Molecular mechanism of the recovery in infantile reversible cytochrome c oxidase (COX) deficiency myopathy

Lead Research Organisation: Newcastle University
Department Name: Institute of Neuroscience

Abstract

Childhood-onset mitochondrial diseases are usually severe, progressive conditions with fatal outcome. However, ?benign? (better, ?reversible?) cytochrome c oxidase deficiency myopathy is an exception because it shows spontaneous complete recovery if infants survive a critical postnatal period of severe weakness and respiratory failure. Although potentially benign, this myopathy is life-threatening in the first months of life and patients require vigorous life-sustaining measures. We have recently found that reversible COX deficiency myopathy is caused by a homoplasmic mt-tRNAGlu mutation m.14674T C. Neither the exact mechanism nor the molecular basis of the recovery is currently understood. Interestingly, some homoplasmic mutation carriers (siblings of patients) do not develop any signs of myopathy, strongly suggesting the existence of protective disease modifiers. Understanding the spontaneous improvement in this mitochondrial condition may reveal a more general insight in the disease pathomechanism, and similar compensatory factors may offer clues towards molecular therapies of at least some mitochondrial diseases. The long-term goal of this approach would be to upregulate or boost compensatory factors in patients with mitochondrial disease and exploit them for therapy.

Technical Summary

We have recently identified the molecular genetic cause of a puzzling clinical syndrome, initially termed ?benign infantile mitochondrial myopathy due to reversible cytochrome c oxidase (COX) deficiency?. While childhood-onset mitochondrial encephalomyopathies are usually severe, relentlessly progressive conditions with fatal outcome, this syndrome stands out by showing complete (or almost complete) spontaneous recovery. We have detected the homoplasmic m.14674T C mutation in the mitochondrial mt-tRNAGlu gene in 17 affected individuals from 12 independent families of different ethnic origins. The m.14674T C mutation affects the discriminator base of mt-tRNAGlu, the last base at the 3‘-end of the molecule, where the amino acid via the terminal CCA is attached, therefore thought to impair mitochondrial translation, as reflected by the COX-negative fibres and the multiple respiratory chain defects in skeletal muscle. The identification of a homoplasmic mt-tRNA mutation in reversible COX deficiency myopathy raised a number of important issues.
We will investigate, i) why patients with homoplasmic m.14674T C show an isolated muscle involvement, ii) why symptoms start uniformly in the first days or weeks of life, and iii) what is behind the molecular basis of the age-dependent, spontaneous recovery. The spontaneous recovery of the patients suggests the existence of so far unknown cellular compensatory mechanisms. We will study mt-tRNA processing and function in human primary cells and muscle of patients with reversible COX deficiency myopathy, and based on the results we will extend the investigations on different types of mitochondrial disease.
The identification of the pathomechanism of reversible COX deficiency myopathy may have implications in other mitochondrial conditions. The long-term goal of this approach would be to upregulate or boost compensatory factors in patients with different types of mitochondrial disease with the aim to open new avenues for therapy.

Publications

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100,000 Genomes Project Pilot Investigators (2021) 100,000 Genomes Pilot on Rare-Disease Diagnosis in Health Care - Preliminary Report. in The New England journal of medicine

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Balreira A (2014) ANO10 mutations cause ataxia and coenzyme Q10 deficiency. in Journal of neurology

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Bansagi B (2016) Phenotypic convergence of Menkes and Wilson disease. in Neurology. Genetics

 
Description as Chair of the mitochondrial group within the ERN-NMD I participate in endorsing and making guidelines for mitochondrial diseases
Geographic Reach Europe 
Policy Influence Type Influenced training of practitioners or researchers
Impact As the Chair of the mitochondrial group within the EURO-NMD reference network I participate in making diagnosis and management of patients with mitochondrial diseases harmonised in Europe
URL https://ern-euro-nmd.eu/
 
Description FP7 ERC Starter Grants
Amount £1,400,000 (GBP)
Funding ID 309548 
Organisation European Research Council (ERC) 
Sector Public
Country Belgium
Start 03/2013 
End 02/2018
 
