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Yang P, Zhang W, Zeng L, Tao X, Ding K, Wang Z. A novel splice variant in intron 10 of PEX6 is associated with Zellweger Syndrome in a Chinese neonate. Gene 2024; 928:148767. [PMID: 39013483 DOI: 10.1016/j.gene.2024.148767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 04/20/2024] [Accepted: 07/12/2024] [Indexed: 07/18/2024]
Abstract
BACKGROUND Zellweger Syndrome (ZS), or cerebrohepatorenal syndrome, is a rare disorder due to PEX gene mutations affecting peroxisome function. While PEX6 coding mutations are known to cause ZS, the impact of noncoding mutations is less clear. METHODS A Chinese neonate and his family were subjected to whole exome sequencing (WES) and bioinformatics to assess variant pathogenicity. A minigene assay was also performed for detailed splicing variant analysis. RESULTS WES identified compound heterozygous PEX6 variants: c.315G>A (p. Trp105Ter) and c.2095-3 T>G. Minigene assays indicated that the latter variant led to abnormal mRNA splicing and the loss of exon 11 in PEX6 expression, potentially causing nonsense-mediated mRNA decay (NMD) or truncated protein structure. CONCLUSION The study suggests that PEX6: c.2095-3 T>G might be a genetic contributor to the patient's condition, broadening the known mutation spectrum of PEX6. These insights lay groundwork for potential gene therapy for such variants.
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Affiliation(s)
- Pin Yang
- School of Medicine, Department of Medicine, Wuhan University of Science and Technology, Wuhan 430081, China; Division of Neonatology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College, Huazhong University of Science & Technology, Wuhan 430010, China
| | - Weihong Zhang
- Department of Rehabilitation Medicine, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College, Huazhong University of Science & Technology, Wuhan 430010, China
| | - Lingkong Zeng
- Division of Neonatology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College, Huazhong University of Science & Technology, Wuhan 430010, China.
| | - Xuwei Tao
- Division of Neonatology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College, Huazhong University of Science & Technology, Wuhan 430010, China
| | - Kaiwei Ding
- Division of Neonatology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College, Huazhong University of Science & Technology, Wuhan 430010, China
| | - Zuo Wang
- Division of Neonatology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College, Huazhong University of Science & Technology, Wuhan 430010, China
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Bloch-Zupan A, Rey T, Jimenez-Armijo A, Kawczynski M, Kharouf N, Dure-Molla MDL, Noirrit E, Hernandez M, Joseph-Beaudin C, Lopez S, Tardieu C, Thivichon-Prince B, Dostalova T, Macek M, Alloussi ME, Qebibo L, Morkmued S, Pungchanchaikul P, Orellana BU, Manière MC, Gérard B, Bugueno IM, Laugel-Haushalter V. Amelogenesis imperfecta: Next-generation sequencing sheds light on Witkop's classification. Front Physiol 2023; 14:1130175. [PMID: 37228816 PMCID: PMC10205041 DOI: 10.3389/fphys.2023.1130175] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 03/06/2023] [Indexed: 05/27/2023] Open
Abstract
Amelogenesis imperfecta (AI) is a heterogeneous group of genetic rare diseases disrupting enamel development (Smith et al., Front Physiol, 2017a, 8, 333). The clinical enamel phenotypes can be described as hypoplastic, hypomineralized or hypomature and serve as a basis, together with the mode of inheritance, to Witkop's classification (Witkop, J Oral Pathol, 1988, 17, 547-553). AI can be described in isolation or associated with others symptoms in syndromes. Its occurrence was estimated to range from 1/700 to 1/14,000. More than 70 genes have currently been identified as causative. Objectives: We analyzed using next-generation sequencing (NGS) a heterogeneous cohort of AI patients in order to determine the molecular etiology of AI and to improve diagnosis and disease management. Methods: Individuals presenting with so called "isolated" or syndromic AI were enrolled and examined at the Reference Centre for Rare Oral and Dental Diseases (O-Rares) using D4/phenodent protocol (www.phenodent.org). Families gave written informed consents for both phenotyping and molecular analysis and diagnosis using a dedicated NGS panel named GenoDENT. This panel explores currently simultaneously 567 genes. The study is registered under NCT01746121 and NCT02397824 (https://clinicaltrials.gov/). Results: GenoDENT obtained a 60% diagnostic rate. We reported genetics results for 221 persons divided between 115 AI index cases and their 106 associated relatives from a total of 111 families. From this index cohort, 73% were diagnosed with non-syndromic amelogenesis imperfecta and 27% with syndromic amelogenesis imperfecta. Each individual was classified according to the AI phenotype. Type I hypoplastic AI represented 61 individuals (53%), Type II hypomature AI affected 31 individuals (27%), Type III hypomineralized AI was diagnosed in 18 individuals (16%) and Type IV hypoplastic-hypomature AI with taurodontism concerned 5 individuals (4%). We validated the genetic diagnosis, with class 4 (likely pathogenic) or class 5 (pathogenic) variants, for 81% of the cohort, and identified candidate variants (variant of uncertain significance or VUS) for 19% of index cases. Among the 151 sequenced variants, 47 are newly reported and classified as class 4 or 5. The most frequently discovered genotypes were associated with MMP20 and FAM83H for isolated AI. FAM20A and LTBP3 genes were the most frequent genes identified for syndromic AI. Patients negative to the panel were resolved with exome sequencing elucidating for example the gene involved ie ACP4 or digenic inheritance. Conclusion: NGS GenoDENT panel is a validated and cost-efficient technique offering new perspectives to understand underlying molecular mechanisms of AI. Discovering variants in genes involved in syndromic AI (CNNM4, WDR72, FAM20A … ) transformed patient overall care. Unravelling the genetic basis of AI sheds light on Witkop's AI classification.
