Disease mechanisms and therapy for inherited disorders of the neuromuscular synapse.

Lead Research Organisation: University of Oxford
Department Name: Clinical Neurosciences

Abstract

This programme of work will study a group of inherited diseases called congenital myasthenic syndromes (CMS) in which the transfer of the signal for muscle contraction from nerve to muscle is disrupted. These are rare disorders, present in around 1 in 100,000 of the UK population, that may be life-threatening and can cause severe disability in children and adults, but we are frequently able to work out what is going wrong and as a result devise appropriate therapy. In the last two years we have found mutations in four new genes that cause CMS and have been at the forefront of showing that treatments usually used for asthma can result in remarkable improvement for our patients. Research success led our laboratory to be the basis for a National Referral Centre for CMS, and through this service our goal is to provide tailored therapy for each of our patients. To move towards this goal this programme of work will address the following questions:

i) Which genes are responsible for additional cases of CMS? We have around 40 cases in which we have not been able to find the genetic cause of the patient's condition. Patients, above all, want a definitive diagnosis. We will use the latest DNA sequencing techniques to search for the genetic defects in these patients, and new patients who are referred to our clinic.

ii) How do the genetic defects in the genes that we recently identified cause disease? If we can work out how the mutations are disrupting the information transfer from nerves to muscle we can often devise appropriate therapy. Therefore if we can find out how the mutations in these four new genes result in disease it should help in their treatment.

iii) Can we find new available treatments? We have found that certain drugs commonly used for asthma can work exceptionally well for some of our patients. We want to find out exactly how these are having their effects and then see if there are other similar but potentially even better drugs available.

iv) Can we experiment to find novel treatments? The site where information is passed from nerve to muscle is called a synapse. We have noted that when one of the proteins we study, DOK7, is produced at high levels in muscles is generates greatly enlarged synapses in their correct location, which we call 'super synapses'. When we generated these 'super synapses' in a disease model for DOK7 CMS is completely cured the disease. We want to perform studies on the super synapses to define exactly why they work so well and also we want to try this novel therapy in other CMS disease models. Moreover, it could potentially be applicable to some other more common diseases that feature defects in the neuromuscular junction synapse such as motor neurone disease or spinal muscular atrophy.

Technical Summary

Congenital myasthenic syndromes (CMS) stem from genetic defects that affect signal transmission at the neuromuscular synapse. They provide a rare example of genetic muscle disorders that are treatable if the underlying molecular mechanisms are understood. At least 19 causative genes have been uncovered with mutations identified in proteins involved in signal transfer, synaptic stability, or glycosylation.
There are four objectives to this proposal:
i) to use next generation sequencing techniques to resolve the genetics behind our residual undefined CMS cases;
ii) to find out the mechanisms through which glycosylation mutations impair neuromuscular transmission;
iii) to study molecular mechanism to explain how treatment with beta2-adrenergic receptor (beta2-ADR) agonists results in dramatic clinical improvement;
iv) when over-expressed in muscle DOK7 generates correctly located but greatly enlarged neuromuscular junctions or 'super synapses'. We will test the potential of these 'super synapses' as a novel gene therapy.
Within the laboratory there is expertise for the analysis of neuromuscular junction proteins. Next generation sequencing techniques will be used to screen for genes with new CMS-causing mutations. Molecular genetic (including CRISPR/Cas9 genome editing), biochemical and fluorescence microscopy techniques will be used to generate and study disease models in fibroblast or muscle cells. Effects of beta2-ADR agonists will be studied in transgenic models, in myotube cultures, and within AChR clusters. Detailed analysis of molecular dynamics within AChR clusters will use super-resolution microscopy in combination with temporal and spatial optogenetic stimulation. Therapy, including adeno-associated virus delivery of DOK7 to generate 'super synapses', will be given to transgenic mouse disease models and analysed in vivo by strength tests and electromyography and ex vivo by electrophysiology, microscopy, and biochemical analysis.

