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Borgia P, Baldassari S, Pedemonte N, Alkhunaizi E, D'Onofrio G, Tortora D, Calì E, Scudieri P, Balagura G, Musante I, Diana MC, Pedemonte M, Vari MS, Iacomino M, Riva A, Chimenz R, Mangano GD, Mohammadi MH, Toosi MB, Ashrafzadeh F, Imannezhad S, Karimiani EG, Accogli A, Schiaffino MC, Maghnie M, Soler MA, Echiverri K, Abrams CK, Striano P, Fortuna S, Maroofian R, Houlden H, Zara F, Fiorillo C, Salpietro V. Genotype-phenotype correlations and disease mechanisms in PEX13-related Zellweger spectrum disorders. Orphanet J Rare Dis 2022; 17:286. [PMID: 35854306 PMCID: PMC9295491 DOI: 10.1186/s13023-022-02415-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 06/26/2022] [Indexed: 11/26/2022] Open
Abstract
Background Pathogenic variants in PEX-genes can affect peroxisome assembly and function and cause Zellweger spectrum disorders (ZSDs), characterized by variable phenotypes in terms of disease severity, age of onset and clinical presentations. So far, defects in at least 15 PEX-genes have been implicated in Mendelian diseases, but in some of the ultra-rare ZSD subtypes genotype–phenotype correlations and disease mechanisms remain elusive. Methods We report five families carrying biallelic variants in PEX13. The identified variants were initially evaluated by using a combination of computational approaches. Immunofluorescence and complementation studies on patient-derived fibroblasts were performed in two patients to investigate the cellular impact of the identified mutations. Results Three out of five families carried a recurrent p.Arg294Trp non-synonymous variant. Individuals affected with PEX13-related ZSD presented heterogeneous clinical features, including hypotonia, developmental regression, hearing/vision impairment, progressive spasticity and brain leukodystrophy. Computational predictions highlighted the involvement of the Arg294 residue in PEX13 homodimerization, and the analysis of blind docking predicted that the p.Arg294Trp variant alters the formation of dimers, impairing the stability of the PEX13/PEX14 translocation module. Studies on muscle tissues and patient-derived fibroblasts revealed biochemical alterations of mitochondrial function and identified mislocalized mitochondria and a reduced number of peroxisomes with abnormal PEX13 concentration. Conclusions This study expands the phenotypic and mutational spectrum of PEX13-related ZSDs and also highlight a variety of disease mechanisms contributing to PEX13-related clinical phenotypes, including the emerging contribution of secondary mitochondrial dysfunction to the pathophysiology of ZSDs.
Supplementary Information The online version contains supplementary material available at 10.1186/s13023-022-02415-5.
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Affiliation(s)
- Paola Borgia
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16132, Genoa, Italy.,Pediatric Neurology and Muscular Diseases Unit, IRCCS Giannina Gaslini Institute, 16147, Genoa, Italy
| | - Simona Baldassari
- Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, 16147, Genoa, Italy
| | - Nicoletta Pedemonte
- Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, 16147, Genoa, Italy
| | - Ebba Alkhunaizi
- Department of Genetics, North York General Hospital, University of Toronto, Toronto, ON, Canada
| | - Gianluca D'Onofrio
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16132, Genoa, Italy.,Pediatric Neurology and Muscular Diseases Unit, IRCCS Giannina Gaslini Institute, 16147, Genoa, Italy
| | - Domenico Tortora
- Neuroradiology Unit, IRCCS Istituto Giannina Gaslini, 16147, Genoa, Italy
| | - Elisa Calì
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Paolo Scudieri
- Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, 16147, Genoa, Italy
| | - Ganna Balagura
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16132, Genoa, Italy
| | - Ilaria Musante
- Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, 16147, Genoa, Italy
| | - Maria Cristina Diana
- Pediatric Neurology and Muscular Diseases Unit, IRCCS Giannina Gaslini Institute, 16147, Genoa, Italy
| | - Marina Pedemonte
- Pediatric Neurology and Muscular Diseases Unit, IRCCS Giannina Gaslini Institute, 16147, Genoa, Italy
| | - Maria Stella Vari
- Pediatric Neurology and Muscular Diseases Unit, IRCCS Giannina Gaslini Institute, 16147, Genoa, Italy
| | - Michele Iacomino
- Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, 16147, Genoa, Italy
| | - Antonella Riva
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16132, Genoa, Italy.,Pediatric Neurology and Muscular Diseases Unit, IRCCS Giannina Gaslini Institute, 16147, Genoa, Italy
| | - Roberto Chimenz
- Unit of Pediatric Nephrology and Dialysis, Department of Human Pathology in Adult and Developmental Age "Gaetano Barresi", University of Messina, Via Consolare Valeria 1, 98125, Messina, Italy
| | - Giuseppe D Mangano
- Department Pro.M.I.S.E. "G. D'Alessandro", University of Palermo, Palermo, Italy
| | | | - Mehran Beiraghi Toosi
- Pediatric Neurology Department, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Farah Ashrafzadeh
- Department of Pediatrics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Shima Imannezhad
- Pediatric Neurology Department, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Ehsan Ghayoor Karimiani
