Acetylcholine
Is a chemical substance which helps to transmit a signal from the nerve to the muscle causing it to contract.
Acetylcholine receptors or AChRs
Are proteins found in the membrane surrounding the muscle cell to which acetylcholine binds.
Adeno-Associated Virus or AAV
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 affective vehicle for delivering genes into cells such as in gene therapy.
Amino acids
Are the ‘building blocks’ of proteins. The sequence of amino acids determines the shape, properties and role of the protein.
Androgen and Androgen receptor
Any one of several hormones, such as testosterone, that promote the development of male characteristics.
An androgen receptor is 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
Are animals with conditions similar to those affecting humans, which can be used to study disease processes and test potential therapies. They can 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, with the relevant ethical permissions.
Antibodies
Are proteins made by the body to protect itself from foreign and sometimes dangerous substances such as bacteria or viruses.
Antisense Oligonucleotide
Are 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 both in clinical trial and a small number have approvals for Duchenne. 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.
Apoptosis
is 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.
Atrophy
Refers to muscle wasting.
Autoimmune Disorders
Are conditions in which the immune system produces antibodies that attack the body’s own cells, for example, dermatomyositis, polymyositis and myasthenia gravis.
Autologous
Is 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).
Axon
Refers to the long, hair-like extension of a nerve cell that carries a message to the target cell such as a muscle cell
Becker (BMD)
Is a genetic disorder in which the muscle cells break down, causing progressive muscle weakness. Becker muscular dystrophy usually affects only boys and men and is caused by a lack of dystrophin protein. The condition resembles Duchenne but is usually less severe.
Biomarker
Is 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.
Biopsy
Refers to the removal of a sample of tissue such as muscle from the body. The tissue is examined under a microscope to assist in diagnosis.
Bilevel positive airway pressure (BPAP / BiPAP)
Is a type of non-invasive ventilation that helps with breathing by providing a flow of air delivered through a face mask. The air is pressurised 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.
Carbohydrates
Is an essential structural component of living cells and source of energy for animals; includes simple sugars as well as complex carbohydrates such as starches.
Cardiac
Relates to the heart.
Cardiomyopathy
Relates to 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.
Carrier
Is the word used to describe 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
Is 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.
Cell
Refers to 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
Is 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
Is 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
Refers to the cells grown in a petri dish in the laboratory that can be used to study disease processes and test potential therapies
Central nervous system (CNS)
Refers to the brain and spinal cord.
Chromosomes
Refer to cylindrical shaped bundles of DNA in the cell nucleus which is the core or centre 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.
Congenital
Means present at birth, or soon afterwards.
Contracture
Refers to an abnormal, often permanent contraction or shortening of the muscle or tendon.
Corticosteroid or glucocorticoid steroid
Refers to a 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 and Becker. 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 steroids used in Australia are prednisolone (prednisone in the USA) and Deflazacort. These are not “anabolic steroids” which is what athletes use illegally to build up muscle- these do not have an effect in Duchenne. Sometimes also referred to as ‘glucocorticoids.
Creatine kinase or CK
Is a type of protein found in muscle. High levels of creatine kinase in a blood test indicate muscles are damaged due to disease or injury, the creatine kinase leaks into the bloodstream and cause a high reading which the Dr will use to request further genetic testing for a dystrophinopathies such as Duchenne or Becker and can be elevated in carrier females.
CRISPR or Clustered Regularly Interspaced Short Palindromic Repeats
Is a technology that can be used to edit genes. The essence of CRISPR is a way of finding a specific bit of DNA inside a cell. After that, the next step in CRISPR gene editing is usually to alter that piece of DNA which are the hallmark of a bacterial defence system that forms the basis for CRISPR-Cas9 genome editing technology.
Cytoplasm
Is 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
Results from the loss of genetic material from a chromosome or gene.
Diagnosis or diagnostic criteria
Refer to the guidelines, rules or characteristics used by a clinician, pathologist, geneticist to diagnose somebody with a particular condition.
Diaphragm
Refers to the essential muscle used by the respiratory system for breathing.
Deoxyribonucleic acid or 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, recipe, or 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
Is the 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. This is commonly the cause of a female with the manifesting symptoms and characteristics of Duchenne.
Double blind study / trial
Is a clinical trial where neither the researchers nor the patients know whether they are receiving the placebo or the trial drug.
Duchenne / DMD / Duchenne muscular dystrophy
Is 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, this can occur anywhere in the chromosome or gene.
Dysphagia
Refers to difficulty in swallowing.
