Determining how mutations in actin lead to skeletal muscle weakness
Lead Research Organisation:
King's College London
Department Name: Ctr of Human & Aerospace Physiolog Sci
Abstract
Skeletal muscles are composed of a large number of cells called myofibres. Each myofibre have myofibrils consisting of sarcomeres in series and parallel. Each sarcomere is formed by overlapping arrays of thick filaments and thin filaments also known as myosin and actin filaments. Myosin and actin filaments represent the contractile machinery.
There are many acquired and inherited diseases affecting myosin and actin filaments. Among them, actinopathies are the most common and are caused by mutations in actin. Actinopathies are usually life threatening, as they are associated with severe weakness affecting limbs and respiratory muscles. How mutations in actin lead to muscle weakness remains obscure and will be addressed in the present research project. Deciphering this will undoubtedly help designing efficient therapeutic interventions.
There are many acquired and inherited diseases affecting myosin and actin filaments. Among them, actinopathies are the most common and are caused by mutations in actin. Actinopathies are usually life threatening, as they are associated with severe weakness affecting limbs and respiratory muscles. How mutations in actin lead to muscle weakness remains obscure and will be addressed in the present research project. Deciphering this will undoubtedly help designing efficient therapeutic interventions.
Technical Summary
Importance and main objective: Diseases related to mutations in actin are characterized by severe skeletal muscle weakness often leading to premature death. The understanding of this group of disorders has advanced in recent years through the identification of the causative ACTA1 gene mutations. Nevertheless, the exact mechanisms leading to muscle dysfunction remain unclear, which hampers the development of efficient therapies. Therefore, the main objective of the present research project is to clearly characterise the cascade of molecular and cellular events triggering muscle wasting.
Methods: We will mainly use muscle samples and isolated myofibres from two transgenic mouse models perfectly recapitulating the human condition and expressing either His40Tyr or Asp286Gly single amino acid substitution in actin. We will then perform a broad range of experiments including small-angle X-ray scattering, polarised fluorescence, myofibre mechanics, confocal microscopy, immunohistochemistry and micro-array analysis.
Feasibility and outcomes: The availability and knowledge of these unique techniques in combination with experience in undertaking challenging studies put us in a unique position to tackle the problem posed. We expect to demonstrate that mutations in actin directly impair actin filament extensibility, inducing a disruption (i) of myosin binding and (ii) of the intrinsic force-generating capacity, directly promoting myofibre atrophy. Successfully proving this would grandly facilitate the design of efficient therapeutic interventions that would target the actin-myosin interface.
Methods: We will mainly use muscle samples and isolated myofibres from two transgenic mouse models perfectly recapitulating the human condition and expressing either His40Tyr or Asp286Gly single amino acid substitution in actin. We will then perform a broad range of experiments including small-angle X-ray scattering, polarised fluorescence, myofibre mechanics, confocal microscopy, immunohistochemistry and micro-array analysis.
Feasibility and outcomes: The availability and knowledge of these unique techniques in combination with experience in undertaking challenging studies put us in a unique position to tackle the problem posed. We expect to demonstrate that mutations in actin directly impair actin filament extensibility, inducing a disruption (i) of myosin binding and (ii) of the intrinsic force-generating capacity, directly promoting myofibre atrophy. Successfully proving this would grandly facilitate the design of efficient therapeutic interventions that would target the actin-myosin interface.
Planned Impact
1. Impact by training:
As with any reputable scientific centre we are concerned that young scientists who come for training should be given as wide a scope as possible in order to keep their future scientific options open. This project will allow the development of the appointed individual to develop a range of unique and specialist skills such as:
(i) Learning new techniques; and
(ii) Gaining communication skills by presenting his/ her work to the scientific and medical communities and to a more general audience.
2. Impact on basic research and academia:
The effort to tackle rare diseases is hampered due to the complex phenotypes and low number of specialized research groups. The present research project combining state-of-the-art methods and unique techniques has the potential to move the field into completely uncharted scientific territory. We predict that the findings of the present proposal, at the interface between physiology and biophysics, will be of great interest for:
(i) Geneticists who focus on gene mutations and their consequences;
(ii) Structural and cell/ molecular biologists, who are interested in actin structure and function;
(iii) Biophysicists who use similar techniques including small-angle x-ray scattering;
(iv) Physiologists who investigate skeletal/ cardiac muscle structure and function in health and disease; and
(v) Clinicians who try to understand the pathophysiology of muscle diseases.
