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"Echo": Echocardiogram. The use of ultrasound to produce images of the heart.

A

AAV: Adeno-associated virus. A small virus that infects humans and some other primate species. AAV is not currently known to cause disease and it provokes only a very mild immune response. This makes AAV a possible "vehicle" (vector) for delivering gene therapy into cells. AAV vectors are currently being tested in early clinical trials for SMA. (See also Vector and Virus.)

Abdomen: The part of the upper body, below the chest and above the pelvis, also known as the stomach or belly.

Acute: Sudden or rapid onset.

Adeno-associated virus : AAV. A small virus that infects humans and some other primate species. AAV is not currently known to cause disease and it provokes only a very mild immune response. This makes AAV a possible "vehicle" (vector) for delivering gene therapy into cells. AAV vectors are currently being tested in early clinical trials for SMA. (See also Vector and Virus.)

Aetiology: Also known as Etiology. Cause (of a disease / condition).

AFO: Ankle Foot Orthosis. Plastic brace to support / minimise contractures and / or aid standing.

Airway clearance: Removal of mucus and secretions from the airways in order to make breathing easier.

Allele: An alternative form of a single gene. For instance, people can have different alleles for the ability to tongue-roll - the recessive non-rolling allele or the dominant tongue-rolling allele.

Ambulant: Able to walk.

Amino acid: The individual building blocks of proteins. There are 20 different amino acids that are naturally incorporated into proteins. The specific order of the amino acids determines the structure and function of a protein.

Amniocentesis: The removal of a sample of amniotic fluid (the fluid around an unborn baby) for prenatal testing. Cells in the fluid can be tested for certain genetic disorders.

Amniotic fluid: The fluid surrounding a foetus in the womb.

Animal model: Animals used to study and model human diseases and to test potential therapies. The most widely used mammalian animal model is the mouse (see mouse model). These animals usually possess mutations in single genes that have been linked to specific human diseases. The mutation is either naturally occurring in the animals or the animals are genetically engineered in the laboratory to have the mutation.

Ankle Foot Orthosis : AFO. Plastic brace to support / minimise contractures and / or aid standing.

ANS: Autonomic Nervous System. The ANS forms part of the peripheral nervous system (PNS). It acts to subconsciously control the function of internal organs. Amongst other things, the ANS is involved in the regulation of heart rate, respiration rate, digestion and sweating.

Anterior: Front or forward.

Anterior Horn: The front part of the spinal cord where the cell bodies of the lower motor neurons are located. Long, slender projections of the motor neurons called axons migrate out from the anterior horn in large bundles of nerves in order to reach muscles.

Anterior Horn Cell: The nerve cells that make up the anterior horn of the spinal cord. Also known as lower motor neurons, these cells are the main cell type affected in SMA.

Antibodies: 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) with a precise sequence of nucleotides, which can bind to a specific gene and change how the genetic code is read. They can be used as tools to manipulate the genetic code. The approach being investigated for SMA is to try to affect how the Survival Motor Neuron 2 gene is read so that it produces more functional Survival Motor Neuron protein.

Apnoea: Short-term stopping of breathing.

Arterial Blood Gases: Measurement of oxygen and carbon dioxide in the blood by taking a blood sample from an artery, usually from the wrist.

Aspiration: Passage of food, fluid or vomit into the airway / lungs.

Aspiration pneumonia: Inflammation of the lungs and airways to the lungs (bronchial tubes) caused by the passage of foreign substances, usually food or fluid, into the ariways / lungs.

Atelectasis: Collapse of the lung (or part of it).

Atrophy: The wasting or shrinkage of a part of the body. SMA is called Spinal Muscular Atrophy because the lower motor neurons within the spinal cord degenerate, which leads to the wasting of skeletal muscles.

Autologous: The body’s own tissues, cells or DNA.

Autonomic Nervous System: ANS. The ANS forms part of the peripheral nervous system (PNS). It acts to subconsciously control the function of internal organs. Amongst other things, the ANS is involved in the regulation of heart rate, respiration rate, digestion and sweating.

Autosomal inheritance: Inheritance of a faulty gene on one of the autosomes - the chromosomes other than the sex chromosomes. Autosomal inheritance usually affects both males and females equally.

Autosomal recessive inheritance: When a genetic disorder is recessive, two faulty copies of a gene, one from each parent, must come together for the disease to occur. If a person has only one faulty copy, they do not usually have the symptoms of the disease, but are known as carriers because they can pass on the faulty gene to their children. A disease is autosomal when the faulty gene is found on one of the autosomes. SMA is an autosomal recessive condition.

Autosome: Any of the 22 pairs of chromosomes found in the human body that are not involved in the determination of sex. They are identical in both males and females. Each pair of autosomes (one from the father, one from the mother) contain genes for the same traits (characteristics).

Axon: The long, slender main projections of a nerve cell. Axons carry electrical impulses away from the cell body (where the nucleus is) to its target such as muscles.

