Fig. 1

a Immunoblotting and quantification of MMUT and b its enzyme activity in control and MMA kidney cells, n = 3 biologically independent experiments. β-actin was used as a loading control. c, g Cells were transduced with adenoviral particles carrying the mitochondrially targeted green fluorescent protein (Ad-mito-GFP, green). c After 24 h post-transduction, the cells were immunostained for MMUT (red) and imaged by confocal microscopy. Yellow indicates the colocalization. d Quantification of methylmalonic acid (MMA) levels by liquid chromatography tandem mass spectrometry (LC-MS/MS, n = 3 biologically independent samples). e Representative electron micrographs and quantification of the shape (expressed as circularity) of the mitochondrial network in control and MMA cells; n = 527 mitochondria pooled from 24 control cells and n = 310 mitochondria pooled from 20 MMA cells. Values are pooled from two biologically independent experiments. Dotted yellow squares represent regions of the respective panels magnified. f Representative electron micrographs showing the mitochondrial network in kidney biopsies from an individual healthy control subject and a patient with MMA. g Representative inverted images (left) and quantification of shape (expressed as circularity, top right) or interconnectivity (bottom right) of the mitochondrial network in control and MMA cells; each point representing the average values for circularity or interconnectivity in a cell, n = 10 cells per each condition pooled from two biologically independent experiments. Plots represent mean ± SEM. Two-tailed Student’s t-test, *P < 0.05, ***P < 0.001 and ^#P < 0.0001 relative to control cells. Scale bars are 10 μm in c and g, and 1 μm (top) and 250 nm (bottom) in e and 2 μm in f. Unprocessed scans of original blots are shown in Supplementary Fig. 13. Source data are provided as a Source Data file.