TRAK1 and Hypertonia: To determine the effect of hypertonia-associated mutation on Trak1 function, we took advantage of the Trak1 depletion phenotype (Fig. 1) and performed rescue experiments by expressing shTrak1-resistant GFP-tagged full-length wild-type Trak1 protein (Trak1 WT), hypertonia-associated Trak1 mutant (Trak1 hyrt), or GFP control in Trak1-depleted cells and assessing their abilities to rescue the mitochondrial morphological defects (Fig. 3B–D).