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A chemical substance which helps to transmit a signal from the nerve to the muscle causing it to contract.
- Acetylcholine receptors (AChRs)
Proteins found in the membrane surrounding the muscle cell to which acetylcholine binds.
- Adeno-associated virus (AAV)
AAV (Adeno-Associated Virus) is a small virus, which infects humans and some other primate species. AAV is not currently known to cause disease and causes a very mild immune response. These features make AAV a very attractive vehicle for delivering genes into cells (gene therapy).
- Amino acids
The ‘building blocks’ of proteins. The sequence of amino acids determines the shape, properties and role of the protein.
The removal of a sample of amniotic fluid (the fluid around an unborn baby) for prenatal testing. Cells in the fluid are tested for certain abnormalities.
Any one of several hormones, such as testosterone, that promote the development of male characteristics.
- Androgen receptor
A specialised protein found in a number of tissues, to which androgen binds. Mutations in the androgen receptor gene can cause spinal and bulbar muscular atrophy.
- Animal models
Animals with conditions similar to those affecting humans, which can be used to study disease processes and test potential therapies. Animal models with a genetic condition have a similar mutation to the one present in humans with the condition. The mutation has either occurred naturally in the animals or has been induced in the laboratory.
Proteins made by the body to protect itself from “foreign” substances such as bacteria or viruses
- Antisense oligonucleotide
A short piece of genetic material (DNA or RNA) which can bind to a specific gene and change how the code is read. They can be used as a “molecular patch” to mask errors in the genetic code, this is known as exon skipping and this is in clinical trial for Duchenne muscular dystrophy. Certain types of antisense oligonucleotides are also being investigated in the laboratory for their ability to completely switch off genes, this is known as gene silencing.
A process of programmed cell death by which cells undergo an ordered sequence of events which lead to death of the cell. Cells may undergo apoptosis if they have sustained unrepairable damage.
- Autoimmune disorders
Conditions in which the immune system produces antibodies that attack the body’s own cells, for example, dermatomyositis, polymyositis and myasthenia gravis.
The body’s own tissues or DNA.
- Autosomal inheritance
Affects both males and females equally. The abnormal gene is not on the X or Y chromosomes (known as the sex chromosomes).
The long, hair-like extension of a nerve cell that carries a message to the target cell such as a muscle cell
- Becker muscular dystrophy
A genetic disorder in which the muscle cells break down, causing progressive muscle weakness. Becker muscular dystrophy usually affects only boysand men. It is caused by a lack of dystrophin protein. The condition resembles Duchenne muscular dystrophy, but is less severe.
A biological substance found in blood, urine or other parts of the body that can be used as an indicator of health or disease. A biomarker may be used to help clinicians diagnose a condition and monitor how it is progressing, but can also be used to see how well the body responds to a treatment.
The removal of a sample of tissue (such as muscle) from the body. The tissue is examined under a microscope to assist in diagnosis.
- BPAP ventilation (or BiPAP)
Bilevel positive airway pressure. A type of noninvasive ventilation that helps with breathing by providing a flow of air delivered through a face mask. The air is pressurized by a machine, which delivers it to the face mask through long, plastic tubing. The machine delivers the air at two different pressures which alternate: A higher pressure to breathe in (called inspiratory positive airway pressure, or IPAP) and a lower pressure for breathing out (called expiratory positive airway pressure, or EPAP).
- Calpain 3
A protein that is lacking or deficient in individuals with limb-girdle muscular dystrophy type 2A. The exact function of this protein is not known.
An essential structural component of living cells and source of energy for animals; includes simple sugars as well as complex carbohydrates such as starches
Related to the heart.
Disease of the heart muscle. The changes to your heart are different for each type of cardiomyopathy. You can read more about cardiomyopathy on the British Heart Foundation website.
An individual who has inherited a genetic mutation but does not have any symptoms. They have one normal and one abnormal copy of a pair of genes which cause a genetic disorder. A carrier will usually remain unaffected throughout his or her life but may pass the faulty gene on to their children.
- Carrier testing
Genetic testing to find out whether a person with no symptoms of a condition ‘carries’ a copy of a faulty gene which could be passed on to their children.
The structural and functional unit of all known living organisms. They are often called the building bricks of life. Humans have an estimated 100 trillion cells.
- Cell signalling
The ‘communication’, via chemical signals, between and within cells of an organism. This signalling ‘tells’ other cells to grow, change or produce proteins at specific times.
- Cell therapy
A technology that relies on replacing diseased or dysfunctional cells with healthy, functioning ones. These cells could be from a donor or the patient’s own cells that have been modified in some way. Stem cells are an important type of cells used for cell therapy.