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Affiliation(s)
- Agnes Bloch-Zupan
- Université de Strasbourg, Faculté de Chirurgie Dentaire, Strasbourg, France
- Université de Strasbourg, Institut d’études avancées (USIAS), Strasbourg, France
- Hôpitaux Universitaires de Strasbourg (HUS), Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpital Civil, Centre de référence des maladies rares orales et dentaires, O-Rares, Filiére Santé Maladies rares TETE COU, European Reference Network ERN CRANIO, Strasbourg, France
- Université de Strasbourg, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), IN-SERM U1258, CNRS- UMR7104, Illkirch, France
- Eastman Dental Institute, University College London, London, United Kingdom
| | - Tristan Rey
- Université de Strasbourg, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), IN-SERM U1258, CNRS- UMR7104, Illkirch, France
- Hôpitaux Universitaires de Strasbourg, Laboratoires de diagnostic génétique, Institut de Génétique Médicale d’Alsace, Strasbourg, France
| | - Alexandra Jimenez-Armijo
- Université de Strasbourg, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), IN-SERM U1258, CNRS- UMR7104, Illkirch, France
| | - Marzena Kawczynski
- Hôpitaux Universitaires de Strasbourg (HUS), Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpital Civil, Centre de référence des maladies rares orales et dentaires, O-Rares, Filiére Santé Maladies rares TETE COU, European Reference Network ERN CRANIO, Strasbourg, France
| | - Naji Kharouf
- Université de Strasbourg, Laboratoire de Biomatériaux et Bioingénierie, Inserm UMR_S 1121, Strasbourg, France
| | | | - Muriel de La Dure-Molla
- Rothschild Hospital, Public Assistance-Paris Hospitals (AP-HP), Reference Center for Rare Oral and Den-tal Diseases (O-Rares), Paris, France
| | - Emmanuelle Noirrit
- Centre Hospitalier Universitaire (CHU) Rangueil, Toulouse, Competence Center for Rare Oral and Den-tal Diseases, Toulouse, France
| | - Magali Hernandez
- Centre Hospitalier Régional Universitaire de Nancy, Université de Lorraine, Competence Center for Rare Oral and Dental Diseases, Nancy, France
| | - Clara Joseph-Beaudin
- Centre Hospitalier Universitaire de Nice, Competence Center for Rare Oral and Dental Diseases, Nice, France
| | - Serena Lopez
- Centre Hospitalier Universitaire de Nantes, Competence Center for Rare Oral and Dental Diseases, Nantes, France
| | - Corinne Tardieu
- APHM, Hôpitaux Universitaires de Marseille, Hôpital Timone, Competence Center for Rare Oral and Dental Diseases, Marseille, France
| | - Béatrice Thivichon-Prince
- Centre Hospitalier Universitaire de Lyon, Competence Center for Rare Oral and Dental Diseases, Lyon, France
| | | | - Tatjana Dostalova
- Department of Stomatology (TD) and Department of Biology and Medical Genetics (MM) Charles University 2nd Faculty of Medicine and Motol University Hospital, Prague, Czechia
| | - Milan Macek
- Department of Stomatology (TD) and Department of Biology and Medical Genetics (MM) Charles University 2nd Faculty of Medicine and Motol University Hospital, Prague, Czechia
| | | | - Mustapha El Alloussi
- Faculty of Dentistry, International University of Rabat, CReSS Centre de recherche en Sciences de la Santé, Rabat, Morocco
| | - Leila Qebibo
- Unité de génétique médicale et d’oncogénétique, CHU Hassan II, Fes, Morocco
| | | | | | - Blanca Urzúa Orellana
- Instituto de Investigación en Ciencias Odontológicas, Facultad de Odontología, Universidad de Chile, Santiago, Chile
| | - Marie-Cécile Manière
- Université de Strasbourg, Faculté de Chirurgie Dentaire, Strasbourg, France
- Hôpitaux Universitaires de Strasbourg (HUS), Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpital Civil, Centre de référence des maladies rares orales et dentaires, O-Rares, Filiére Santé Maladies rares TETE COU, European Reference Network ERN CRANIO, Strasbourg, France
| | - Bénédicte Gérard
- Hôpitaux Universitaires de Strasbourg, Laboratoires de diagnostic génétique, Institut de Génétique Médicale d’Alsace, Strasbourg, France
| | - Isaac Maximiliano Bugueno
- Université de Strasbourg, Faculté de Chirurgie Dentaire, Strasbourg, France
- Hôpitaux Universitaires de Strasbourg (HUS), Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpital Civil, Centre de référence des maladies rares orales et dentaires, O-Rares, Filiére Santé Maladies rares TETE COU, European Reference Network ERN CRANIO, Strasbourg, France
- Université de Strasbourg, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), IN-SERM U1258, CNRS- UMR7104, Illkirch, France
| | - Virginie Laugel-Haushalter
- Université de Strasbourg, Faculté de Chirurgie Dentaire, Strasbourg, France
- Université de Strasbourg, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), IN-SERM U1258, CNRS- UMR7104, Illkirch, France
- Hôpitaux Universitaires de Strasbourg, Laboratoires de diagnostic génétique, Institut de Génétique Médicale d’Alsace, Strasbourg, France
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Schieferdecker A, Wendler P. Structural Mapping of Missense Mutations in the Pex1/Pex6 Complex. Int J Mol Sci 2019; 20:ijms20153756. [PMID: 31374812 PMCID: PMC6696164 DOI: 10.3390/ijms20153756] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 07/25/2019] [Accepted: 07/26/2019] [Indexed: 01/05/2023] Open
Abstract
Peroxisome biogenesis disorders (PBDs) are nontreatable hereditary diseases with a broad range of severity. Approximately 65% of patients are affected by mutations in the peroxins Pex1 and Pex6. The proteins form the heteromeric Pex1/Pex6 complex, which is important for protein import into peroxisomes. To date, no structural data are available for this AAA+ ATPase complex. However, a wealth of information can be transferred from low-resolution structures of the yeast scPex1/scPex6 complex and homologous, well-characterized AAA+ ATPases. We review the abundant records of missense mutations described in PBD patients with the aim to classify and rationalize them by mapping them onto a homology model of the human Pex1/Pex6 complex. Several mutations concern functionally conserved residues that are implied in ATP hydrolysis and substrate processing. Contrary to fold destabilizing mutations, patients suffering from function-impairing mutations may not benefit from stabilizing agents, which have been reported as potential therapeutics for PBD patients.