Description Horizon 2020
Amount € 15,000,000 (EUR)
Organisation European Union 
Sector Public
Country European Union (EU)
Start 01/2018 
End 12/2023
 
Description Investigate new treatment options in zebrafish models of mtDNA depletion syndromes
Amount £62,432 (GBP)
Organisation The Lily Foundation 
Sector Charity/Non Profit
Country United Kingdom
Start 07/2019 
End 07/2021
 
Description MRC Confidence in Concept Fund (co-investigator with Professor Hanns Lochmüller)
Amount £37,852 (GBP)
Funding ID no number yet 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 03/2016 
End 09/2016
 
Description MRC Reserach Grant
Amount £686,866 (GBP)
Funding ID MR/N025431/1 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 09/2016 
End 09/2019
 
Description Wellcome Trust Investigator Award
Amount £1,150,000 (GBP)
Funding ID 109915/Z/15/Z 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2016 
End 03/2021
 
Description Wellcome Trust Pathfinder Award 201064/Z/16/Z co-Investigator with Professor Lochmuller
Amount £170,000 (GBP)
Funding ID 201064/Z/16/Z 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2016 
End 09/2017
 
Title BN-PAGE 
Description functional analysis of human patient cell lines 
Type Of Material Cell line 
Provided To Others? No  
Impact we revealed the pathomechanism of mitochondrial disease in 20 patients 
 
Title Seahorse analysis 
Description Measuring the oxidative capacity of patient cell lines. 
Type Of Material Cell line 
Year Produced 2013 
Provided To Others? Yes  
Impact We used this method in several projects and publications. 
 
Title TRMU cells 
Description we have obtained cells (fibrobalsts and myoblasts) from a patient and established a special technique to study 2-thiolation of mt-tRNAs 
Type Of Material Cell line 
Provided To Others? No  
Impact We are currently investigating the possible role of 2-thiolation as a possible disease mechanism in reversible COX deficiency as part of the project 
 
Title induced neuronal progenitor cells 
Description We can successfully convert human finroblasts into induced neuronal progenitor cells. 
Type Of Material Model of mechanisms or symptoms - human 
Provided To Others? No  
Impact We have already converted 4 patient and 2 contol cell lines into induced neuronal progenitor cells. Currently the analysis of mitochondrial function is in progress in these cells. 
 
Title studying the neuromuscular junction 
Description co-investigator on a multi-user equipment funded by Wellcome to study electrophysiology of the neuromuscular junction 
Type Of Material Physiological assessment or outcome measure 
Year Produced 2018 
Provided To Others? Yes  
Impact no impact yet, equipment is currently being set up 
 
Title zebrafish 
Description I used zebrafish to model human disease. 
Type Of Material Model of mechanisms or symptoms - mammalian in vivo 
Provided To Others? No  
Impact Published a paper (Boczonadi et al. 2014) 
 
Title Metabolic shift underlies recovery in reversible infantile respiratory chain deficiency. 
Description We deposited large exome and RNAseq datasets for data sharing 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact We deposited large number of WES and RNAseq data which is shared with other researchers worldwide. 
URL https://www.repository.cam.ac.uk/handle/1810/317428
 
Title bioinformatic analysis of RNAseq 
Description performed RNAseq in several human cell and muscle samples and analysed different parameters to gain understanding of the metabolic signature of neurogenetic diseases 
Type Of Material Data analysis technique 
Year Produced 2017 
Provided To Others? No  
Impact papers are currently in progress 
 
Title proteomic analysis of cells/tissues 
Description performed proteomic analysis of paatient cells and skeletal muscle samples 
Type Of Material Data analysis technique 
Year Produced 2017 
Provided To Others? Yes  
Impact papers in progress 
 
Description Consequitur - cohort of patients from Turkey for WES 
Organisation Dokuz Eylül University
Country Turkey 
Sector Academic/University 
PI Contribution We collaborate with Dr. Yavuz Oktay and Dr. Semra Hiz on identiying new disease genes in consanguineous Turkish families with various neurogenetic diseases.
Collaborator Contribution Collected 400 families and DNA samples, perfomred phenotyping
Impact We are currently writing abstracts for conferences from the first results and drafting papers.
Start Year 2016
 
