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Myelin basic protein mRNA translocation in oligodendrocytes is inhibited by astrocytes in vitro
S Amur-Umarjee1, T Phan, A T Campagnoni
1Mental Retardation Research Center, UCLA School of Medicine 90024.
Abstract:
Myelin basic protein (MBP) mRNAs are translocated from cell bodies into the slender processes connecting oligodendrocyte somas with the myelin sheath in vivo. This translocation was observed in mixed glial cultures prepared from newborn mouse brains and it occurred in approximately 25% of the cells expressing the gene. However, when "enriched" oligodendrocytes were prepared by shaking them free of other glial cells, MBP mRNA translocation occurred into the processes of essentially all of the cells. When enriched oligodendrocytes were plated back onto astrocytes, MBP mRNA was observed to be confined to the cell bodies of almost all the cells, indicating a marked inhibition of translocation of the mRNA. This inhibition of mRNA translocation did not appear to be mediated through soluble factors secreted by astrocytes or by "astromatrix," but rather through physical contact between the oligodendrocytes and astrocytes. Intact, but not necessarily live, astrocytes were required for the inhibition of mRNA translocation in the oligodendrocytes. Fibroblasts and a neuroblastoma cell line, SKN-SH, did not inhibit MBP mRNA translocation in oligodendrocytes suggesting that astrocyte surface-specific components might be involved in the interaction between astrocytes and oligodendrocytes in culture. These results suggest that contact between these two cell types can influence intramolecular events related to myelinogenesis.
Insights
Oligodendrocyte contact with astrocytes inhibits myelin basic protein (MBP) mRNA translocation into cell processes. This physical interaction, not soluble factors, regulates myelin formation in the central nervous system.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Myelin basic protein (MBP) mRNA is essential for myelin sheath formation.
- MBP mRNA translocation into oligodendrocyte processes is crucial for myelinogenesis in vivo.
- Regulation of MBP mRNA localization is key to understanding myelin development.
Purpose of the Study:
- To investigate the regulation of MBP mRNA translocation in oligodendrocytes.
- To determine the role of cell-cell interactions in controlling mRNA localization.
- To elucidate the cellular mechanisms influencing myelin basic protein synthesis.
Main Methods:
- Primary mixed glial cultures from newborn mouse brains.
- Enrichment of oligodendrocytes via cell shaking techniques.
- Co-culture of enriched oligodendrocytes with astrocytes, fibroblasts, and cell lines.
- Microscopic observation of MBP mRNA localization within cells.
Main Results:
- MBP mRNA translocation occurred in ~25% of cells in mixed cultures.
- Translocation occurred in nearly all enriched oligodendrocytes.
- Physical contact with astrocytes, but not soluble factors, inhibited MBP mRNA translocation.
- Intact astrocytes were necessary for this inhibitory effect.
Conclusions:
- Astrocyte-oligodendrocyte physical contact regulates MBP mRNA translocation.
- This interaction influences intracellular events critical for myelinogenesis.
- Astrocyte surface components may mediate this specific cell-cell communication.