B

Baseline: The starting point to compare other tests. A medical test taken primarily to provide a starting point against which future repetitions of the same test can be compared to show any changes in a patient's condition. For example, a baseline echocardiogram.

Bilevel positive airway pressure ventilation: BiPAP / BPAP. The name of a specific portable machine (ventilator) connected to a face mask that supplies respiratory support using two different levels of positive air pressure - when breathing in and out. The ventilator delivers the air at two different pressures which alternate: a higher pressure to breath in (called Inspiratory Positive Airway Pressure, or IPAP); and a lower pressure for breathing out (called Expiratory Positive Airway Pressure, or EPAP).

Biomarker: A biological substance found in blood, urine or other parts of the body that can be measured to give an indication of health or disease. A biomarker may be used to help diagnose a condition and monitor how it is progressing. It can also be used to see how well the body responds to a treatment.

Biopsy: The removal of a sample of tissue, such as muscle, from the body. The tissue is examined under a microscope to help with diagnosis.

BiPAP ventilation: Bilevel positive airway pressure ventilation (also known as BPAP ventilation). The name of a specific portable machine (ventilator) connected to a face mask that supplies respiratory support using two different levels of positive air pressure - when breathing in and out. The ventilator delivers the air at two different pressures which alternate: a higher pressure to breath in (called Inspiratory Positive Airway Pressure, or IPAP); and a lower pressure for breathing out (called Expiratory Positive Airway Pressure, or EPAP).

Blinded trial: A trial where, in order to avoid bias, a patient is not told what treatment they are receiving. See also double-blind clinical trial and placebo-controlled clinical trial.

BPAP ventilation: Bilevel positive airway pressure ventilation (also known as BiPAP ventilation). The name of a specific portable machine (ventilator) connected to a face mask that supplies respiratory support using two different levels of positive air pressure - when breathing in and out. The ventilator delivers the air at two different pressures which alternate: a higher pressure to breath in (called Inspiratory Positive Airway Pressure, or IPAP); and a lower pressure for breathing out (called Expiratory Positive Airway Pressure, or EPAP).

Bronchial drainage: A method of airway clearance involving chest percussion (rhythmic slapping) and positioning to help clear the lungs of secretions.

Bulbar muscles: Muscles around the mouth and throat. When these muscles are affected, swallowing and speaking may become difficult.

C

Cannula: A tube inserted into a vein to supply fluids / medications directly into the body. The term can also be used to describe a tube inserted through the nose in order to supply oxygen.

Carbon dioxide: A gas that is produced as a waste product of cells using oxygen to make energy. It is removed from the body by breathing out.

Cardiac: Of, or related to, the heart.

Carrier: This term relates to autosomal recessive inheritance and X-linked recessive inheritance patterns. A person who has both a faulty copy and a healthy copy of a gene is a carrier. Carriers usually have no symptoms due to the healthy copy of the gene, but they may pass on a condition to their children. In the case of SMA, carriers have one faulty copy of the Survival Motor Neuron 1 (SMN1) gene and one healthy copy of SMN1. Two individuals who each carry the SMN1 mutation have a 25% (1 in 4) chance of having a child with SMA for each pregnancy. A child must inherit two copies of the faulty SMN1 gene to develop SMA, one copy from each parent.

Carrier testing: A genetic test to find out if a person is a carrier of a faulty gene.

Cell: The basic building block of all known living organisms. Cells come in many different forms such as motor neurons (a type of nerve cell), keratinocytes (main cell type of the skin), or erythrocytes (red blood cells).

Cell culture: The process of growing cells in a liquid medium in the laboratory. The medium possesses all the nutrients and molecules required to support growth and division of the cells so that the cells can be used to study the mechanisms and processes involved in diseases and to test potential therapies.

Cell signalling: The communication, via chemical signals, between and within cells. Amongst other things, this signalling tells other cells to grow, change or produce proteins at specific times.

Cell therapy: Cell therapy involves replacing diseased or faulty 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 cell used for cell therapy.

Central nervous system : CNS. The central nervous system consists of the brain and the spinal cord. The CNS is connected to other tissues and organs in the body, such as skeletal muscles, by the peripheral nervous system (PNS).

Centromere: The centre of chromosomes.

Cervical spine: The top part of the spine, found above the chest.

Chest percussion: A method of rhythmic slapping (with a cupped hand) to loosen secretions in the airways.

Chest physiotherapy: Physical treatments and movements designed to improve respiratory efficiency, promote expansion of the lungs, strengthen respiratory muscles, and remove secretions from the respiratory system.

Chromosomes: Chromosomes are compact bundles of DNA. Humans have 46 chromosomes in each cell (with a few exceptions, including sperm and egg cells). They inherit 23 from their mother and 23 from their father to make 23 pairs.

Chronic: Lasting for a long period of time.

