What disease mechanisms contribute to multisystem tissue involvement in dominant optic atrophy due to OPA1 mutations?
Lead Research Organisation:
Newcastle University
Department Name: Institute of Neuroscience
Abstract
Autosomal dominant optic atrophy (DOA) affects the optic nerve, causing insidious visual loss from early childhood. It is the most common inherited optic nerve disorder and the majority of patients carry mutations in OPA1, a nuclear gene critical for normal mitochondrial function. Mitochondria are essential components of all human cells, containing multiple copies of their own DNA (MtDNA), and forming long branching networks which fuel the cell‘s energy requirements.
About 20% of patients with OPA1 mutations will develop a more severe form of the disease (DOA+), associated with a worse visual prognosis and additional neurological complications. The risk of developing DOA+ is three times higher with missense mutations located within the GTPase gene region. Using a range of human tissue samples, I will investigate whether this specific mutational subgroup results in greater fragmentation of the mitochondrial network and more marked mtDNA damage, thus contributing to accelerated cell death. I will also explore the possibility of rescuing the fragmentation defect by manipulating the level of expression of OPA1 and other mitochondrial proteins involved in network fusion and fission. Visual loss in DOA is progressive and the neurological features develop in later life, providing a clear window of opportunity for therapeutic intervention.
About 20% of patients with OPA1 mutations will develop a more severe form of the disease (DOA+), associated with a worse visual prognosis and additional neurological complications. The risk of developing DOA+ is three times higher with missense mutations located within the GTPase gene region. Using a range of human tissue samples, I will investigate whether this specific mutational subgroup results in greater fragmentation of the mitochondrial network and more marked mtDNA damage, thus contributing to accelerated cell death. I will also explore the possibility of rescuing the fragmentation defect by manipulating the level of expression of OPA1 and other mitochondrial proteins involved in network fusion and fission. Visual loss in DOA is progressive and the neurological features develop in later life, providing a clear window of opportunity for therapeutic intervention.
Technical Summary
Autosomal dominant optic atrophy (DOA) is the most common inherited optic nerve disorder and the majority of patients harbour pathogenic OPA1 mutations. Although DOA is characterised by the preferential loss of retinal ganglion cells (RGC), about 20% of OPA1 carriers will develop a more severe form of the disease (DOA+), associated with a worse visual prognosis and additional debilitating neurological complications. The risk of developing DOA+ is three times higher with missense OPA1 mutations affecting the catatytic GTPase domain. I will explore the pathogenenetic mechanisms underlying this key observation by comparing tissue samples; skeletal muscle biopsies, fibroblasts, and myoblasts, collected from DOA+ patients with missense GTPase mutations (n=10), and pure DOA patients carrying frameshift deletions (n=5) and splice site mutations (n=5).
(i) Do missense OPA1 GTPase mutations result in increased mitochondrial network fragmentation?
OPA1 is a mitochondrial inner membrane protein with important pro-fusional properties. In conjunction with the mitochondrial outer membrane proteins MFN1 and MFN2, OPA1 counterbalances the influence of hFIS1 and DRP1, two pro-fission proteins found in the mitochondrial outer membrane and cytosol, respectively. Our preliminary data suggest that missense GTPase mutations lead to greater mitochondrial fragmentation compared with other OPA1 mutational subgroups. I will confirm these initial findings, investigating at the same time the pathological consequences of the observed fragmentation defect on cellular function and viability.
(ii) Do missense OPA1 GTPase mutations lead to greater mitochondrial DNA (mtDNA) instability?
Our pilot data, based on next-generation ultra-deep-sequencing, suggest that OPA1 GTPase mutations result in greater mtDNA instability. I will therefore compare the pattern and mutational burden of somatic mtDNA abnormalities in a larger group of DOA+ and pure DOA patients, relating them to two classical disorders of mtDNA maintenance (POLG1 and PEO1), and to normal ageing. I will use the generated biological data to model possible OPA1 disease mechanisms leading to accelerated mtDNA mutagenesis and the development of DOA+ features.
(iii) Are these deleterious consequences secondary to a dominant-negative effect?
HEK293 cells will be transfected with mutant cDNA extracted from OPA1 fibroblasts harbouring missense GTPase mutations. If these mutations exert a dominant-negative effect, mitochondrial fragmentation will be observed despite normal levels of the endogenous, wild-type OPA1 protein. Finally, I will explore the possibility of rescuing the fragmentation phenotype by manipulating the expression of the major pro-fusion and pro-fission mitochondrial proteins. These experiments could pave the way for gene therapy aimed initially at halting RGC loss and progressive visual decline.
(i) Do missense OPA1 GTPase mutations result in increased mitochondrial network fragmentation?
OPA1 is a mitochondrial inner membrane protein with important pro-fusional properties. In conjunction with the mitochondrial outer membrane proteins MFN1 and MFN2, OPA1 counterbalances the influence of hFIS1 and DRP1, two pro-fission proteins found in the mitochondrial outer membrane and cytosol, respectively. Our preliminary data suggest that missense GTPase mutations lead to greater mitochondrial fragmentation compared with other OPA1 mutational subgroups. I will confirm these initial findings, investigating at the same time the pathological consequences of the observed fragmentation defect on cellular function and viability.
(ii) Do missense OPA1 GTPase mutations lead to greater mitochondrial DNA (mtDNA) instability?
Our pilot data, based on next-generation ultra-deep-sequencing, suggest that OPA1 GTPase mutations result in greater mtDNA instability. I will therefore compare the pattern and mutational burden of somatic mtDNA abnormalities in a larger group of DOA+ and pure DOA patients, relating them to two classical disorders of mtDNA maintenance (POLG1 and PEO1), and to normal ageing. I will use the generated biological data to model possible OPA1 disease mechanisms leading to accelerated mtDNA mutagenesis and the development of DOA+ features.
(iii) Are these deleterious consequences secondary to a dominant-negative effect?
HEK293 cells will be transfected with mutant cDNA extracted from OPA1 fibroblasts harbouring missense GTPase mutations. If these mutations exert a dominant-negative effect, mitochondrial fragmentation will be observed despite normal levels of the endogenous, wild-type OPA1 protein. Finally, I will explore the possibility of rescuing the fragmentation phenotype by manipulating the expression of the major pro-fusion and pro-fission mitochondrial proteins. These experiments could pave the way for gene therapy aimed initially at halting RGC loss and progressive visual decline.
Organisations
- Newcastle University, United Kingdom (Lead Research Organisation)
- Hebrew University of Jerusalem (Collaboration)
- Cardiff University, United Kingdom (Collaboration)
- National Institute of Health and Medical Research (INSERM) (Collaboration)
- Angers University Hospital (CHU Angers) (Collaboration)
- University of Bologna, Italy (Collaboration)
- Moorfields Eye Hospital NHS Foundation Trust (Collaboration)
- Eberhard Karls University Tuebingen, Germany (Collaboration)
- University of Cambridge, United Kingdom (Fellow)
People |
ORCID iD |
Patrick Yu Wai Man (Principal Investigator / Fellow) |
Publications

