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Pelizaeus-Merzbacher disease
Arnulf H Koeppen1, Yves Robitaille
1Neurology Research Service, Stratton VA Medical Center and Albany Medical College, NY 12208, USA.
Abstract:
Pelizaeus-Merzbacher disease (PMD) can now be defined as an X-linked recessive leukodystrophy that is caused by a mutation in the proteolipid protein (PLP) gene on chromosome Xq22. The most common mutation is gene duplication followed in frequency by missense mutations, insertions, and deletions. The clinical spectrum ranges from severe neonatal cases to relatively benign adult forms and X-linked recessive spastic paraplegia type 2. The lack of PLP is accompanied by deficits in the other myelin proteins of the central nervous system, including myelin basic protein, myelin-associated glycoprotein, and cyclic nucleotide phosphodiesterase. Surprisingly, the total absence of PLP due to gene deletion or a null allele causes a relatively benign form of PMD. Abnormal PLP is thought to impair protein trafficking and to induce apoptosis in oligodendroglia. Immunocytochemistry with specific antibodies reveals the PLP deficiency and insufficient generation of myelin sheaths with the remaining proteins. Both excessive biosynthesis of PLP, as in gene duplications, or conformational change of the protein, as in missense mutations, are detrimental to myelination. Several naturally occurring and transgenic animal models with PLP gene mutations or deletions have contributed to our understanding of dysmyelination in PMD and the general knowledge of myelination and myelin repair.
Insights
Pelizaeus-Merzbacher disease (PMD) is an X-linked leukodystrophy caused by mutations in the proteolipid protein (PLP) gene. Surprisingly, complete PLP absence leads to milder PMD, while abnormal PLP impairs myelin sheath formation.
Area of Science:
- Neuroscience
- Genetics
- Cell Biology
Background:
- Pelizaeus-Merzbacher disease (PMD) is an X-linked recessive leukodystrophy.
- It is characterized by mutations in the proteolipid protein (PLP) gene located on chromosome Xq22.
- The clinical presentation varies widely, from severe neonatal forms to milder adult presentations.
Purpose of the Study:
- To define Pelizaeus-Merzbacher disease (PMD) based on its genetic cause and clinical spectrum.
- To investigate the impact of different mutations in the proteolipid protein (PLP) gene on myelination.
- To understand the mechanisms underlying dysmyelination in PMD.
Main Methods:
- Analysis of mutations in the proteolipid protein (PLP) gene, including gene duplication, missense mutations, insertions, and deletions.
- Assessment of myelin protein deficits using immunocytochemistry with specific antibodies.
- Utilizing naturally occurring and transgenic animal models with PLP gene mutations.
Main Results:
- The most frequent mutation is PLP gene duplication, followed by missense mutations, insertions, and deletions.
- A complete absence of PLP, due to gene deletion or null alleles, results in a surprisingly benign form of PMD.
- Abnormal PLP is implicated in impaired protein trafficking and oligodendrocyte apoptosis, leading to insufficient myelin sheath generation.
Conclusions:
- PMD pathogenesis is linked to both the quantity and quality of proteolipid protein (PLP).
- Excessive PLP biosynthesis or conformational changes are detrimental to myelination.
- Animal models are crucial for understanding PMD and myelin repair mechanisms.