Representative images of normal (control) (**A**) and G93A muscle fibers (**B**). The first image was taken 2 min after the photoactivation because it took a couple of minutes to reconfigure the confocal microscope system to conduct the simultaneous scan. The photoactivation region inside the fiber was marked with the box (white dashed line). Bar: 10 µm. (**C**) is the time course of mt-PAGFP migration. The linear regression was used to fit the data to evaluate the migration rate. Solid lines are the linear regression of the data after 2 minutes of the photoactivation. By assuming the migration step is zero at time zero, the linear regression was applied to determine the migration rate during the first 2 min (dashed line). The migration rates are listed in Table **1**. (P<0.01).