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Martucci M, Moretton A, Tarrés-Solé A, Ropars V, Lambert L, Vernet P, Solà M, Falkenberg M, Farge G, van den Wildenberg S. The mutation R107Q alters mtSSB ssDNA compaction ability and binding dynamics. Nucleic Acids Res 2024:gkae354. [PMID: 38742632 DOI: 10.1093/nar/gkae354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Revised: 04/02/2024] [Accepted: 04/22/2024] [Indexed: 05/16/2024] Open
Abstract
Mitochondrial single-stranded DNA-binding protein (mtSSB) is essential for mitochondrial DNA (mtDNA) replication. Recently, several mtSSB variants have been associated with autosomal dominant mitochondrial optic atrophy and retinal dystrophy. Here, we have studied at the molecular level the functional consequences of one of the most severe mtSSB variants, R107Q. We first studied the oligomeric state of this variant and observed that the mtSSBR107Q mutant forms stable tetramers in vitro. On the other hand, we showed, using complementary single-molecule approaches, that mtSSBR107Q displays a lower intramolecular ssDNA compaction ability and a higher ssDNA dissociation rate than the WT protein. Real-time competition experiments for ssDNA-binding showed a marked advantage of mtSSBWT over mtSSBR107Q. Combined, these results show that the R107Q mutation significantly impaired the ssDNA-binding and compacting ability of mtSSB, likely by weakening mtSSB ssDNA wrapping efficiency. These features are in line with our molecular modeling of ssDNA on mtSSB showing that the R107Q mutation may destabilize local interactions and results in an electronegative spot that interrupts an ssDNA-interacting-electropositive patch, thus reducing the potential mtSSB-ssDNA interaction sites.
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Affiliation(s)
- Martial Martucci
- Université Clermont Auvergne, CNRS, Laboratoire de Physique de Clermont, F-63000 Clermont-Ferrand, France
| | - Amandine Moretton
- Université Clermont Auvergne, CNRS, Laboratoire de Physique de Clermont, F-63000 Clermont-Ferrand, France
| | - Aleix Tarrés-Solé
- Structural MitoLab, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona Science Park, Barcelona 08028, Spain
| | - Virginie Ropars
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Louise Lambert
- Université Clermont Auvergne, CNRS, Laboratoire de Physique de Clermont, F-63000 Clermont-Ferrand, France
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Patrick Vernet
- Université Clermont Auvergne, CNRS, Laboratoire de Physique de Clermont, F-63000 Clermont-Ferrand, France
| | - Maria Solà
- Structural MitoLab, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona Science Park, Barcelona 08028, Spain
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Geraldine Farge
- Université Clermont Auvergne, CNRS, Laboratoire de Physique de Clermont, F-63000 Clermont-Ferrand, France
| | - Siet van den Wildenberg
- Université Clermont Auvergne, CNRS, Laboratoire de Physique de Clermont, F-63000 Clermont-Ferrand, France
- Université Clermont Auvergne, CNRS, IRD, Université Jean Monnet Saint Etienne, LMV, F-63000 Clermont-Ferrand, France
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2
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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] [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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Chang YH, Kang EYC, Liu L, Jenny LA, Khang R, Seo GH, Lee H, Chen KJ, Wu WC, Hsiao MC, Wang NK. Maternal mosaicism in SSBP1 causing optic atrophy with retinal degeneration: implications for genetic counseling. Orphanet J Rare Dis 2023; 18:131. [PMID: 37259171 PMCID: PMC10233871 DOI: 10.1186/s13023-023-02748-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 05/18/2023] [Indexed: 06/02/2023] Open
Abstract
BACKGROUND Optic atrophy-13 with retinal and foveal abnormalities (OPA13) (MIM #165510) is a mitochondrial disease in which apparent bilateral optic atrophy is present and sometimes followed by retinal pigmentary changes or photoreceptors degeneration. OPA13 is caused by heterozygous mutation in the SSBP1 gene, associated with variable mitochondrial dysfunctions. RESULTS We have previously reported a 16-year-old Taiwanese male diagnosed with OPA13 and SSBP1 variant c.320G>A (p.Arg107Gln) was identified by whole exon sequence (WES). This variant was assumed to be de novo since his parents were clinically unaffected. However, WES and Sanger sequencing further revealed the proband's unaffected mother carrying the same SSBP1 variant with a 13% variant allele frequency (VAF) in her peripheral blood. That finding strongly indicates the maternal gonosomal mosaicism contributing to OPA13, which has not been reported before. CONCLUSIONS In summary, we described the first case of OPA13 caused by maternal gonosomal mosaicism in SSBP1. Parental mosaicism could be a serious issue in OPA13 diagnosis, and appropriate genetic counseling should be considered.
