Understanding and Ameliorating perturbed signalling and pathogenesis in FSHD

Diseases can be treated more effectively if the causes/mechanisms underlying the symptoms are known. For muscular dystrophy, the causative defect is changes in genes or DNA that in turn, produce changes to proteins. However, it is generally poorly understood how such defects result in the progressive skeletal muscle weakness and wasting typical of muscular dystrophies.

Every cell in the body contains the same DNA, which is divided into genes, each of which carries the instructions to make a protein(s): the molecules that build, maintain and operate the body. The selection of genes that are expressed (active) in a particular cell type, such as in a muscle fibre, dictate which proteins are made. This gives the cell its special characteristics and functions. For example, muscle genes are not expressed in skin cells, and skin genes are not expressed in muscle cells.

Facioscapulohumeral muscular dystrophy (FSHD) is caused by a change in a particular region of DNA that leads to production of a protein called DUX4, that is not normally present in muscle. DUX4 is a 'transcription factor' meaning that it can control the expression of other genes by binding to their regulatory regions, and so can alter the type of proteins that are made by a cell. Thus the carefully coordinated pattern of gene expression and protein production that enables skeletal muscle to function effectively, is perturbed by the presence of DUX4. This ultimately leads to muscle weakness and wasting.

We have examined gene expression changes during human muscle formation in FSHD cells and used mathematical tools to understand which signalling process are perturbed. We found that pathways that control generation of mitochondria and processes associated with mitochondrial function such as dealing with by-products of metabolism/respiration called reactive oxygen species (oxidative stress) are suppressed. It is well known that FSHD cells are more sensitive to oxidative stress, and a recent clinical trial (clinicaltrials.gov number: NCT01596803) reported that administration of anti-oxidants, improved aspects of muscle function in FSHD patients.

We have found that inhibiting pathways that control generation of mitochondria in healthy human muscle cells makes them appear like FSHD muscle fibres. Conversely augmenting the action of these pathways controlling generation of mitochondria in FSHD muscle cells makes them more like healthy human muscle cells.

This project will investigate how regulation of this pathway controlling generation of mitochondria is perturbed in FSHD and test potential therapeutic strategies to improve its function.

Thus in summary, we will generate tools and models of FSHD that will both further reveal disease mechanisms and also provide a platform for testing potential therapies for FSHD, to underpin possible clinical trials. Better understanding the disease mechanism in FSHD may also highlight other potential therapeutic interventions.

Facioscapulohumeral muscular dystrophy (FSHD) is the third commonest inherited myopathy, characterised by a descending, often asymmetric, dystrophy with initial involvement of facial and proximal upper limb musculature, and later progression to certain lower limb muscles.

We have examined gene expression changes during muscle formation in human FSHD cells and used mathematical tools to understand which signalling process are perturbed. We found that pathways that control generation of mitochondria and processes associated with mitochondrial function such as dealing with reactive oxygen species are suppressed. It is well known that FSHD cells are more sensitive to oxidative stress, and a recent clinical trial (clinicaltrials.gov number: NCT01596803) reported that administration of anti-oxidants improved aspects of muscle function in FSHD patients.

We have found that inhibiting pathways that control generation of mitochondria in healthy human muscle cells generates myofibres with an atrophic phenotype: characteristic of FSHD muscle fibres. Conversely augmenting the action of these pathways controlling generation of mitochondria in FSHD muscle cells makes them generate myofibres that are larger and indistinguishable from healthy human muscle.

This project will investigate how regulation of this pathway controlling generation of mitochondria is perturbed in FSHD and test potential therapeutic strategies to improve its function.

Main objectives
1. Determine if drugs that increase mitochondrial biogenesis improve the FSHD phenotype in vivo.
2. Validate the mechanism of perturbed mitochondrial biogenesis in FSHD myoblasts.
3. Decipher the action of drugs that improve mitochondrial biogenesis in ameliorating FSHD.
4. Understand the regulation of mitochondrial biogenesis pathways in FSHD.
5: Determine if mitochondrial biogenesis improves DUX4 induced myopathy in vivo.

This research is directed at understanding pathology of the FSHD, which will inform development/optimisation of treatments. FSHD is autosomal dominant with poorly understood pathophysiology and there is no cure. FSHD presents as an asymmetric, progressive descending skeletal muscle weakness and wasting affecting many muscles that severely affects quality of life: around 30% use a wheelchair. For example, patients can undergo surgery to fix the scapular to the ribcage to stabilize the shoulder, which significantly incapacitates patients for months. FSHD is also associated with sensorineural hearing loss, which can progress to deafness, and a retinal vascular abnormality, which can compromise vision. Lifespan is not attenuated, but means that economic burden lasts many years.

FSHD is the third most common inherited myopathy (prevalence ~1/20,000 http://www.orpha.net). Recent figures indicate that 52 people/year are newly diagnosed with FSHD in the Netherlands, a prevalence of 12/100,000 (1/8333).

Financial Costs: An estimated 70,000 people in the UK in 2010 had a neuromuscular condition, (http://www.muscular-dystrophy.org/assets/0002/0463/Cost_of_Living_with_Muscle_Disease.pdf), creating a considerable financial burden. The Access Economics research published in 2007 put costs of muscular dystrophy for the 3500 Australian patients in 2005 at £258 million a year (http://www.mda.org.au/media/accesslaunch/Gullotta.asp). More recently, calculated annual per-patient costs for neuromuscular disease in the US are $63,693 for ALS, $50,952 for DMD, and $32,236 for DM. Population-wide national costs were $1,023 million (ALS), $787 million (DMD) and $448 million (DM) (Larkindale et al. Muscle Nerve (2014) 49: 431-8). For FSHD, cost per patient year in Germany is 26,240 Euros (Schepelmann et al. J. Neurol. (2010) 257: 15). In addition, > 50% of adult members of the FSHD registry reported that symptoms adversely affected their employment by forced disability, early retirement, or job loss, or that their job had been modified to accommodate physical limitations (http://www.ncbi.nlm.nih.gov/pubmed/22155025).

Quality of Life: 29.6% of FSHD registry members report use of wheelchairs for short or long distances, with 8.3% reporting as "always" using wheelchairs for both. 11.3% of FSHD registry members report use of leg braces at enrolment. The EQ-VAS quality of life score is 0.75 +/- 0.21 (0.81) for FSHD and such a low score associated with increased risk of depression (Winter et al. J. Neurol. (2010) 257(9):1473-81). FSHD registry paper: Moreover, psychological problems occurred in 28.1% of FSHD registry members, with more than one-third reporting having received psychological counselling (Hilbert et al. Contemp. Clin. Trials (2012) 33:302-11).

Direct beneficiaries with immediate impact from the work will include academics, clinicians, and the pharmaceutical industry. Researchers/clinicians will benefit as better understanding pathomechanisms will inform treatment and development of therapies, particularly relevant to progressing from the recent clinical trial involving antioxidants for FSHD that showed improvement in certain parameters (clinicaltrials.gov number: NCT01596803). Pharmaceutical companies and translational researchers will benefit as this will inform planning pre-clinical/clinical trials.

Longer term, patients and carers will benefit from relief of disease burden from better understanding disease pathology and improved therapy. Thus society and the economy benefits from improved treatments, due to reduction in NHS and care costs and both reduced loss of earnings and benefit payments for patients and carers. Biochanin A is available in food supplements and clinically tested, so could be rapidly adopted for FSHD, also encompassing MRC Priorities for Nutrition Research
https://www.mrc.ac.uk/funding/science-areas/population-systems-medicine/mrc-priorities-for-nutrition-research/