- Cellular model
Cells grown in a Petri dish in the laboratory that can be used to study disease processes and test potential therapies
- Central nervous system
The brain and spinal cord.
- Charcot-Marie-Tooth disease
A condition that affects the nerves which carry signals to and from the muscles in the legs and arms. These nerves are known as the peripheral nerves. It is characterised by progressive weakness and wasting of the muscles in the calves, lower arms, hands and feet. There may also be loss of sensation in the hands and feet.
- Chorionic villus sampling (also known as CVS)
Chorionic villi are cells on the wall of the womb that have the same genetic make-up as an unborn baby. These cells can be tested to detect certain genetic abnormalities.
Cylindrical shaped bundles of DNA in the cell nucleus (the core or center of a cell). They consist of long, threadlike strands of DNA coiled upon themselves many times. Humans have 46 chromosomes in each cell; they inherit 23 from their mother and 23 from their father. The only exceptions are sperm and egg cells which contain just 23 chromosomes each. Genes are located on the DNA which is packaged into the chromosome ‘bundles’.
Present at birth, or soon afterwards.
- Congenital muscular dystrophy
Muscular dystrophy that is diagnosed at birth or shortly after. Symptoms vary widely depending on the type and can be caused by mutations in different genes.
An abnormal, often permanent contraction or shortening of the muscle (or tendon).
- Corticosteroid (or glucocorticoid steroid)
A type of drug similar to natural hormones produced by the adrenal glands that reduce inflammation and suppress the immune response. They are often prescribed to boys with Duchenne muscular dystrophy. These steroids may have an effect on stabilising or even improving muscle strength for a period of time but not all boys respond to treatment. The main steroid that is used is called prednisolone (prednisone in the USA). Deflazacort is also used in some countries. These are not “anabolic steroids” which is what athletes use illegally to build up muscle- these do not have an effect in Duchenne muscular dystrophy. Sometimes also refered to as ‘glucocorticoids’.
- Creatine kinase
A type of protein found in muscle. Some forms of muscular dystrophy are associated with high levels of creatine kinase in a blood test because when muscles are damaged due to disease or injury, the creatine kinase leaks into the bloodstream.
The fluid that fills a cell. It contains various structures (or organelles) including the nucleus, mitochondria and ribosomes. It also contains proteins, enzymes, fatty acids, amino acids and sugars that are used to keep the cell working properly.
- Deletion mutation
The loss of genetic material from a chromosome or gene.
A protein which is important in muscle cell architecture and structure since it connects many components of the cell. Mutations in the gene coding for desmin cause a very rare neuromuscular condition called desmin myopathy.
- Diagnostic criteria
Guidelines, rules or characteristics used by a clinician to diagnose somebody with a particular condition.
The muscle responsible for breathing.
Double vision caused by weakness of the eye muscles. When the muscles on each side are not affected equally it causes the eyes to point in slightly different directions.
Away from the centre of the body, for example, the hands and feet.
- Distal myopathies
A group of conditions predominantly affecting the muscles farthest away from the centre of the body, for example the hands and feet.
Deoxyribonucleic acid (DNA) is the molecule that contains the genetic instructions for the functioning of all known living organisms. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints, a recipe, or a code, since it contains the instructions needed to construct other components of cells, such as proteins. DNA is divided into segments called genes.
- Dominant inheritance
A method of genetic inheritance, whereby a single abnormal copy of a gene causes disease, even though a good copy of the gene is also present. We inherit one copy of each gene from our mother and one from our father. Individuals with a dominant condition have a 50% chance of passing on the altered gene, and resulting disease, to their children.
- Double-blind trial
A clinical trial where neither the researchers nor the patients know what they are getting.
- Duchenne muscular dystrophy
A genetic disorder in which muscle cells break down, and are eventually lost, causing progressive muscle weakness. The condition usually affects only boys and is caused by a lack of dystrophin protein.
- Duplication mutation
The repetition of part of a chromosome or gene.
The DUX4 gene is inappropriately switched on in people with facioscapulohumeral muscular dystrophy (FSHD) and produces DUX4 protein in their muscles. DUX4 protein is damaging to muscles and is thought to cause inflammation and muscle wasting in people with FSHD.
A protein absent in people with limb-girdle muscular dystrophy type 2B and Miyoshi myopathy. Dysferlin is thought to be involved in muscle cell repair.
Difficulty in swallowing.
Relating to, or afflicted with dystrophy. Muscles affected by muscular dystrophy may be described as dystrophic.
The protein missing in people who have Duchenne muscular dystrophy and reduced in those who have Becker muscular dystrophy. The dystrophin protein normally sits in the membrane that surrounds muscle fibres like a skin, and protects the membrane from damage during muscle contraction. Without dystrophin the muscle fibre membranes become damaged and eventually the muscle fibres die.