3. Impact on the clinic:
Rare diseases affect more than 25 million people in Europe. Only a few of these disorders are well enough understood to be treated effectively. Thus, rare diseases are still an important public health challenge. Our research project has the potential to contribute to the nation's health by
(i) Generating attention from affected patients, family members, general practitioners, myologists, neurologists, pathologists and physiotherapists; and
(ii) Setting an example for tackling other rare (muscle) diseases such as cardiomyopathies, which are also frequently related to mutations in genes encoding actin.
4. Impact on pharmaceutical industry:
Actinopathies start at a very young age. Hence, the economic consequences are large (loss of ability to work, large medical expenses) and the impact on family members is enormous, as they need to take care of the affected patients as long as they live. The fact that we will unravel the pathophysiological mechanisms underlying weakness in a group of rare disorders termed actinopathies will:
(i) Provide a clear understanding of how mutations in actin cause disease; and
(ii) Give opportunities for industrial applications; in other words, help to increase the speed of developing therapeutic interventions by identifying potential drug targets.
5. Impact on society via engagement of the public in science:
The PI of this application is a member of various scientific societies and takes active roles in trying to engage interested members of the public, particularly younger people, in science. The Centre of Human and Aerospace Physiological Sciences has an outstanding track record in linking its research to public engagement and activities for engaging young people. This includes endeavours such as "Mission Discovery", a weeklong summer school using the physiology of human space flight to facilitate and engage children in biomedical science and designing experiments, which run on the International Space Station:
http://www.kcl.ac.uk/newsevents/news/newsrecords/2014/January/missiondiscovery-lift-off.aspx)
As with any reputable scientific centre we are concerned that young scientists who come for training should be given as wide a scope as possible in order to keep their future scientific options open. This project will allow the development of the appointed individual to develop a range of unique and specialist skills such as:
(i) Learning new techniques; and
(ii) Gaining communication skills by presenting his/ her work to the scientific and medical communities and to a more general audience.
2. Impact on basic research and academia:
The effort to tackle rare diseases is hampered due to the complex phenotypes and low number of specialized research groups. The present research project combining state-of-the-art methods and unique techniques has the potential to move the field into completely uncharted scientific territory. We predict that the findings of the present proposal, at the interface between physiology and biophysics, will be of great interest for:
(i) Geneticists who focus on gene mutations and their consequences;
(ii) Structural and cell/ molecular biologists, who are interested in actin structure and function;
(iii) Biophysicists who use similar techniques including small-angle x-ray scattering;
(iv) Physiologists who investigate skeletal/ cardiac muscle structure and function in health and disease; and
(v) Clinicians who try to understand the pathophysiology of muscle diseases.
3. Impact on the clinic:
Rare diseases affect more than 25 million people in Europe. Only a few of these disorders are well enough understood to be treated effectively. Thus, rare diseases are still an important public health challenge. Our research project has the potential to contribute to the nation's health by
(i) Generating attention from affected patients, family members, general practitioners, myologists, neurologists, pathologists and physiotherapists; and
(ii) Setting an example for tackling other rare (muscle) diseases such as cardiomyopathies, which are also frequently related to mutations in genes encoding actin.
4. Impact on pharmaceutical industry:
Actinopathies start at a very young age. Hence, the economic consequences are large (loss of ability to work, large medical expenses) and the impact on family members is enormous, as they need to take care of the affected patients as long as they live. The fact that we will unravel the pathophysiological mechanisms underlying weakness in a group of rare disorders termed actinopathies will:
(i) Provide a clear understanding of how mutations in actin cause disease; and
(ii) Give opportunities for industrial applications; in other words, help to increase the speed of developing therapeutic interventions by identifying potential drug targets.