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Affiliation(s)
- Anne Schieferdecker
- Institute of Biochemistry and Biology, University of Potsdam, D-14476 Potsdam, Germany
| | - Petra Wendler
- Institute of Biochemistry and Biology, University of Potsdam, D-14476 Potsdam, Germany.
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4
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Yu HL, Shen Y, Sun YM, Zhang Y. Two novel mutations of PEX6 in one Chinese Zellweger spectrum disorder and their clinical characteristics. ANNALS OF TRANSLATIONAL MEDICINE 2019; 7:368. [PMID: 31555682 DOI: 10.21037/atm.2019.06.42] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background Zellweger spectrum disorder (ZSD) is an autosomal recessive peroxisome biogenesis disorder (PBD) caused by bi-allelic mutations in any of the 13 PEX family genes. Methods We reported a Chinese PBD-ZSD patient with compound heterozygous mutations of PEX6 detected by target sequencing and Sanger sequencing. The clinical materials were collected. In silico analysis were used to evaluate the pathogenicity of the two mutations. An updated review summarized the genotype-phenotype correlation of PBD patients with PEX6 mutations. Results The patient was diagnosed as PBD-ZSD and displayed retinitis pigmentosa, bilateral sensorineural hearing loss, hypotonia, developmental delay, ovarian and enamel dysplasia. Elevated very long chain fatty acids were shown and a pattern of leukodystrophy was displayed through MRI. The two mutations were novel with p.Cys358* and p.Leu83Pro, both classified as pathogenic according to American College of Medical Genetics and Genomics guideline. Phenotype-genotype correlations were shown in the reported patients with PBD-ZSD continuum. Conclusions we reported the first Chinese PBD-ZSD patient with 2 novel mutations in PEX6. Target sequencing and VLFAC were helpful in diagnosis.
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Affiliation(s)
- Hui-Ling Yu
- Department & Institute of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Yan Shen
- Department & Institute of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Yi-Min Sun
- Department & Institute of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Yue Zhang
- Department & Institute of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
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5
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A pex1 missense mutation improves peroxisome function in a subset of Arabidopsis pex6 mutants without restoring PEX5 recycling. Proc Natl Acad Sci U S A 2018; 115:E3163-E3172. [PMID: 29555730 DOI: 10.1073/pnas.1721279115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Peroxisomes are eukaryotic organelles critical for plant and human development because they house essential metabolic functions, such as fatty acid β-oxidation. The interacting ATPases PEX1 and PEX6 contribute to peroxisome function by recycling PEX5, a cytosolic receptor needed to import proteins targeted to the peroxisomal matrix. Arabidopsis pex6 mutants exhibit low PEX5 levels and defects in peroxisomal matrix protein import, oil body utilization, peroxisomal metabolism, and seedling growth. These defects are hypothesized to stem from impaired PEX5 retrotranslocation leading to PEX5 polyubiquitination and consequent degradation of PEX5 via the proteasome or of the entire organelle via autophagy. We recovered a pex1 missense mutation in a screen for second-site suppressors that restore growth to the pex6-1 mutant. Surprisingly, this pex1-1 mutation ameliorated the metabolic and physiological defects of pex6-1 without restoring PEX5 levels. Similarly, preventing autophagy by introducing an atg7-null allele partially rescued pex6-1 physiological defects without restoring PEX5 levels. atg7 synergistically improved matrix protein import in pex1-1 pex6-1, implying that pex1-1 improves peroxisome function in pex6-1 without impeding autophagy of peroxisomes (i.e., pexophagy). pex1-1 differentially improved peroxisome function in various pex6 alleles but worsened the physiological and molecular defects of a pex26 mutant, which is defective in the tether anchoring the PEX1-PEX6 hexamer to the peroxisome. Our results support the hypothesis that, beyond PEX5 recycling, PEX1 and PEX6 have additional functions in peroxisome homeostasis and perhaps in oil body utilization.
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Cho DH, Kim YS, Jo DS, Choe SK, Jo EK. Pexophagy: Molecular Mechanisms and Implications for Health and Diseases. Mol Cells 2018; 41:55-64. [PMID: 29370694 PMCID: PMC5792714 DOI: 10.14348/molcells.2018.2245] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 12/28/2017] [Accepted: 12/29/2017] [Indexed: 02/06/2023] Open
Abstract
Autophagy is an intracellular degradation pathway for large protein aggregates and damaged organelles. Recent studies have indicated that autophagy targets cargoes through a selective degradation pathway called selective autophagy. Peroxisomes are dynamic organelles that are crucial for health and development. Pexophagy is selective autophagy that targets peroxisomes and is essential for the maintenance of homeostasis of peroxisomes, which is necessary in the prevention of various peroxisome-related disorders. However, the mechanisms by which pexophagy is regulated and the key players that induce and modulate pexophagy are largely unknown. In this review, we focus on our current understanding of how pexophagy is induced and regulated, and the selective adaptors involved in mediating pexophagy. Furthermore, we discuss current findings on the roles of pexophagy in physiological and pathological responses, which provide insight into the clinical relevance of pexophagy regulation. Understanding how pexophagy interacts with various biological functions will provide fundamental insights into the function of pexophagy and facilitate the development of novel therapeutics against peroxisomal dysfunction-related diseases.