Planned Impact

Impact statement:
The research proposed in this application is predicted to have a direct and immediate impact on patients with congenital myasthenic syndrome and their care. It may have longer term but significant implications for patients with autoimmune myasthenia gravis, and patients with some less common neurological disorders such as some forms of limbic encephalitis.
At an immediate level the results of a genetic diagnosis will be fed back to patients through the Oxford-based National Diagnostic and Advisory Service for Congenital Myasthenic Syndromes.
For patients and their families this provides:
i) A definitive diagnosis
ii) A basis for genetic counselling, prenatal diagnosis, and prognostic advice.
iii) Inappropriate diagnosis and treatments will be avoided. For challenging cases, prior to genetic analysis, the patient will often have had immunosuppression and undergone a thymectomy.
There are at least six different effect drugs that can be used either independently or in combination for the congenital myasthenic syndromes. Knowledge of the disease mechanism for particular mutations provides the basis for appropriate therapy. Correct therapy can have a dramatic beneficial effect both on muscle strength and quality of life. For instance, we first defined DOK7 mutations as a cause of congenital myasthenic syndrome and by treating these patients appropriately we are often able to get patients who were wheel chair-dependent leading near normal lives. A tailored treatment service will continue to provide
iv) Dramatic improvement in quality of life for patients and their families.
For the broader UK economy appropriate therapy for a disabling and sometimes life-threatening disorder will:
i) Reduced clinical burden of these disorders
ii) Reduce or prevent ITU admissions which are frequent for patients with certain subtypes of congenital myasthenic syndrome, but may occur for all forms.
iii) Improved performance and quality of life in employment.
iv) Reduce burden of caring performed by family members and social services
v) Facilitate employment
vi) Reduce the overall costs in benefits that are required for a disabled person
vii) Reduce the requirement for one-to-one support in school or outside
Other NHS benefits:
i) The NHS will benefit from definitive diagnosis
ii) Improved education of clinicians on managing these disorders
iii) Increased understanding of principle of translating basic research into clinical solutions e.g. 'bench to beside'

These benefits will be rapidly transferred from laboratory to patients through the National Service for Congenital Myasthenic Syndromes, where patients are quickly offered consultations once the genetics and disease mechanism of their condition is defined.

Patients are regularly updated on advances from the laboratory through Patient open days, or through the Myasthenia Gravis Association and Muscular Dystrophy Campaign charities.
Named researchers have been part of this programme for many years and are uniquely qualified to educate clinical fellows and research students on these specialised disorders and the techniques used for functional analysis of mutations.

We are exploring novel therapeutic approaches based on the biology of the DOK7 protein. Though at an early research stage, this approach may potentially have applications in a wide variety of neuromuscular disorders that feature defective neuromuscular junction structure during disease progression such as ALS, SMA, or sarcopenia which are intractable and multifactorial diseases.

Publications


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Rodríguez Cruz PM (2016) Clinical features of the myasthenic syndrome arising from mutations in GMPPB. in Journal of neurology, neurosurgery, and psychiatry
Zoltowska Katarzyna M (2015) Collagen Q--a potential target for autoantibodies in myasthenia gravis. in Journal of the neurological sciences
Klein A (2015) Congenital myasthenic syndrome caused by mutations in DPAGT. in Neuromuscular disorders : NMD
Rodríguez Cruz PM (2014) Congenital myasthenic syndromes and the neuromuscular junction. in Current opinion in neurology
Beeson D (2016) Congenital myasthenic syndromes: recent advances. in Current opinion in neurology
 
Description Defined treatment for patient subsets
Geographic Reach Multiple continents/international 
Policy Influence Type Influenced training of practitioners or researchers
Impact Defined that ephedrine or other b2-adrenergic receptor agonists have a dramatic beeneficial effect for patients with DOK7 CMS. Thus this is now standard treatment for this genetic condition. many patients regain ambulation from previous requirement of a wheel chair. We have now defined other patient subsets for which appropriate treatment combinations leads to life-transforming improvement in quality of life. May patients regain ambulation from previously being wheel chair-bound.
 
