Original articleRestoration of biochemical function of the peroxisome in the temperature-sensitive mild forms of peroxisome biogenesis disorder in humans
Introduction
The peroxisome is often an encountered organelle involved in vital metabolic functions, such as the oxidative processes involving H2O2, beta-oxidation of fatty acids, and biosynthesis of plasmalogens. Peroxisome biogenesis disorders (PBDs) are lethal diseases characterized by multiple defects in peroxisomal functions. PBDs are genetically classified into at least 11 complementation groups (CGs) [1], [2], [3], and each CG contains various clinical phenotypes, such as Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD). ZS represents the severest form of PBD, and is characterized by severe neurologic, hepatic, and renal abnormalities, mental retardation, and death in early infancy. NALD, the next severe, whereas IRD is the mildest, with significantly different in clinical features such as age of death and severity of neurological abnormalities. Notwithstanding the cloning of the causal genes and identification of the mutations for several CGs [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], it is unknown at the molecular level why such diverse phenotypes occur in the same complementation groups.
We have found that peroxisome assembly is temperature-sensitive (ts) in the fibroblasts from mild forms of PBDs [17]. In these cells, peroxisomes were formed, and the number of peroxisomes was increased at 30°C after several days but not at 37°C, whereas virtually no peroxisomes were seen in ZS cells even at 30°C. The biochemical activities of peroxisomes were greatly elevated after incubation at 30°C. In this paper, we dicussed the correlation between morphological change and biochemical functions of peroxisome using a time course trial in these cells.
Section snippets
Cell lines and strains
Skin fibroblasts from normal controls and patients with PBDs were cultured in Ham's F12 medium supplemented with 10% fetal calf serum. F-01 and E-14 were the fibroblasts of ZS in CG-F and CG-E, respectively. F-05 and E-06 were the fibroblasts of IRD in each CG, revealed ts as described [17]. All strains were classified by complementation analysis of cell fusion as described [18], [19].
Immunofluorescence study
For the detection of peroxisomes, cell lines were fixed, permeabilized with 0.1% Triton X-100 and processed for
Results
In the fibroblasts of the IRD patient (F-05) revealing ts, peroxisomes were gradually formed at 30°C and the number of peroxisome increased daily (Fig. 1). However, in those of ZS patient (F-01, E-14), no peroxisomes were found at either 30 or 37°C (data not shown). Catalase and 70 kDa peroxisomal membrane protein (PMP70) were co-localized in the ts cells after 4 days incubation at 30°C (Fig. 1, Fig. 2), hereby confirming the identity of these catalase-positive granules as peroxisomes. The
Discussion
Peroxisomal biogenesis disorders (PBDs) are a group of lethal autosomal recessive diseases caused by defects in peroxisomal matrix protein import with the accompanying loss of multiple peroxisomal enzyme activities. In spite of the variations in the clinical features, the fibroblasts from the patients of all the three PBD phenotypes mostly lack peroxisomes. The oxidation of very-long-chain fatty acids (VLCFA), such as lignoceric acids (C24), was severely disturbed, and then, the accumulation of
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A novel compound heterozygous PEX1 variant in Heimler syndrome
2023, Experimental Eye ResearchHeimler Syndrome Is Caused by Hypomorphic Mutations in the Peroxisome-Biogenesis Genes PEX1 and PEX6
2015, American Journal of Human GeneticsCitation Excerpt :We saw different types of cells, including cells with normal peroxisomal staining, cells with a reduced number of peroxisomes, and cells with only peroxisomal membrane remnants, referred to as “ghosts,” but no import of matrix protein. Peroxisomal mosaicism has been described previously for hypomorphic variants in PEX1 and PEX6 and is typically associated with mild PBDs.29,30 Consistent with cells displaying peroxisomal mosaicism, the cells from individuals F1-II:3 and F5-II:2 showed a more severe peroxisomal phenotype when cultured at an elevated temperature (40°C), and the vast majority of cells lacked catalase-positive peroxisomes (Figure 3).
Genetics and molecular basis of human peroxisome biogenesis disorders
2012, Biochimica et Biophysica Acta - Molecular Basis of DiseaseCitation Excerpt :This peroxisomal mosaicism is temperature sensitive, meaning that when fibroblasts of patients homozygous for p.G843D are cultured at 30 °C, peroxisomes regain the ability to import catalase and other peroxisomal matrix proteins and the various peroxisomal metabolic functions normalize. In contrast, when cultured at higher temperatures, peroxisomes become deficient and the phenotype becomes worse [66,68]. The second most common mutation in PEX1 is c.2097_2098insT (or c.2097dup), which results in a frame shift theoretically predicted to cause a truncated PEX1 protein [69].
Catalase-less peroxisomes. Implication in the milder forms of peroxisome biogenesis disorder
2000, Journal of Biological ChemistryCitation Excerpt :Accordingly, we examined this possibility with the fibroblasts from an NALD patient of CG-C (C-11)2 and an NALD and IRD patient of CG-E (E-13 and E-24, respectively; see Ref. 13). The responsible genes of CG-C and CG-E are PEX6 (16, 25, 26) andPEX1 (27-29), respectively, both coding for the members of the AAA-ATPase family. Interaction between these two peroxins was shown (30-32), and hence it would seem reasonable that a defect in either of them would result in similar phenotypes.