Chronic villus sampling : CVS. CVS is a way to test if an unborn baby has SMA. A sample of chorionic villous cells (placental tissue) is removed using a needle. This is usually done between the eleventh and fourteenth week of a pregnancy. The cells can then be genetically tested for SMA.

Clinical: The observation and treatment of patients, rather than laboratory studies that do not directly involve patients.

Clinical trial: A trial done on humans, usually to test a treatment or intervention, or to find out more about a disease. (See also Phase 1, Phase 2, Phase 2a and 2b, Phase 3 and Phase 4 clinical trials.)

CNS: Central nervous system. The central nervous system consists of the brain and the spinal cord. The CNS is connected to other tissues and organs in the body, such as skeletal muscles, by the peripheral nervous system (PNS).

Cobb angle: A measurement of curvature of the spine.

Codon: A sequence of three nucleotides in messenger RNA (mRNA) that specifies an amino acid in a protein.

Concave: Curved or sunken inwards.

Congenital: Present at birth, or soon afterwards.

Congestion: Excessive or abnormal build-up of secretions in the lungs or airways.

Continuous Positive Airway Pressure: A type of ventilation, through a mask, that is driven by a specifically designed non-invasive ventilation machine called a CPAP. It provides a continuous flow of air to help with breathing.

Contracture: A tightness in the connective tissue and tendons around a joint that results from weakness and inability to move a joint through its full range of motion.

Convex: Curved outwards.

Copy number (of a gene): The number of copies of a particular gene a person has. In SMA, the copy number is mainly important in the context of Survival Motor Neuron 2 (SMN2). While SMA is usually caused by a mutation in the Survival Motor Neuron 1 (SMN1) gene, there is evidence that having more copies of the SMN2 gene may help to make SMA less severe, although other factors also play a role.

Cough assistance: Help given by a caregiver or a specifically designed machine to aid a person to produce a cough with enough force to get rid of secretions in the airways.

Cough peak flow: CPF (also known as peak cough flow - PCF). Coughing is an important means of clearing secretions from the lungs to reduce the risk of chest infections. PCF / CPF is a measurement of the strength of a person's cough. It may be carried out as part of a breathing assessment of patients with neuromuscular conditions such as SMA.

CPAP: Continuous Positive Airway Pressure. A type of ventilation, through a mask, that is driven by a specifically designed non-invasive ventilation machine called a CPAP. It provides a continuous flow of air to help with breathing.

CPF: Cough peak flow (also known as peak cough flow - PCF). Coughing is an important means of clearing secretions from the lungs to reduce the risk of chest infections. PCF / CPF is a measurement of the strength of a person's cough. It may be carried out as part of a breathing assessment of patients with neuromuscular conditions such as SMA.

CVS: Chronic villus sampling. CVS is a way to test if an unborn baby has SMA. A sample of chorionic villous cells (placental tissue) is removed using a needle. This is usually done between the eleventh and fourteenth week of a pregnancy. The cells can then be genetically tested for SMA.

D

De novo mutation: An alteration in a gene that arises for the first time in one family member as a result of a mutation in an egg or sperm cell of one of the parents, or in the fertilised egg itself. Neither parent will have the mutation themselves.

Deletion mutation: Genetic material (part of the DNA) missing from a chromosome or gene.

Denervation: The degeneration (breaking down) of nerve cells. When lower motor neurons denervate, they are no longer able to efficiently contact and stimulate their target muscle, which affects movement.

Deoxyribonucleic acid: DNA. DNA is the molecule that contains the genetic instruction manual to build all known organisms. 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.

Diagnosis: Identifying a disease from its signs and symptoms or from its genetic cause. A clinical diagnosis is given when a doctor sees enough signs or symptoms to be confident that a person has the disease in question. In genetic disorders, a genetic diagnosis is given when a genetic test has been performed and the fault in the gene that is known to cause the disease is found. Doctors who are experts in SMA can usually diagnose the condition with a high degree of accuracy from the clinical signs and symptoms alone. However, genetic tests are usually recommended for all genetic disorders to increase certainty, to make sure any treatment is correctly targeted and to enable the family to have prenatal testing in future pregnancies if they wish.

Diagnostic criteria: Guidelines, rules or characteristics used by a clinician to diagnose a particular condition.

Distal: Anatomical term meaning situated away from the centre of the body, towards the extremities. Distal muscles, such as those found in the hands and feet, are typically less affected by the more common forms of SMA compared to proximal muscles, such as those involved in breathing.

DNA: Deoxyribonucleic acid. DNA is the molecule that contains the genetic instruction manual to build all known organisms. 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.

Dominant inheritance: A method of genetic inheritance where having a single faulty copy of a gene is enough to cause a genetic disorder, even though a healthy 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 the resulting genetic disorder, to their children.

