Related Experiment Videos
A combination of PLP and DM20 transgenes promotes partial myelination in the jimpy mouse
N L Nadon1, H Arnheiter, L D Hudson
1Biology Department, University of Tulsa, OK 74104-3189.
Abstract:
Mutations in the myelin proteolipid protein (PLP) gene, such as that found in the jimpy mouse, result in an abnormal structure of the myelin, severe dysmyelination, and a reduction in the number of mature oligodendrocytes. To examine the functions of the two alternatively spliced isoforms of proteolipid protein, transgenic mice were generated that express either PLP or DM20 cDNAs placed under control of the PLP upstream regulatory region. The transgenes were bred into jimpy mice, and the effect of the transgenes on the dysmyelinating phenotype was analyzed. Neither the PLP transgene nor the DM20 transgene alone had an effect on myelination in the jimpy mice. Combining the two transgenes substantially increased the number of myelinated axons, suggesting that the two alternatively spliced products of the PLP locus perform distinct functions in oligodendrocytes. The enhanced myelination was not sufficient, however, for completely correcting the dysmyelinating phenotype of the jimpy mice, nor was it accompanied by the restoration of normal levels of myelin gene expression. The inability to rescue the jimpy phenotype is most likely attributable to a dominant negative action of the abnormal proteolipid proteins present in jimpy mice. These results demonstrate the complexity of proteolipid protein function in myelination.
Insights
Mutations in the myelin proteolipid protein (PLP) gene cause severe dysmyelination. Expressing both PLP and DM20 isoforms in transgenic mice improved myelination, indicating distinct functions in myelin development.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Mutations in the myelin proteolipid protein (PLP) gene lead to dysmyelination and oligodendrocyte loss.
- The PLP gene encodes two alternatively spliced isoforms, PLP and DM20, with incompletely understood functions.
Purpose of the Study:
- To investigate the distinct functional roles of PLP and DM20 isoforms in oligodendrocyte development and myelination.
- To analyze the effects of PLP and DM20 transgenes on the dysmyelination phenotype in jimpy mice.
Main Methods:
- Generation of transgenic mice expressing either PLP or DM20 cDNA under the PLP regulatory region.
- Breeding transgenes into jimpy mice to assess their impact on the dysmyelinating phenotype.
- Analysis of myelinated axon counts and myelin gene expression levels.
Main Results:
- Neither PLP nor DM20 transgenes alone rescued the jimpy phenotype.
- Co-expression of both PLP and DM20 transgenes significantly increased myelinated axons in jimpy mice.
- Enhanced myelination was insufficient to fully correct the dysmyelination or restore normal myelin gene expression.
Conclusions:
- The PLP and DM20 isoforms of proteolipid protein perform distinct, cooperative functions in oligodendrocyte myelination.
- The dominant-negative effect of abnormal PLP in jimpy mice hinders complete phenotype rescue.
- These findings highlight the complex role of PLP in myelin structure and function.