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Affiliation(s)
- Dong-Hyung Cho
- Graduate School of East-West Medical Science, Kyung Hee University, Yongin 17104,
Korea
| | - Yi Sak Kim
- Department of Microbiology, Chungnam National University School of Medicine, Daejeon 35015,
Korea
- Department of Medical Science, Chungnam National University School of Medicine, Daejeon 35015,
Korea
- Infection Control Convergence Research Center, Chungnam National University School of Medicine, Daejeon 35015,
Korea
| | - Doo Sin Jo
- Graduate School of East-West Medical Science, Kyung Hee University, Yongin 17104,
Korea
| | - Seong-Kyu Choe
- Department of Microbiology and Center for Metabolic Function Regulation, Wonkwang University School of Medicine, Iksan 54538,
Korea
| | - Eun-Kyeong Jo
- Department of Microbiology, Chungnam National University School of Medicine, Daejeon 35015,
Korea
- Department of Medical Science, Chungnam National University School of Medicine, Daejeon 35015,
Korea
- Infection Control Convergence Research Center, Chungnam National University School of Medicine, Daejeon 35015,
Korea
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7
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Rydzanicz M, Stradomska TJ, Jurkiewicz E, Jamroz E, Gasperowicz P, Kostrzewa G, Płoski R, Tylki-Szymańska A. Mild Zellweger syndrome due to a novel PEX6 mutation: correlation between clinical phenotype and in silico prediction of variant pathogenicity. J Appl Genet 2017; 58:475-480. [PMID: 29047053 DOI: 10.1007/s13353-017-0414-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 09/25/2017] [Accepted: 09/27/2017] [Indexed: 01/26/2023]
Abstract
Zellweger syndrome (ZS) is a consequence of a peroxisome biogenesis disorder (PBD) caused by the presence of a pathogenic mutation in one of the 13 genes from the PEX family. ZS is a severe multisystem condition characterized by neonatal appearance of symptoms and a shorter life. Here, we report a case of ZS with a mild phenotype, due to a novel PEX6 gene mutation. The patient presented subtle craniofacial dysmorphic features and slightly slower psychomotor development. At the age of 2 years, he was diagnosed with adrenal insufficiency, hypoacusis, and general deterioration. Magnetic resonance imaging showed a symmetrical hyperintense signal in the frontal and parietal white matter. Biochemical tests showed elevated liver transaminases, elevated serum very long chain fatty acids, and phytanic acid. After the death of the child at the age of 6 years, molecular diagnostics were continued in order to provide genetic counseling for his parents. Next generation sequencing (NGS) analysis with the TruSight One™ Sequencing Panel revealed a novel homozygous PEX6 p.Ala94Pro mutation. In silico prediction of variant severity suggested its possible benign effect. To conclude, in the milder phenotypes, adrenal insufficiency, hypoacusis, and leukodystrophy together seem to be pathognomonic for ZS.
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Affiliation(s)
- Małgorzata Rydzanicz
- Department of Medical Genetics, Medical University of Warsaw, Pawinskiego 3c, 02-106, Warsaw, Poland
| | - Teresa Joanna Stradomska
- Department of Biochemistry, Radioimmunology and Experimental Medicine, The Children's Memorial Health Institute, Dzieci Polskich 20, 04-730, Warsaw, Poland
| | - Elżbieta Jurkiewicz
- Department of Diagnostic Imaging, The Children's Memorial Health Institute, Dzieci Polskich 20, 04-730, Warsaw, Poland
| | - Ewa Jamroz
- Department of Child Neurology, Medical University of Silesia, Medykow 16, 40-752, Katowice, Poland
| | - Piotr Gasperowicz
- Department of Medical Genetics, Medical University of Warsaw, Pawinskiego 3c, 02-106, Warsaw, Poland
| | - Grażyna Kostrzewa
- Department of Forensic Medicine, Medical University of Warsaw, W. Oczki 1, 02-007, Warsaw, Poland
| | - Rafał Płoski
- Department of Medical Genetics, Medical University of Warsaw, Pawinskiego 3c, 02-106, Warsaw, Poland.
| | - Anna Tylki-Szymańska
- Department of Pediatric, Nutrition and Metabolic Diseases, The Children's Memorial Health Institute, Dzieci Polskich 20, 04-730, Warsaw, Poland
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Gonzalez KL, Fleming WA, Kao YT, Wright ZJ, Venkova SV, Ventura MJ, Bartel B. Disparate peroxisome-related defects in Arabidopsis pex6 and pex26 mutants link peroxisomal retrotranslocation and oil body utilization. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 92:110-128. [PMID: 28742939 PMCID: PMC5605450 DOI: 10.1111/tpj.13641] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 06/22/2017] [Accepted: 07/18/2017] [Indexed: 05/29/2023]
Abstract
Catabolism of fatty acids stored in oil bodies is essential for seed germination and seedling development in Arabidopsis. This fatty acid breakdown occurs in peroxisomes, organelles that sequester oxidative reactions. Import of peroxisomal enzymes is facilitated by peroxins including PEX5, a receptor that delivers cargo proteins from the cytosol to the peroxisomal matrix. After cargo delivery, a complex of the PEX1 and PEX6 ATPases and the PEX26 tail-anchored membrane protein removes ubiquitinated PEX5 from the peroxisomal membrane. We identified Arabidopsis pex6 and pex26 mutants by screening for inefficient seedling β-oxidation phenotypes. The mutants displayed distinct defects in growth, response to a peroxisomally metabolized auxin precursor, and peroxisomal protein import. The low PEX5 levels in these mutants were increased by treatment with a proteasome inhibitor or by combining pex26 with peroxisome-associated ubiquitination machinery mutants, suggesting that ubiquitinated PEX5 is degraded by the proteasome when the function of PEX6 or PEX26 is reduced. Combining pex26 with mutations that increase PEX5 levels either worsened or improved pex26 physiological and molecular defects, depending on the introduced lesion. Moreover, elevating PEX5 levels via a 35S:PEX5 transgene exacerbated pex26 defects and ameliorated the defects of only a subset of pex6 alleles, implying that decreased PEX5 is not the sole molecular deficiency in these mutants. We found peroxisomes clustered around persisting oil bodies in pex6 and pex26 seedlings, suggesting a role for peroxisomal retrotranslocation machinery in oil body utilization. The disparate phenotypes of these pex alleles may reflect unanticipated functions of the peroxisomal ATPase complex.
