Oligodendroglial myelination requires astrocyte-derived lipids

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Myelination is crucial for rapid nerve impulse propagation in the vertebrate nervous system.
• Oligodendrocytes and Schwann cells are traditionally considered the sole synthesizers of myelin components.
• The cell-autonomous assembly of myelin membranes has been the prevailing hypothesis.

Purpose of the Study:

• To investigate the contribution of non-myelinating glial cells, specifically astrocytes, to CNS myelin lipid synthesis.
• To determine the role of sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP) in glial lipid biosynthesis and myelination.
• To elucidate the mechanisms of lipid supply for myelin formation in vivo.

Main Methods:

• Conditional knockout mouse models with targeted deletion of SCAP in oligodendrocytes and/or astrocytes.
• Analysis of central nervous system (CNS) myelination in mutant mice at different developmental stages.
• Investigation of lipid incorporation into myelin membranes and the effect of dietary lipid supplementation.

Main Results:

• Oligodendrocyte-specific SCAP inactivation led to transiently retarded CNS myelination.
• Deletion of SCAP in astrocytes, alone or with oligodendrocytes, caused persistent hypomyelination.
• Inhibition of astroglial lipid synthesis prompted oligodendrocytes to utilize circulating lipids, and lipid-enriched diets rescued hypomyelination.

Conclusions:

• Astrocytes significantly contribute lipids to CNS myelin, challenging the cell-autonomous myelin assembly model.
• Horizontal lipid flux from astrocytes to oligodendrocytes is a critical process in normal brain development and myelination.
• Targeting glial lipid synthesis pathways offers potential therapeutic avenues for myelin disorders.