Temperature-sensitive mutation in PEX1 moderates the phenotypes of peroxisome deficiency disorders |
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Authors: | Imamura A; Tamura S; Shimozawa N; Suzuki Y; Zhang Z; Tsukamoto T; Orii T; Kondo N; Osumi T; Fujiki Y |
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Institution: | Department of Pediatrics, Gifu University School of Medicine, Gifu 500- 8076, Japan. |
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Abstract: | The peroxisome biogenesis disorders (PBDs), including Zellweger syndrome
(ZS), neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease
(IRD), are autosomal recessive diseases caused by deficiency of peroxisome
assembly as well as malfunction of peroxisomes, where >10 genotypes have
been reported. ZS patients manifest the most severe clinical and
biochemical abnormalities, while those with NALD and IRD show the least
severity and the mildest features, respectively. PEX1 is the causative gene
for PBDs of complementation group I (CG1), the highest incidence PBD, and
encodes the peroxin, Pex1p, a member of the AAA ATPase family. In the
present work, we found that peroxisomes were morphologically and
biochemically formed at 30 but not 37 degrees C, in the fibroblasts from
all CG1 IRD patients examined, whereas almost no peroxisomes were seen in
ZS and NALD cells, even at 30 degrees C. A point missense mutation, G843D,
was identified in the PEX1 allele of most CG1 IRD patients. The mutant
PEX1, termed HsPEX1G843D, gave rise to the same temperature-sensitive
phenotype on CG1 CHO cell mutants upon transfection. Collectively, these
results demonstrate temperature-sensitive peroxisome assembly to be
responsible for the mildness of the clinical features of PEX1 - defective
IRD of CG1.
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