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Borrelli E, Bandello F, Boon CJF, Carelli V, Lenaers G, Reibaldi M, Sadda SR, Sadun AA, Sarraf D, Yu-Wai-Man P, Barboni P. Mitochondrial retinopathies and optic neuropathies: The impact of retinal imaging on modern understanding of pathogenesis, diagnosis, and management. Prog Retin Eye Res 2024; 101:101264. [PMID: 38703886 DOI: 10.1016/j.preteyeres.2024.101264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 03/18/2024] [Accepted: 04/26/2024] [Indexed: 05/06/2024]
Abstract
Advancements in ocular imaging have significantly broadened our comprehension of mitochondrial retinopathies and optic neuropathies by examining the structural and pathological aspects of the retina and optic nerve in these conditions. This article aims to review the prominent imaging characteristics associated with mitochondrial retinopathies and optic neuropathies, aiming to deepen our insight into their pathogenesis and clinical features. Preceding this exploration, the article provides a detailed overview of the crucial genetic and clinical features, which is essential for the proper interpretation of in vivo imaging. More importantly, we will provide a critical analysis on how these imaging modalities could serve as biomarkers for characterization and monitoring, as well as in guiding treatment decisions. However, these imaging methods have limitations, which will be discussed along with potential strategies to mitigate them. Lastly, the article will emphasize the potential advantages and future integration of imaging techniques in evaluating patients with mitochondrial eye disorders, considering the prospects of emerging gene therapies.
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Affiliation(s)
- Enrico Borrelli
- Department of Surgical Sciences, University of Turin, Turin, Italy; Department of Ophthalmology, "City of Health and Science" Hospital, Turin, Italy.
| | - Francesco Bandello
- Vita-Salute San Raffaele University, Milan, Italy; IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Camiel J F Boon
- Department of Ophthalmology, Amsterdam University Medical Centers, Amsterdam, the Netherlands; Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands
| | - Valerio Carelli
- Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna, Italy; IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
| | - Guy Lenaers
- Equipe MitoLab, Unité MitoVasc, INSERM U1083, Université d'Angers, 49933, Angers, France; Service de Neurologie, CHU d'Angers, 49100, Angers, France
| | - Michele Reibaldi
- Department of Surgical Sciences, University of Turin, Turin, Italy; Department of Ophthalmology, "City of Health and Science" Hospital, Turin, Italy
| | - Srinivas R Sadda
- Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Doheny Eye Institute, Los Angeles, CA, USA
| | - Alfredo A Sadun
- Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Doheny Eye Institute, Los Angeles, CA, USA
| | - David Sarraf
- Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Retinal Disorders and Ophthalmic Genetics Division, Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Patrick Yu-Wai-Man
- John van Geest Centre for Brain Repair and MRC Mitochondrial Biology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK; Cambridge Eye Unit, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK; Institute of Ophthalmology, University College London, London, UK
| | - Piero Barboni
- IRCCS San Raffaele Scientific Institute, Milan, Italy; Studio Oculistico d'Azeglio, Bologna, Italy.
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Wei X, Li H, Zhu T, Yao F, Sui R. FDXR-associated disease in a Chinese cohort: Unraveling expanded ocular phenotypes and genetic spectrum. Exp Eye Res 2023; 234:109600. [PMID: 37481223 DOI: 10.1016/j.exer.2023.109600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 07/06/2023] [Accepted: 07/19/2023] [Indexed: 07/24/2023]
Abstract
FDXR: associated disease is characterized by optic atrophy, acoustic neuropathy, and developmental delays. This study evaluated the ocular phenotypes and genetic features of patients with biallelic FDXR variants. Five individuals from unrelated non-consanguineous Chinese families with biallelic FDXR variants were identified using whole exome sequencing, Sanger sequencing, and co-segregation validation. In addition to optic atrophy and diverse extraocular manifestations, all patients presented with retinal dystrophy, and electroretinogram showed severely impaired cone and rod functions in their first decades. Three of the five patients showed attenuated retinal vessels that appeared as white lines on the fundus, and fundus fluorescein angiography (FFA) further revealed vascular abnormalities including delayed filling, completely occluded retinal vasculature, and severe retinal vascular nonperfusion of the peripheral retina. Five novel FDXR variants were identified: c.383C > T (p.A128V), c.963delG (p.R322fs*7), c.1052_1053delTC (p.L351Pfs*12), c.394-11T > G and c.1002+1G > A. Retinal dystrophy with attenuated retinal vessels appearing as white lines was observed in this cohort, and the FFA images revealed that retinal vascular occlusion could be a distinct clinical characteristic of FDXR-associated disease. Probands with FDXR revealed severe early onset ophthalmic features with rapid-progression, indicating the importance of early diagnosis and treatment. Moreover, this is the first study to report FFA manifestations in an FDXR cohort, expanding the FDXR-associated ocular disease phenotype and genetic spectrum.