Angebault C
(2015)
Recessive Mutations in RTN4IP1 Cause Isolated and Syndromic Optic Neuropathies.
in American journal of human genetics

Astuti D
(2017)
Monogenic diabetes syndromes: Locus-specific databases for Alström, Wolfram, and Thiamine-responsive megaloblastic anemia.
in Human mutation

Bailie M
(2013)
Visual and psychological morbidity among patients with autosomal dominant optic atrophy.
in Acta ophthalmologica

Bannwarth S
(2014)
A mitochondrial origin for frontotemporal dementia and amyotrophic lateral sclerosis through CHCHD10 involvement.
in Brain : a journal of neurology

Bannwarth S
(2014)
Reply: Mutations in the CHCHD10 gene are a common cause of familial amyotrophic lateral sclerosis.
in Brain : a journal of neurology

Bannwarth S
(2014)
Reply: Two novel mutations in conserved codons indicate that CHCHD10 is a gene associated with motor neuron disease.
in Brain : a journal of neurology

Bannwarth S
(2014)
Reply: Are CHCHD10 mutations indeed associated with familial amyotrophic lateral sclerosis?
in Brain : a journal of neurology

Bannwarth S
(2015)
Reply: CHCHD10 mutations in Italian patients with sporadic amyotrophic lateral sclerosis.
in Brain : a journal of neurology

