This episode features Dr. Kole, who shares fascinating insights into the world of myelination in parvalbumin-expressing (PV+) basket cells, a type of fast-spiking inhibitory interneurons vital for regulating local circuit activity and oscillations.

PV+ axons are often myelinated, but the electrical and metabolic implications of interneuron myelination remain an open question in neuroscience. To delve deeper into this, Dr. Kole and his team developed viral constructs for cell type-specific investigation of mitochondria using genetically encoded fluorescent probes.

Their investigations revealed a selective clustering of mitochondria to myelinated segments of PV+ basket cells. Interestingly, while the mitochondrial density increases in excitatory axons, cuprizone-induced demyelination erased mitochondrial clustering in PV+ axons.

When the myelin basic protein was genetically deleted, they still observed mitochondrial clustering at internodes wrapped by noncompacted myelin, signifying that myelin compaction is not mandatory for this process.

In the final part of their study, two-photon imaging was used to monitor action potential-evoked calcium (Ca2+) responses, which revealed that interneuron myelination reduces both the cytosolic and mitochondrial Ca2+ transients.

These findings propose a unique role of oligodendrocyte ensheathment of PV+ axons in assembling mitochondria to selectively fine-tune metabolic demands. Join us as we uncover the mysteries of interneuron myelination with Dr. Kole.

Key Words: Parvalbumin-expressing Basket Cells, Myelination, Mitochondrial Clustering, Cuprizone-induced Demyelination, Two-photon Imaging, Calcium Transients, Oligodendrocyte Ensheathment.

Kole, K., et al. Parvalbumin basket cell myelination accumulates axonal mitochondria to internodes. Nat Commun 13, 7598 (2022). https://doi.org/10.1038/s41467-022-35350-x