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Affiliation(s)
- Xing Wei
- Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China
| | - Hui Li
- Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China
| | - Tian Zhu
- Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China
| | - Fengxia Yao
- Medical Research Center, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China
| | - Ruifang Sui
- Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China.
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Masnada S, Previtali R, Erba P, Beretta E, Camporesi A, Chiapparini L, Doneda C, Iascone M, Sartorio MUA, Spaccini L, Veggiotti P, Osio M, Tonduti D, Moroni I. FDXR-associated disease: a challenging differential diagnosis with inflammatory peripheral neuropathy. Neurol Sci 2023; 44:3037-3043. [PMID: 37046037 PMCID: PMC10096094 DOI: 10.1007/s10072-023-06790-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 03/29/2023] [Indexed: 04/14/2023]
Abstract
BACKGROUND AND AIMS Mutations in FDXR gene, involved in mitochondrial pathway, cause a rare recessive neurological disorder with variable severity of phenotypes. The most common presentation includes optic and/or auditory neuropathy, variably associated to developmental delay or regression, global hypotonia, pyramidal, cerebellar signs, and seizures. The review of clinical findings in previously described cases from literature reveals also a significant incidence of sensorimotor peripheral polyneuropathy (22.72%) and ataxia (43.18%). To date, 44 patients with FDXR mutations have been reported. We describe here on two new patients, siblings, who presented with a quite different phenotype compared to previously described patients. METHODS Clinical, neurophysiological, and genetic features of two siblings and a systematic literature review focused on the clinical spectrum of the disease are described. RESULTS Both patients presented with an acute-sub-acute onset of peripheral neuropathy and only in later stages of the disease developed the typical features of FDXR-associated disease. INTERPRETATION The peculiar clinical presentation at onset and the evolution of the disease in our patients and in some cases revised from the literature shed lights on a new possible phenotype of FDXR-associated disease: a peripheral neuropathy which can mimic an acute inflammatory disease.
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Affiliation(s)
- Silvia Masnada
- Pediatric Neurology Unit, Buzzi Children's Hospital, Milan, Italy.
| | - Roberto Previtali
- Pediatric Neurology Unit, Buzzi Children's Hospital, Milan, Italy
- University of Milan, Milan, Italy
| | - Paola Erba
- Department of Pediatrics, Buzzi Children's Hospital, Milan, Italy
| | - Elena Beretta
- Acquired Brain Injury Unit, Scientific Institute IRCCS Eugenio Medea, Lecco, Italy
| | - Anna Camporesi
- Division of Anesthesia and Intensive Care, Buzzi Children's Hospital, Milan, Italy
| | - Luisa Chiapparini
- Neuroradiology Department, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Chiara Doneda
- Department of Pediatric Radiology and Neuroradiology, Buzzi Children's Hospital, Milan, Italy
| | - Maria Iascone
- Medical Genetics Laboratory, ASST Papa Giovanni XXIII, Bergamo, Italy
| | | | - Luigina Spaccini
- Clinical Genetics Unit, Department of Obstetrics and Gynecology, Buzzi Children's Hospital, University of Milan, Milan, Italy
| | - Pierangelo Veggiotti
- Pediatric Neurology Unit, Buzzi Children's Hospital, Milan, Italy
- University of Milan, Milan, Italy
| | - Maurizio Osio
- Department of Neurology ASST Fatebenefratelli Sacco, Milan, Italy
| | - Davide Tonduti
- Pediatric Neurology Unit, Buzzi Children's Hospital, Milan, Italy
- University of Milan, Milan, Italy
| | - Isabella Moroni
- Department of Pediatric Neurosciences, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
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Yi S, Zheng Y, Yi Z, Wang Y, Jiang Y, Ouyang J, Li S, Xiao X, Sun W, Wang P, Zhang Q. FDXR-Associated Oculopathy: Congenital Amaurosis and Early-Onset Severe Retinal Dystrophy as Common Presenting Features in a Chinese Population. Genes (Basel) 2023; 14:genes14040952. [PMID: 37107710 PMCID: PMC10137360 DOI: 10.3390/genes14040952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 04/10/2023] [Accepted: 04/20/2023] [Indexed: 04/29/2023] Open
Abstract
Variants in FDXR reportedly cause autosomal recessive auditory neuropathy and optic atrophy, expanding to retinal dystrophy. This study aimed to further clarify associated phenotypes. FDXR variants were selected from our in-house whole-exome sequencing dataset of 6397 families with different eye conditions. The clinical data of the identified patients were summarized. Biallelic pathogenic or likely pathogenic FDXR variants were identified in 11 unrelated patients, including 14 missense variants of which 10 were novel. Fundus observation showed complete optic disc pallor, silver wiring or severe attenuation of retinal vessels, and varying degrees of generalized retinal degeneration. Before the detection of FDXR variants, four patients were clinically diagnosed as congenital amaurosis due to the presence of nystagmus a few months after birth, while seven were diagnosed as early-onset severe retinal dystrophy due to the presence of nyctalopia and/or poor vision in early childhood. Biallelic FDXR variants are a frequent cause of congenital or early-onset severe retinal dystrophy, especially for patients with severe optic atrophy and retinal dystrophy in early childhood.
