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Myelin protein expression in the myelin-deficient rat brain and cultured oligodendrocytes
N K Zeller1, M Dubois-Dalcq, R A Lazzarini
1Laboratory of Molecular Genetics, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
Abstract:
The myelin-deficient (MD) rat does not express the major protein of CNS myelin, proteolipid protein (PLP). Here we further analyze whether this defect is reflected at the level of mRNA and whether the expression of other myelin proteins is affected in oligodendrocytes in vivo and in vitro. Both myelin basic protein (MBP) and PLP message levels were reduced in MD rats to 10-20% of the normal littermate controls, while the level of expression of an astrocyte-specific gene, glial fibrillary acidic protein (GFAP), was normal. Although MBP and PLP mRNAs were equally depressed, only MBP was detected with immunolabeling of corpus callosum, while PLP was absent in oligodendrocytes both in vivo and in vitro. A reduced number of MD rat oligodendrocytes express MBP in vitro compared to controls. The MD rat optic nerve contains normal numbers of 0-2A progenitors, but they tend to differentiate into GC-positive oligodendrocytes faster than oligodendrocytes from control littermates. In conclusion, the absence of PLP and reduced levels of MBP in the MD rats point to similarities with the jimpy mouse lesion. Moreover, the defect influences the expression of other myelin proteins and the oligodendrocyte developmental pathway.
Insights
The myelin-deficient rat lacks proteolipid protein (PLP) and has reduced myelin basic protein (MBP) mRNA and protein. This defect impacts oligodendrocyte development and myelin protein expression.
Area of Science:
- Neuroscience
- Molecular Biology
- Developmental Biology
Background:
- The myelin-deficient (MD) rat model exhibits a deficiency in proteolipid protein (PLP), a major component of central nervous system (CNS) myelin.
- Investigating the molecular basis of this deficiency is crucial for understanding myelin formation and oligodendrocyte function.
Purpose of the Study:
- To determine if the absence of PLP in MD rats is reflected at the mRNA level.
- To assess the impact of the MD defect on the expression of other myelin proteins in oligodendrocytes, both in vivo and in vitro.
- To analyze oligodendrocyte development and differentiation in MD rats.
Main Methods:
- Quantitative analysis of myelin basic protein (MBP) and PLP mRNA levels using RT-PCR.
- Immunolabeling techniques to detect MBP and PLP protein expression in the corpus callosum and oligodendrocytes.
- In vitro culture of oligodendrocytes from MD and control rats to assess protein expression and differentiation.
- Analysis of oligodendrocyte progenitor cells (0-2A progenitors) and their differentiation into GC-positive oligodendrocytes in the optic nerve.
Main Results:
- MBP and PLP mRNA levels were significantly reduced (10-20% of controls) in MD rats, while glial fibrillary acidic protein (GFAP) expression remained normal.
- MBP protein was detected in the corpus callosum, but PLP protein was absent in oligodendrocytes from MD rats, both in vivo and in vitro.
- Fewer MD rat oligodendrocytes expressed MBP in vitro compared to controls.
- MD rat optic nerves showed normal numbers of 0-2A progenitors, but accelerated differentiation into GC-positive oligodendrocytes.
Conclusions:
- The MD rat exhibits reduced MBP and absent PLP, sharing similarities with the jimpy mouse mutation.
- The genetic defect in MD rats affects not only PLP but also alters the expression of other myelin proteins.
- The study reveals a significant influence of the myelin deficiency on the oligodendrocyte developmental pathway.