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Human PEX1 cloned by functional complementation on a CHO cell mutant is responsible for peroxisome-deficient
Insights
Researchers identified the PEX1 gene as the cause of complementation group I peroxisomal disorders, including Zellweger syndrome. Restoring PEX1 function in cells corrected peroxisome biogenesis defects, offering insights into these rare genetic diseases.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Peroxisome biogenesis disorders (PBDs) are inherited conditions affecting peroxisome assembly.
- Zellweger syndrome (ZS) and neonatal adrenoleukodystrophy (NALD) are severe PBDs with multiple genetic causes.
- At least 10 complementation groups (CGs) of PBDs have been identified, indicating genetic heterogeneity.
Purpose of the Study:
- To identify the specific gene responsible for complementation group I (CG-I) PBDs.
- To investigate the function of the identified gene in peroxisome assembly and protein import.
Main Methods:
- Functional complementation of a Chinese hamster ovary (CHO) cell line (ZP107) deficient in peroxisome biogenesis using a human PEX1 cDNA (HsPEX1).
- Biochemical and morphological analysis of restored CHO cells and patient-derived fibroblasts.
- Mutation analysis of the PEX1 gene in a CG-I Zellweger syndrome patient.
Main Results:
- Isolation and characterization of HsPEX1, encoding a protein (Pex1p) homologous to AAA-type ATPases.
- HsPEX1 expression restored peroxisome biogenesis and protein import in ZP107 cells and fibroblasts from CG-I patients.
- Identification of inactivating mutations in PEX1 in a CG-I Zellweger syndrome patient, confirming its role in the disorder.
Conclusions:
- PEX1 is the causative gene for CG-I peroxisomal disorders.
- Defects in PEX1 lead to impaired peroxisome assembly and function.
- Understanding PEX1 mutations provides a molecular basis for CG-I PBDs and potential therapeutic targets.
Abstract:
The peroxisome biogenesis disorders (PBDs), including Zellweger syndrome (ZS) and neonatal adrenoleukodystrophy (NALD), are autosomal recessive diseases caused by defects in peroxisome assembly, for which at least 10 complementation groups have been reported. We have isolated a human PEX1 cDNA (HsPEX1) by functional complementation of peroxisome deficiency of a mutant Chinese hamster ovary (CHO) cell line, ZP107, transformed with peroxisome targeting signal type 1-tagged "enhanced" green fluorescent protein. This cDNA encodes a hydrophilic protein (Pex1p) comprising 1,283 amino acids, with high homology to the AAA-type ATPase family. A stable transformant of ZP107 with HsPEX1 was morphologically and biochemically restored for peroxisome biogenesis. HsPEX1 expression restored peroxisomal protein import in fibroblasts from three patients with ZS and NALD of complementation group I (CG-I), which is the highest-incidence PBD. A CG-I ZS patient (PBDE-04) possessed compound heterozygous, inactivating mutations: a missense point mutation resulting in Leu-664 --> Pro and a deletion of the sequence from Gly-634 to His-690 presumably caused by missplicing (splice site mutation). Both PBDE-04 PEX1 cDNAs were defective in peroxisome-restoring activity when expressed in the patient fibroblasts as well as in ZP107 cells. These results demonstrate that PEX1 is the causative gene for CG-I peroxisomal disorders.