Double-blind clinical trial: A clinical trial where neither the patient nor the investigator knows what treatment the patient is receiving. This helps eliminate potential bias caused by the patient's or the investigator's opinion on whether or not a particular treatment will be effective.

Duplication mutation: A type of mutation where part of a chromosome or gene is repeated.

Dysarthria: Difficulty speaking.

Dysphagia: Difficulty swallowing.

Dyspnoea: Difficulty breathing.

E

ECG: Electrocardiogram. A test that records the electrical activity of the heart through electrodes attached to the skin.

Echocardiogram : "Echo". The use of ultrasound to produce images of the heart.

Electrocardiogram: ECG. A test that records the electrical activity of the heart through electrodes attached to the skin.

Electromyogram: 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: intramuscular and surface. An intramuscular EMG involves inserting a needle electrode, or a needle containing two fine-wire electrodes, through the skin into the muscle. A surface EMG involves placing an electrode on the surface of the skin.

Embryo: The name given to the development stage from fertilised egg up until about eight weeks of pregnancy when the embryo becomes a foetus.

Embryonic stem cells: Immature cells from an early-stage embryo that have the potential to develop and differentiate 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 the informed consent of the donors. They have the ability to multiply in number indefinitely when grown in the laboratory. This makes them a useful tool for research.

EMG: Electromyogram. 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: intramuscular and surface. An intramuscular EMG involves inserting a needle electrode, or a needle containing two fine-wire electrodes, through the skin into the muscle. A surface EMG involves placing an electrode on the surface of the skin.

Enzyme: A protein which initiates, facilitates or speeds up a chemical reaction. Almost all of the processes that occur in our body require enzymes. Examples include the digestion of food and the growth and building of cells.

Epilepsy: Disordered electrical impulses within the brain causing seizures (more commonly referred to as ‘fits’).

Etiology : Also known as Aetiology. Cause (of a disease / condition).

Exon: Genes are divided into regions called exons and introns. Exons are the sections of DNA that provide the code that enables proteins to be produced.

Extracellular matrix: The extracellular matrix surrounds the cells in our bodies. The matrix is made of proteins and other substances that form a structured network. It is important for cell stability and also plays a role in communication between cells.

F

Fasciculation: A small involuntary muscle twitch that can occur in any muscle in the body.

Fatigue: Great tiredness. A common symptom of neuromuscular conditions.

Fetus: Also known as foetus. The term used for an unborn baby after the eighth week of development until birth.

Fine motor skills: The use of muscles for small movement, for example, when writing.

Foetus : Also known as fetus. The term used for an unborn baby after the eighth week of development until birth.

Forced Vital Capacity: FVC. Measurement of a deep breath out. FVC is the total volume of air breathed into a measuring machine called a spirometer.

Frog-legged: Describes the appearance of legs that flop outwards with knees bent when a person is lying on their back. In babies and young infants, lying in this position suggests low muscle tone and therefore this may be an early sign that a child is affected by SMA.

FVC: Forced Vital Capacity. Measurement of a deep breath out. FVC is the total volume of air breathed into a measuring machine called a spirometer.

G

G Tube: Gastric tube (also known as Gastrostomy). Feeding tube placed in the stomach in a surgical procedure. Sometimes referred to as a PEG (percutaneous endoscopic gastrostomy).

Gastric tube: G Tube (also known as Gastrostomy). Feeding tube placed in the stomach in a surgical procedure. Sometimes referred to as a PEG (percutaneous endoscopic gastrostomy).

Gastroesophageal reflux: Food / liquid that has been swallowed but moves back up the oesophagus (food pipe) from the stomach. It can cause pain, choking or increased secretions.

Gastrostomy: Also known as Gastric tube (G Tube). Feeding tube placed in the stomach in a surgical procedure. Sometimes referred to as a PEG (percutaneous endoscopic gastrostomy).

Gene: A section of DNA that carries the information to produce a specific protein. Genes are the unit of heredity that are passed from one generation to the next. We usually possess two copies of each gene, one inherited from each of our parents. When genes are altered through mutation, this can affect the structure and function of the proteins that they produce, leading to disease.

Gene regulation: This process affects how a gene is read and processed. For example, increasing or decreasing the amount of protein produced by a gene.

Gene therapy: The treatment of a genetic disorder by introducing a new gene into a cell in order to try and repair or replace a faulty gene. Viruses, such as adeno-associated virus (AAV), are often used to get the new gene into the cells.

Gene transcript: The messenger RNA (mRNA) produced from a gene by the process of transcription.

Genetic counselling: Information and support provided by a genetic specialist to people who have genetic disorders in their families or are concerned about a genetically transmitted condition. Genetic counselling helps families understand things like how the condition is passed on, what the chances are of children being affected, and which other family members may be at risk of carrying the affected gene. It also helps affected teenagers / young adults to understand their future choices.

Genetic disorders: Conditions resulting from alterations to an individual's genes. Genetic disorders can be caused by defects in one or more genes, or whole chromosomes.