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Affiliation(s)
| | | | | | | | | | | | - Bonnie Bartel
- Corresponding author: Bonnie Bartel, Department of Biosciences, MS-140, Rice University, 6100 Main St., Houston TX, USA. Phone: 713-348-5602, Fax: 713-348-5154;
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Nariman-Saleh-Fam Z, Bastami M, Somi MH, Behjati F, Mansoori Y, Daraei A, Saadatian Z, Nariman-Saleh-Fam L, Mahmoodzadeh H, Makhdoumi Y, Tabrizi FV, Ebrahimi-Sharif B, Hezarian A, Naghashi S, Abbaszadegan MR, Tavakkoly-Bazzaz J. miRNA-Related Polymorphisms in miR-423 (rs6505162) and PEX6 (rs1129186) and Risk of Esophageal Squamous Cell Carcinoma in an Iranian Cohort. Genet Test Mol Biomarkers 2017; 21:382-390. [PMID: 28430524 DOI: 10.1089/gtmb.2016.0346] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
AIMS Iran is located in the Asian esophageal cancer belt. It is a high-risk region for esophageal squamous cell carcinoma (ESCC). The extent to which genetic components, especially variants within miRNAs or their binding sites, contribute to risk of ESCC in the region is not yet fully understood. Herein, tests were done on an Iranian cohort to evaluate the association of miRNA-related polymorphisms in miR-423 (rs6505162) and peroxisomal biogenesis factor 6 (PEX6) (rs1129186 within a miR-149-5p-binding site) with the risk of ESCC risk. METHODS This study recruited 200 ESCC patients and 300 healthy individuals. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism method. Target genes and biological processes that are regulated by miR-423 and may be affected by a change in miR-423 expression were identified by in silico analysis. RESULTS Logistic regression analyses revealed an association between rs6505162 and ESCC, assuming codominant (AA vs. CC, odds ratios, OR [95% confidence interval, CI]: 0.32 [0.15-0.69], p-value: 0.0076), recessive (AA vs. CC+CA, OR [95% CI]: 0.35 [0.16-0.73], p-value: 0.0027), and log-additive models (OR [95% CI]: 0.69 [0.52-0.91], p-value: 0.0084). No significant association was observed for PEX6 rs1129186. In silico analyses revealed several genes and biological processes that are regulated by miR-423 in ESCC. CONCLUSION This study identified the first evidence of an association of a miRNA-related variant with risk of ESCC in an Iranian cohort. PEX6 rs1129186 may not modulate the risk of ESCC in the cohort.
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Affiliation(s)
- Ziba Nariman-Saleh-Fam
- 1 Medical Genetics Department, School of Medicine, Tehran University of Medical Sciences , Tehran, Iran
| | - Milad Bastami
- 2 Department of Medical Genetics, Faculty of Medicine, Tabriz University of Medical Sciences , Tabriz, Iran
| | - Mohammad Hossein Somi
- 3 Liver and Gastrointestinal Disease Research Center, Tabriz University of Medical Sciences , Tabriz, Iran
| | - Farkhondeh Behjati
- 4 Genetics Research Center, University of Social Welfare and Rehabilitation Sciences , Tehran, Iran
| | - Yaser Mansoori
- 1 Medical Genetics Department, School of Medicine, Tehran University of Medical Sciences , Tehran, Iran
| | - Abdolreza Daraei
- 5 Genetics Department, Faculty of Medicine, Babol University of Medical Sciences , Babol, Iran
| | - Zahra Saadatian
- 6 Medical Genetics Department, School of Medicine, Shahid Beheshti University of Medical Sciences , Tehran, Iran
| | | | - Habibollah Mahmoodzadeh
- 8 Cancer Institute, Imam Khomeini Hospital, Tehran University of Medical Sciences , Tehran, Iran
| | | | | | - Bahador Ebrahimi-Sharif
- 10 Department of Genetics and Biotechnology, Varamin-Pishva Branch, Islamic Azad University , Varamin, Iran
| | - Azam Hezarian
- 11 Medical Laboratory, Modarres Hospital, Shahid Beheshti University of Medical Sciences , Tehran, Iran
| | - Shahnaz Naghashi
- 3 Liver and Gastrointestinal Disease Research Center, Tabriz University of Medical Sciences , Tabriz, Iran
| | - Mohammad Reza Abbaszadegan
- 12 Division of Human Genetics, Immunology Research Center, Avicenna Research Institute, Mashhad University of Medical Sciences , Mashhad, Iran
| | - Javad Tavakkoly-Bazzaz
- 1 Medical Genetics Department, School of Medicine, Tehran University of Medical Sciences , Tehran, Iran
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10
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Tan D, Blok NB, Rapoport TA, Walz T. Structures of the double-ring AAA ATPase Pex1-Pex6 involved in peroxisome biogenesis. FEBS J 2015; 283:986-92. [PMID: 26476099 DOI: 10.1111/febs.13569] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 10/12/2015] [Accepted: 10/15/2015] [Indexed: 11/27/2022]
Abstract
The Pex1 and Pex6 proteins are members of the AAA family of ATPases and are involved in peroxisome biogenesis. Recently, cryo-electron microscopy structures of the Pex1-Pex6 complex in different nucleotide states have been determined. This Structural Snapshot describes the structural features of the complex and their implications for its function, as well as questions that still await answers.