Description Identifying novel disease genes in hereditary motor neuropathies 
Organisation University of Miami
Country United States 
Sector Academic/University 
PI Contribution We have identified mutations in a novel disease gene in a family with autosomal dominant hereditary motor neuropathy.
Collaborator Contribution The collaborators also had one family with another mutation in the same gene.
Impact We have published a paper together in AJHG.
Start Year 2014
 
Description Metablic testing of serum and lymphoblastoid cells of patients with motor neuropathy 
Organisation University of Antwerp
Country Belgium 
Sector Academic/University 
PI Contribution We collected serum and blood samples of patients with hereditary motor neuropathies and Prof. Vincent Timmermann`s group converted them to lymphoblastoid cells and conduct metabolomics studies
Collaborator Contribution Prof. Timmermann`s group convert the blood cells to lymphoblastoid cells.
Impact samples are currently being analysed
Start Year 2016
 
Description Metabolic measurements in mitochondrial carrier protein deficiency 
Organisation University of Cambridge
Country United Kingdom 
Sector Academic/University 
PI Contribution We have patient samples for metabolic measurements to Dr. Christian Frezza`s laboratory.
Collaborator Contribution We will receive the results soon and will have a joint publication.
Impact no output yet
Start Year 2013
 
Description Next Generation Sequencing 
Organisation Broad Institute
Country United States 
Sector Charity/Non Profit 
PI Contribution Prof. Daniel McArthur`s group in the Broad Institute agreed to perform WES in >300 Turkish families with neurogenetic disease.
Collaborator Contribution Performed WES for free.
Impact currently writing up conference abstracts and papers.
Start Year 2016
 
Description Search for modifyers in reversible COX deficiency 
Organisation Columbia University Medical Center
Department Neurological Institute of New York
Country United States 
Sector Academic/University 
PI Contribution I contribute a large family and performed exome sequencing
Collaborator Contribution contributing further families
Impact currently being worked up
Start Year 2011
 
Description Studying 2-thiolation of mt-tRNA Glu, Lys, Gln 
Organisation McGill University
Department Department of Molecular Neurogenetics
Country Canada 
Sector Academic/University 
PI Contribution I have started to collaborate on the function of TRMU
Collaborator Contribution common publication
Impact There is a Hom Mol Genet paper (Sasarman et al. 2011) already out of this collaboration.
Start Year 2011
 
Description Studying a novel mitochondrial carriers in a patient mitochondrial disease 
Organisation Medical Research Council (MRC)
Department MRC Mitochondrial Biology Unit
Country United Kingdom 
Sector Academic/University 
PI Contribution We identified a patient with mutations in a novel mitochondrial carrier protein.
Collaborator Contribution Dr. Edmund Kunji`s laboratory performed functional analysis of the carrier to prove that the mutation is pathogenic.
Impact We are currently drafting a manuscript.
Start Year 2014
 
Description Studying the function of the exosome in human disease. 
Organisation Hebrew University of Jerusalem
Department Hebrew University Hadassah Medical School
Country Israel 
Sector Academic/University 
PI Contribution We have identified a novel disease gene and performed functional studies.
Collaborator Contribution The partner had another family with mutations in the same gene.
Impact We published a nice paper together (Boczonadi et al. 2014)
Start Year 2014
 
Description mitochondrial fusion/fission 
Organisation Pontifical Catholic University of Chile
Country Chile 
Sector Academic/University 
PI Contribution I have sent cell lines to Dr. Veronica Eisner for studiying mitochondrial fusion/fission.
Collaborator Contribution studying mitochondrial fission in cells with a special technique
Impact A novel mechanism causing imbalance of mitochondrial fusion and fission in human myopathies. Bartsakoulia M, Pyle A, Troncosco D, Vial J, Paz-Fiblas MV, Duff J, Griffin H, Boczonadi V, Lochmüller H, Kleinle S, Chinnery PF, Grünert S, Kirschner J, Eisner V, Horvath R. Hum Mol Genet. 2018 Jan 19. doi: 10.1093/hmg/ddy033. [Epub ahead of print] PMID: 29361167
Start Year 2015
 