Genetic markers: Genetic markers are specific sequences of DNA with known locations on a chromosome. They can be used to help locate the genes responsible for genetic disorders.

Genetic testing: The examination of an individual’s genes to identify any faults that could cause a genetic disorder.

Genetics: The study of genes and inheritance.

Genome: The complete set of DNA in a person or an organism. In humans this includes all 44 autosomes, 2 sex chromosomes, and mitochondrial DNA.

Genotype: The genetic makeup of an individual. Genotype can refer to an organism's entire genetic makeup or the alleles at a particular genetic location (locus).

Glial Cell: A type of cell found within the nervous system. Amongst other things, they play a role in supplying nutrients, maintaining the physical structure of neurons (nerve cells), transmitting electrical signals, and removing waste products.

H

Heredity: The passing of traits (characteristics) through the inheritance of genes from one generation to the next.

Heterozygous: Having two different alleles of a gene for a particular trait (characteristic). For example, someone with one copy of the dominant tongue-rolling gene (allele) and one copy of the recessive non-rolling gene (allele) is said to be heterozygous for this gene. Individuals who are heterozygous for a trait are referred to as heterozygotes. See also homozygous.

Homozygous: Having two identical alleles of a gene on both chromosomes in a pair. In other words, homozygous refers to a genotype consisting of two identical alleles of a gene for a particular trait (characteristic). For example, someone with two copies of the dominant tongue-rolling gene (allele) is said to be homozygous for this gene. Individuals who are homozygous for a trait are referred to as homozygotes. See also heterozygous.

Hypercapnia : Also known as hypercarbia. The presence of an increased amount of carbon dioxide in the blood.

Hypercarbia: Also known as hypercapnia. The presence of an increased amount of carbon dioxide in the blood.

Hypotonia: Decreased / low muscle tone, sometimes described as floppiness.

Hypoventilation: A reduced rate and depth of breathing (too shallow or too slow), which leads to an increase of carbon dioxide in the body.

Hypoxia: Decreased blood oxygen levels.

I

Immune response: The body’s response to "foreign" substances, such as bacteria or viruses. 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 can be used to prevent the body rejecting a transplanted organ or to treat autoimmune conditions, i.e. diseases in which the body’s immune system attacks a particular cell type or tissue within the body due to failing to recognise it as a "non-foreign" substance.

In vitro fertilisation: IVF. A process by which eggs are fertilised by sperm outside the womb. The fertilised egg is then transferred into the womb to try to establish a successful pregnancy.

Induced pluripotent stem cell: iPS cell. A type of stem cell that has been genetically engineered by "reprogramming" an adult cell, such as a skin cell, in the laboratory. Adult cells are reprogrammed by altering their genes and encouraging them to revert to an immature state where they have a non-specialised role within the body. These cells then have the ability to develop and differentiate into almost any specialised cell type in the body. Some researchers are trialling the use of iPS cells in SMA mouse models as a way to replace the lower motor neurons that degenerate.

Inflammation: The body's reaction to injury or infection. Inflammation results in redness, pain, swelling, and warmth, due to increased blood flow in the injured / infected 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 to initiate the healing process.

Inheritance: The process by which an individual acquires traits (characteristics) from his or her parents.

Intermediate SMA: Also known as SMA Type 2 or Type II SMA.

Intermittent Positive Pressure Breathing : IPPB. The use of a machine that gives an extra "push" of air with each breath in, usually via a facemask or mouthpiece. It is used to help with breathing, to assist with coughing to clear secretions, or to help deliver medications.

Intron: Genes are divided into regions called exons and introns. The protein-coding exons are interspersed with introns, which have structural and regulatory roles.

Intubatation: A procedure to insert a tube through the mouth or nose and into the main airway (trachea) to enable artificial breathing. Intubation may be carried out as part of a planned procedure, for example to protect the airway during survey, or as an emergency for a person who is critically ill.

Invasive ventilation: This term describes mechanical assistance with breathing which is delivered through a device or tube which enters the body. Usually this would require intubation or a tracheostomy. This is in contrast to non-invasive ventilation which may be delivered by a facemask or mouthpiece.

IPPB: Intermittent Positive Pressure Breathing. The use of a machine that gives an extra "push" of air with each breath in, usually via a facemask or mouthpiece. It is used to help with breathing, to assist with coughing to clear secretions, or to help deliver medications.

I

iPS cell: Induced pluripotent stem cell. A type of stem cell that has been genetically engineered by "reprogramming" an adult cell, such as a skin cell, in the laboratory. Adult cells are reprogrammed by altering their genes and encouraging them to revert to an immature state where they have a non-specialised role within the body. These cells then have the ability to develop and differentiate into almost any specialised cell type in the body. Some researchers are trialling the use of iPS cells in SMA mouse models as a way to replace the lower motor neurons that degenerate.