Dystrophic
Relates to muscles affected by Duchenne or Becker which are described as dystrophic.
Dystrophin
Is the protein missing in people who have Duchenne and reduced in those who have Becker. 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 and cannot repair themselves.
Dystrophin-glycoprotein complex
Is 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.
Dystrophy
Originates from two Greek words, ‘dys’ meaning faulty and ‘trophe’ meaning nourishment, muscular dystrophy refers to a group of disorders characterised by progressive muscle weakness and loss of muscle tissue.
Echo or echocardiogram
Is the use of ultrasound to produce images of the heart.
ECG or electrocardiography
Is a test which records the electrical activity of the heart through electrodes attached to the skin.
EMG or electromyography
Is 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.
Embryonic stem cells
Are unspecialised cells from an embryo that have the potential to mature and develop into a wide variety of specialised cell types.
Enzyme
Is a protein which initiates, facilitates or speeds up a reaction. Almost all of the processes that occur in our body require enzymes. Examples of an enzyme include the digestion of food, the growth and building of cells, and all reactions involving transformation of energy.
Exon
Refers to when 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.
Exon skipping
Is an approved therapy which for a number of mutations in Duchenne and also remain in clinical trial for Duchenne. It involves small pieces of DNA called ‘molecular patches or band aids’ 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 is divided into 79 exons. It is called ‘skipping’ because the molecular patch or band aid causes the body to ignore or skip-over an exon.
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.
Fatigue
Refers to tiredness caused especially by hard work or effort and is commonly used in Duchenne and Becker to describe the tiredness experienced by those with the condition.
Gene regulation
Is increasing or decreasing the amount of protein produced by a gene.
Gene therapy
Refers to a 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 specific 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
Refers to the information and support provided by a genetic counsellor, geneticist or specialist doctor to people who have genetic conditions in their families or are concerned about a genetic and or rare condition.
Genetic disorders
Are 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
Is a DNA sequence used to identify a specific location on a particular chromosome.
Genetic testing
Is the examination of an individual’s genetic material to identify any faults which could cause a disorder.
Genome
Refers to the complete set of genes in an organism.
Glycoprotein
Is a protein with a carbohydrate (sugar) molecule attached.
Immune response
Is 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
Is 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-frame mutation
Is 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 in Becker.
Induced pluripotent stem cells or iPS
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.
Inflammation
Is 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.
Inheritance
Is the process by which an individual acquires characteristics from his or her parents or ancestors.
Intron
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 protein, they may have structural and regulatory roles.
Macrophage
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.
MRI or Magnetic resonance imaging
Is a non-invasive body imaging procedure that uses powerful magnets and radio waves to construct pictures of the internal structures of the body and are commonly used in dystrophinopathies to perform a heart examination.
Manifesting carrier
Refers to a female carrier of an X-linked condition such as Duchenne who exhibits symptoms such as muscle weakness, these females have a dystrophinopathies.
MDX mouse
Is a mouse model of Duchenne. These mice have a mutation in the dystrophin gene – the gene that is mutated in boys with Duchenne and 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, manual bag or ambu bag compressions.
Membrane
Is 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.
Mitochondria
Refer to 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.
Molecular patch
Is 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. Also called an antisense oligonucleotide which is often abbreviated to AO or AON.
Molecule
Refers to 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.
Mouse model
Is a strain or breed of mice which has a disease that is similar to a human disorder. For example, the ‘mdx’ mouse model of Duchenne 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.
Muscle cell
Is the basic unit of muscle fibre.
Muscle fibre
Is the basic unit of muscle tissue, formed by the fusion of groups of muscle cells.
Mutation
Is 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 Duchenne and Becker. Mutations can be passed on from generation to generation.
Myelin
Is the insulating material that surrounds nerves and allows the quick conduction of nerve impulses.
Myoblast
Is the cell that is a precursor to muscle fibres.
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.
Myometry
Is the use of an apparatus which measures muscle contraction.
Myostatin
Is 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.
Nerves
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
Is where a muscle fibre and a nerve meet.
Neuron
Is 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).
Neutrophil
Is 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
Is a technology that allows researchers to ‘read’ the whole of an individual’s genome. Researchers and pathologists use it for finding new genes and diagnosing genetic conditions more accurately.
Nonsense mutation
A nonsense mutation is a point mutation, where a single nucleotide (or base of DNA) is replaced by a different one that creates what is called a premature stop codon. Stop codons give the specific instruction of terminating the synthesis of the protein at that site. When a nonsense mutation occurs, we therefore have a premature termination of the protein at that specific site preventing the production of a full-length, functional protein. Nonsense mutations in the DMD gene account for a proportion of 10-15% of boys with Duchenne.