- Dystrophin-glycoprotein complex
A group of proteins including dystrophin bound together which form a critical link between the inside and outside of muscle cells. This complex is essential for the structure and function of muscle cells.
The word originates from two Greek words, ‘dys’ (‘faulty’) and ‘trophe’ (‘nourishment’). Muscular dystrophy refers to a group of disorders characterised by progressive muscle weakness and loss of muscle tissue.
The use of ultrasound to produce images of the heart.
- Electrocardiography (ECG)
A test which records the electrical activity of the heart through electrodes attached to the skin.
- Electromyography (EMG)
A test that assesses the electrical activity of the muscles and the nerves controlling the muscles. It is used to help diagnose neuromuscular disorders. There are two kinds of EMG in widespread use: intramuscular (needle) and surface EMG. To perform intramuscular EMG, a needle electrode or a needle containing two fine-wire electrodes is inserted through the skin into the muscle tissue. Intramuscular EMG may be considered too invasive or unnecessary in some cases and an electrode placed on the surface of the skin is used.
A fertilised egg that has the potential to develop into a foetus.
- Embryonic stem cells
Unspecialised cells from the embryo that have the potential to mature and develop into a wide variety of specialised cell types. They are obtained from embryos that develop from eggs that have been fertilised by sperm in the laboratory (in vitro fertilisation – IVF) and then donated for research purposes with informed consent of the donors. They have the ablility to multiply in number indefinitely when grown in the laboratory which makes them a useful tool for research.
A protein found in the nuclear membrane of muscle cells. Emerin is absent in individuals with the X-linked recessive form of Emery-Dreifuss muscular dystrophy.
- Emery-Dreifuss muscular dystrophy
A genetic disorder characterised by muscle wasting and contractures. The heart may also be affected. Emery-Dreifuss muscular dystrophy 1 is associated with mutations in the emerin gene; Emery-Dreifuss muscular dystrophy 2 is linked to mutations in the lamin A/C gene.
A protein which initiates, facilitates or speeds up a reaction. Almost all of the processes that occur in our body require enzymes. Examples include the digestion of food, the growth and building of cells, and all reactions involving transformation of energy.
Genes are divided into regions called exons and introns. Exons are the sections of DNA that code for the protein and they are interspersed with introns which are also sometimes called ‘junk DNA’.
- Exon skipping
A therapeutic approach currently in clinical trial for Duchenne muscular dystrophy. It involves small pieces of DNA called ‘molecular patches’ which mask a portion of a gene where there is a mistake, or mutation. The name comes from ‘exon’ which are the segments that genes are divided into. For example, the dystrophin gene (which is affected in Duchenne muscular dystrophy) is divided into 79 exons. It is called ‘skipping’ because the molecular patch causes the body to ignore or skip-over an exon. For a more detailed explanation please see: What is exon skipping and how does it work?
- Extracellular matrix
The extracellular matrix surrounds the cells in our bodies. The matrix is made of scaffolding proteins – forming a structured network. It is important for cell structure and stability and also plays a role in communication between cells.
- Facioscapulohumeral muscular dystrophy (FSHD)
A muscle wasting condition, caused by a genetic defect. The name describes the distribution of weakened muscles: ‘facio’ – facial; ‘scapulo’ – shoulder blade; ‘humeral’ – upper arm.
Great tiredness caused especially by hard work or effort.
- Foetus (fetus)
The term used for an unborn baby after the eighth week of development until birth.
- Gene regulation
Increasing or decreasing the amount of protein produced by a gene.
- Gene therapy
Treatment of a disease by introducing a new gene into a cell. The new gene may be used to replace a function that is missing because of a defective gene. Viruses are often used to deliver the new gene into the cells.
Genes are made of DNA and each carries instructions for the production of a specific protein. Genes usually come in pairs, one inherited from each parent. They are passed on from one generation to the next, and are the basic units of inheritance. Any alterations in genes (mutations) can cause inherited disorders.
- Genetic counselling
Information and support provided by a specialist, usually a doctor or nurse, to people who have genetic conditions in their families, or are concerned about a genetically transmitted condition.
- Genetic disorders
Conditions resulting from alterations in the genetic make-up of an individual. They may be caused by defects in single genes or whole chromosomes, parts of which may be lost, duplicated, misplaced or replaced. Genetic disorders can be caused by defects in one or more genes.
- Genetic markers
A DNA sequence used to identify a particular location on a particular chromosome.
- Genetic testing
The examination of an individual’s genetic material to identify any faults which could cause a disorder.
The complete set of genes in an organism.
A protein with a carbohydrate (sugar) molecule attached.