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Affiliation(s)
- Shutong Yi
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Yuxi Zheng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Zhen Yi
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Yingwei Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Yi Jiang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Jiamin Ouyang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Shiqiang Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Xueshan Xiao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Wenmin Sun
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Panfeng Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
| | - Qingjiong Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, 54 Xianlie Road, Guangzhou 510060, China
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Abstract
The adrenal is a small, anatomically unimposing structure that escaped scientific notice until 1564 and whose existence was doubted by many until the 18th century. Adrenal functions were inferred from the adrenal insufficiency syndrome described by Addison and from the obesity and virilization that accompanied many adrenal malignancies, but early physiologists sometimes confused the roles of the cortex and medulla. Medullary epinephrine was the first hormone to be isolated (in 1901), and numerous cortical steroids were isolated between 1930 and 1949. The treatment of arthritis, Addison's disease, and congenital adrenal hyperplasia (CAH) with cortisone in the 1950s revolutionized clinical endocrinology and steroid research. Cases of CAH had been reported in the 19th century, but a defect in 21-hydroxylation in CAH was not identified until 1957. Other forms of CAH, including deficiencies of 3β-hydroxysteroid dehydrogenase, 11β-hydroxylase, and 17α-hydroxylase were defined hormonally in the 1960s. Cytochrome P450 enzymes were described in 1962-1964, and steroid 21-hydroxylation was the first biosynthetic activity associated with a P450. Understanding of the genetic and biochemical bases of these disorders advanced rapidly from 1984 to 2004. The cloning of genes for steroidogenic enzymes and related factors revealed many mutations causing known diseases and facilitated the discovery of new disorders. Genetics and cell biology have replaced steroid chemistry as the key disciplines for understanding and teaching steroidogenesis and its disorders.
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Affiliation(s)
- Walter L Miller
- Department of Pediatrics, Center for Reproductive Sciences, and Institute for Human Genetics, University of California, San Francisco, CA, USA
| | - Perrin C White
- Division of Pediatric Endocrinology, University of Texas Southwestern Medical Center, Dallas, TX, USA
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Jurkute N, D'Esposito F, Robson AG, Pitceathly RDS, Cordeiro F, Raymond FL, Moore AT, Michaelides M, Yu-Wai-Man P, Webster AR, Arno G. SSBP1-Disease Update: Expanding the Genetic and Clinical Spectrum, Reporting Variable Penetrance and Confirming Recessive Inheritance. Invest Ophthalmol Vis Sci 2021; 62:12. [PMID: 34905022 PMCID: PMC8684315 DOI: 10.1167/iovs.62.15.12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 11/19/2021] [Indexed: 11/24/2022] Open
Abstract
Purpose To report novel genotypes and expand the phenotype spectrum of SSBP1-disease and explore potential disease mechanism. Methods Five families with previously unsolved optic atrophy and retinal dystrophy underwent whole genome sequencing as part of the National Institute for Health Research BioResource Rare-Diseases and the UK's 100,000 Genomes Project. In silico analysis and protein modelling was performed on the identified variants. Deep phenotyping including retinal imaging and International Society for Clinical Electrophysiology of Vision standard visual electrophysiology was performed. Results Seven individuals from five unrelated families with bilateral optic atrophy and/or retinal dystrophy with extraocular signs and symptoms in some are described. In total, 6 SSBP1 variants were identified including the previously unreported variants: c.151A>G, p.(Lys51Glu), c.335G>A p.(Gly112Glu), and c.380G>A, p.(Arg127Gln). One individual was found to carry biallelic variants (c.380G>A p.(Arg127Gln); c.394A>G p.(Ile132Val)) associated with likely autosomal recessive SSBP1-disease. In silico analysis predicted all variants to be pathogenic and Three-dimensional protein modelling suggested possible disease mechanisms via decreased single-stranded DNA binding affinity or impaired higher structure formation. Conclusions SSBP1 is essential for mitochondrial DNA replication and maintenance, with defects leading to a spectrum of disease that includes optic atrophy and/or retinal dystrophy, occurring with or without extraocular features. This study provides evidence of intrafamilial variability and confirms the existence of an autosomal recessive inheritance in SSBP1-disease consequent upon a previously unreported genotype.