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Affiliation(s)
- Yin-Hsi Chang
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan, Taiwan
- College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Eugene Yu-Chuan Kang
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan, Taiwan
- College of Medicine, Chang Gung University, Taoyuan, Taiwan
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Laura Liu
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan, Taiwan
- College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Laura A Jenny
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University Irving Medical Center, Columbia University, 635 West 165th Street, New York, NY, 10032, USA
| | - Rin Khang
- Division of Medical Genetics, 3Billion Inc., Seoul, South Korea
| | - Go Hun Seo
- Division of Medical Genetics, 3Billion Inc., Seoul, South Korea
| | - Hane Lee
- Division of Medical Genetics, 3Billion Inc., Seoul, South Korea
| | - Kuan-Jen Chen
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan, Taiwan
- College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Wei-Chi Wu
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan, Taiwan
- College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Meng-Chang Hsiao
- Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, USA
| | - Nan-Kai Wang
- Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University Irving Medical Center, Columbia University, 635 West 165th Street, New York, NY, 10032, USA.
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Chang YH, Kang EYC, Liu L, Jenny LA, Khang R, Seo GH, Lee H, Chen KJ, Wu WC, Hsiao MC, Wang NK. Maternal Mosaicism in SSBP1 Causing Optic Atrophy with Retinal Degeneration: Implications for Genetic Counseling. RESEARCH SQUARE 2023:rs.3.rs-2554402. [PMID: 36993412 PMCID: PMC10055506 DOI: 10.21203/rs.3.rs-2554402/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
Background: Optic atrophy-13 with retinal and foveal abnormalities (OPA13) (MIM #165510) is a mitochondrial disease in which apparent bilateral optic atrophy is present and sometimes followed by retinal pigmentary changes or photoreceptors degeneration. OPA13 is caused by heterozygous mutation in the SSBP1 gene, associated with variable mitochondrial dysfunctions. Results: We have previously reported a 16-year-old Taiwanese male diagnosed with OPA13 and SSBP1 variant c.320G>A (p.Arg107Gln) was identified by whole exon sequence (WES). This variant was assumed to be de novo since his parents were clinically unaffected. However, WES and Sanger sequencing further revealed the proband’s unaffected mother carrying the same SSBP1 variant with a 13% variant allele frequency (VAF) in her peripheral blood. That finding strongly indicates the maternal gonosomal mosaicism contributing to OPA13, which has not been reported before. Conclusions: In summary, we described the first case of OPA13 caused by maternal gonosomal mosaicism in SSBP1 . Parental mosaicism could be a serious issue in OPA13 diagnosis, and appropriate genetic counseling should be considered.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Meng-Chang Hsiao
- Columbia University Medical Center: Columbia University Irving Medical Center
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Jun JW, Seo Y, Han SH, Han J. The importance of genome sequencing: unraveling SSBP1 variant missed by exome sequencing. Ophthalmic Genet 2022; 44:286-290. [PMID: 35946466 DOI: 10.1080/13816810.2022.2109685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Abstract
