MICA: Determining how mutations in myosin cause skeletal muscle disease

Lead Research Organisation: University of Leeds
Department Name: Inst of Molecular & Cellular Biology

Abstract

Skeletal muscle makes up about 40% of the human body. Not surprisingly there are a wide range of diseases that affect muscle structure and function. One of these is a type of muscle wasting disease, which is caused by mutations in a protein called myosin.
Skeletal muscle is a highly regular structure, consisting of muscle fibres that run from end to end, where they end in the muscle tendons. Muscle fibres are formed by the fusion of many thousands of cells together to form a a single giant cell that contains thousands of nuclei. Within the muscle fibre the two main proteins that interact to make the muscle fibre shorten are organised into a highly regular pattern of repeating units called muscle sarcomeres. These are organised end to end into long structures called myofibrils, which run from one end of the fibre to the other. A single fibre is packed full of myofibrils, which make up about 80% of the total volume of the fibre.
A single fibre can be about 200 mm long, whereas a single sarcomere is only about 2 microns long, which means there are around 100,000 sarcomeres from one end of the myofibril to the other. Inside each sarcomere, myosin is organised into thick filaments and between them actin is organised into thin filaments. When muscle contracts, projections (crossbridges) from myosin in the thick filaments interact with actin in the thin filaments. These pull on the thin filaments causing each sarcomere to shorten by about 10%. Each of these small movements within each sarcomere are summed along the muscle fibre to generate much larger movements at their ends, enabling movement of joints by the muscle.
For all of this to work, myosin must be precisely organised into the thick filaments. Indeed each thick filament contains exactly 294 molecules of myosin. In some types of muscle wasting diseases, such as Laing early onset distal myopathy, the part of the myosin that is important for making the thick filaments is mutated. We think this means that thick filaments do not form properly, causing the muscle wasting observed. Our research will shed light on this idea, to help us understand how myosin mutations result in muscle wasting. We will investigate the effects of the mutations on the structure of this part of the myosin, and determine how the mutations affect the ability of the myosin to integrate into thick filaments.

Technical Summary

Laing early onset distal myopathy (MPD1) is a skeletal muscle wasting disease that almost exclusively affects myosin, one of the two main contractile proteins. All the mutations discovered so far are found in the filament forming region of the slow (beta-cardiac) myosin heavy chain isoform. An analysis of these mutations and their positions suggest to us that they are likely to disrupt the structure of the coiled-coil, and this may result in a failure of myosin to incorporate into thick filaments, or it may incorporate less stably and/or disrupt thick filament structure once incorporated into the thick filaments. To investigate this, we plan to use a wide range of approaches to determine how the mutations affect myosin structure, thick filament structure and incorporation of mutant myosins into thick filaments. This will provide a molecular basis for the understanding of this disease that will be crucial for developing future therapies.

Planned Impact

The main beneficiaries of this research are:
Academic researchers who investigate myosin structure and function
Academic researchers who are interested in muscle structure and function
Academic researchers and Clinicians who are interested in muscle disease
Academic researchers who use cultures of muscle cells in their research
Our collaborators: Orla Technologies, who market novel peptide surfaces for optimising cell culture, and related companies.

The research has the potential to contribute to the nation's health and wealth by providing a clearer understanding of how mutations in myosin cause disease, and by generating novel peptide surfaces for cell culture of muscle, that will be marketed by Orla Technologies.

Staff involved in the project will expand their experimental skill set, learning new techniques and approaches in addition to their pre-existing skills. They will gain communication skills by publishing and presenting their work. They will gain skills in product commercialisation through our collaboration with Orla Technologies. They will also gain skills in communicating their science to a more general audience, through their participation in a science fair.
 
Description BBSRC DTP CASE award
Amount £80,000 (GBP)
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 09/2017 
End 09/2021
 
Description Understanding how mutations in subfragment-2 of beta-cardiac myosin heavy chain contribute to hypertrophic cardiomyopathy
Amount £208,184 (GBP)
Funding ID PG/15/2/31208 
Organisation British Heart Foundation (BHF) 
Sector Charity/Non Profit
Country United Kingdom
Start 04/2015 
End 04/2018
 
Description Understanding the mechanisms underlying myosinopathies
Amount £915,341 (GBP)
Funding ID MR/S023593/1 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 08/2019 
End 09/2022
 
Description Bio-engineering 
Organisation Orla Protein Technnologies
Country United Kingdom 
Sector Private 
PI Contribution We designed peptides for Orla to engineer, and we tested the peptides.
Collaborator Contribution Orla made the peptides, and gave them to us to test.
Impact A paper on our findings - has now been published. Peptides we tested are now commercially available
Start Year 2012
 
Description Café-Scientifique debate 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact This was a debate funded by the BSA, on 'does it matter who funds science'. I was on the panel, and took part in a debate with the audience on this topic. There was a lot of discussion on who should fund science, if we can trust the outcomes of science, does it matter if it is industry or universities that do the science and so on. The conclusion was, that the audience did go away with a generally favourable view of how science is done, and that it is important for the public to fund it.
Year(s) Of Engagement Activity 2017
URL https://www.ypsyork.org/events/cafe-scientifique-debate-november/
 
Description Pint of Science 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact I presented our research on heart disease as part of the Leeds 'Pint of Science' event https://www.leeds.ac.uk/forstaff/news/article/5686/pint_of_science_2017
Year(s) Of Engagement Activity 2017
URL http://www.leedsinspired.co.uk/events/our-body-heart-hack
 
Description Royal Society MP Pairing Scheme 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact I took part in the Royal Society MP Pairing Scheme in November 2015. I visited parliament, and shadowed an MP (Chris Green from Bolton West). Chris is due to make a return visit to the University in April 2016.
Year(s) Of Engagement Activity 2015,2016
URL https://royalsociety.org/grants-schemes-awards/pairing-scheme/