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Affiliation(s)
- Dongyan Tan
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Neil B Blok
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA.,Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA
| | - Tom A Rapoport
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA.,Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA
| | - Thomas Walz
- The Rockefeller University, New York, NY, USA
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11
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Tran C, Hewson S, Steinberg SJ, Mercimek-Mahmutoglu S. Late-onset Zellweger spectrum disorder caused by PEX6 mutations mimicking X-linked adrenoleukodystrophy. Pediatr Neurol 2014; 51:262-5. [PMID: 25079577 DOI: 10.1016/j.pediatrneurol.2014.03.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Revised: 03/16/2014] [Accepted: 03/22/2014] [Indexed: 12/19/2022]
Abstract
BACKGROUND Zellweger spectrum disorder is an autosomal recessively inherited multisystem disorder caused by one of the 13 different PEX gene defects resulting in defective peroxisomal assembly and multiple peroxisomal enzyme deficiencies. We report a new patient with late-onset Zellweger spectrum disorder mimicking X-linked adrenoleukodystrophy. PATIENT DESCRIPTION This 8.5-year-old boy with normal development until 6.5 years of age presented with bilateral sensorineural hearing loss during a school hearing test. He then developed acute-onset diplopia, clumsiness, and cognitive dysfunction at age 7 years. Magnetic resonance imaging of the brain revealed symmetric leukodystrophy, although without gadolinium enhancement. Elevated plasma very long chain fatty acid levels were suggestive of X-linked adrenoleukodystrophy, but his ABCD1 gene had normal coding sequence and dosage. Additional studies of cultured skin fibroblasts were consistent with Zellweger spectrum disorder. Molecular testing identified disease-causing compound heterozygous mutations in the PEX6 gene supporting the Zellweger spectrum disorder diagnosis in this patient. CONCLUSIONS We describe a new patient with late-onset Zellweger spectrum disorder caused by PEX6 mutations who presented with an acute neurodegenerative disease course mimicking X-linked adrenoleukodystrophy. This finding provides an additional reason that molecular confirmation is important for the genetic counseling and management of patients with a clinical and biochemical diagnosis of X-linked adrenoleukodystrophy.
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Affiliation(s)
- Christel Tran
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Stacy Hewson
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Steven J Steinberg
- Institute of Genetic Medicine and Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Saadet Mercimek-Mahmutoglu
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada; Genetics & Genome Biology Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
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12
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Ratzel SE, Lingard MJ, Woodward AW, Bartel B. Reducing PEX13 expression ameliorates physiological defects of late-acting peroxin mutants. Traffic 2010; 12:121-34. [PMID: 20969679 DOI: 10.1111/j.1600-0854.2010.01136.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Proteins are targeted to the peroxisome matrix via processes that are mechanistically distinct from those used by other organelles. Protein entry into peroxisomes requires peroxin (PEX) proteins, including early-acting receptor (e.g. PEX5) and docking peroxins (e.g. PEX13 and PEX14) and late-acting PEX5-recycling peroxins (e.g. PEX4 and PEX6). We examined genetic interactions among Arabidopsis peroxin mutants and found that the weak pex13-1 allele had deleterious effects when combined with pex5-1 and pex14-2, which are defective in early-acting peroxins, as shown by reduced matrix protein import and enhanced physiological defects. In contrast, combining pex13-1 with pex4-1 or pex6-1, which are defective in late-acting peroxins, unexpectedly ameliorated mutant growth defects. Matrix protein import remained impaired in pex4-1 pex13-1 and pex6-1 pex13-1, suggesting that the partial suppression of pex4-1 and pex6-1 physiological defects by a weak pex13 allele may result from restoring the balance between import and export of PEX5 or other proteins that are retrotranslocated from the peroxisome with the assistance of PEX4 and PEX6. Our results suggest that symptoms caused by pex mutants defective in late-acting peroxins may result not only from defects in matrix protein import but also from inefficient removal of PEX5 from the peroxisomal membrane following cargo delivery.
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Affiliation(s)
- Sarah E Ratzel
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005, USA
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13
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Krause C, Rosewich H, Gärtner J. Rational diagnostic strategy for Zellweger syndrome spectrum patients. Eur J Hum Genet 2009; 17:741-8. [PMID: 19142205 DOI: 10.1038/ejhg.2008.252] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Zellweger syndrome spectrum (ZSS) comprises a clinically and genetically heterogeneous disease entity, which is caused by mutations in any of the 12 different human PEX genes leading to impaired biogenesis of the peroxisome. Patients potentially suffering from ZSS are diagnosed biochemically by measuring elevated levels of very long chain fatty acids, pristanic acid and phytanic acid in plasma and serum and reduced levels of ether phospholipids in erythrocytes. Published reports on diagnostic procedures for ZSS patients are restricted either to biochemical markers or to defined mutations in a subset of PEX genes. Clarification of the primary genetic defect in an affected patient is crucial for genetic counselling, carrier testing or prenatal diagnosis. In this study, we present a rational diagnostic strategy for patients suspected of ZSS. By combining cell biology and molecular genetic methods in an appropriate sequence, we were able to detect the underlying mutation in various PEX genes within adequate time and cost. We applied this method on 90 patients who presented at our institute, Department of Pediatrics and Pediatric Neurology at Georg August University, and detected 174 mutant alleles within six different PEX genes, including two novel deletions and three new missense mutations in PEX6. Furthermore, this strategy will extend our knowledge on genotype-phenotype correlation in various PEX genes. It will contribute to a better understanding of ZSS pathogenesis, allowing the investigation of the effects of diverse mutations on the interaction between PEX proteins and peroxisomal function in vivo.
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Affiliation(s)
- Cindy Krause
- Department of Pediatrics and Pediatric Neurology, Faculty of Medicine, Georg August University, Göttingen, Germany
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14
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Steinberg SJ, Dodt G, Raymond GV, Braverman NE, Moser AB, Moser HW. Peroxisome biogenesis disorders. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:1733-48. [PMID: 17055079 DOI: 10.1016/j.bbamcr.2006.09.010] [Citation(s) in RCA: 338] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Revised: 09/05/2006] [Accepted: 09/06/2006] [Indexed: 01/02/2023]
Abstract
Defects in PEX genes impair peroxisome assembly and multiple metabolic pathways confined to this organelle, thus providing the biochemical and molecular bases of the peroxisome biogenesis disorders (PBD). PBD are divided into two types--Zellweger syndrome spectrum (ZSS) and rhizomelic chondrodysplasia punctata (RCDP). Biochemical studies performed in blood and urine are used to screen for the PBD. DNA testing is possible for all of the disorders, but is more challenging for the ZSS since 12 PEX genes are known to be associated with this spectrum of PBD. In contrast, PBD-RCDP is associated with defects in the PEX7 gene alone. Studies of the cellular and molecular defects in PBD patients have contributed significantly to our understanding of the role of each PEX gene in peroxisome assembly.
