In vivo time-lapse imaging of mitochondria in healthy and diseased peripheral myelin sheath

• We report a novel approach to analyze mitochondria in Schwann cell of living mice.
• Mitochondria are more abundant in paranodal and perinuclear regions of Schwann cells.
• We characterized mitochondria speed, shape and fusion/fission events in vivo.
• At presymptomatic stages OPA1 mice display fragmented mitochondria in Schwann cells.

The myelin sheath that covers a large amount of neurons is critical for their homeostasis, and myelinating glia mitochondria have recently been shown to be essential for neuron survival. However morphological and physiological properties of these organelles remain elusive. Here we report a method to analyze mitochondrial dynamics and morphology in myelinating Schwann cells of living mice using viral transduction and time-lapse multiphoton microscopy. We describe the distribution, shape, size and dynamics of mitochondria in live cells. We also report mitochondrial alterations in Opa1delTTAG mutant mice cells at presymptomatic stages, suggesting that mitochondrial defects in myelin contribute to OPA1 related neuropathy and represent a biomarker for the disease.