Single molecule tracking of myelin basic protein during oligodendrocyte differentiation

This study aimed to expand our understanding of myelin basic protein (MBP), a key component of central nervous system myelin, by tracking and quantifying individual MBP particles during oligodendrocyte differentiation. MBP particle directionality, confinement and diffusion were tracked by rapid TIRF and HILO imaging of dendra2 tagged MBP in three stages of mouse oligodendroglia: oligodendrocyte precursors, early myelinating oligodendrocytes, and mature myelinating oligodendrocytes. The directionality and confinement of MBP particles increased at each stage consistent with the progressive transport towards, and recruitment into, emerging myelin structures. Unexpectedly, diffusion data presented a more complex pattern with sub-populations of the most diffusive particles disappearing at the transition between the precursor and early myelinating stage, before re-emerging in the membrane sheets of mature oligodendrocytes. This diversity of particle behaviours, which would be undetectable by conventional ensemble averaged methods, are consistent with a multifunctional view of MBP involving roles in myelin expansion and compaction.