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Affiliation(s)
- Steven J Steinberg
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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15
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Steinberg S, Chen L, Wei L, Moser A, Moser H, Cutting G, Braverman N. The PEX Gene Screen: molecular diagnosis of peroxisome biogenesis disorders in the Zellweger syndrome spectrum. Mol Genet Metab 2004; 83:252-63. [PMID: 15542397 DOI: 10.1016/j.ymgme.2004.08.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Revised: 08/14/2004] [Accepted: 08/20/2004] [Indexed: 10/26/2022]
Abstract
Peroxisome biogenesis disorders in the Zellweger syndrome spectrum (PBD-ZSS) are caused by defects in at least 12 PEX genes required for normal organelle assembly. Clinical and biochemical features continue to be used reliably to assign patients to this general disease category. Identification of the precise genetic defect is important, however, to permit carrier testing and early prenatal diagnosis. Molecular analysis is likely to expand the clinical spectrum of PBD and may also provide data relevant to prognosis and future therapeutic intervention. However, the large number of genes involved has thus far impeded rapid mutation identification. In response, we developed the PEX Gene Screen, an algorithm for the systematic screening of exons in the six PEX genes most commonly defective in PBD-ZSS. We used PCR amplification of genomic DNA and sequencing to screen 91 unclassified PBD-ZSS patients for mutations in PEX1, PEX26, PEX6, PEX12, PEX10, and PEX2. A maximum of 14 reactions per patient identified pathological mutations in 79% and both mutant alleles in 54%. Twenty-five novel mutations were identified overall. The proportion of patients with different PEX gene defects correlated with frequencies previously identified by complementation analysis. This systematic, hierarchical approach to mutation identification is therefore a valuable tool to identify rapidly the molecular etiology of suspected PBD-ZSS disorders.
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Affiliation(s)
- Steven Steinberg
- Peroxisomal Diseases Laboratory, Kennedy Krieger Institute and Department of Neurology, Johns Hopkins University, Baltimore, MD, USA.
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16
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Stasyk OV, Nazarko VY, Pochapinsky OD, Nazarko TY, Veenhuis M, Sibirny AA. Identification of intragenic mutations in the Hansenula polymorpha PEX6 gene that affect peroxisome biogenesis and methylotrophic growth. FEMS Yeast Res 2003; 4:141-7. [PMID: 14613878 DOI: 10.1016/s1567-1356(03)00153-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
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 37 degrees C but not at 28 degrees C. 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.
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Affiliation(s)
- Oleh V Stasyk
- Institute of Cell Biology, Drahomanov Str. 14/16, 79005, Lviv, Ukraine
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17
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Abstract
The peroxisome biogenesis disorders (PBDs) comprise 12 autosomal recessive complementation groups (CGs). The multisystem clinical phenotype varies widely in severity and results from disturbances in both development and metabolic homeostasis. Progress over the last several years has lead to identification of the genes responsible for all of these disorders and to a much improved understanding of the biogenesis and function of the peroxisome. Increasing availability of mouse models for these disorders offers hope for a better understanding of their pathophysiology and for development of therapies that might especially benefit patients at the milder end of the clinical phenotype.
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Affiliation(s)
- Sabine Weller
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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18
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Raas-Rothschild A, Wanders RJA, Mooijer PAW, Gootjes J, Waterham HR, Gutman A, Suzuki Y, Shimozawa N, Kondo N, Eshel G, Espeel M, Roels F, Korman SH. A PEX6-defective peroxisomal biogenesis disorder with severe phenotype in an infant, versus mild phenotype resembling Usher syndrome in the affected parents. Am J Hum Genet 2002; 70:1062-8. [PMID: 11873320 PMCID: PMC379104 DOI: 10.1086/339766] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2001] [Accepted: 01/14/2002] [Indexed: 11/03/2022] Open
Abstract
Sensorineural deafness and retinitis pigmentosa (RP) are the hallmarks of Usher syndrome (USH) but are also prominent features in peroxisomal biogenesis defects (PBDs); both are autosomal recessively inherited. The firstborn son of unrelated parents, who both had sensorineural deafness and RP diagnosed as USH, presented with sensorineural deafness, RP, dysmorphism, developmental delay, hepatomegaly, and hypsarrhythmia and died at age 17 mo. The infant was shown to have a PBD, on the basis of elevated plasma levels of very-long- and branched-chain fatty acids (VLCFAs and BCFAs), deficiency of multiple peroxisomal functions in fibroblasts, and complete absence of peroxisomes in fibroblasts and liver. Surprisingly, both parents had elevated plasma levels of VLCFAs and BCFAs. Fibroblast studies confirmed that both parents had a PBD. The parents' milder phenotypes correlated with relatively mild peroxisomal biochemical dysfunction and with catalase immunofluorescence microscopy demonstrating mosaicism and temperature sensitivity in fibroblasts. The infant and both of his parents belonged to complementation group C. PEX6 gene sequencing revealed mutations on both alleles, in the infant and in his parents. This unique family is the first report of a PBD with which the parents are themselves affected individuals rather than asymptomatic carriers. Because of considerable overlap between USH and milder PBD phenotypes, individuals suspected to have USH should be screened for peroxisomal dysfunction.