Description mitochondrial tRNA synthetase related diseases 
Organisation University of Manchester
Country United Kingdom 
Sector Academic/University 
PI Contribution I started a collaboration with Prof. William Newman on mt tRNA synthetase diseases. I sent him DNA samples of patients with potential Perrault syndrome.
Collaborator Contribution Dr. Newmn is sequencing with a NGS panel novel genes which could cause Perrault syndrorme.
Impact no output yet
Start Year 2015
 
Description search for biomarkers in CMT 
Organisation University of Antwerp
Country Belgium 
Sector Academic/University 
PI Contribution We have performed targeted proteomics on serum of patients with CMT. We extended the analysis on mouse models of CMT.
Collaborator Contribution We have received serum from mouse models of CMT from Prof. Vincent Timmermann`s team. We search for biomarkers in CMT in this collaboration.
Impact submitted an abstract to the UK MRC Translational Research Conference (22-23 April, UCL)
Start Year 2019
 
Title A Study of Bezafibrate in Mitochondrial Myopathy" (NUTH NHS Trust, 2015) 
Description We are testing the feasibility of bezafibrate supplementation in MELAS. Trial has been finished. We published the paper very recently in EMBO Mol Med 
Type Therapeutic Intervention - Drug
Current Stage Of Development Early clinical assessment
Year Development Stage Completed 2019
Development Status Under active development/distribution
Impact trial has not shown clinical benefit 
 
Title Long-term Deferiprone Treatment in Patients with Pantothenate Kinase-Associated Neurodegeneration (TIRCON-EXT) (ApoPharma, 2016) 
Description Trial will start in a week. 
Type Therapeutic Intervention - Drug
Current Stage Of Development Early clinical assessment
Year Development Stage Completed 2016
Development Status Under active development/distribution
Impact trial is ongoing 
 
Title The effect of triheptanoic acid in GLUT1 deficiency (Ultragenyx, PI for UK, 2015) 
Description I am the PI of the onging clinical trial The effect of triheptanoic acid in GLUT1 deficiency (Ultragenyx, started in 2015). 
Type Therapeutic Intervention - Drug
Current Stage Of Development Early clinical assessment
Year Development Stage Completed 2016
Development Status Under active development/distribution
Impact This trial is currently ongoing inseveral international centres. 
 
Description Ataxia UK Conference 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Participants in your research and patient groups
Results and Impact About 60 patients and their families attended this meeting.

Patients appreciated my answers on their questions.
Year(s) Of Engagement Activity 2014
 
Description Euromit Meeting, Tampere, Patient Session 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact I gave presentations for the patients.

Patients learned about their condition and about potential treatments, diagnostics methods.
Year(s) Of Engagement Activity 2014
 
Description Patient Session at UMDF meeting 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Type Of Presentation Workshop Facilitator
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact I was participating in the patient session and answered the questions of patients at the United Mitochondriaql Disease Foundation Meeting (Newport Beach, USA)

I hope tha patients profited from my answers
Year(s) Of Engagement Activity 2013
 
Description SSIEM 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact 1500 congress participiants were listening my presentation on Coenzyem Q10 deficiencies

referral of patients with CoQ10 defect
Year(s) Of Engagement Activity 2011
 
Description Talk at Newcastle High School for Girls about career choices 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact I gave a presentation about my career as a clinical academic from graduation to my current post.
Year(s) Of Engagement Activity 2017
 
Description creating video about patient journey for European Joint Program 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact We actively participated in making a video about a patient journey of a Turkish patient who we dignosed within our research for the European Joint Program activities.
Year(s) Of Engagement Activity 2019
URL https://twitter.com/GA4GH/status/1186993739991900165?s=17