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Myelin basic protein gene dosage effects in the PNS
1Department of Neurology, University of Connecticut Health Center, Farmington 06030, USA.
Abstract:
Myelin basic protein (MBP) plays an essential adhesive role in the formation of compact myelin in the central nervous system (CNS), but not in the peripheral nervous system (PNS). Morphologic data suggest that MBP controls the number of cytoplasmic channels or Schmidt-Lanterman incisures (SLI) present in PNS myelin. The levels of connexin-32 (Cx32) and myelin-associated glycoprotein (MAG), two components of the incisures, are inversely proportional to the levels of MBP in sciatic nerves of mice affected by the shiverer (shi) mutation, while protein zero (P0) and peripheral membrane protein 22 (PMP22), two structural components of compact myelin, remain constant. The levels of P0, PMP22, Cx32, and MAG mRNA do not vary in relationship to the levels of MBP. This indicates that MBP exerts its effect on Cx32 and MAG at a posttranscriptional level and suggests a new function for MBP in regulating gene expression in the PNS.
Insights
Myelin basic protein (MBP) regulates peripheral nervous system (PNS) myelin structure by affecting connexin-32 and myelin-associated glycoprotein levels post-transcriptionally. This reveals a novel role for MBP in gene expression regulation within the PNS.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Myelin basic protein (MBP) is crucial for compact myelin formation in the central nervous system (CNS).
- Its role in the peripheral nervous system (PNS) is less understood, though it may influence Schmidt-Lanterman incisures (SLI).
- SLI are cytoplasmic channels within PNS myelin, containing proteins like connexin-32 (Cx32) and myelin-associated glycoprotein (MAG).
Purpose of the Study:
- To investigate the role of MBP in regulating the levels of Cx32 and MAG in PNS myelin.
- To determine if MBP affects the expression of Cx32 and MAG at the transcriptional or post-transcriptional level.
- To explore a potential new function for MBP in PNS gene expression regulation.
Main Methods:
- Analysis of protein and mRNA levels in sciatic nerves of shiverer (shi) mutant mice, which have reduced MBP levels.
- Quantification of MBP, Cx32, MAG, protein zero (P0), and peripheral membrane protein 22 (PMP22) in both protein and mRNA forms.
- Comparison of protein and mRNA levels to assess post-transcriptional regulation.
Main Results:
- MBP levels were inversely proportional to Cx32 and MAG levels in shi mutant mouse sciatic nerves.
- Levels of P0 and PMP22, structural components of compact myelin, remained constant.
- mRNA levels for P0, PMP22, Cx32, and MAG did not change in relation to MBP levels.
Conclusions:
- MBP influences Cx32 and MAG levels in the PNS at a post-transcriptional level.
- This suggests a novel function for MBP in regulating gene expression in the PNS, beyond its role in compact myelin adhesion.
- MBP's impact on SLI formation and composition is mediated post-transcriptionally.