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Mutations causing childhood ataxia with central nervous system hypomyelination reduce eukaryotic initiation factor 2B
Jonathan P Richardson1, Sarah S Mohammad, Graham D Pavitt
1Biomolecular Sciences, University of Manchester Institute of Science and Technology, Manchester M60 1QD, United Kingdom.
Molecular and Cellular Biology
|March 3, 2004
Summary
Childhood ataxia with central nervous system hypomyelination (CACH), or vanishing white matter leukoencephalopathy (VWM), is a fatal brain disorder. Mutations in eukaryotic initiation factor 2B (eIF2B) cause protein structure defects, impairing its function and leading to disease.
Area of Science:
- Molecular Biology
- Neuroscience
- Genetics
Background:
- Childhood ataxia with central nervous system hypomyelination (CACH), also known as vanishing white matter leukoencephalopathy (VWM), is a fatal pediatric brain disorder.
- This condition is caused by mutations in the eukaryotic initiation factor 2B (eIF2B) gene, which is crucial for protein synthesis and cellular stress response.
Purpose of the Study:
- To investigate the functional consequences of CACH/VWM-associated mutations in eIF2B.
- To determine if these mutations specifically impair stress-induced translation regulation or cause general protein structure defects.
Main Methods:
- Mutagenesis was used to introduce 12 human CACH/VWM equivalent mutations into yeast (Saccharomyces cerevisiae) eIF2B subunits.
- Assessed effects on cell growth, translation, gene expression under normal and stress conditions.
- Performed biochemical analyses to examine subunit stability, complex formation, and eIF2B activity.
Main Results:
- None of the yeast mutations were lethal or temperature-sensitive, but most impaired eIF2B function, affecting growth or gene expression.
- Mutations in eIF2Balpha and -epsilon reduced subunit levels; eIF2Bbeta(V341D) formed unstable complexes with reduced activity.
- eIF2Bdelta was excluded from eIF2Bbeta(V341D) complexes, but its overexpression could rescue function.
Conclusions:
- CACH/VWM mutations in eIF2B primarily cause protein structure defects, leading to impaired eIF2B activity, rather than specifically disrupting stress-response pathways.
- These findings suggest that altered protein folding, a mechanism implicated in other diseases like cystic fibrosis and neurodegenerative disorders, is central to CACH/VWM pathogenesis.