Novel mutations in the PEX2 gene of four unrelated patients with a peroxisome biogenesis disorder

Area of Science:

• Genetics
• Cell Biology
• Biochemistry

Background:

• Peroxisome biogenesis disorders (PBDs) are a heterogeneous group of genetic conditions.
• Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD) are key PBDs with shared symptoms like liver disease and neurodevelopmental issues.
• Complementation group 10 (CG10) PBDs involve mutations in the PEX2 gene, encoding a protein vital for peroxisomal protein import.

Purpose of the Study:

• To identify and characterize mutations in the PEX2 gene in four patients with PBDs belonging to CG10.
• To investigate the correlation between novel PEX2 mutations and the clinical phenotypes observed in these patients.
• To understand the functional impact of PEX2 mutations on protein structure and peroxisomal import.

Main Methods:

• Genetic analysis of the PEX2 gene in four PBD patients.
• Sequencing to identify mutations within the PEX2 gene.
• Correlation of identified mutations with patient clinical presentations and PEX2 protein domains.

Main Results:

• Four distinct PEX2 mutations were identified in the four CG10 PBD patients, with three being novel.
• Two patients with homozygous mutations had truncated PEX2 proteins lacking transmembrane and zinc-binding domains, correlating with severe phenotypes.
• One patient with a W223X mutation (lacking the zinc-binding domain) exhibited a mild phenotype, while a C247R mutation (affecting the zinc-binding domain) resulted in a severe phenotype.

Conclusions:

• The study identified novel PEX2 mutations in PBD patients, expanding the known mutational spectrum for CG10.
• Genotype-phenotype correlations in PEX2 mutations are complex, with some mutations affecting critical domains leading to varied disease severity.
• The findings suggest that PEX2 protein instability or dominant-negative effects may contribute to the observed phenotypic variability in PBDs.