- Molecular and Clinical Sciences Institute, St. George's, University of London, Cranmer Terrace, London, SW170RE, UK.,Innovative Medical Research Center, Mashhad Branch, Islamic Azad University, Mashhad, Iran
| | - Andrea Accogli
- Division of Medical Genetics, Department of Specialized Medicine, Montreal Children's Hospital, McGill University Health Centre (MUHC), Montreal, QC, H4A 3J1, Canada.,Department of Human Genetics, McGill University, Montreal, QC, Canada
| | - Maria Cristina Schiaffino
- Pediatric Clinic and Endocrinology Unit, Department of General and Specialist Pediatric Sciences, University of Genoa, 16147, Genoa, Italy
| | - Mohamad Maghnie
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16132, Genoa, Italy.,Pediatric Clinic and Endocrinology Unit, Department of General and Specialist Pediatric Sciences, University of Genoa, 16147, Genoa, Italy
| | - Miguel Angel Soler
- Computational Modelling of Nanoscale and Biophysical Systems Laboratory, Italian Institute of Technology, 16163, Genoa, Italy
| | - Karl Echiverri
- Departments of Neurology and Ophthalmology, University of Kentucky, Lexington, 40506, USA
| | - Charles K Abrams
- Department of Neurology and Rehabilitation, College of Medicine, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Pasquale Striano
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16132, Genoa, Italy.,Pediatric Neurology and Muscular Diseases Unit, IRCCS Giannina Gaslini Institute, 16147, Genoa, Italy
| | - Sara Fortuna
- Computational Modelling of Nanoscale and Biophysical Systems Laboratory, Italian Institute of Technology, 16163, Genoa, Italy.,Department of Chemical and Pharmaceutical Sciences, University of Trieste, 34134, Trieste, Italy
| | - Reza Maroofian
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Henry Houlden
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Federico Zara
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16132, Genoa, Italy.,Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, 16147, Genoa, Italy
| | - Chiara Fiorillo
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16132, Genoa, Italy. .,Pediatric Neurology and Muscular Diseases Unit, IRCCS Giannina Gaslini Institute, 16147, Genoa, Italy.
| | - Vincenzo Salpietro
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK. .,Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, 67100, L'Aquila, Italy.
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Benson MD, Papp KM, Casey GA, Radziwon A, St Laurent CD, Doucette LP, MacDonald IM. PEX6 Mutations in Peroxisomal Biogenesis Disorders: An Usher Syndrome Mimic. OPHTHALMOLOGY SCIENCE 2021; 1:100028. [PMID: 36249295 PMCID: PMC9559095 DOI: 10.1016/j.xops.2021.100028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 04/29/2021] [Accepted: 05/14/2021] [Indexed: 06/16/2023]
Abstract
PURPOSE Peroxisomal biogenesis disorders (PBDs) represent a spectrum of conditions that result in vision loss, sensorineural hearing loss, neurologic dysfunction, and other abnormalities resulting from aberrant peroxisomal function caused by mutations in PEX genes. With no treatments currently available, we sought to investigate the disease mechanism in a patient with a PBD caused by defects in PEX6 and to probe whether overexpression of PEX6 could restore peroxisome function and potentially offer therapeutic benefit. DESIGN Laboratory-based study. PARTICIPANTS A 12-year-old boy sought treatment with hearing loss and retinopathy. After negative results in an Usher syndrome panel, targeted genetic testing revealed compound heterozygous mutations in PEX6. These included a 14-nucleotide deletion (c.802_815del: p.(Asp268Cysfs∗8)) and a milder missense variant (c.35T→C:(p.Phe12Ser)). METHODS Patient-derived skin fibroblasts were cultured, and a PEX6 knockout cell line was developed using clustered regularly interspaced short palindromic repeats and Cas9 technology in HEK293T cells to emulate a more severe disease phenotype. Immunoblot analysis of whole cell lysates was performed to assess peroxisome number. Immunofluorescence studies used antibodies against components of the peroxisomal protein import pathway to interrogate the effects of mutations in PEX6 on protein trafficking. MAIN OUTCOME MEASURES Primary outcome measures were peroxisome abundance and matrix protein import. RESULTS Peroxisome number was not significantly different between control fibroblasts and patient fibroblasts; however, fewer peroxisomes were observed in PEX6 knockout cells compared with wild-type cells (P = 0.04). Analysis by immunofluorescent microscopy showed significantly impaired peroxisomal targeting signal 1- and peroxisomal targeting signal 2-mediated matrix protein import in both patient fibroblasts and PEX6 knockout cells. Overexpressing PEX6 resulted in improved matrix protein import in PEX6 knockout cells. CONCLUSIONS Mutations in PEX6 were responsible for combined hearing loss and retinopathy in our patient. The primary peroxisomal defect in our patient's skin fibroblasts was impaired peroxisomal protein import as opposed to reduction in the number of peroxisomes. Genetic strategies that introduce wild-type PEX6 into cells deficient in PEX6 protein show promise in restoring peroxisome function. Future studies of patient-specific induced pluripotent stem cell-derived retinal pigment epithelium cells may clarify the role of PEX6 in the retina and the potential for gene therapy in these patients.
