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Developmental expression of the myelin gene MOBP in the rat nervous system
1Brain Research Institute, University of Zurich, Switzerland.
Abstract:
The myelin-associated/oligodendrocyte basic proteins (MOBPs) are recently discovered constituents of myelin and are small, cytoplasmic, and highly basic proteins exclusively expressed postnatally by oligodendrocytes. Due to a clustering of positively charged amino acids observed in the most abundant MOBP isoform similar to myelin basic protein (MBP) and P0, it was speculated that MOBP could function in myelin sheath compaction. The present report strongly supports this view. A direct comparison of MBP and proteolipid protein (PLP) gene expression with that of MOBP by in situ hybridization revealed a very similar regional distribution. It was found that MOBP expression was abundant in the rat CNS at postnatal day 15 (P 15) but is restricted to densely myelinated regions. In contrast to MBP and PLP, expression of MOBP was undetectable in the peripheral nervous system during the entire development. Interestingly, MOBP mRNA was localized in oligodendrocyte processes even at early postnatal stages and throughout development. MOBP showed a very specific timing of expression: in spinal cord and brain, MOBP gene expression occurred significantly later (2-3 days) than that of MBP and PLP, but slightly earlier than myelin oligodendrocyte glycoprotein gene expression. MOBP proteins appeared in spinal cord and brain stem also after MBP protein, suggesting that the MOBPs functionally act after the structural myelin proteins MBP and PLP. Our findings imply a function of MOBP during the late steps of myelin formation, presumably at the initiation of sheath compaction.
Insights
Myelin-associated/oligodendrocyte basic proteins (MOBPs) are newly identified myelin components. Their expression timing suggests a role in late-stage myelin sheath compaction, following other structural myelin proteins.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Myelin-associated/oligodendrocyte basic proteins (MOBPs) are recently identified myelin constituents.
- MOBPs are small, cytoplasmic, highly basic proteins exclusively expressed postnatally by oligodendrocytes.
- The positive amino acid clustering in MOBPs suggests a potential role in myelin sheath compaction, similar to MBP and P0.
Purpose of the Study:
- To investigate the expression patterns and potential function of MOBPs in myelin formation.
- To compare MOBP expression with established myelin proteins like MBP and PLP.
Main Methods:
- In situ hybridization was used to compare the gene expression of MOBP, MBP, and PLP.
- Analysis of MOBP mRNA and protein localization in the developing rat central nervous system (CNS).
Main Results:
- MOBP gene expression showed a similar regional distribution to MBP and PLP in the rat CNS, peaking at postnatal day 15.
- MOBP expression was restricted to densely myelinated CNS regions and was undetectable in the peripheral nervous system.
- MOBP gene and protein expression occurred later than MBP and PLP, suggesting a role in later stages of myelination.
Conclusions:
- MOBPs are specifically expressed in the CNS and their expression timing indicates a function in the late steps of myelin formation.
- Findings support the hypothesis that MOBPs are involved in initiating myelin sheath compaction.