BACKGROUND Single-stranded DNA-binding protein 1 (SSBP1) plays an essential role in mitochondrial DNA (mtDNA) replication and maintenance, as well as development of retina. Here, we describe the clinical findings and genetic basis of a family with two members affected with bilateral optic atrophy. MATERIALS AND METHODS Clinical data were retrospectively collected from an electronic medical record system. Genetic results were obtained using exome sequencing (ES) and genome sequencing (GS). RESULTS A 36-year-old man presented with low vision in both eyes since early childhood, with a best-corrected visual acuity of 20/500 in both eyes. He exhibited generalized optic atrophy and diffuse retinal nerve fiber layer thinning without retinal degeneration in both eyes. The family history was consistent with autosomal dominant traits. ES was performed; however, we did not identify any pathogenic variants in the known dominant optic atrophy genes. Subsequently, GS was performed, and it revealed a novel heterozygous c.364A>G p.(Lys122Glu) variant in SSBP1. In silico prediction supported it as deleterious, while segregation analysis detected it in his affected mother and his unaffected sister. No foveopathy or retinal degeneration was observed in the patient's family members. CONCLUSIONS We report a novel pathogenic heterozygous SSBP1 variant in a family with autosomal dominant optic atrophy and incomplete penetrance. Furthermore, we demonstrated that GS is advantageous over ES even for the discovery of coding variants, providing uniform coverage. Therefore, GS should be emphasized to improve the molecular diagnostic rate of inherited optic neuropathy.
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Affiliation(s)
- Jae Won Jun
- Department of Ophthalmology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea
| | - Yuri Seo
- Department of Ophthalmology, Yongin Severance Hospital, Yonsei University College of Medicine, Yongin, Korea
| | - Sueng-Han Han
- Department of Ophthalmology, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea
| | - Jinu Han
- Department of Ophthalmology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea
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Zeviani M, Carelli V. Mitochondrial Retinopathies. Int J Mol Sci 2021; 23:210. [PMID: 35008635 PMCID: PMC8745158 DOI: 10.3390/ijms23010210] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/14/2021] [Accepted: 12/18/2021] [Indexed: 12/13/2022] Open
Abstract
The retina is an exquisite target for defects of oxidative phosphorylation (OXPHOS) associated with mitochondrial impairment. Retinal involvement occurs in two ways, retinal dystrophy (retinitis pigmentosa) and subacute or chronic optic atrophy, which are the most common clinical entities. Both can present as isolated or virtually exclusive conditions, or as part of more complex, frequently multisystem syndromes. In most cases, mutations of mtDNA have been found in association with mitochondrial retinopathy. The main genetic abnormalities of mtDNA include mutations associated with neurogenic muscle weakness, ataxia and retinitis pigmentosa (NARP) sometimes with earlier onset and increased severity (maternally inherited Leigh syndrome, MILS), single large-scale deletions determining Kearns-Sayre syndrome (KSS, of which retinal dystrophy is a cardinal symptom), and mutations, particularly in mtDNA-encoded ND genes, associated with Leber hereditary optic neuropathy (LHON). However, mutations in nuclear genes can also cause mitochondrial retinopathy, including autosomal recessive phenocopies of LHON, and slowly progressive optic atrophy caused by dominant or, more rarely, recessive, mutations in the fusion/mitochondrial shaping protein OPA1, encoded by a nuclear gene on chromosome 3q29.
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Affiliation(s)
- Massimo Zeviani
- Department of Neurosciences, The Clinical School, University of Padova, 35128 Padova, Italy
- Veneto Institute of Molecular Medicine, Via Orus 2, 35128 Padova, Italy
| | - Valerio Carelli
- Department of Biomedical and Neuromotor Sciences, University of Bologna, 40139 Bologna, Italy
- Programma di Neurogenetica, IRCCS Istituto delle Scienze Neurologiche di Bologna, Via Altura 6, 40139 Bologna, Italy
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