kinase 4 (AK4) knockdown. a Representative electron microscope images of cells in normoxic condition. Left panel: HeLa cells transfected with control short hairpin (sh)RNA. Right panel: HeLa cells expressing adenylate kinase 4 (AK4) shRNA. The arrows indicate mitochondria. Right: The graphs show the relative mitochondrial counts and cross-sectional area, as indicated. Mitochondrial numbers were counted in ten random pictures taken at a magnification of 10,000. Mitochondrial size was determined using BZ-II analyzer (Keyence) software. We examined 70 mitochondria in control shRNA cells and 100 mitochondria for in AK4 shRNA cells. b Relative mitochondrial (mt)DNA copy number under the conditions indicated. mtDNA was measured by real-time PCR using the Human mtDNA Monitoring Primer Set (Takara Japan). Briefly, we measured mtDNA (ND1 and ND5), then normalized to the nuclear DNA level (SLCO2B1 and SERPINA1). The mtDNA content index was the ratio of mtDNA/nuclear DNA, calculated by dividing the ND1 and ND5 signals by the SLCO2B1 and SERPINA1 signals. P < 0.05, **P < 0.01