Figure 1.

Analysis of Fh1-deficient (Fh1−/−) MEFs. (A) FH activity was compared between Fh1+/+ and Fh1−/− MEFs. Skin fibroblast cells from FH-deficient patients (28) and FH+/+ patients were used as negative and positive controls, respectively. Fh1−/− MEFs show no detectable FH activity, whereas the Fh1+/+ MEFs and normal human skin fibroblasts show equivalent levels of activity. (B) Analysis of intracellular fumarate in cell extracts of Fh1−/− and Fh1+/+ MEFs. (C) Analysis of lactate levels in cellular extracts of Fh1−/− and Fh1+/+ MEFs. Fh1−/− MEFs show increased levels of intracellular lactate compared with Fh1+/+ MEFs. (D) Oxygen consumption was significantly reduced in Fh1−/− MEFs compared with Fh1+/+ MEFs. All data are shown as mean ± SD of triplicate assays.