- Hereditary motor and sensory neuropathies
A group of genetic disorders which affect the peripheral nerves (the nerves that run from the spinal cord to all other parts of the body) or the myelin sheath which surrounds these nerves. This group of disorders includes Charcot-Marie-Tooth disease which is characterised by progressive weakness and wasting of the muscles in the calves, lower arms, hands and feet.
- Human genome project
The internationl project which aimed to understand the genetic makeup of humans. A primary goal of the project was to determine the sequence of chemical base pairs which make up DNA and to identify and map the approximately 20,000 to 25,000 genes of the human genome. This 13 year project was completed in 2003, but analysis of the data will continue for many years.
- Immune response
The body’s response to ‘foreign’ material, such as bacteria or a virus. The immune system includes certain types of white blood cells. It also includes chemicals and proteins in the blood, such as antibodies.
- Immunosuppressive therapy
The use of drugs to decrease the activity of the body’s immune system. This is used to prevent the body rejecting a transplanted organ or to treat autoimmune conditions.
- In vitro fertilisation (IVF)
A process by which eggs are fertilised by sperm outside the womb. The fertilised egg is then transferred to the patient’s womb to try to establish a successful pregnancy.
- In-frame mutation
A mutation where the protein production machinery can continue to read the DNA sequence after the mutation. It may result in a protein with sections missing or substituted, but since the majority of the protein remains intact it may still be partially functional. This generally results in milder symptoms such as those seen for Becker muscular dystrophy. See also out-of frame mutation.
- Induced pluripotent stem (iPS) cells
Stem cells artificially produced in the laboratory by ‘reprogramming’ adult cells such as skin cells.
Induced: refers to the fact that these skin cells have been ‘reprogrammed’ by altering their genes and encouraging them to revert to a state where they have a non-specialised role within the body.
Pluripotent: refers to a cell which has the ability to develop into any specialised cell type in the body.
Stem cells: a type of cell that has the ability to regenerate itself indefinitely and which can specialise to produce a range of cells, each with different functions.
The body’s reaction to injury or infection. Inflammation results in redness, pain, swelling, and warmth, due to increased blood flow in the traumatized area. It is a protective attempt by the body to remove whatever is causing the injury or infection (for example a splinter in your finger or a virus in your lungs) as well as initiate the healing process.
The process by which an individual acquires characteristics from his or her parents or ancestors.
Genes are divided into regions called exons and introns. Exons are the sections of DNA that code for the protein and they are interspersed with introns which are also sometimes called ‘junk DNA’. Although introns do not directly code for the protein they may have structural and regulatory roles.
The process of being exposed to radiation. Irradiation is used to treat cancer and is known as radiation therapy or radiotherapy.
- Lamin A/C
A protein found in the inner membrane surrounding a cell’s nucleus. A lack of lamin A/C is associated with Emery-Dreifuss muscular dystrophy 2, limb girdle muscular dystrophy type 1B, Charcot-Marie Tooth disease type II and four other disorders not related to muscular dystrophy.
- Lay panel
is a group of people who themselves have a neuromuscular condition or their families are affected by muscle disease. The purpose of the panel is to give affected families a voice in the process of deciding which research receives grants from Muscular Dystrophy UK.
- Limb girdle muscular dystrophy (LGMD)
A group of conditions affecting primarily the limb girdle muscles (i.e. the muscles around the shoulders and hips). There are at least 19 different forms of LGMD and the genes involved in 15 of these have been identified. The symptoms of the condition appear differently in different people, with regard to age of onset, areas of muscle weakness, heart and respiratory involvement, rate of progression and severity.
- Linkage studies
Tests carried out on various family members to establish how a particular piece of genetic information ‘runs through’ a family. They can sometimes be used to predict if an individual has inherited a faulty gene.
A large white blood cell that acts as a vacuum, sucking up cell debris from damaged tissues and foreign material such as bacteria and viruses. It also releases substances that stimulate other cells of the immune system.
- Magnetic resonance imaging (MRI)
A non-invasive body imaging procedure that uses powerful magnets and radio waves to construct pictures of the internal structures of the body
- Manifesting carrier
A female carrier of an X-linked condition (such as Duchenne muscular dystrophy) who exhibits symptoms such as muscle weakness.
- mdx mouse
A mouse model of Duchenne muscular dystrophy. These mice have a mutation in the dystrophin gene – the gene that is mutated in boys with Duchenne. The muscles of these mice have many features in common with the muscles of boys with Duchenne.
- Mechanical ventilation
The medical procedure used to aid or replace breathing when a patient is unable to breathe adequately themselves. This usually involves a ventilator machine or manual bag compression.
A type of average used by statisticians. It is the middle number in an ordered sequence of numbers- for example the 4 is the median of 1, 3, 4, 8, and 9. The advantage of using this type of average is that it isn’t influenced by any unusually low or high values (outliers).
