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Fate of jimpy-type oligodendrocytes in jimpy heterozygote
1National Institute for Physiological Sciences, Okazaki National Research Institutes, Aichi, Japan.
Abstract:
In the jimpy mutant mouse, as well as in many other animals with mutations in the myelin proteolipid protein (PLP) gene, oligodendrocytes degenerate before their maturation. To analyze whether this degeneration is caused by the loss of function of PLP gene products related to oligodendrocyte maturation/survival acting extrinsically, expression of the PLP gene was investigated in the jimpy heterozygote, in which one-half of the cells are jimpy type and the other half are wild type due to random X-chromosome inactivation. We first showed that jimpy PLP gene expression is normally regulated at the early stages of development in brains of jimpy hemizygotes and heterozygotes, at least to day 2 after birth. However, the great increase in the level of PLP gene transcripts observed in wild-type mouse brain is suppressed in jimpy mouse brain. This increase was also suppressed in the jimpy heterozygote, and by 2 months after birth, very few jimpy-type PLP gene transcripts were detected in heterozygotes. These results indicate that jimpy-type oligodendrocytes cannot survive or are still in the immature stage in the brain of jimpy heterozygotes. Thus, degeneration of jimpy oligodendrocytes is not caused merely by the lack of trophic factors.
Insights
Oligodendrocyte degeneration in jimpy mutant mice is not solely due to a lack of extrinsic trophic factors. The myelin proteolipid protein (PLP) gene
Area of Science:
- Neuroscience
- Genetics
- Cell Biology
Background:
- Oligodendrocytes are crucial for myelin sheath formation in the central nervous system.
- Mutations in the myelin proteolipid protein (PLP) gene lead to oligodendrocyte degeneration before maturation in jimpy mice.
- The role of PLP gene products in oligodendrocyte survival and maturation is not fully understood.
Purpose of the Study:
- To investigate whether oligodendrocyte degeneration in jimpy mutant mice is caused by the loss of extrinsic PLP gene products.
- To analyze PLP gene expression in jimpy heterozygotes to understand oligodendrocyte survival mechanisms.
Main Methods:
- Analysis of PLP gene expression in jimpy hemizygote and heterozygote mouse brains at different developmental stages.
- Comparison of PLP gene transcript levels between wild-type and jimpy-mutant oligodendrocytes.
Main Results:
- PLP gene expression is normally regulated in early development (up to 2 days after birth) in jimpy mutants.
- The significant increase in PLP gene transcripts observed in wild-type brains is suppressed in jimpy mouse brains.
- In jimpy heterozygotes, PLP gene transcript levels remain suppressed, with very few jimpy-type transcripts detected by 2 months of age.
Conclusions:
- Jimpy-type oligodendrocytes in heterozygotes either do not survive or remain immature.
- Oligodendrocyte degeneration in jimpy mutants is not simply due to a lack of trophic factors.
- The findings suggest an intrinsic defect in jimpy-type oligodendrocytes related to PLP gene function.