Bannwarth S
(2015)
Reply: Is CHCHD10 Pro34Ser pathogenic for frontotemporal dementia and amyotrophic lateral sclerosis?
in Brain : a journal of neurology
Description | Investigating disease mechanisms and therapeutic strategies in inherited optic neuropathies |
Amount | £85,000 (GBP) |
Organisation | University of Cambridge |
Department | Isaac Newton Trust |
Sector | Academic/University |
Country | United Kingdom |
Start | 07/2019 |
End | 06/2021 |
Description | MRC Centenary Early Career Award |
Amount | £15,000 (GBP) |
Organisation | Medical Research Council (MRC) |
Sector | Public |
Country | United Kingdom |
Start | 10/2012 |
End | 09/2013 |
Description | Moorfields Special Trustees Research Award |
Amount | £130,000 (GBP) |
Organisation | Moorfields Eye Charity |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 10/2016 |
End | 09/2019 |
Description | NIHR Rare Diseases Translational Research Collaboration |
Amount | £310,000 (GBP) |
Organisation | National Institute for Health Research |
Department | NIHR Biomedical Research Centre |
Sector | Public |
Country | United Kingdom |
Start | 09/2016 |
End | 08/2018 |
Description | NIHR Rare Diseases Translational Research Collaboration |
Amount | £250,000 (GBP) |
Organisation | National Institute for Health Research |
Sector | Public |
Country | United Kingdom |
Start | 08/2014 |
End | 08/2016 |
Description | Small Grants Award |
Amount | £15,000 (GBP) |
Funding ID | 24TP171 |
Organisation | Fight for Sight |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 01/2018 |
End | 12/2018 |
Description | Angers OPA1 Collaboration |
Organisation | Angers University Hospital (CHU Angers) |
Department | Department of Biochemistry and Genetics |
Country | France |
Sector | Academic/University |
PI Contribution | Exchange of patient data and tissue samples |
Collaborator Contribution | Exchange of patient data and tissue samples |
Impact | PMID:20974897 PMID:20157015 |
Start Year | 2007 |
Description | Bologna OPA1 Collaboration |
Organisation | University of Bologna |
Department | Department of Neurologial Sciences |
Country | Italy |
Sector | Academic/University |
PI Contribution | We are working closely with Dr Carelli's team in Bologa to understand the development of multisystem disease in patients harbouring OPA1 mutations. |
Collaborator Contribution | Dr Carelli's team have provided us with clinical data for a meta-analysis of the phenotypes seen in patients with OPA1 mutations. |
Impact | PMID: 20974897 PMID: 20157015 |
Start Year | 2007 |
Description | Cardiff OPA1 Mouse Collaboration |
Organisation | Cardiff University |
Department | School of Optometry and Vision Sciences |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | I have analysed these OPA1 mouse tissues as part of my ongoing PhD research project. |
Collaborator Contribution | Our collaborators in Cardiff have provided us with tissues from an OPA1 mouse model of dominant optic atrophy. |
Impact | PMID: 19443720 PMID: 20157015 |
Start Year | 2008 |
Description | Jerusalem Hadassah Collaboration |
Organisation | Hebrew University of Jerusalem |
Department | Hebrew University Hadassah Medical School |
Country | Israel |
Sector | Academic/University |
PI Contribution | Analysis of tissue samples from patients with inherited neurodegenerative diseases. |
Collaborator Contribution | Provision of tissue samples from patients with inherited neurodegenerative diseases. |
Impact | PMID: 26561570 |
Start Year | 2015 |
Description | Montpellier OPA1 Collaboration |
Organisation | National Institute of Health and Medical Research (INSERM) |
Department | Institute of Neuroscience Montpellier |
Country | France |
Sector | Academic/University |
PI Contribution | We are working with Dr Guy Lenaers team in Montpellier to investigate the role of OPA1 in mitochondrial DNA replication. |
Collaborator Contribution | Dr Leaners' team have provided tissue samples and experimental data for our research in Newcastle. |