The barrier between the inside and outside of a cell or between two compartments of a cell. Membranes act like a skin to protect cells and control which substances leave or enter them.
- Merosin (laminin alpha 2)
The protein absent in congenital muscular dystrophy type 1A. This protein is located on the outside surface of muscle cells and is essential for maintaining the structure and function of muscles.
Small structures inside our cells that act like ‘batteries’. They convert the energy from the food that we eat into the energy that the cells are able to use for their everyday processes. Mitochondria have their own DNA, which is inherited from the mother and contains several genes important for energy production.
- Mitochondrial myopathies
Genetic disorders of muscle which affect the mitochondria- the ‘energy factories’ of cells. Without a sufficient supply of energy the cells fail to function properly, causing disease.
- Molecular patch
A short piece of genetic material (DNA or RNA) which can bind to a specific gene and change how the code is read. They can be used to mask errors in the genetic code, this is known as exon skipping and this is in clinical trial for Duchenne muscular dystrophy. Also called an antisense oligonucleotide which is often abbreviated to AO or AON.
Two or more atoms chemically bonded together. For example, water is a molecule made up of two hydrogen atoms and one oxygen atom bonded together.
- Morpholino antisense oligonucleotide
Antisense oligonucleotides are small pieces of DNA which can bind to a specific piece of genetic code and change how the code is read. They are termed morpholino if the small pieces of DNA have been chemically modified so that they are not easily degraded by the body. They can be used as a ‘molecular patch’ to overcome small errors in the genetic code, or to block parts of the gene.
- Motor neuron
Nerves that carry signals from the central nervous system to the muscle. They are responsible for telling the muscle to contract. The motor neurons are affected in spinal muscular atrophy (SMA).
- Mouse model
Is a strain or breed of mouse which has a disease that is similar to a human disorder. For example the ‘mdx’ mouse model of Duchenne muscular dystrophy has a mutation in the dystrophin gene and the muscles of these mice have many features in common with the muscles of boys with Duchenne muscular dystrophy.
- Muscle cell
The basic unit of muscle fibre.
- Muscle fibre
The basic unit of muscle tissue, formed by the fusion of groups of muscle cells.
A permanent change in the DNA code that makes up a gene. Depending on where the mutation occurs, and the type of mutation, they can either have no effect or result in genetic diseases such as muscular dystrophy . Mutations can be passed on from generation to generation.
- Myasthenia gravis
A chronic, autoimmune disorder which causes muscle weakness and excessive muscle fatigue. It is an autoimmune condition where the immune system instead of attacking infections such as viruses, mistakenly attacks proteins in the body. In myasthenia gravis the immune system specifically attacks proteins on the muscle called ‘acetylcholine receptors’ (AChRs) which normally receive the signals from nerves which tell the muscles to contract.
The insulating material that surrounds nerves and allows the quick conduction of nerve impulses.
A cell that is a precursor to muscle fibers.
- Myoblast transfer
A potential method of treatment for some forms of muscular dystrophy, which involves transplanting billions of healthy donor cells into dystrophic muscle. Sometimes referred to as cell therapy.
the use of an apparatus which measures muscle contraction.
Any disease of the muscles that is not caused by nerve dysfunction.
A condition affecting muscle, usually without involvement of the nerves.
A protein that helps mammals regulate muscle building, acting as a signal for muscles to stop consuming resources and stop growing. Scientists think that by blocking the activity of myostatin, it might be possible to build up muscle size and strength in people with muscle disease.
A condition in which muscles are slow to relax after contracting (muscle stiffness).
- Myotonic dystrophy
A genetic disorder with symptoms of muscle stiffness, progressive muscle wasting and weakness, especially affecting the face, jaw and neck muscles. Caused by an increased number of repeated units of genetic material (called triplet repeats) within a gene. Age at onset is very variable. Symptoms may appear at any time from birth to later in life.
- Myotonin protein kinase
The gene which is mutated in patients with myotonic dystrophy 1 (DM1). In DM1 a three letter code in this gene is repeated many hundreds of times instead of the usual number which is less than thirty. This repeated section of genetic code interferes with the functions of other proteins in the cell. The gene is also known as myotonic dystrophy protein kinase (DMPK).
The protein absent in individuals with myotubular (centronuclear) myopathy.
A protein found in skeletal muscle thought to control the thin filaments within the muscle. Individuals with nemaline myopathy have a reduced level of nebulin.
- Nemaline myopathy
A very rare genetic condition that causes muscle weakness from birth. Difficulties with feeding and breathing are common.
The cord-like bundles of fibres or “wires” which transmit signals around the body. Nerves form a network of pathways for conducting information throughout the body. For example, the brain sends a signal down the nerves to tell a muscle to contract.
