To compare the ability of fusion competent (L76P, W740S) and fusion incompetent (R94Q) Mfn2 mutants to mediate mitochondrial transport, we reintroduced these mutants into Mfn2-/- neurons and assessed their ability to rescue the mitochondrial transport abnormality. As compared to wtMfn2, neither the fusion competent (L76P, W740S) nor fusion incompetent (R94Q) mutants were able to fully restore mitochondrial pause time (A, B) (n = # of axons from which kymographs were generated) or mitochondrial velocities (C).