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Myelination in the jimpy mouse in the absence of proteolipid protein
I D Duncan1, J P Hammang, S Goda
1Department of Medical Sciences, University of Wisconsin School of Veterinary Medicine, Madison 53706.
Abstract:
A point mutation in the gene for proteolipid protein (PLP) has been suggested to account for the dysmyelination seen in the jimpy mouse mutant. Despite the absence of PLP, the major integral membrane protein of central nervous system (CNS) myelin, this study shows that there are many scattered myelinated fibers present in the spinal cord of this murine mutant which are immunocytochemically positive for myelin basic protein (MBP), yet negative for PLP. This lack of PLP results in an abnormal compaction of the extracellular leaflets of the myelin sheath and the formation of an abnormal intraperiod line. These results are similar to those seen in another X-linked myelin mutant, the myelin-deficient rat (Duncan et al.: Proc. Natl. Acad. Sci. U.S.A., 84:6287-6291, 1987), and show that a multilamellar membrane can be formed in the absence of its major integral membrane protein.
Insights
The jimpy mouse mutant spinal cord contains scattered myelinated fibers positive for myelin basic protein (MBP) but lacking proteolipid protein (PLP). This indicates multilamellar membranes can form without PLP, despite abnormal myelin compaction.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- The jimpy mouse mutant exhibits dysmyelination, a condition affecting myelin formation.
- Proteolipid protein (PLP) is the primary integral membrane protein in central nervous system (CNS) myelin.
Purpose of the Study:
- To investigate the presence and characteristics of myelinated fibers in the jimpy mouse mutant despite the absence of PLP.
- To understand the structural consequences of PLP deficiency on myelin sheath formation.
Main Methods:
- Immunocytochemistry was used to detect myelin basic protein (MBP) and proteolipid protein (PLP) in the spinal cord of jimpy mice.
- Analysis of myelin sheath structure, focusing on extracellular leaflet compaction and intraperiod line formation.
Main Results:
- Scattered myelinated fibers positive for MBP were observed in the jimpy mouse spinal cord.
- These fibers were immunocytochemically negative for PLP, confirming its absence.
- The lack of PLP led to abnormal compaction of myelin sheath extracellular leaflets and an abnormal intraperiod line.
Conclusions:
- A multilamellar membrane structure can form in the central nervous system even in the absence of its major integral membrane protein, PLP.
- The findings provide insights into the essentiality of PLP for normal myelin compaction and structure.