MFN2 and Parkinson disease: Quantification of TH immunoreactivity showed that MPTP caused less reduction of TH immunoreactivity in the striatum in MPTP-MFN2 mice (~30%) compared to MPTP-WT mice (~60%) (Figure 5B), which suggests that Mfn2 OE inhibits MPTP-induced degeneration of dopaminergic axons in the PD model.