I

IVF: In vitro fertilisation. A process by which eggs are fertilised by sperm outside the womb. The fertilised egg is then transferred into the womb to try to establish a successful pregnancy.

K

Kugelberg-Welander Disease: Also known as SMA Type 3 or Type III SMA.

Kyphoscoliosis: Abnormal curvature (rounding) of the spine with both sideways curvature (scoliosis) and forward or backward curvature (kyphosis).

Kyphosis: Outward (front-to-back) curvature (rounding) of the spine.

L

Lordosis: Inward curvature (rounding) of the spine.

Lumbar spine: A lower part of the spine below the thoracic region, and above the sacral spine.

M

Macrophage: A large white blood cell that acts as a hoover, sucking up cell debris from damaged tissues and "foreign" substances such as bacteria and viruses. It also stimulates other immune system cells to help defend the body.

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.

Marketing authorisation: The process of gaining approval to sell (market) a drug in a particular country. Before a drug can be prescribed by doctors to patients who are not taking part in a clinical trial, it has to have marketing authorisation from the relevant regulatory authority for the country in question. In the UK this is the Medicines and Healthcare Products Regulatory Agency (MHRA). Once marketing authorisation has been granted, it is legal to market the drug, but this does not necessarily mean it will be available on the NHS in the UK.

Mechanical ventilation: The medical procedure used to assist or replace breathing when an individual is unable to breathe adequately themselves. This usually involves a ventilator machine or manual bag compression. The term is most commonly used to refer to invasive forms of ventilation such as intubation or tracheostomy. However, in some cases, short term mechanical ventilation can be non-invasive - see Intermittent Positive Pressure Breathing (IPPB).

Membrane: 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 the substances that leave or enter them.

Messenger RNA : mRNA. An intermediate molecule between DNA and proteins. It acts as a template that can be read by the ribosomes in order to produce proteins.

Metabolism: The chemical processes that occur within the body to maintain life.

Metabolite: Any substance that is produced by metabolism.

Mitochondria: Distinct structures found within cells. Mitochondria are often referred to as the "powerhouses" of cells as they generate most of a cell’s energy supply.

Molecule: 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 (H2O).

Morbidity: The incidence or rate at which a disease or illness occurs in a group of individuals.

Motor function: Also known as motor performance. An individual's ability to coordinate and carry out successful movement of their muscles.

Motor function scales: Tests that are used to measure an individual's motor function / performance in a standardised way.

Motor neurons: The nerve cells that connect the brain and spinal cord to skeletal muscles allowing conscious muscle contraction (movement). They act as a message delivery system: electrical signals originating in the brain are fired down the spinal cord along upper motor neurons; the electrical signals continue along lower motor neurons, which project out to skeletal muscles to control movement. Lower motor neurons are located in the anterior horn of the spinal cord and are the main cell type affected by SMA. In SMA, low levels of the Survival Motor Neuron (SMN) protein cause the deterioration of lower motor neurons leading to muscle weakness and atrophy.

Motor performance: Also known as motor function. An individual's ability to coordinate and carry out successful movement of their muscles.

Mouse model: A strain / breed of mouse used to "model" and investigate a human genetic disorder such as SMA. Spontaneous or genetically engineered mutations in mouse genes allow scientists to study disease processes in a live animal. All mice of a particular breed will be almost genetically identical so that the effects of mutations in genes known to cause genetic disorders in humans can be studied. SMA mice are used to learn more about the molecular and cellular processes underlying SMA symptoms and to test potential treatments before human clinical trials are started.

MRI: Magnetic resonance imaging. A non-invasive body imaging procedure that uses powerful magnets and radio waves to construct pictures of the internal structures of the body.

M

mRNA: Messenger RNA. An intermediate molecule between DNA and proteins. It acts as a template that can be read by the ribosomes in order to produce proteins.

M

Muscle biopsy: Removal of a small amount of muscle tissue for analysis.

Muscle cell: The basic unit of a muscle fibre.

Muscle fibre: The basic unit of muscle tissue, formed by the fusion of groups of muscle cells.

Mutation: A permanent change in the DNA sequence of a gene that can be inherited by subsequent generations. Dependent upon the type of mutation and where it occurs within the gene, it might have no effect on the protein produced, or it might disturb the protein's function causing a genetic disorder such as SMA.

Myoblast: A cell that develops into a muscle fibre.

Myoblast transfer: A potential method of treatment for some forms of muscular dystrophy, which involves transplanting billions of healthy donor cells into affected muscle. Sometimes referred to as cell therapy.

Myometry: The use of a piece of equipment that measures muscle force.

Myopathy: Disorder, primarily of the muscle.

Myostatin: A protein that helps mammals regulate muscle building It acts as a signal for muscles to stop using resources and stop growing. Scientists think that by blocking the activity of myostatin, it might be possible to increase muscle size and strength in people with muscle disease.