- Neuromuscular junction
Where a muscle fibre and a nerve meet.
Also called a “nerve cell”. The neurons are responsible for transmitting messages throughout the body. They are important for both involuntary functions (like your heartbeat) and voluntary functions (like walking).
A medical term describing disorders of the nerves which carry signals to and from the muscles in the legs and arms. These nerves are known as the peripheral nerves. Charcot-Marie-Tooth disease is one example of a neuropathy.
The most abundant type of white blood cells in humans which help the body fight infection. Neutrophils are one of the first types of cells to migrate toward the site of inflammation by following chemical signals given off by the damaged or infected tissue. They are capable of ingesting and killing bacteria and viruses or other particles.
- Next generation sequencing
A cutting edge technology that allows researchers to ‘read’ the whole of an individual’s genome. Researchers have recently started to use it for finding new genes and diagnosing genetic conditions more accurately.
- Nonsense mutation
A change in the DNA which causes a premature stop signal to occur in a gene. When this happens the protein is not produced.
The structural unit (building block) of DNA and RNA.
- Nucleus (plural nuclei)
The control centre of a cell, which contains the cell’s chromosomal DNA.
- Oculopharyngeal muscular dystrophy
Oculopharyngeal muscular dystrophy(OPMD) is a genetic condition in which there is progressive muscle weakness in the eye and throat muscles. It is caused by a faulty gene (PABP2) and is an autosomal dominant disorder.
A short sequence of genetic material (DNA or RNA).
- Open-label clinical trial
A type of clinical trial in which both the researchers and participants know which treatment is being given. This contrasts with single blind and double blind clinical trial, where participants are not aware of what treatment they are receiving (researchers are also unaware in a double blind trial).
Difficulty in moving the eyes.
Devices or aids to prevent or assist movement of the spine or limbs.
- Out of frame mutation
The removal or addition of one or more nucleotides which severely disrupts the production of the protein, e.g. some Duchenne muscular dystrophy mutations. The result of this is that the protein produced is completely non-functional or not produced at all. Also known as ‘frame-shift mutation’. See also In-frame mutation. For a more in-depth explanation please see our FAQ ‘What is exon skipping and how does it work?’.
- Oxidative capacity
This is a measure of a muscle’s maximal capacity to use oxygen in microlitres of oxygen consumed per gram of muscle per hour. The higher the oxidative capacity the healthier the muscle is.
Study of the changes in tissues and organs of the body which cause disease.
- Phase 0 clinical trial
A trial conducted very early in a small number of patients (perhaps less than 10). The purpose of phase 0 trials is to discover the therapeutic potential of a drug and to evaluate whether the drug development is worth continuing further. Unlike the phase I clinical trials, phase 0 trials are not used to evaluate in detail the drug dosage, treatment safety or side effects.
- Phase I clinical trial
The first stage of testing a drug or treatment in human subjects. Researchers test a new drug or treatment in a small group of people – often healthy volunteers rather than patients. This phase is to evaluate the treatment’s safety, determine a safe dosage range, and identify side effects. About 70 percent of experimental drugs pass the initial phase of testing.
- Phase II clinical trial
This is designed to test how well the drug or treatment works as well as to continue safety assessments on a larger group of patients (20-300). When the development process for a new drug fails, this usually occurs during Phase II trials when the drug is discovered not to work as planned, or to have toxic effects. Only one-third of experimental drugs successfully complete both phase I and phase II studies.
- Phase IIa and Phase IIb clinical trial
Phase II studies are sometimes divided into Phase IIa and Phase IIb. Phase 2a is specifically designed to assess dosing requirements (how much drug should be given), whereas Phase IIb is specifically designed to study efficacy (how well the drug works at the prescribed dose(s)).
- Phase III clinical trial
This tests a new drug on a larger number of patients after it has been shown to be effective in a phase II trial. Phase III trials often enroll large numbers of people and may be conducted at many centres nationally or internationally. These phase III studies allow researchers to determine the tolerance and the effectiveness of the product and therefore to assess the benefit/risk ratio of the drug. Seventy to 90 percent of drugs entering phase III will be candidates for a marketing approval application.
- Phase IV clinical trial
Evaluates the long term risks and benefits of a drug or treatment once it’s available on the market. They are designed to detect any rare or long-term effects in a much larger patient population and over a longer time period than was possible during the Phase I to III clinical trials.
An inactive substance designed to resemble the drug being tested. It is used to rule out any benefits a drug might exhibit because the recipients believe they are taking it.
