782 research outputs found

    Molecular Basis of Proxysomal Disorders in Zellweger Syndrome

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    Peroxisomes are organelles present in all eukaryotic cells from yeast to human cells. It is now well known that approximately fifty different biochemical reactions occur within the peroxisome, including synthesis of bile acids, cholesterol, ether-phospholipids (plasmalogens), docosahexaenoic acid and catabolism of certain fatty acids, particularly very long chain fatty acids (VLCFAs). Proteins involved in peroxisomal function are known as peroxins. At least 29 peroxins are required for peroxisome membrane biogenesis, fission, and protein import. So far, mutations in 13 genes that encode peroxins are associated with human disease. Peroxisomal disorders currently falling into one of three groups peroxisome biogenesis disorders (PBDs), peroxisomal multi-enzyme disorders, and peroxisomal single-enzyme disorders. Infantile Refsum’s disease (IRD), neonatal adrenoleukodystrophy (NALD) and Zellweger’s syndrome (ZS) are different variants of a group of congenital diseases known as peroxisome biogenesis disorders. These disorders are characterized by the absence of normal peroxisomes in the cells of the body which mostly are fatal. Here we describe molecular events that cause these deficiencies and we introduce current molecular approaches for diagnosis of these disorders like mutation analysis and fibroblasts characterization derived from the patients

    A clinical approach to the diagnosis of patients with leukodystrophies and genetic leukoencephelopathies

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    Leukodystrophies (LD) and genetic leukoencephalopathies (gLE) are disorders that result in white matter abnormalities in the central nervous system (CNS). Magnetic resonance (MR) imaging (MRI) has dramatically improved and systematized the diagnosis of LDs and gLEs, and in combination with specific clinical features, such as Addison’s disease in Adrenoleukodystrophy or hypodontia in Pol-III related or 4H leukodystrophy, can often resolve a case with a minimum of testing. The diagnostic odyssey for the majority LD and gLE patients, however, remains extensive – many patients will wait nearly a decade for a definitive diagnosis and at least half will remain unresolved. The combination of MRI, careful clinical evaluation and next generation genetic sequencing holds promise for both expediting the diagnostic process and dramatically reducing the number of unresolved cases. Here we present a workflow detailing the Global Leukodystrophy Initiative (GLIA) consensus recommendations for an approach to clinical diagnosis, including salient clinical features suggesting a specific diagnosis, neuroimaging features and molecular genetic testing. We also discuss recommendations on the use of broad-spectrum next-generation sequencing in instances of ambiguous MRI or clinical findings. We conclude with a proposal for systematic trials of genome-wide agnostic testing as a first line diagnostic in LDs and gLEs given the increasing number of genes associated with these disorders

    Peroxisomes and disease - an overview.

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    Peroxisomes are indispensable for human health and development. They represent ubiquitous subcellular organelles which compartmentalize enzymes responsible for several crucial metabolic processes such as β-oxidation of specific fatty acids, biosynthesis of ether phospholipids and metabolism of reactive oxygen species. Peroxisomes are highly flexible organelles that rapidly assemble, multiply and degrade in response to metabolic needs. Basic research on the biogenesis of peroxisomes and their metabolic functions have improved our knowledge about their crucial role in several inherited disorders and in other pathophysiological conditions. The goal of this review is to give a comprehensive overview of the role of peroxisomes in disease. Besides the genetic peroxisomal disorders in humans, the role of peroxisomes in carcinogenesis and in situations related to oxidative stress such as inflammation, ischemia-reperfusion, and diabetes will be addressed.This work was supported by the German Research Foundation (DFG SCHR518/6-1)

    A Novel Mutation in PEX11β Gene: A Case Report

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    PEX11β ([OMIM] 614920) mutation causes an extremely rare subgroup of peroxisomal biogenesis disorders, with only six cases reported to date. In this article, we reported a patient with episodic migrainelikeattacks, delirium, mood and behavior change, polyneuropathy, and history of congenital cataract. Whole exome sequencing showednovel c.743_744delTCinsA mutation in the exon 4 of the PEX11β gene. In contrast to previously reported patients, our case presented milder features and extended the spectrum of the clinical phenotype of this mutation. This study helps to extend the phenotype of this syndrome; besides, recognizing novel mutation variants will provide a better genotype-phenotype correlation and improve clinical clue

    Refsum disease

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    Identification of intragenic mutations in the Hansenula polymorpha PEX6 gene that affect peroxisome biogenesis and methylotrophic growth