N

Nasogastric Tube: NG Tube. A thin, flexible feeding tube passed through the nose. The end of the tube goes into the stomach.

Nasojejunal Tube: NJ Tube. A thin, flexible feeding tube inserted through the nose. The end of the tube goes into the jejunum (the middle part of the small intestine).

Nerve Cells: Also called neurons, nerve cells allow the quick transmission of electrical signals throughout the body. Different types of nerve cell make up the nervous system which functions to allow us to perceive and react to our surroundings. For example, the brain sends a signal along the nerves to tell a muscle to contract (move). Nerve cells are important for both involuntary (unconscious) functions like the beating of the heart and voluntary (conscious) functions like moving your arm.

Neuromuscular: Anything that relates to the nerves, muscles or the neuromuscular junction.

Neuromuscular Junction : NMJ. The specialised connection, known as a synapse, between the lower motor neurons and skeletal muscles fibres. The NMJ allows signals from the nerves to get through to the muscles enabling them to contract (move).

Neuropathy: A medical term describing disorders of the peripheral nerves that relay signals to and from the legs and arms.

Neutrophil: The most abundant type of white blood cells in humans that help the body fight infection. Neutrophils are one of the first types of cells to move towards the site of inflammation by following chemical signals given off by the damaged or infected tissue. They are capable of killing bacteria and viruses.

Next generation sequencing: A cutting-edge technology that allows researchers to "read" parts or the whole of an individual’s genome. Researchers have recently started to use it to find new genes and for the more accurate diagnosis of genetic disorders.

NG Tube: Nasogastric Tube. A thin flexible feeding tube passed through the nose. The end of the tube goes into the stomach.

NIPD: Non-invasive prenatal diagnosis (NIPD). NIPD works by extracting and testing an unborn baby’s DNA from a sample of the pregnant mother’s blood to determine whether or not the foetus has SMA.

NIV: Non-invasive ventilation. Breathing support provided by a machine using a face or nose mask.

NJ Tube: Nasojejunal Tube. A thin, flexible feeding tube inserted through the nose. The end of the tube goes into the jejunum (the middle part of the small intestine).

NMJ: Neuromuscular Junction. The specialised connection, known as a synapse, between the lower motor neurons and skeletal muscle fibres. The NMJ allows signals from the nerves to get through to the muscles enabling them to contract (move).

Non-ambulant: Not able to walk.

Non-invasive prenatal diagnosis: NIPD works by extracting and testing an unborn baby’s DNA from a sample of the pregnant mother’s blood to determine whether or not the foetus has SMA.

Non-invasive ventilation : NIV. Breathing support provided by a machine using a face or nose mask.

Nonsense mutation: A change in the DNA that causes a stop signal to occur in a gene. When this happens, the protein is shortened or not produced.

Nucleotide: The individual building block of our DNA and RNA. A nucleotide consists of a base, one of four chemicals: adenine (A), cytosine (C), guanine (G) and thymine (T), plus a molecule of sugar and one of phosphoric acid. Within DNA, A pairs with T, and C with G. Within RNA the thymine is replaced by uracil (U).

Nucleus: The control centre of a cell that contains the DNA wrapped up within chromosomes.

O

Occupational Therapy: The use of assessment and treatment to help promote independent daily living skills.

Oligonucleotide: A short sequence of genetic material (DNA or RNA). See also antisense oligonucleotide.

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 clinical trials where participants are not aware of what treatment they are receiving, and double-blind clinical trials.

Orphan drug: A drug that is intended to treat a rare disease. To be classed as an orphan drug in the European Union (EU), the product must be intended to treat a condition whose prevalence is not more than 5 in 10,000. Treatments for SMA are normally eligible for orphan designation. Orphan designation gives companies financial and other incentives to develop treatments for rare diseases.

Orthopaedic: Relating to the musculoskeletal system: the body's muscles and skeleton, including the joints, ligaments, tendons, and nerves.

Orthoses : Also known as orthosis and orthotics. Devices or aids manufactured to prevent or assist movement of the spine or limbs or to provide support for joints and muscles. For example: splints, spinal jacket / brace, ankle-foot orthoses (AFOs), knee-foot orthoses (KAFOs).

Orthosis: Also orthoses and orthotics. Devices or aids manufactured to prevent or assist movement of the spine or limbs or to provide support for joints and muscles. For example: splints, spinal jacket / brace, ankle-foot orthoses (AFOs), knee-foot orthoses (KAFOs).

Orthotics: Also known as orthoses and orthosis. Devices or aids manufactured to prevent or assist movement of the spine or limbs or to provide support for joints and muscles. For example: splints, spinal jacket / brace, ankle-foot orthoses (AFOs), knee-foot orthoses (KAFOs).

Osmosis: Movement of water from a weak solution to a strong solution through a semi permeable membrane.

Osmotic medicine: Medicine that works though osmosis.

