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Novel PEX1 coding mutations and 5' UTR regulatory polymorphisms
Megan A Maxwell1, Pamela B Leane, Barbara C Paton
1Cell Biology Program, Eskitis Institute for Cell and Molecular Therapies, Nathan, Queensland, Australia.
Human Mutation
|August 10, 2005
Summary
This study identifies novel PEX1 gene mutations and polymorphisms in Zellweger spectrum disorders. These genetic variations, including regulatory polymorphisms, contribute to disease severity and phenotypic heterogeneity in affected individuals.
Area of Science:
- Genetics
- Biochemistry
- Molecular Biology
Background:
- Zellweger spectrum disorders are a group of inherited diseases affecting peroxisome function.
- Mutations in the PEX1 gene are a common cause, accounting for about two-thirds of patient mutations.
- PEX1 encodes a AAA ATPase protein crucial for importing proteins into peroxisomes.
Purpose of the Study:
- To identify and characterize novel PEX1 gene mutations and polymorphisms in an Australasian cohort.
- To investigate the impact of these genetic variations on PEX1 protein function and Zellweger spectrum disease phenotypes.
- To explore the role of PEX1 promoter polymorphisms in disease heterogeneity.
Main Methods:
- Mutation screening of the PEX1 gene in Zellweger spectrum patients.
- Analysis of PEX1 mutations and their correlation with disease severity.
- Functional studies using cultured skin fibroblasts to assess peroxisomal protein import.
- Reporter assays to evaluate the regulatory effects of PEX1 5' UTR polymorphisms on gene expression.
Main Results:
- Four novel PEX1 mutations and two polymorphisms were identified.
- Severe Zellweger phenotypes were associated with mutations leading to premature termination codons (c.1108_1109insA and c.2391_2392delTC).
- A milder phenotype was linked to compound heterozygosity for missense mutations (I989T and R998Q) in the AAA domain, with residual PTS1 import at ~20% of normal.
- PEX1 5' UTR polymorphisms (c.-137T>C and c.-53C>G) differentially affected PEX1 expression, with combined presence leading to near-normal expression.
Conclusions:
- Novel PEX1 mutations contribute to the genetic basis of Zellweger spectrum disorders.
- The location and type of PEX1 mutation significantly influence disease severity.
- PEX1 promoter polymorphisms can modulate PEX1 expression, potentially contributing to phenotypic heterogeneity, especially in conjunction with other PEX gene mutations.