Oligodendrocytes express synaptic proteins that modulate myelin sheath formation

Area of Science:

• Neuroscience
• Cell Biology
• Developmental Biology

Background:

• Vesicular release from neurons is crucial for synaptic function.
• Oligodendrocytes, the myelin-producing cells in the central nervous system, express synaptic-like proteins, suggesting shared communication mechanisms with synapses.
• The precise molecular mechanisms governing axon-myelin interactions during myelination are not fully understood.

Purpose of the Study:

• To investigate whether synaptic vesicle release and associated proteins play a role in myelin sheath formation.
• To determine if oligodendrocytes utilize similar molecular machinery as postsynaptic densities at axon-myelin contacts.
• To identify specific transsynaptic adhesion molecules involved in mediating axon-glial communication for myelin growth.

Main Methods:

• Utilized fusion proteins to track synaptic vesicle dynamics and membrane fusion in zebrafish during developmental myelination.
• Examined the expression and localization of postsynaptic density protein 95 (PSD95) in oligodendrocytes.
• Disrupted candidate PDZ-binding transsynaptic adhesion proteins in oligodendrocytes to assess their impact on myelination.

Main Results:

• Synaptic vesicles were observed to accumulate and undergo exocytosis at myelin sheath ensheathment sites.
• PSD95 localization in oligodendrocytes often mirrored the pattern of synaptic vesicle exocytosis sites.
• Disruption of certain transsynaptic adhesion proteins, notably Cadm1b, affected myelin sheath length and number, with Cadm1b directly mediating sheath growth through PDZ binding and axonal adhesion.

Conclusions:

• Axon-glial communication, analogous to synaptic communication, is involved in regulating myelin sheath formation and plasticity.
• Cadm1b is identified as a key transsynaptic adhesion molecule mediating myelin sheath growth.
• These findings reveal novel molecular targets for understanding and potentially treating developmental myelination disorders.