Dataset Information

Vanishing white matter: Eukaryotic initiation factor 2B model and the impact of missense mutations.

ABSTRACT:

Background

Vanishing white matter (VWM) is a leukodystrophy, caused by recessive mutations in eukaryotic initiation factor 2B (eIF2B)-subunit genes (EIF2B1-EIF2B5); 80% are missense mutations. Clinical severity is highly variable, with a strong, unexplained genotype-phenotype correlation.

Materials and methods

With information from a recent natural history study, we severity-graded 97 missense mutations. Using in silico modeling, we created a new human eIF2B model structure, onto which we mapped the missense mutations. Mutated residues were assessed for location in subunits, eIF2B complex, and functional domains, and for information on biochemical activity.

Results

Over 50% of mutations have (ultra-)severe phenotypic effects. About 60% affect the ε-subunit, containing the catalytic domain, mostly with (ultra-)severe effects. About 55% affect subunit cores, with variable clinical severity. About 36% affect subunit interfaces, mostly with severe effects. Very few mutations occur on the external eIf2B surface, perhaps because they have minor functional effects and are tolerated. One external surface mutation affects eIF2B-substrate interaction and is associated with ultra-severe phenotype.

Conclusion

Mutations that lead to (ultra-)severe disease mostly affect amino acids with pivotal roles in complex formation and function of eIF2B. Therapies for VWM are emerging and reliable mutation-based phenotype prediction is required for propensity score matching for trials and in the future for individualized therapy decisions.

SUBMITTER: Slynko I

PROVIDER: S-EPMC8104162 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Vanishing white matter (VWM) is a leukodystrophy caused by biallelic pathogenic variants in eukaryotic translation initiation factor 2B. Neuropathology includes lack of reactive gliosis, paucity of myelin, and axonal abnormalities. Alteration in proteins involved in cellular metabolism has also been implicated in the disease. It, however, remains unclear which factors contribute to VWM pathogenesis. Here, we aimed at gaining insight into the basis of VWM pathogenesis using the 2b5ho mouse model of VWM. We first investigated the temporal proteome in the cerebellum, corpus callosum, cortex, and brainstem of 2b5ho and wild type (WT) mice. Protein changes observed in 2b5ho mice were then cross-referenced with published proteomic datasets from post mortem VWM patient brain tissue to define alterations relevant to the human disease. By comparing 2b5ho mice with their region- and age-matched WT counterparts, we identified region-specific protein changes associated with disease development and progression. We showed that the proteome in the cerebellum and cortex of 2b5ho mice was already deregulated prior to pathology development, whereas proteome changes in the corpus callosum only occurred after onset of pathology. Remarkably, protein changes in the brainstem were transient, indicating that a compensatory mechanism might occur in this region throughout the disease course. Gene ontology overrepresentation analysis revealed that proteome changes observed in 2b5ho mouse brains reflect alterations in features well-known in VWM. Side-by-side comparison of the 2b5ho mouse and VWM patient brain proteomes revealed that part of protein changes were the same as in VWM patients. These could represent relevant changes that contribute to the disease or even drive its progression in VWM patients. Taken together, we show that the proteome in the brain of 2b5ho mice is affected in a region-specific and time-dependent manner. We found that the 2b5ho mouse model partly replicates the human disease at the protein level, and provides a spatiotemporal proteome resource to study aspects of VWM pathogenesis. This resource highlights alterations presenting from early to late disease stages, and those that possibly drive disease progression.