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Key Words
- CRISPR, clustered regularly interspaced short palindromic repeats
- DTM, docking translocation module
- GFP, green fluorescent protein
- HEK293T, human embryonic kidney 293T
- Hearing loss
- PBD, peroxisomal biogenesis disorder
- PBS, phosphate-buffered saline
- PEX6
- PTS1, peroxisomal targeting signal 1
- PTS2, peroxisomal targeting signal 2
- Peroxisomal biogenesis disorders
- Peroxisome
- RPE, retinal pigment epithelium
- Retinal degeneration
- Usher syndrome
- WT, wild-type
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Affiliation(s)
- Matthew D. Benson
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Canada
| | - Kimberly M. Papp
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Canada
| | - Geoffrey A. Casey
- Department of Medical Genetics, University of Alberta, Edmonton, Canada
| | - Alina Radziwon
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Canada
| | - Chris D. St Laurent
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Canada
| | - Lance P. Doucette
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Canada
| | - Ian M. MacDonald
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Canada
- Department of Medical Genetics, University of Alberta, Edmonton, Canada
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Daich Varela M, Jani P, Zein WM, D'Souza P, Wolfe L, Chisholm J, Zalewski C, Adams D, Warner BM, Huryn LA, Hufnagel RB. The peroxisomal disorder spectrum and Heimler syndrome: Deep phenotyping and review of the literature. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2020; 184:618-630. [PMID: 32866347 DOI: 10.1002/ajmg.c.31823] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 07/14/2020] [Accepted: 07/21/2020] [Indexed: 12/20/2022]
Abstract
The spectrum of peroxisomal disorders is wide and comprises individuals that die in the first year of life, as well as people with sensorineural hearing loss, retinal dystrophy and amelogenesis imperfecta. In this article, we describe three patients; two diagnosed with Heimler syndrome and a third one with a mild-intermediate phenotype. We arrived at these diagnoses by conducting complete ophthalmic (National Eye Institute), auditory (National Institute of Deafness and Other Communication Disorders), and dental (National Institute of Dental and Craniofacial Research) evaluations, as well as laboratory and genetic testing. Retinal degeneration with macular cystic changes, amelogenesis imperfecta, and sensorineural hearing loss were features shared by the three patients. Patients A and C had pathogenic variants in PEX1 and Patient B, in PEX6. Besides analyzing these cases, we review the literature regarding mild peroxisomal disorders, their pathophysiology, genetics, differential diagnosis, diagnostic methods, and management. We suggest that peroxisomal disorders are considered in every child with sensorineural hearing loss and retinal degeneration. These patients should have a dental evaluation to rule out amelogenesis imperfecta as well as audiologic examination and laboratory testing including peroxisomal biomarkers and genetic testing. Appropriate diagnosis can lead to better genetic counseling and management of the associated comorbidities.
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Affiliation(s)
- Malena Daich Varela
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Priyam Jani
- National Institute of Dental and Craniofacial Research, NIH, Bethesda, Maryland, USA
| | - Wadih M Zein
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Precilla D'Souza
- Office of the Clinical Director, National Human Genome Research Institute, NIH, Bethesda, Maryland, USA
| | - Lynne Wolfe
- Undiagnosed Diseases Program, Common Fund, NIH, Bethesda, Maryland, USA
| | - Jennifer Chisholm
- Audiology Unit, Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland, USA
| | - Christopher Zalewski
- Audiology Unit, Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland, USA
| | - David Adams
- Office of the Clinical Director, National Human Genome Research Institute, NIH, Bethesda, Maryland, USA.,Undiagnosed Diseases Program, Common Fund, NIH, Bethesda, Maryland, USA
| | - Blake M Warner
- National Institute of Dental and Craniofacial Research, NIH, Bethesda, Maryland, USA
| | - Laryssa A Huryn
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Robert B Hufnagel
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health (NIH), Bethesda, Maryland, USA
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