(a) HeLa cells transfected with plasmids encoding GFP or GFP-IRGMd were stained with MTR and imaged by live-cell confocal microscopy. Scale bars, 5 μm. (b-d) Quantification of mitochondrial morphologies in cells transfected with IRGMd, IRGMdS47N or IRGMb GFP fusions (control cells express GFP only). 