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Mutation of the proteolipid protein gene PLP in a human X chromosome-linked myelin disorder
L D Hudson1, C Puckett, J Berndt
1Laboratory of Viral and Molecular Pathogenesis, National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, MD 20892.
Abstract:
Myelin is a highly specialized membrane unique to the nervous system that ensheaths axons to permit the rapid saltatory conduction of impulses. The elaboration of a compact myelin sheath is disrupted in a diverse spectrum of human disorders, many of which are of unknown etiology. The X chromosome-linked human disorder Pelizaeus-Merzbacher disease is a clinically and pathologically heterogeneous group of disorders that demonstrate a striking failure of oligodendrocyte differentiation. This disease appears pathologically and genetically to be similar to the disorder seen in the dysmyelinating mouse mutant jimpy, which has a point mutation in the gene encoding an abundant myelin protein, proteolipid protein (PLP). We report that the molecular defect in one Pelizaeus-Merzbacher family is likewise a point mutation in the PLP gene. A single T----C transition results in the substitution of a charged amino acid residue, arginine, for tryptophan in one of the four extremely hydrophobic domains of the PLP protein. The identification of a mutation in this Pelizaeus-Merzbacher family should facilitate the molecular classification and diagnosis of these X chromosome-linked human dysmyelinating disorders.
Insights
Researchers identified a specific mutation in the proteolipid protein (PLP) gene causing Pelizaeus-Merzbacher disease. This finding advances the molecular understanding and diagnosis of X-linked dysmyelinating disorders.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
Background:
- Myelin, crucial for nerve impulse conduction, is disrupted in various neurological disorders.
- Pelizaeus-Merzbacher disease is an X-linked disorder characterized by failed oligodendrocyte differentiation and myelin sheath formation.
- The mouse mutant jimpy shares similarities with Pelizaeus-Merzbacher disease, linked to a mutation in the proteolipid protein (PLP) gene.
Purpose of the Study:
- To investigate the molecular basis of Pelizaeus-Merzbacher disease in a human family.
- To determine if mutations in the proteolipid protein (PLP) gene are responsible for the disease in this cohort.
- To contribute to the molecular classification and diagnosis of X-linked dysmyelinating disorders.
Main Methods:
- Genetic analysis of affected individuals from a Pelizaeus-Merzbacher disease family.
- DNA sequencing to identify mutations in the proteolipid protein (PLP) gene.
- Analysis of the mutation's impact on the PLP protein structure.
Main Results:
- A specific point mutation (T-C transition) was identified in the PLP gene of the affected family.
- This mutation leads to the substitution of tryptophan with arginine in a hydrophobic domain of the PLP protein.
- The identified mutation is consistent with a dysmyelinating defect.
Conclusions:
- The study identifies a causative PLP gene mutation in a Pelizaeus-Merzbacher disease family.
- This discovery facilitates molecular diagnosis and classification of X-linked dysmyelinating disorders.
- Understanding the genetic basis of these disorders is crucial for future therapeutic strategies.