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19
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Percy AK, Rutledge SL. Adrenoleukodystrophy and related disorders. MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS 2002; 7:179-89. [PMID: 11553934 DOI: 10.1002/mrdd.1026] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- A K Percy
- Department of Pediatrics, Neurology, and Neurobiology, School of Medicine, University of Alabama at Birmingham, USA.
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20
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Suzuki Y, Shimozawa N, Imamura A, Fukuda S, Zhang Z, Orii T, Kondo N. Clinical, biochemical and genetic aspects and neuronal migration in peroxisome biogenesis disorders. J Inherit Metab Dis 2001; 24:151-65. [PMID: 11405337 DOI: 10.1023/a:1010310816743] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Peroxisome biogenesis disorders (PBDs) are severe autosomal recessive neurological diseases caused by a defect of peroxisomal assembly factors. Zellweger syndrome, the most severe phenotype, is characterized by hypotonia, psychomotor retardation and neuronal migration disorder. Neonatal adrenoleukodystrophy and infantile Refsum disease are milder phenotypes of this disease. Thirteen complementation groups have been established since the genetic heterogeneity of PBDs was elucidated in 1988. Eleven genes for PBDs have been identified either by a functional complementation cloning or by EST homology searches. In 1992, the first gene for PBDs, PEX2, was identified. It encodes peroxisomal integral membrane protein with a RING finger domain. PEX5 and PEX7 are the genes for peroxisomal targeting signal (PTS)-1 and -2 receptors, respectively. PEX3, PEX16 and PEX19 are considered to be required for the early stage of peroxisome biogenesis. PEX13 protein has an SH3 docking site that binds to the PTS-1 receptor. PEX1 and PEX6 encode ABC protein, and PEX10 and PEX12 also encode integral membrane protein, with RING finger. Temperature-sensitivity, whereby peroxisomal biogenesis and metabolic dysfunctions are restored at 30 degrees C in cells from mild phenotypes, is a useful event for predicting the clinical severity and for elucidation of peroxisome biogenesis. Investigations using knockout mice are expected to facilitate understanding of migration disorders.
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Affiliation(s)
- Y Suzuki
- Department of Pediatrics, Gifu University School of Medicine, Japan.
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21
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Imamura A, Shimozawa N, Suzuki Y, Zhang Z, Tsukamoto T, Fujiki Y, Orii T, Osumi T, Wanders RJ, Kondo N. Temperature-sensitive mutation of PEX6 in peroxisome biogenesis disorders in complementation group C (CG-C): comparative study of PEX6 and PEX1. Pediatr Res 2000; 48:541-5. [PMID: 11004248 DOI: 10.1203/00006450-200010000-00020] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Peroxisome biogenesis disorders (PBD), including Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum disease, are a group of genetically heterogeneous autosomal-recessive diseases caused by mutations in PEX genes that encode peroxins, proteins required for peroxisome biogenesis. Zellweger syndrome patients present the most severe phenotype, whereas neonatal adrenoleukodystrophy patients are intermediate and infantile Refsum disease patients have the mildest features. PEX6 is a causative gene for PBD of complementation group C (CG-C) and encodes the peroxin Pex6p, one of the ATPases associated with diverse cellular activities and a member of the same family of proteins as Pex1p, a causative protein for PBD of CG-E (CG1). Here, we identified the temperature sensitivity of peroxisomes in the fibroblasts of a patient with neonatal adrenoleukodystrophy in CG-C. Peroxisomes were morphologically and biochemically formed at 30 degrees C but not at 37 degrees C. This patient was homozygous for a missense mutation, T-->C at nucleotide 170 resulting in a change from leucine to proline at amino acid 57 (L57P) in Pex6p. CG-C cell mutants (ZP92) in the Chinese hamster ovary transfected with L57P in HsPEX6 revealed the same temperature-sensitive phenotype. However, PEX1-deficient Chinese hamster ovary cell mutants (ZP101) transfected with L111P in PEX1, the counterpart to L57P in PEX6, showed no temperature sensitivity. In addition, ZP92 transfected with G708D in PEX6, the counterpart to the temperature-sensitive mutation G843D in PEX1, revealed no temperature-sensitive phenotype. These results indicate that L57P in Pex6p is a temperature-sensitive mutation causing the milder phenotype in a patient with PBD in CG-C. They also indicate that the amino acid residues responsible for temperature sensitivity do not seem to be conserved between Pex6p and Pex1p.
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Affiliation(s)
- A Imamura
- Department of Pediatrics, Gifu University School of Medicine, Gifu 500-8705, Japan
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22
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Abstract
Genetically determined human peroxisomal disorders are subdivided into two major categories: disorders of peroxisome biogenesis (PBD), in which the organelle is not formed normally, and those that involve a single peroxisomal enzyme. Twelve PBD have been identified, and the molecular defects have been defined in 10. All involve defects in the import of proteins into the organelle. Factors required for this import are now referred to as peroxins (PEX) and form the basis of a new and preferred classification system. The PBD are associated with four clinical phenotypes, named before their association with the organelle was recognized: Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and rhizomelic chondrodysplasia punctata (RCDP). The first three are associated with 9 of the 10 PEX defects that have been defined so far, and represent a clinical continuum with variant severity, with ZS the most severe, NALD intermediate, and IRD the least severe. RCDP is associated with PEX7. Genotype-phenotype correlations are complicated by the fact that the clinical manifestations of the ZS-NALD-IRD continuum can be mimicked by disorders that affect single enzymes of peroxisomal fatty acid oxidation, and PEX7 by disorders of plasmalogen synthesis enzymes. Furthermore, clinical manifestations of each of the PEX disorders may vary. Phenotypic expression varies with the nature of the mutation, the milder phenotypes being associated with mutations that do not abolish function completely, or with mosaicism. Definition of the molecular defects is of great value for genetic counseling and may be of aid in establishing prognosis.
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Affiliation(s)
- H W Moser
- Department of Neurogenetics, Kennedy Krieger Institute, Johns Hopkins University, 707 North Broadway, Baltimore, Maryland, 21205, USA
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