Description Studentship supported by the UK Myasthenia charity
Amount £85,000 (GBP)
Organisation Myaware 
Sector Charity/Non Profit
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 10/2016 
End 09/2019
 
Description Wellcome Trust Clinical Training fellowship
Amount £256,000 (GBP)
Funding ID 103406/Z/13/Z 
Organisation The Wellcome Trust Ltd 
Department Wellcome Trust Bloomsbury Centre; Wellcome Trust
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 10/2014 
End 09/2017
 
Description Crystal structures 
Organisation University of Oxford
Department Structural Genomics Consortium (SGC)
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Charity/Non Profit 
PI Contribution Collaborating on crystalisation of mutant proteins of mutations found in CMS patients
Collaborator Contribution We supply information on mutants and constructs for the expression of these proteins, our partners peform crystalisation and structural analysis
Impact N/A
Start Year 2015
 
Description MRC neuromuscular centre 
Organisation Medical Research Council (MRC)
Department MRC Centre for Neuromuscular Diseases
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Public 
PI Contribution Supplied patient data, mutation data, functional laboratory studies
Collaborator Contribution Provision of patients and scientific data
Impact Publications identifying a new gene in which mutations can underlie congenital myasthenic syndromes, and characterisation of the syndrome phenotype
Start Year 2010
 
Description WGS500 consortium 
Organisation Wellcome Trust Centre for Human Genetics
Department DNA Sequencing Hub (Oxford)
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution Providing patient DNA and analysis of identified variants for identification rare Mendelian disorders
Collaborator Contribution Identification of appropriate DNA samples Functional analysis of variants to determine if they are pathogenic
Impact Pathogenic mutations in new genes identified Cossins et al. (submitted)
Start Year 2011
 
Description WGS500 consortium 
Organisation Wellcome Trust Centre for Human Genetics
Department Wellcome Trust Case Control Consortium 2 (WTCCC)
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Charity/Non Profit 
PI Contribution Providing patient DNA and analysis of identified variants for identification rare Mendelian disorders
Collaborator Contribution Identification of appropriate DNA samples Functional analysis of variants to determine if they are pathogenic
Impact Pathogenic mutations in new genes identified Cossins et al. (submitted)
Start Year 2011
 
Description Congenital myasthenic syndrome open day 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Patients, carers and/or patient groups
Results and Impact Patient day. Patients are given a series of lectures on scientific research updates, and then in the afternoon there are a series of workshops for particular patient groups where needs that have been identified or areas of special interest are addressed. Typically this might involve treatments, exercise, benefits, future therapy updates.

Patients and researchers are both enthused about the research effort
Year(s) Of Engagement Activity 2006,2008,2010,2013,2014
URL http://www.ouh.nhs.uk/services/referrals/neurosciences/myasthenia.aspx
 
Description Lectures to patient groups 
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 Regularly give talks to small patient groups and parents who have an obvious interest in inherited myasthenic disorders

Useful patient researcher contact.
Year(s) Of Engagement Activity 2006,2007,2008,2009,2013
 
Description Patient information pamphlet 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Patients, carers and/or patient groups
Results and Impact The pamphlet is used by families to inform them about their disorder and to take to their schools to inform them about the disorder that the children have. This enables the schools to understand the childs condition and to put in place appropriate safeguards and facilities to ensure the patient is safe and to enable adaptations to allow a full potential for learning to be in place.

Should help school, social workers to understand patient disabilities and their special needs when at school.
Year(s) Of Engagement Activity 2010,2011,2012,2013,2017
URL http://www.ouh.nhs.uk/services/referrals/neurosciences/myasthenia.aspx
 
Description Talks to patient group 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach Regional
Primary Audience Participants in your research and patient groups
Results and Impact Updating patient support groups on the research activities.


Patients are always interested in their disorders and usually ask lots of questions.
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,
 
Description Work experience 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Schools
Results and Impact Individual students spend a week in the laboratory learning about scientific research.

School comes back each year requesting further pupil experience.
Year(s) Of Engagement Activity 2008,2009,2010,2011,2012