Genotype-phenotype correlation in inherited brain myelination defects due to proteolipid protein gene mutations. Clinical European Network on Brain Dysmyelinating Disease.
ABSTRACT Pelizaeus-Merzbacher disease (PMD) and spastic paraplegia type 2 (SPG2) are X-linked developmental defects of myelin formation affecting the central nervous system (CNS). They differ clinically in the onset and severity of the motor disability but both are allelic to the proteolipid protein gene (PLP), which encodes the principal protein components of CNS myelin, PLP and its spliced isoform, DM20. We investigated 52 PMD and 28 SPG families without large PLP duplications or deletions by genomic PCR amplification and sequencing of the PLP gene. We identified 29 and 4 abnormalities respectively. Patients with PLP mutations presented a large range of disease severity, with a continuum between severe forms of PMD, without motor development, to pure forms of SPG. Clinical severity was found to be correlated with the nature of the mutation, suggesting a distinct strategy for detection of PLP point mutations between severe PMD, mild PMD and SPG. Single amino-acid changes in highly conserved regions of the DM20 protein caused the most severe forms of PMD. Substitutions of less conserved amino acids, truncations, absence of the protein and PLP-specific mutations caused the milder forms of PMD and SPG. Therefore, the interactions and stability of the mutated proteins has a major effect on the severity of PLP-related diseases.
SourceAvailable from: Takashi Shiihara
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ABSTRACT: Major gaps in our understanding of the leukodystrophies result from their rarity and the lack of tissue for the interdisciplinary studies required to extend our knowledge of the pathophysiology of the diseases. This study details the natural evolution of changes in the CNS of the shaking pup (shp), a model of the classical form of the X-linked disorder Pelizaeus-Merzbacher disease, in particular in glia, myelin, and axons, which is likely representative of what occurs over time in the human disease. The mutation in the proteolipid protein gene, PLP1, leads to a delay in differentiation, increased cell death, and a marked distension of the rough endoplasmic reticulum in oligodendrocytes. However, over time, more oligodendrocytes differentiate and survive in the spinal cord leading to an almost total recovery of myelination, In contrast, the brain remains persistently hypomyelinated. These data suggest that shp oligodendrocytes may be more functional than previously realized and that their early recruitment could have therapeutic value. Copyright © 2014. Published by Elsevier Inc.Neurobiology of Disease 01/2015; 75. DOI:10.1016/j.nbd.2014.12.023 · 5.62 Impact Factor
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ABSTRACT: Pelizaeus-Merzbacher Disease (PMD) is a rare X-linked recessive leukodystrophy caused by mutations in the proteolipid protein 1 gene on the Xq22 chromosome. PMD is a dysmyelinating disorder characterized by variable clinical presentation and course. Symptoms range from mild motor deficits to progressive spasticity and neurologic decline resulting in death at an early age. There is no definitive curative treatment. This report presents the clinical course of 2 young boys with PMD who are the first known patients to receive umbilical cord blood transplantation as a therapeutic intervention to stabilize disease progression. Pretransplantation evaluation revealed that both patients had significant motor deficits as well as delayed cognitive function as compared with age-matched peers. Brain imaging revealed varying degrees of hypomyelination. Both patients received myeloablative chemotherapy followed by an unrelated donor umbilical cord blood infusion, which they tolerated well with no major transplantation-related complications. At 7-years and 1-year posttransplantation, respectively, both boys are making slow neurocognitive improvements and show no evidence of functional decline. Imaging results show stable or improving myelination. Although the results of unrelated donor umbilical cord blood transplantation in these 2 boys with PMD are encouraging, longer-term follow-up will be necessary to assess the effect of this treatment on the variable natural disease course.Pediatrics 10/2014; 134(5). DOI:10.1542/peds.2013-3604 · 5.30 Impact Factor