Abstract: Optimal propagation of neuronal electrical impulses depends on the insulation of axons by myelin, produced in the central nervous system by oligodendrocytes. Myelin is an extension of the oligodendrocyte plasma membrane, which wraps around an axon to form a compact multi-layered sheath. Myelin is composed of a substantially higher proportion of lipids compared to other biological membranes and enriched in a small number of specialized proteins. Myelin internodes are plastic, with the capacity to make relatively subtle changes in thickness, elongate or retract, or more dramatically add or delete segments, in response to stimuli such as neuronal activity or memory formation, and during maturation and aging (de Faria et al., 2021). For myelin to rapidly adapt, the capacity to regulate the synthesis and degradation of lipids and myelin-specific proteins is essential. During myelin compaction, the cytoplasm is largely excluded from extending oligodendrocyte processes, and is eventually restricted to the paranodal loops that border the nodes of Ranvier and to specialized myelinic channels that connect paranodal cytoplasm to the cell body (Figure 1A). Paranodal loops contain a rich complement of organelles, including peroxisomes (Kassmann et al., 2011), endoplasmic reticulum-like tubules (Nakamura et al., 2020), and mitochondria (Nakamura et al., 2020; Nakamura and Kennedy, 2021). Mitochondria traveling through the cytoplasmic channels of myelin-like compact membrane of oligodendrocytes have been visualized in vitro (Nakamura et al., 2020; Nakamura and Kennedy, 2021), suggesting that similar migration traversing the internode occurs in vivo. To ensure appropriate myelin growth and maintenance, migrating mitochondria will likely be anchored where local lipid turnover is needed. However, no mitochondrial docking protein in oligodendrocytes had been identified. In axons, mitochondria are anchored to microtubules at metabolically demanding sites by the docking protein syntaphilin (SNPH; Lin and Sheng, 2015). Our recent findings demonstrate that SNPH is also expressed by oligodendrocytes and associated with mitochondria (Nakamura et al., 2023). Identifying how mitochondrial dynamics and migration are regulated in myelinating oligodendrocytes is critical to understand the role of mitochondrial metabolism in myelination.