miR-451 represses mitochondrial respiration during erythropoiesis. (A) Mitochondrial complex IV activity in WT and KO FL erythroblasts. (B) Mitochondrial membrane potential in WT and KO FL erythroblasts measured by flow cytometry quantification of TMRM uptake. (C) Mitochondrial respiration in WT and KO FL erythroblasts measured by cellular OCR at baseline and after treatment with various inhibitors. The OCR prior to addition of oligomycin depicts basal respiration, after oligomycin depicts proton leak, and after carbonyl cyanide-4 (trifluoromethoxy) phenylhydrazone (FCCP) depicts maximal respiratory capacity. Antimycin (Ant.) A plus rotenone arrests all mitochondrial respiration. (D) Mitochondrial mass measured by flow cytometry quantification of MitoTracker uptake. (E) Flow cytometry analysis of mitochondrial membrane potential and mitochondrial mass in WT and KO FL erythroblasts at specific developmental stages. Bar graphs show mean fluorescent intensity (MFI) of mitochondrial dyes TMRM (membrane potential) and MitoTracker (mass). (F) Effect of Cox10 knockdown on mitochondrial membrane potential in WT and KO FL erythroblasts measured by flow cytometry quantitation of TMRM dye. Short hairpin RNA (shRNA) targeting Luciferase is used as a control. Bar graphs show mean plus or minus SEM for data from the indicated number (n) of biological replicates. *P < .05, **P < .01, ***P < .001. (G) Proposed mechanism through which miR-451 represses Cox10 mRNA to inhibit mitochondrial respiration.