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Affiliation(s)
- Neringa Jurkute
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Fabiana D'Esposito
- Imperial College Ophthalmic Research Unit, Western Eye Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
- Eye Clinic, Department of Neurosciences, Reproductive Sciences and Dentistry, Federico II University, Naples, Italy
| | - Anthony G. Robson
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Robert D. S. Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Francesca Cordeiro
- Imperial College Ophthalmic Research Unit, Western Eye Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - F. Lucy Raymond
- NIHR BioResource - Rare Diseases, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, United Kingdom
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Anthony T. Moore
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States
| | - Michel Michaelides
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Patrick Yu-Wai-Man
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
- Cambridge Eye Unit, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, United Kingdom
- John van Geest Centre for Brain Repair and MRC Mitochondrial Biology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Andrew R. Webster
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Gavin Arno
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
- North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - for the Genomics England Research Consortium
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
- Imperial College Ophthalmic Research Unit, Western Eye Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
- Eye Clinic, Department of Neurosciences, Reproductive Sciences and Dentistry, Federico II University, Naples, Italy
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, United Kingdom
- NIHR BioResource - Rare Diseases, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, United Kingdom
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States
- Cambridge Eye Unit, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, United Kingdom
- John van Geest Centre for Brain Repair and MRC Mitochondrial Biology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
- North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
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Abstract
Most steroidogenesis disorders are caused by mutations in genes encoding the steroidogenic enzymes, but work in the past 20 years has identified related disorders caused by mutations in the genes encoding the cofactors that transport electrons from NADPH to P450 enzymes. Most P450s are microsomal and require electron donation by P450 oxidoreductase (POR); by contrast, mitochondrial P450s require electron donation via ferredoxin reductase (FdxR) and ferredoxin (Fdx). POR deficiency is the most common and best-described of these new forms of congenital adrenal hyperplasia. Severe POR deficiency is characterized by the Antley-Bixler skeletal malformation syndrome and genital ambiguity in both sexes, and hence is easily recognized, but mild forms may present only with infertility and subtle disorders of steroidogenesis. The common POR polymorphism A503V reduces catalysis by P450c17 (17-hydroxylase/17,20-lyase) and the principal drugmetabolizing P450 enzymes. The 17,20-lyase activity of P450c17 requires the allosteric action of cytochrome b5, which promotes interaction of P450c17 with POR, with consequent electron transfer. Rare b5 mutations are one of several causes of 17,20-lyase deficiency. In addition to their roles with steroidogenic mitochondrial P450s, Fdx and FdxR participate in the synthesis of iron-sulfur clusters used by many enzymes. Disruptions in the assembly of Fe-S clusters is associated with Friedreich ataxia and Parkinson disease. Recent work has identified mutations in FdxR in patients with neuropathic hearing loss and visual impairment, somewhat resembling the global neurologic disorders seen with mitochondrial diseases. Impaired steroidogenesis is to be expected in such individuals, but this has not yet been studied.
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Affiliation(s)
- Walter L. Miller
- Department of Pediatrics, Center for Reproductive Sciences and Institute for Human Genetics, University of California, San Francisco, CA, USA,Address for correspondence: Walter L. Miller Department of Pediatrics, University of California, San Francisco, San Francisco CA 94143, USA
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