Nucleotide
Is the structural unit or building block of DNA and RNA.
Nucleus (plural nuclei)
Is the control centre of a cell, which contains the cell’s chromosomal DNA.
Oligonucleotide
Is a short sequence of genetic material DNA or RNA.
Open label clinical trial
Is 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.
Orthotics or orthoses
Are devices or aids to prevent or assist movement of the spine or limbs. In Duchenne and Becker these are commonly known as leg splints from the knee to ankle to aid keeping the muscles stretched and reduce the chance of contractures.
Out of frame mutation
Is the removal or addition of one or more nucleotides which severely disrupts the production of the protein, e.g. some Duchenne 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’.
Oxidative capacity
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.
Pathology
Is the study of the changes in tissues and organs of the body which cause disease.
Phase 0 clinical trial
Refers to 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 1 clinical trial
Is 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 2 clinical trial
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 2a and Phase 2b clinical trials
Phase 2 studies are sometimes divided into Phase 2a and Phase 2b. Phase 2a is specifically designed to assess dosing requirements (how much drug should be given), whereas Phase 2b is specifically designed to study efficacy (how well the drug works at the prescribed dose(s)).
Phase 3 clinical trials
Tests a new drug on a larger number of patients after it has been shown to be effective in a phase 2 trial. Phase 3 trials often enrol large numbers of people and may be conducted at many centres nationally or internationally. These phase 3 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 3 will be candidates for a marketing approval application.
Phase 4 clinical trials
Evaluate 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 1 to 3 clinical trials.
Placebo
Is 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
Is 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 treatment 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.
Pneumonia
Is 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
Is 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 or PGD
Is the testing of very early embryos for a specific genetic condition such as Duchenne and Becker, 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 in the gene.
Prenatal testing
Is 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.
Prognosis
Predicted course and outcome of a disorder.
Promotor region
Is a segment of DNA which ‘switches on’ an associated gene.
Protein
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.
Proximal
Refers to close to the centre of the body.
Pulmonary
Refers to the lungs. Clinicians measure pulmonary function, or lung function to assess how well a patient is able to breath.
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.
Recessive
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.
Ribosome
The machinery of the cell which builds proteins.
RNA or Ribonucleic acid
Is 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).
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.
Scoliosis
Refers to curvature of the spine.
Self-cells
Are cells from your own body.
Sex chromosomes
Are 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
Is a series of chemical signals through which cells communicate with their surroundings.
Six-minute walk test
Is a standardised way of measuring a patient’s mobility. It involves measuring how far a person can walk in six minutes.
Skeletal muscle
Is 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 muscles such as blood vessels, stomach, intestines.
Splicing
Is the removal of introns from a section of genetic code to leave only the useful exons.
Sporadic
Refers to conditions that are not inherited or passed onto subsequent generations.
Stem cells
Are 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
Is a section of DNA code that terminates protein production.
Systemic
Is the 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.
Telomere
Is the end of a chromosome.
Tissue
Is a group of cells that carry out a particular job or function.
Transcription
Is the first stage in the production of proteins, when information in DNA is transferred to RNA.
Transgene
Refers to genes integrated into the germ line reproductive cells of transgenic organisms.
Transgenic
Refers to an organism which has had genes from another organism added into its genome.
Translation
Refers to the process after transcription, when proteins are made from the instructions on a section of RNA.
Translational research
Is the application of knowledge gained from scientific medical research in the laboratory to studies in humans.
Trial
Is an experimental run. Testing certain therapies on animals or humans, for example.
Ultrasound
Is 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.
Utrophin
Refers to a protein similar to dystrophin. Utrophin is present in everyone – including individuals with
Duchenne
But at very low levels.
Vector
Is 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.
Vesicles
Are 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.
Virus
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 and 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.
White blood cells
Are 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-Chromosome Inactivation
This is a random process that happens individually in each of a female’s cells. One X chromosome, from the mother or father, is randomly switched off so that both males and females have only one working copy of the X chromosome in each cell. For manifesting carriers, the X chromosome with the Dystrophin gene variant might be active in most of their cells, causing symptoms.
X linked inheritance
Is 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 Duchenne. Importantly, zebrafish embryos are transparent, so we can easily observe their muscles developing. Finally, the embryos can be used to look for drugs which may prevent or slow the progression of a disease.