5. Impact on society via engagement of the public in science:
The PI of this application is a member of various scientific societies and takes active roles in trying to engage interested members of the public, particularly younger people, in science. The Centre of Human and Aerospace Physiological Sciences has an outstanding track record in linking its research to public engagement and activities for engaging young people. This includes endeavours such as "Mission Discovery", a weeklong summer school using the physiology of human space flight to facilitate and engage children in biomedical science and designing experiments, which run on the International Space Station:
http://www.kcl.ac.uk/newsevents/news/newsrecords/2014/January/missiondiscovery-lift-off.aspx)
People |
ORCID iD |
Julien Ochala (Principal Investigator) |
Publications
Buono S
(2018)
Reducing dynamin 2 (DNM2) rescues DNM2-related dominant centronuclear myopathy.
in Proceedings of the National Academy of Sciences of the United States of America
Chan C
(2016)
Myopathy-inducing mutation H40Y in ACTA1 hampers actin filament structure and function.
in Biochimica et biophysica acta
Fan J
(2018)
Molecular Consequences of the Myopathy-Related D286G Mutation on Actin Function.
in Frontiers in physiology
Jungbluth H
(2017)
Current and future therapeutic approaches to the congenital myopathies
in Seminars in Cell & Developmental Biology
Jungbluth H
(2018)
Congenital myopathies: disorders of excitation-contraction coupling and muscle contraction.
in Nature reviews. Neurology
Jungbluth, Heinz
(2017)
Current and future therapeutic approaches to the congenital myopathies
Laitila JM
(2020)
Nebulin nemaline myopathy recapitulated in a compound heterozygous mouse model with both a missense and a nonsense mutation in Neb.
in Acta neuropathologica communications
Levy Y
(2018)
Prelamin A causes aberrant myonuclear arrangement and results in muscle fiber weakness.
in JCI insight
Lindqvist J
(2016)
Modulating myosin restores muscle function in a mouse model of nemaline myopathy.
in Annals of neurology
Ochala J
(2016)
Novel myosin-based therapies for congenital cardiac and skeletal myopathies.
in Journal of medical genetics
Ross JA
(2017)
Exploring the Role of PGC-1a in Defining Nuclear Organisation in Skeletal Muscle Fibres.
in Journal of cellular physiology
Ross JA
(2019)
Impairments in contractility and cytoskeletal organisation cause nuclear defects in nemaline myopathy.
in Acta neuropathologica
Ross JA
(2018)
SIRT1 regulates nuclear number and domain size in skeletal muscle fibers.
in Journal of cellular physiology
Ross JA
(2020)
rAAV-related therapy fully rescues myonuclear and myofilament function in X-linked myotubular myopathy.
in Acta neuropathologica communications
Tinklenberg JA
(2018)
Myostatin inhibition using mRK35 produces skeletal muscle growth and tubular aggregate formation in wild type and TgACTA1D286G nemaline myopathy mice.
in Human molecular genetics
Description | Research grant |
Amount | $135,000 (USD) |
Organisation | A Foundation Building Strength for Nemaline Myopathy |
Sector | Charity/Non Profit |
Country | United States |
Start | 04/2018 |
End | 01/2020 |
Description | Research grant |
Amount | £112,535 (GBP) |
Funding ID | 17GRO-PS48-0077 |
Organisation | Muscular Dystrophy UK |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 01/2018 |
End | 12/2021 |
Description | Nemaline Myopathy |
Organisation | University of Western Australia |
Department | Western Australian Institute for Medical Research |
Country | Australia |
Sector | Academic/University |
PI Contribution | We are studying how muscle physiology is changed in these mouse models |
Collaborator Contribution | They are providing muscle tissue from various mouse models |
Impact | We have published a few scientific papers and a couple more are currently written |
Start Year | 2017 |
Description | Outreach/fundraising event for Muscular Dystrophy UK |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | It is an event to raise awareness and funds for the charity titled Muscular Dystrophy UK. I will talk about why it is important to fund research related to muscle diseases and what my research is about. |
Year(s) Of Engagement Activity | 2018 |
Description | Webinar (A Foundation Building Strength for Nemaline Myopathy) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Patients, carers and/or patient groups |
Results and Impact | I take active roles in trying to engage members of the public, particularly patients and their relatives. In fact, in 2016 and 2017, I have given two webinars aiming at informing patients and their families about the latest research advances in the field of genetic diseases and congenital myopathies (organised by the "Foundation Building Strength for Nemaline Myopathy"). |
Year(s) Of Engagement Activity | 2016,2017 |
Description | Webinar about Genetic Muscle Diseases for the Asociación Conquistando Escalones |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Patients, carers and/or patient groups |
Results and Impact | 20 patients diagnosed with genetic muscle diseases (LGMD) attended the webinar where I presented my recent work on the mechanisms underlying congenital myopathies and dystrophies. |
Year(s) Of Engagement Activity | 2018 |