In 2015 the Myotubular Trust awarded a 3 year grant to Dr Jocelyn Laporte and his team at the world renowned laboratory, IGBMC, in Strasbourg, France. Dr Laporte’s laboratory is where the MTM1 and BIN1 genes were identified as the cause of myotubular and centronuclear myopathy, and contributed to the identification of DNM2 with the team of Dr Marc Bitoun.  The team has significantly contributed to the knowledge and understanding of the interaction between these genes, providing major advances to research in this field.

The Research
The idea being proposed by Dr Laporte and his team was based on the interaction between the proteins causing two different forms of centronuclear myopathy.  They knew that the proteins created by the genes MTM1, BIN1 and DNM2 work together in muscle, and that regulation of these links is important for normal muscle function. Their hypothesis therefore was that myotubularin, the protein produced by the MTM1 gene, somehow regulated levels of dynamin 2, the protein created by the DNM2 gene.  Their idea was that if levels of DNM2 could be reduced in patients suffering from x-linked myotubular myopathy, then symptoms of muscle weakness could be reduced.

Source: IGBMC, France

The team had already shown that reducing dynamin 2 levels by genetic means improved lifespan and clinical signs of the disease in myopathic mice which do not produce myotubularin (Cowling et al. 2014). The application to the Myotubular Trust was to take this work further, and to support their team to:

1) target dynamin 2 as a novel therapeutic strategy in x-linked myotubular myopathy
…to carry out the pre-clinical work that would mean that this form of treatment could be brought to clinical trial
2) analyse the long term effects of reducing DNM2 in x-linked myotubular myopathy
…to ensure that the implications of reduced levels of DNM2 were understood
3) determine if reducing DNM2 can rescue other myopathies
…to focus this potential treatment on all forms of centronuclear myopathy

As we all expect that there will likely be a number of different treatments required for this condition, what was really important to Myotubular Trust about this grant was that it was a whole new approach. Equally importantly, this grant was going to target not just the x-linked form of the condition, but in fact all forms, beginning with BIN1 and DNM2.  It was also the first example of a cross therapy in muscle disease – where the decrease of a protein created by one gene (DNM2) altered in one form of the condition, rescues other forms (MTM1 and BIN1)

The Achievements
Firstly, this grant explored a number of different ways to reduce dynamin 2 expression – the work covered both a drug type called antisense oligonucleotides, as well as a gene therapy approach.

Secondly, DNM2 is a protein that is expressed throughout the body, so it was important to observe what happens in the non-muscle parts of the body when DNM2 is reduced. The project demonstrated no major drawbacks (in an experimental setting).

Finally, the grant looked at treating other forms of centronuclear myopathy and established that reducing DNM2 also improved life span and muscle strength for BIN1 too.

Additionally, through the in-depth understanding gained in these experiments and other work, the team also hypothesised that if they altered levels of the protein created by the gene BIN1, in this case increasing BIN1 in x-linked myotubular myopathy, this would also improve symptoms. These experiments were also successful and the team have identified increasing BIN1 as a novel therapeutic target for XLMTM.

This latter outcome has now further expanded the fascinating and promising idea developed by the team at IGBMC of a of ‘cross therapy’ approach to treatment – where “modulation of a CNM gene rescues phenotypes (i.e. symptoms) due to the alteration of another CNM gene”

To see and hear more about this work, and some really great explanatory diagrams, you can see Dr Belinda Cowling’s presentation at the European Family Conference.

As part of the work in reducing DNM2, and to bring this to potential treatment to clinical trial, and to patients, the biotechnology company Dynacure was created late in 2016.  See Chris Freitag, Chief Medical Officer’s presentation at the European Family Conference.

Significance
In the words of Jocelyn Laporte and the team at IGBMC…
“Through this project we have:
-validated a deliverable approach  to efficiently target DNM2 in vivo and rescue XLCNM in an animal model
-shown that DNM2 reduction can rescue a second form of CNM, thus identifying the first therapeutic concept that could be applied to several CNM forms.
-identified BIN1 as a novel therapeutic target for XLCNM
These data are very valuable for developing further in clinic 2 therapeutic targets for XLCNM (myotubular myopathy) and expand the number of patients who could be potentially treated.”
Publications and presentations
The importance of the world on DNM2 downregulation by Dr Laporte, Dr Cowling and their team is reflected in the number of publications and presentations:

Publications
·     Amphiphysin (BIN1) negatively regulates dynamin 2 for normal muscle maturation. Journal of Clinical Investigation, December 2017.
·     Single Intramuscular Injection of AAV-shRNA Reduces DNM2 and Prevents Myotubular Myopathy in Mice. Molecular Therapy, February 2018
·     Centronuclear myopathies under attack: a plethora of therapeutic targets. Journal of Neuromuscular Disorders, July 2018

Presentations at national / international meetings
·     New Directions in Biology and Disease of Skeletal Muscle Conference (New Orleans, USA, 2018-06-26). V Lionello, poster and poster award
·     Keystone symposia on Phosphoinositide Biology (Taos, USA, 2018-02-14). J Laporte, talk
·     World muscle society (St Malo, France, 2017-10-07). B Cowling, talk
·     Journées d’Actualités Physiopathologiques (Strasbourg, France, 2017-12-08). B Cowling, talk
·     Skeletal Muscle Biology in Health & Disease Conference in Gainesville (Gainsville, USA, 2017-03-08). B Cowling, poster
·     World Muscle Society meeting (Brighton, UK, 2015-10-03). B Cowling, talk and young Investigator (Elsevier) award

Summer 2018 – End of grant report by Dr Jocelyn Laporte and team Reducing DNM2 as a novel therapeutic target for centronuclear myopathy’.