Peroxisomal organization in normal and cerebrohepatorenal (Zellweger) syndrome fibroblasts.

Abstract

The reported absence of morphologicafly detectable peroxisomes in liver and kidney tissue cells from patients affected by the autosomic recessive, inherited metabolic disease known as cerebrohepatorenal, or Zeflweger, syndrome was studied in fibroblasts, assuming it to be a generalized defect.Normal cultured fibroblasts were shown to contain peroxisomes according to morphological, biochemical, and subcellular fractionation criteria: particle-bound catalase and fatty acyl-CoA oxidase copurify in subcellular fractionation by differential centrifugation or isopycnic equilibrium in continuous density gradients and peroxidase-positive organelles of =O.1 ,um in diameter are detected in the cytoplasm. In Zellweger cultured fibroblasts, these peroxisomal enzymes are present; however, they behave as cytosolic enzymes in the different subcellular fractionation procedures employed and peroxisomes are not detected cytochemically. These rindings support the hypothesis that the lack of peroxisomes in this genetic disease is the consequence of a defect in the assembly of the peroxisomal constituents. Furthermore, the value offibroblasts for subcellular analysis of peroxisomal defects is illustrated.Recent evidence supports the hypothesis that in some inherited metabolic disorders, defects in peroxisomal function are pathogenic. The initial observation that peroxisomes are absent in liver and kidney from children affected with the cerebrohepatorenal (Zellweger) syndrome (1) later correlated with the greatly reduced plasmalogen content found in their tissues (2), a phenomenon attributed to a lack of peroxisomal enzymes involved in plasmalogen biosynthesis (2, 3). It has also been correlated with the accumulation in fibroblasts of very long-chain fatty acids (4), supposedly the consequence of a defect in the peroxisomal fatty acid oxidation system capable of oxidizing very long-chain fatty acids (5, 6). The lack of peroxisomes would also explain the increased blood level of bile acid precursors (7,8) and possibly of pipecolic acid (9), assuming it reflects a deficiency in glutaryl-CoA oxidation (10). Adrenoleukodystrophy constitutes another hereditary disorder in which the accumulation of very longchain fatty acids (11) and also myelin degeneration (12, 13) apparently reflect a peroxisomal defect. As new findings increase the scope of the possible peroxisomal involvement in metabolic inherited disorders, their participation is being considered for hyperpipecolatemia (8,14), glutaric aciduria (10), dicarboxylic aciduria (15, 16), hyperoxaluria (14, 17), glycinuria (17), testicular feminization (18), and cerebrotendinous xanthomatosis (8,14). A single enzymatic defect might explain some of these conditions; however, in the Zellweger syndrome the whole organelle would be missing, perhaps reflecting the deficit of a protein essential for the assembly of peroxisomes. Consequently, as already suggested (14, 19-24), this pathologic condition would constitute a unique example of a genetic disorder expressed as absence of a cell o...

Zellweger Syndrome Amniocytes: Morphological Appearance and a Simple Sedimentation Method for Prenatal Diagnosis

“…The morphological deficiency of peroxisomes in Zellweger amniocytes agrees with the biochemical results on catalase. The morphological results are consistent with similar reports of a deficiency of peroxisomes in fibroblasts cultured from the skin of Zellweger patients (29,33). The rare small structures in Zellweger amniocytes that might contain diaminobenzidine reaction product could represent residual aberrant peroxisomes, but this could not be decided unequivocally.…”

“…In these respects, the peroxisomes of amniocytes resemble those of adrenal cortex (30), heart (3 I), intestine (32), and cultured skin fibroblasts (29,33).…”

“…The specific activities of the other enzymes measured were similar in all three groups. One group of amniocytes was subjected to sonication, which under appropriate conditions has been shown to open fibroblasts without excessive damage to cell organelles (29). The sonicated amniocytes were centrifuged in the same fashion as the homogenized amniocytes.…”

Transport of microinjected proteins into peroxisomes of mammalian cells: inability of Zellweger cell lines to import proteins with the SKL tripeptide peroxisomal targeting signal.

“…In cells from patients with these disorders, typical peroxisomes are absent though peroxisome ghosts can be detected (26,27). These ghosts possess normal amounts of certain peroxisomal membrane proteins but lack peroxisomal matrix proteins, which are either absent altogether or present in the cytoplasm (17,18,28,29,32). Though none of the genes responsible for these human disorders have been identified, defects in any of at least eight different genetic loci may lead to these disorders (1, 21a).…”

Use of vaccinia virus vectors to study protein processing in human disease. Normal nerve growth factor processing and secretion in cultured fibroblasts from patients with familial dysautonomia.

“…This strongly suggests that NGF processing is intact in familial dysautonomia, at the very least in this cell type. (16). A number of lysosomal storage disorders are caused by disturbed targeting into that organelle (17).…”