We found that the ability of exogenous Trak1 to induce mitochondrial hyperfusion was significantly reduced by hypertonia-linked mutation, as only 59.5% ± 8.6% of Trak1 hyrt-expressing cells had hyperfused mitochondria, with predominately elongated mitochondria rather than enlarged mitochondria (Fig. 4B and 4C). Here, TRAK1 is linked to Hypertonia.