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    Two interacting AAA ATPases, Pex1p and Pex6p, are indispensable for peroxisome biogenesis in different organisms. Mutations affecting corresponding genes are the most common cause of the peroxisome biogenesis disorders in humans. By UV mutagenesis of the Hansenula polymorpha pex6 mutant, deficient in peroxisome biogenesis, we isolated a conditional cold-sensitive strain with restored ability to grow in methanol medium at 37degreesC but not at 28degreesC. Sequencing of the pex6 allele revealed a point mutation in the first AAA module of the PEX6 gene that leads to substitution of a conserved amino acid residue (G737E). An additional intragenic mutation identified in the cold-sensitive pex6 allele leads to a conserved amino acid substitution in the second AAA domain (R1000G). Electron microscopic analysis revealed restored peroxisomes in methanol-induced cold-sensitive pex6 cells at both permissive and restrictive temperatures. If separated, the secondary mutation did not affect methylotrophic growth. Our data suggest that H. polymorpha Pex6p may have a complex function in peroxisome biogenesis in which identified amino acid residues are involved. (C) 2003 Published by Elsevier B.V. on behalf of the Federation of European Microbiological Societies

    Characterization of two common 5' polymorphisms in PEX1 and correlation to survival in PEX1 peroxisome biogenesis disorder patients

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    <p>Abstract</p> <p>Background</p> <p>Mutations in PEX1 are the most common primary cause of Zellweger syndrome. In addition to exonic mutations, deletions and splice site mutations two 5' polymorphisms at c.-137 and c.-53 with a potential influence on PEX1 protein levels have been described in the 5' untranslated region (UTR) of the <it>PEX1 </it>gene.</p> <p>Methods</p> <p>We used RACE and in silico promoter prediction analysis to study the 5' UTR of <it>PEX1</it>. We determined the distribution of <it>PEX1 </it>5' polymorphisms in a cohort of 30 Zellweger syndrome patients by standard DNA sequencing. 5' polymorphisms were analysed in relation to the two most common mutations in <it>PEX1 </it>and were incorporated into a novel genotype-phenotype analysis by correlation of three classes of <it>PEX1 </it>mutations with patient survival.</p> <p>Results</p> <p>We provide evidence that the polymorphism 137 bp upstream of the ATG codon is not part of the UTR, rendering it a promoter polymorphism. We show that the first, but not the second most common <it>PEX1 </it>mutation arose independently of a specific upstream polymorphic constellation. By genotype-phenotype analysis we identified patients with identical exonic mutation and identical 5' polymorphisms, but strongly differing survival.</p> <p>Conclusions</p> <p>Our study suggests that two different types of <it>PEX1 </it>5' polymorphisms have to be distinguished: a 5' UTR polymorphism at position c.-53 and a promoter polymorphism 137 bp upstream of the PEX1 start codon. Our results indicate that the exonic <it>PEX1 </it>mutation correlates with patient survival, but the two 5' polymorphisms analysed in this study do not have to be considered for diagnostic and/or prognostic purposes.</p

    Failure of microtubule-mediated peroxisome division and trafficking in disorders with reduced peroxisome abundance

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    In contrast to peroxisomes in normal cells, remnant peroxisomes in cultured skin fibroblasts from a subset of the clinically severe peroxisomal disorders that includes the biogenesis disorder Zellweger syndrome and the single-enzyme defect D-bifunctional protein (D-BP) deficiency, are enlarged and significantly less abundant. We tested whether these features could be related to the known role of microtubules in peroxisome trafficking in mammalian cells. We found that remnant peroxisomes in fibroblasts from patients with PEX1-null Zellweger syndrome or D-BP deficiency exhibited clustering and loss of alignment along peripheral microtubules. Similar effects were observed for both cultured embryonic fibroblasts and brain neurons from a PEX13-null mouse with a Zellweger-syndrome-like phenotype, and a less-pronounced effect was observed for fibroblasts from an infantile Refsum patient who was homozygous for a milder PEX1 mutation. By contrast, such changes were not seen for patients with peroxisomal disorders characterized by normal peroxisome abundance and size. Stable overexpression of PEX11ß to induce peroxisome proliferation largely re-established the alignment of peroxisomal structures along peripheral microtubules in both PEX1-null and D-BP-deficient cells. In D-BP-deficient cells, peroxisome division was apparently driven to completion, as induced peroxisomal structures were similar to the spherical parental structures. By contrast, in PEX1-null cells the majority of induced peroxisomal structures were elongated and tubular. These structures were apparently blocked at the division step, despite having recruited DLP1, a protein necessary for peroxisome fission. These findings indicate that the increased size, reduced abundance, and disturbed cytoplasmic distribution of peroxisomal structures in PEX1-null and D-BP-deficient cells reflect defects at different stages in peroxisome proliferation and division, processes that require association of these structures with, and dispersal along, microtubules.Tam Nguyen, Jonas Bjorkman, Barbara C. Paton and Denis I. Cran
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