MFN2 and Hypertonia: By using co-immunoprecipitation analyses, we found that endogenous Trak1 specifically interacted with Mfn1 and Mfn2 but not with Drp1 (Fig. 6C) and that the ability of Trak1 to interact with mitofusins was not affected by hypertonia-associated mutation (Fig. 6D).