Impact | PMID: 20974897 PMID: 20157015 |
Start Year | 2008 |
Description | Moorfields BRC Collaboration |
Organisation | Moorfields Eye Hospital NHS Foundation Trust |
Department | NIHR Moorfields Biomedical Research Centre |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Patients with inherited optic neuropathies and a confirmed molecular diagnosis. |
Collaborator Contribution | Access to advanced psychophysical testing for the deep phenotyping of patients with inherited optic neuropathies. |
Impact | Joint application to the NIHR Rare Diseases Translational Research Collaboration. |
Start Year | 2013 |
Description | Tuebingen OPA1 Mouse Collaboration |
Organisation | Eberhard Karls University of Tubingen |
Department | Institute for Ophthalmic Research |
Country | Germany |
Sector | Academic/University |
PI Contribution | I have analysed these OPA1 mouse tissues as part of my ongoing PhD research project. |
Collaborator Contribution | Our collaborators in Tuebingen have provided us with tissues from a second OPA1 mouse model of dominant optic atrophy - different from the Cardiff one. |
Impact | PMID: 19815013 PMID: 19181907 |
Start Year | 2008 |
Description | ENMC workshop on neuromuscular disorders of mitochondrial fusion and fission |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | Organisers: Dr. Patrick Yu-Wai-Man (Newcastle, UK); Dr. Valerio Carelli (Bologna, Italia); Prof. Patrick F. Chinnery (Newcastle, UK) Description: The 197th ENMC workshop entitled "Neuromuscular disorders of mitochondrial fusion and fission - molecular mechanisms and therapeutic strategies" took place from the 26th to the 28thof April 2013 in Naarden, The Netherlands. A multidisciplinary group of 19 participants took part in this workshop, including 18 clinical and basic science researchers from 6 different countries (France, Germany, Italy, Spain, the UK, and the USA), and 1 patient representative from CMT UK. The first half of this workshop reviewed the fundamental and interrelated roles mediated by the MFN2 and OPA1 proteins in normal cellular function. The pathogenetic mechanisms directly implicated in the development of CMT2A and DOA were discussed in the context of both in vitro and in vivo disease models. In the second half of this workshop, the participants collectively described the range of clinical features linked to MFN2 and OPA1 mutations, including novel disease manifestations and the natural history of this heterogeneous group of disorders. The final session focused on how to translate recent scientific advances for the benefit of patients and the best way to design future clinical trials in this challenging area of research. The following key deliverables were achieved: 1.A comprehensive description of the expanding neuromuscular phenotypes associated with pathogenic MFN2 and OPA1 mutations. 2.Collaborative biobank access to patient tissue samples and animal models to further explore fundamental disease mechanisms in CMT-2A and DOA. 3.Pooled clinical registry of well-characterised patient cohorts for the purpose of future clinical studies, including treatment trials. |
Year(s) Of Engagement Activity | 2013 |
URL | http://www.enmc.org/workshops/workshop-reports/neuromuscular-disorders-mitochondrial-fusion-and-fiss... |
Description | UK LHON Patient Network |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Participants in your research and patient groups |
Results and Impact | LHON (Leber hereditary optic neuropathy) is an important cause of irreversible blindness among young adults and treatment options are currently limited. Over the past two years, I have been working closely with families that have been affected by LHON in the UK through regular small group meetings and e-mail discussions. The engagement activities described earlier have lead to the setting up a UK LHON charity to support patients and their families (http://www.lhonsociety.org/). |
Year(s) Of Engagement Activity | 2014 |
URL | http://www.lhonsociety.org/ |