MDF Magazine Newsletter Issue 55 April 2018

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MD In 1996, an international research team identified the Friedreich’s ataxia gene on chromosome 9. The FXN gene codes for production of a protein called "frataxin." In the normal version of the gene, a sequence of DNA (labeled “GAA”) is repeated between 7 and 22 times. In the defective FXN gene, the repeat occurs over and over again – hundreds, even up to a thousand times. This abnormal pattern, called a triplet repeat expansion, has been implicated as the cause of several dominantly inherited diseases, but Friedreich's ataxia is the only known recessive genetic disorder caused by the problem. Almost all people with Friedreich's ataxia have two copies of this mutant form of FXN, but it is not found in all cases of the disease. About two percent of affected individuals have other defects in the FXN gene that are responsible for causing the disease. The triplet repeat expansion greatly disrupts the normal production of frataxin. Frataxin is found in the energyproducing parts of the cell called mitochondria. Research suggests that without a normal level of frataxin, certain cells in the body (especially peripheral nerve, spinal cord, brain and heart muscle cells) cannot effectively produce energy and have been hypothesized to have a buildup of toxic byproducts leading to what is called “oxidative stress.” It also may lead to increased levels of iron in the mitochondria. When the excess iron reacts with oxygen, free radicals can be produced. Although free radicals are essential molecules in the body's metabolism, they can also destroy cells and harm the body. Can Friedreich's ataxia be cured or treated? As with many degenerative diseases of the nervous system, there is currently no cure or effective treatment for Friedreich's ataxia. However, many of the symptoms and accompanying complications can be treated to help individuals maintain optimal functioning as long as possible. Doctors can prescribe treatments for diabetes, if present; some of the heart problems can be treated with medication as well. Orthopedic problems such as foot deformities and scoliosis can be corrected with braces or surgery. Physical therapy may prolong use of the arms and legs. Advances in understanding the genetics of Friedreich's ataxia are leading to breakthroughs in treatment. Research has moved forward to the point where clinical trials of proposed treatments are presently occurring for Friedreich’s ataxia. What services are useful to Friedreich's ataxia patients and their families? therapists, and speech therapists to help deal with some of the other associated problems. What research is being done? Researchers are optimistic that they have begun to understand the causes of the disease, and work has begun to develop effective treatments and prevention strategies for Friedreich's ataxia. Scientists have been able to create various models of the disease in yeast and mice which have facilitated understanding the cause of the disease and are now being used for drug discovery and the development of novel treatments. Studies have revealed that frataxin is an important mitochondrial protein for proper function of several organs. Yet in people with the disease, the amount of frataxin in affected cells is severely reduced. It is believed that the loss of frataxin makes the nervous system, heart, and pancreas particularly susceptible to damage from free radicals (produced when the excess iron reacts with oxygen). Once certain cells in these tissues are destroyed by free radicals they cannot be replaced. Nerve and muscle cells also have metabolic needs that may make them particularly vulnerable to this damage. Free radicals have been implicated in other degenerative diseases such as Parkinson's and Alzheimer's diseases. Based upon this information, scientists and physicians have tried to reduce the levels of free radicals, also called oxidants, using treatment with "antioxidants." Initial clinical studies in Europe suggested that antioxidants like coenzyme Q10, vitamin E, and idebenone may offer individuals some limited benefit. However, recent clinical trials in the United States and Europe have not revealed effectiveness of idebenone in people with Friedreich’s ataxia, but more powerful modified forms of this agent and other antioxidants are in trials at this time. There is also a clinical trial to examine the efficacy of selectively removing excess iron from the mitochondria. Scientists also are exploring ways to increase frataxin levels through drug treatments, genetic engineering and protein delivery systems. Several compounds that are directed at increasing levels of frataxin may be brought to clinical trials in the near future. Article online at: https://www.ninds.nih.gov/Disorders/Pa- tient-Caregiver-Education/Fact-Sheets/Friedreichs-Ataxia- Fact-Sheet Genetic testing is essential for proper clinical diagnosis, and can aid in prenatal diagnosis and determining a person’s carrier status. Genetic counselors can help explain how Friedreich's ataxia is inherited. Psychological counseling and support groups for people with genetic diseases may also help affected individuals and their families cope with the disease. A primary care physician can screen people for complications such as heart disease, diabetes and scoliosis, and can refer individuals to specialists such as cardiologists, physical 8
Stem Cell Stem cells – what are they, and could they be a potential therapy? A mouse muscle fibre showing dystrophin protein (red), nuclei (blue) and a satellite cell (green). Image courtesy of Dr Bruno Doreste, University College London. Stem cells are considered to have great potential for treating numerous health conditions. We hope this article will help you understand more about stem cells, and about where research is in developing a stem cell therapy for musclewasting conditions. What are stem cells? Our bodies are made up of many different types of cells that are specialised to perform particular functions. For example, the individual fibres that make up our muscles are specialised for muscle contraction. Stem cells are distinct from other cells in our body in that they are unspecialised. They have the ability to develop into many different types of cell through a process called ‘differentiation’. They are also able to self-renew, which means they can keep dividing and producing identical copies of themselves. These properties therefore make them attractive as a potential therapeutic option for muscle-wasting conditions. Stem cells are important in early life and growth, as they develop into the cells that make up all of our tissues and organs. But their role doesn’t end there. They are continually working throughout our lives to ensure we have all the cells we need. They are essential to the maintenance of tissues such as skin, gut and blood that undergo continuous turnover. They are also vital in maintaining muscle, which can be built up according to the body’s needs and can often get damaged during physical exertion. Types of stem cell By Muscular Dystrophy UK There are two main types of stem cell found naturally inside the body: • embryonic stem cells – as their name suggests, these stem cells originate from an embryo. They supply new cells to the embryo as it grows and develops into a baby. Embryonic stem cells are pluripotent, which means they can develop into any type of cell. • adult (somatic) stem cells – these not only supply new cells as a person grows but also replace cells that get damaged. Somatic stem cells are multipotent, which means they can only change into certain cell types. For example, muscle stem cells (satellite cells) specialise into muscle cells. However, research has found that some adult stem cells are more versatile than previously thought. Stem cells from blood vessels (mesoangioblasts) and even from fat tissue (adipose stem cells) are capable of becoming muscle cells under certain growth conditions (see figure 1 below). Figure 1: Satellite cells are adult stem cells found inside our muscle. They specialise into immature muscle cells called myoblasts, which fuse together to form myotubes. These myotubes align to form mature muscle fibres. This entire process, which is highly regulated, requires different signals to trigger each step. It is also possible to manufacture stem cells in the laboratory by adding a cocktail of ‘reprogramming’ factors to specialised cells such as skin cells. These specialised cells then convert to induced pluripotent stem (iPS) cells, which can subsequently be converted into any type of cell. iPS cells are similar to embryonic stem cells in this way. From a therapeutic perspective, iPS cells can be produced from a patient’s own cells, which makes them useful tools for studying the treatment of human diseases. And, because they’re made from a person’s own cells, they can be used to create cells that can be transplanted back into the person without the risk of immune rejection. For example, iPS cells from someone with a genetic muscle-wasting condition could be genetically ‘corrected’ outside of the body using a gene therapy or genome-editing approach, allowed to differentiate into healthy muscle cells, which are then transplanted back into the body (see figure 2 below). 9
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MDF Magazine Newsletter Issue 55 April 2018

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