- Placebo-controlled clinical trial
A clinical trial where some of the participants receive a placebo treatment – an inactive substance designed to resemble the drug being tested. Usually these trials are “blinded” so that the participants and the researchers do not know who is receiving the real treament and who is receiving the placebo.This clinical trial design is used to rule out any benefits a drug might exhibit because the recipients believe they are taking it and to eliminate any bias on the part of the researchers measuring the benefit of the treatment.
A condition where the lung tissue becomes inflamed and filled with fluid. This can be caused by infection or injury to the lungs, and causes symptoms of coughing, chest pain, and difficulty in breathing.
- Point mutation
A type of genetic mutation that causes a single building block of DNA (nucleotide) to be replaced with a different one.
- Pre-implantation genetic diagnosis (PGD)
The testing of very early embryos for a specific genetic condition before they are implanted into the womb. Couples undergo standard in vitro fertilisation (IVF) during which eggs are fertilised by sperm outside the womb. The embryos are grown in the laboratory until they consist of eight cells. A single cell is then removed from the embryo and the DNA is tested for the presence of the mutation gene.
- Prenatal testing
Testing for diseases or conditions in a foetus or embryo before it is born. This is done by analysing the DNA in a sample of the fluid or tissue surrounding the foetus. The sample is collected by procedures called amniocentesis or chorionic villus sampling.
Predicted course and outcome of a disorder.
- Promoter region
A segment of DNA which ‘switches on’ an associated gene.
Proteins are required for the structure, function, and regulation of the body’s cells, tissues, and organs. They are the building blocks of our bodies. Each protein has unique functions. Proteins are large molecules composed of one or more chains of amino acids in a specific order. The order is determined by the gene that codes for the protein.
- Protein complex
A protein complex is the name given to a group of proteins which come together to form a single larger structure. Often the complex takes on a single role, with different proteins in the complex being responsible for different aspects of that role.
Close to the centre of the body.
the lungs. Clinicians measure pulmonary function, or lung function to assess how well a patient is able to breath.
- Pump priming grant
Funding to give researchers the opportunity to investigate new and innovative ideas and technologies for one year to obtain proof of principle prior to applying for further funding.
- Randomised controlled trial
A clinical trial where treatments and placebo are allocated randomly to participants rather than by conscious decisions of clinicians or patients.
- Reading frame
The genetic code consists of a sequence of letters which are read in groups of three. There are three possible ways of reading the sequence depending on the starting point. If the code reads AGCAGCAGC, for example, the three reading frames are AGC AGC, GCA GCA and CAG CAG.
A form of inheritance in which a faulty copy of a gene is inherited from each parent (in order to develop the disorder an individual has to have two copies of the faulty gene). Includes X-linked recessive and autosomal recessive modes of inheritance.
- Revertant fibres
Occasional fibres seen in muscle biopsies, which contain forms of dystrophin, even though the genetic mutation should prevent the production of this protein. The fibres are generally too rare to be useful.
The machinery of the cell which builds proteins.
Ribonucleic acid, a substance very similar to DNA. When a gene is ‘switched on’, RNA carbon copies of the gene’s code are made. The RNA moves outside the nucleus where they direct the manufacture of proteins. DNA can be thought of as a recipe book in the library that you can’t take out. RNA is a photocopy of a recipe that you can take home to cook something in your kitchen (making the protein).
- Sarcoglycan genes
Genes associated with limb girdle muscular dystrophy types 2C, 2D, 2E and 2F. Mutations in these genes result in the reduction or absence of the sarcoglycan proteins. There are four sarcoglycan genes – gamma-sarcoglycan, alpha-sarcoglycan, beta-sarcoglycan and delta-sarcoglycan.
- Sarcoglycan proteins
There are four sarcoglycan proteins – g-sarcoglycan, a-sarcoglycan, b-sarcoglycan and d-sarcoglycan – which link the inside and outside of the cell across the membrane. They bind to other components in the dystrophin-glycoprotein complex.
Limb girdle muscular dystrophies which involve the sarcoglycan genes.
A membrane or skin surrounding each muscle fibre.
- Satellite cells
Cells which repair damaged muscle fibres. Also called muscle stem cells. Usually dormant, the cells become activated and rapidly increase, when the muscle fibre is damaged or needs to grow. They produce large numbers of myoblasts that fuse together with surviving parts of the damaged muscle fibre to fill any gaps. Satellite cells are a special type of stem cell.
Curvature of the spine.
- Self cells
Cells from your own body.
- Sex chromosomes
The X and Y chromosomes determine the sex of an individual. Females have two X chromosomes; males have an X and Y chromosome.
- Signalling pathway
A series of chemical signals through which cells communicate with their surroundings.
- Six minute walk test
A standardised way of measuring a patients mobility. It involves measuring how far a person can walk in six minutes.
