Scientists have relieved the symptoms of muscular dystrophy in mice by using a gene-editing tool.
Muscular dystrophy is a crippling inherited disorder which is caused by mutations in the genes and weakens muscle fibres.
Researchers used CRISPR to alter the genomes of mice with muscular dystrophy and boost the expression of particular genes.
This provided the mice with crucial instructions that were missing, preventing them from having the hallmark muscle wasting and paralysis symptoms.
Charities said although a ‘cure’ has not been discovered, and human tests are needed, the findings offer a glimmer of hope to sufferers of muscular dystrophy.
Scientists in Canada have relieved the symptoms of muscular dystrophy in mice by using a gene-editing tool (stock photo of DNA)
Muscle wasting conditions such as muscular dystrophy affect 70,000 people in the UK. Most diagnoses are in children, and the symptoms get progressively worse over time.
The researchers from the Program in Genetics and Genome Biology, the Hospital for Sick Children Research Institute, Canada, looked only at a subtype of muscular dystrophy, congenital muscular dystrophy type 1A (MDC1A).
Of the 10,000 people in the UK who have a form of muscular dystrophy, it is thought that about 400 have congenital muscular dystrophy
People with MDC1A usually have diminished muscle tone, meaning they are unable to walk without assistance.
This condition is thought to be the most common type of congenital muscular dystrophy, accounting for between 30 and 40 percent of total cases.
They may also suffer seizures, and have difficulties breathing, feeding, gaining weight and growing generally.
HOW DOES CRISPR DNA EDITING WORK?
The CRISPR gene editing technique is being used an increasing amount in health research because it can change the building blocks of the body.
At a basic level, CRISPR works as a DNA cutting-and-pasting operation.
Technically called CRISPR-Cas9, the process involves sending new strands of DNA and enzymes into organisms to edit their genes.
In humans, genes act as blueprints for many processes and characteristics in the body – they dictate everything from the colour of your eyes and hair to whether or not you have cancer.
The components of CRISPR-Cas9 – the DNA sequence and the enzymes needed to implant it – are often sent into the body on the back of a harmless virus so scientists can control where they go.
Cas9 enzymes can then cut strands of DNA, effectively turning off a gene, or remove sections of DNA to be replaced with the CRISPRs, which are new sections sent in to change the gene and have an effect they have been pre-programmed to produce.
But the process is controversial because it could be used to change babies in the womb – initially to treat diseases – but could lead to a rise in ‘designer babies’ as doctors offer ways to change embryos’ DNA.
Source: Broad Institute
MDC1A is caused by mutations in the gene Lama2, which helps the body make a range of proteins including laminin-α2, necessary for muscle strength.
Rodent studies have shown increasing expression of a related gene, Lama1, which is linked to a similar protein, laminin-α1, can help to ease symptoms in mice with the disease.
However researchers have struggled to target the gene with standard therapy methods. Therefore, Dr Ronald Cohn and colleagues tried CRISPR.
CRISPR gene-editing acts like a pair of ‘molecular scissors’, allowing scientists to go into an organisms’ DNA and change, edit or remove parts.
They targeted the Lama1 gene by introducing an enzyme to the DNA, which increased the expression of the laminin-α1.
Publishing their findings in the journal Nature, the researchers found it significantly reduced clinical symptoms of the disease in mice.
The authors propose that in the future, it might be possible to help treat muscular dystrophy and other genetic disorders by ‘turning up’ protective genes and ‘turning down’ detrimental genes.
Professor Dominic Wells, translational medicine at Royal Veterinary College, said: ‘The study by Kemaladewi and colleagues is an elegant demonstration in mice of the potential to upregulate a compensatory gene to treat muscular dystrophy.
‘This serves as a proof of concept for further development of this approach to therapy for patients affected by congenital muscular dystrophy type 1A (MDC1A) and potentially other muscular dystrophies.’
The CRISPR method used has been deemed safer because instead of breaking the DNA for the desired results, it only edits it.
However, there are still risks that have not been explored and the strategies used have potential to induce gene expression in other areas.
Dr Alena Pance, senior scientist at Wellcome Trust Sanger Institute, said: ‘The “switching on” of the modifier gene needs to occur in specific tissues – in the case of muscular dystrophy, in skeletal muscles and sciatic nerves.
‘But the work does not examine its expression in other tissues in the mouse, where expression of this gene could be undesirable.
‘The major advance of this approach is the potential to treat complex diseases caused by multiple mutations, maybe even affecting different genes.
‘Rather than attempting to repair all the defects, if a modifier gene can be found as was shown in this study, its activation can overcome the pathology of the disease.
‘Furthermore, diseases that today escape all possibilities of treatment could finally have a glimmer of hope.’
The charity Muscular Dystrophy UK said it was an ‘exciting’ piece of research.
Dr Kate Adcock, director of research and innovation, said: ‘It should give hope to people with congenital muscular dystrophy type 1A and their families.
‘Targeting disease modifier genes in this way could benefit a wider range of patients, as the technique doesn’t depend on an individual mutation.
‘We’re encouraged that the technique did not appear to cause unwanted gene editing, but there is still a way to go before any treatment is brought to clinic. The next step will be to replicate the study in other animal models before we extend the study to humans.
‘This may not be a cure, but it’s a step in the right direction to finding a treatment for congenital muscular dystrophy type 1A.’