Understanding how DUX4 affects muscle regeneration in FSHD

Dr Robert Knight at King’s College London is investigating how DUX4 affects muscle stem cell function in a zebrafish model of facioscapulohumeral muscular dystrophy (FSHD). This research will improve our understanding of the underlying biology of FSHD, which is essential for the development of effective treatments in future.

 

The researchers have been making a new zebrafish model of FSHD to investigate the effect of DUX4 on the ability of muscle stem cells to repair muscle. Creation of this zebrafish model requires development of a complex genetic tool, which allows scientists to switch on DUX4 specifically in muscle stem cells.  The genetic tool also includes fluorescent proteins to mark muscle stem cells that have DUX4 switched on with yellow fluorescence. This will help the researchers to easily identify these cells when studying them under a fluorescent microscope.

The researchers have successfully engineered this genetic tool. However, they faced technical difficulties when introducing the tool into the zebrafish and were not yet able to generate the genetically modified zebrafish. These tools will be useful in the development of models to study FSHD.

The researchers had planned to investigate the role of an enzyme called Ret in FSHD. Previous work had shown that found that an existing Ret inhibitor, sunitinib, improved the development of muscle cells with FSHD that were grown in a dish. However, after studying data sets that contain information on the activity of gene and proteins in people with FSHD, the team found evidence to suggest that the RET gene is not affected by DUX4 in FSHD. However, the Ret protein is not the only protein that is affected by sunitinib. Therefore, future work will instead look at different proteins that can be blocked by sunitinib, to understand if they have a role in FSHD.

The work carried out during the project was presented a in a poster at our 2018 National Conference.

The Coronavirus pandemic is having a big financial impact on MDUK. You can read more about this and how we have had to respond here. Because of this, we have had to make some changes and difficult decisions. You can find out what this will mean for some of the key areas of our work, including research, here.  This project was paused in 2019 due to changes in the personnel on this grant. We made the difficult decision to terminate the grant in order to protect as much of our grant portfolio as much as possible. We understand that this is disappointing. We continue to support a wide range of research projects into muscle-wasting conditions- you can read about the current research projects here.

 

What are the aims of the project?

Activation of the DUX4 protein is thought to cause muscle wasting and inflammation in people with facioscapulohumeral muscular dystrophy (FSHD). How DUX4 does this is not fully understood, but previous studies have shown that it affects the ability of muscle stem cells to repair damaged muscle. This research has mostly been carried out in cells grown in the laboratory (in vitro), so how this affects muscle stem cells in living people is not understood.

Dr Robert Knight and his PhD student are aiming to understand how DUX4 affects muscle stem cell function in a whole, living animal (in vivo), the zebrafish. They will create a new zebrafish model of FSHD, where DUX4 is specifically switched on inside muscle stem cells. They will see how this affects the ability of the muscle stem cells to repair muscle, by studying them under a powerful fluorescent microscope.

The researchers will also investigate the immune response following injury to the muscle of the zebrafish models. This will help to explain how DUX4 activity contributes to muscle inflammation in FSHD and how this might affect muscle strength.

In the final part of this PhD studentship, the researchers will investigate the role of an enzyme called Ret in FSHD. They will test a series of drugs that inhibit Ret in the zebrafish model. This builds on a previous MDUK-funded study, where Dr Knight and Professor Peter Zammit found that an existing Ret inhibitor, sunitinib, improved the development of muscle cells with FSHD that were grown in a dish (in vitro). In this new project, they will see if sunitinib can improve muscle regeneration in the zebrafish model (in vivo).

Why is this research important?

Although we know that DUX4 activity is the underlying cause of FSHD, it is currently not clear whether DUX4 acts inside the muscle fibres or inside the muscle stem cells. This project will help to clarify this by developing a new animal model where DUX4 is specifically active in the muscle stem cells. This will improve our understanding of how DUX4 affects muscle stem cell function, and how this might lead to muscle wasting in FSHD.

How will the outcomes of this research benefit people with FSHD?

This project will improve our understanding of FSHD, which is essential for the development of effective treatments in future. The researchers are investigating whether sunitinib – a drug already approved for the treatment of some cancers – could improve muscle regeneration in the zebrafish model. If successful, this drug could be repurposed for the treatment of FSHD and enter clinical trials relatively quickly.

How might this research impact on other neuromuscular conditions?

Zebrafish have many benefits over mouse models. Immature zebrafish (larvae) are completely transparent, which mean it is easy to fluorescently label and visualise the muscle stem cells in live fish under a microscope. And because they live in water, zebrafish are also easily treated with drugs, making them a powerful model for testing potential therapies that promote muscle repair. Many zebrafish models for neuromuscular conditions have been created, allowing scientists to better understand what happens to the muscle and stem cells as the condition progresses. The experimental techniques used in this project will be helpful for scientists studying muscle stem cell function in zebrafish models for other muscle-wasting conditions.

Grant information

Project leader: Dr Robert Knight
Institute: King’s College London
Condition: Facioscapulohumeral muscular dystrophy (FSHD)
Duration: Four years (PhD studentship)
Total cost (£): 113,417
Official title: Modelling of DUX4-induced pathophysiology and screening for pharmacological therapies in a novel zebrafish model of fascioscapulohumeral dystrophy

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