- Skeletal muscle
A type of muscle which is striated in appearance and usually attached to tendons. It is used to create movement, by applying force to bones and joints; via contraction. Other types of muscle include cardiac (heart) and smooth (blood vessels, stomach, intestines) muscle.
- SMN gene (Survival Motor Neuron gene)
Mutations in the SMN gene are the cause of some forms of spinal muscular atrophy (SMA). There are two types of SMN genes- SMN1 and SMN2.
- SMN protein (Survival Motor Neuron protein)
Produced by the SMN genes and reduced in individuals with spinal muscular atrophy. This protein is necessary for normal motor neuron function. Evidence suggests that a lack of SMN might also directly affect muscle cells.
- Spinal and bulbar muscular atrophy
Spinal and bulbar muscular atrophy is a genetic condition caused by mutations in the androgen receptor gene. It affects mainly men and leads to progressive muscle weakness and atrophy.
- Spinal Muscular Atrophy
Genetic conditions resulting in progressive muscle wasting and loss of lower motor neurons in the spinal cord. Spinal Muscular Atrophy is caused by the absence of SMN1 genes and follows an autosomal recessive pattern of inheritance.
The removal of introns from a section of genetic code to leave only the useful exons.
Sporadic conditions are not inherited or passed onto subsequent generations.
- Stem cells
Cells that have not yet specialised to form a particular cell type, and can still become muscle cells or other types of cell.
- Stop codon
A section of DNA code that terminates protein production.
Spread throughout the body and affecting many or all body systems or organs.
- T cell
A type of white blood cell that is of key importance to the immune system. T cells seek out and destroy foreign material in the body such as bacteria and viruses. They are also known as T lymphocytes.
The end of a chromosome.
A group of cells that carry out a particular job or function.
The first stage in the production of proteins, when information in DNA is transferred to RNA.
Genes integrated into the germ line (reproductive cells) of transgenic organisms.
An organism which has had genes from another organism added into its genome.
The process after transcription, when proteins are made from the instructions on a section of RNA.
- Translational research
The application of knowledge gained from scientific medical research in the laboratory to studies in humans.
An experimental run. Testing certain therapies on animals or humans, for example.
The use of reflected sound waves to ‘see’ a hidden object. Now widely used in medicine to obtain images of muscle structure, internal organs or an unborn child.
A protein similar to dystrophin. Utrophin is present in everyone – including individuals with Duchenne muscular dystrophy – but at very low levels. Scientists have shown that increasing the level of utrophin protein can compensate for the loss of dystrophin in a mouse model of Duchenne muscular dystrophy.
A vehicle for transferring genetic material into a cell. Currently, the most common vector for gene therapy is a virus that has been genetically altered to carry normal human DNA. Non-viral vectors include plasmids into which specific genetic material has been added.
Little sacs that store and transport substances within the cell, as well as into and out of the cell. Vesicles have specialised functions depending on what materials they contain, for example they might transport food into the cell, excrete waste out of the cell or release chemical signals for communication with other cells.
Viruses consist of genetic materials (DNA or RNA) surrounded by a protective coat of protein. They are capable of latching onto cells and getting inside them. Viruses are too small to be seen by the naked eye. They can’t multiply on their own, so they have to invade a ‘host’ cell and take over its machinery in order to be able to make more virus particles. They can be made harmless by changing their genetic code.
- Walker-Warburg Syndrome (WWS)
This is a rare form of congenital muscular dystrophy that is associated with brain and eye abnormalities. It is the most severe form of congenital muscular dystrophy, with most affected children not surviving beyond three years of age.
- White blood cells
Cells of the immune system defending the body against both infectious disease and foreign materials. Five different types of white blood cells exist. White blood cells are also known as leukocytes.
- X-linked inheritance
A form of inheritance where a gene lies on the X chromosome. X-linked genes can be dominant, but are usually recessive. Girls who carry an altered gene are usually not affected, since they have a second, normal copy of the gene. They are carriers, however, and can pass the affected gene on in 50% of their pregnancies. Boys who have only one X chromosome do not have a second normal copy of the gene, so will be affected by the disorder. They will pass on the altered gene to all of their daughters, who will be carriers, but to none of their sons.
- Zebrafish model
A tropical freshwater fish belonging to the minnow family. There are many advantages of using zebraﬁsh to study human disease and development: Firstly, zebraﬁsh are small in size, and are easy to keep and breed. They are more similar to humans than you think; many genes are shared between humans and zebraﬁsh, including the genes used to make muscles. The genes of zebraﬁsh can be modified, this means we can create mutations in genes which cause human diseases, such as muscular dystrophy. Importantly, zebrafish embryos are transparent, so we can easily observe their muscles developing. Finally, the embryos can be used too look for drugs which may prevent or slow the progression of a disease.
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