Outcome measure: The tests that investigators perform to decide whether a treatment being tested in a clinical trial is having any effect. In SMA, these are most often a gauge of physical ability along a numerical scale that can be used to determine improvement or decline over time, but other tests like magnetic resonance imaging (MRI) scans can also be used.

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.

P

Palliative care: Palliative care is the active total care of an individual's body, mind and spirit and also involves giving support to the individual's family. It begins when an illness is diagnosed and continues regardless of whether or not a person receives treatment directed at the disease (World Health Organisation definition 1998). Palliative care can be provided in a variety of settings including hospitals, hospices and at home.

Pathogenesis: The mechanism by which the disease is caused; its origin.

Pathology: The study of the changes in tissues and organs of the body that cause disease.

PCF: Peak cough flow (also known as cough peak flow - CPF). Coughing is an important means of clearing secretions from the lungs to reduce the risk of chest infections. PCF / CPF is a measurement of the strength of a person's cough. It may be carried out as part of a breathing assessment of patients with neuromuscular conditions such as SMA.

Peak cough flow: PCF (also known as cough peak flow - CPF). Coughing is an important means of clearing secretions from the lungs to reduce the risk of chest infections. PCF / CPF is a measurement of the strength of a person's cough. It may be carried out as part of a breathing assessment of patients with neuromuscular conditions such as SMA.

Pectus Excavatum: When the breastbone is sunken.

PEEP: Positive End Expiration Pressure. The pressure given at the end of a breath by a machine such as a ventilator.

PEG feeding tube: Percutaneous endoscopic gastrostomy feeding tube. A feeding tube placed through the skin of the abdominal wall into the stomach. The tube is placed by a procedure which uses an endoscopic camera. In some cases it may be carried out using sedation without the need for a general anaesthetic.

Percutaneous endoscopic gastrostomy feeding tube: PEG feeding tube. A feeding tube placed through the skin of the abdominal wall into the stomach. The tube is placed by a procedure which uses an endoscopic camera. In some cases it may be carried out using sedation without the need for a general anaesthetic.

Peripheral nervous system: PNS. Consists of the nerve cell extensions found outside of the central nervous system (CNS). The PNS acts to connect the CNS with the muscles and internal organs. The lower motor neuron axons and their connections with the muscle (neuromuscular junctions) are found within the PNS.

PGD: Pre-implantation genetic diagnosis. The technique used to test very early embryos for a specific genetic disorder 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 have grown into a ball of cells. A small sample of these cells is then removed for genetic testing.

Pharmacokinetics: The study of what happens to substances, such as drugs and chemicals, that are given to a living organism. This includes analysing the rate at which a substance takes effect, how it is absorbed and distributed throughout the body, and how long the effects last.

Phase 0 clinical trial: A very early clinical trial conducted on a small number of people. 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 1 clinical trials, phase 0 trials are not used to evaluate in detail the drug dosage, treatment safety or side effects.

Phase 1 clinical trial: Also written as phase I clinical trial. Phase 1 clinical trials are the first stage of testing a drug or treatment on humans. Researchers will test a new drug or treatment on a small group of people, often healthy volunteers rather than patients. This phase is to evaluate the treatment’s safety, to determine how much of the drug is safe to give, and to identify any side effects. After a Phase 1 clinical trial, it is usually not possible to give an answer about whether or not the drug is effective, as this is not what this phase of trial is designed to discover.

Phase 2 clinical trial: Also written as phase II clinical trial. Phase 2 clinical trials are designed to test how well the drug or treatment works as well as to continue safety assessments on a larger group of people. Only one third of experimental drugs successfully complete both phase 1 and phase 2 clinical trials.

Phase 2a and Phase 2b clinical trial: Also written as phase IIa and IIb clinical trial. Phase 2 clinical trials are sometimes divided into Phase 2a and Phase 2b. Phase 2a is designed to assess how much drug should be given. Phase 2b is designed to study how well the drug works when different amounts are given.

Phase 3 clinical trial: Also written as phase III clinical trial. A Phase 3 clinical trial is designed to test a new drug on a larger number of people after it has been shown to be effective in a phase 2 clinical trial. Phase 3 trials allow researchers to gain a more in-depth understanding of the effectiveness of the drug and to further assess the benefits / risks of the drug.

Phase 4 clinical trial: Also written as phase IV clinical trial. Phase 4 clinical trials evaluate the long term risks and benefits of a drug or treatment after it has become available on the market. They are designed to detect any rare or long-term effects in a much larger number of people and over a longer time period than was possible during the Phase 1, 2 and 3 clinical trials.

Phase I clinical trial: Also written as phase 1 clinical trial. Phase I clinical trials are the first stage of testing a drug or treatment on humans. Researchers will test a new drug or treatment on a small group of people, often healthy volunteers rather than patients. This phase is to evaluate the treatment’s safety, to determine how much of the drug is safe to give, and to identify any side effects. After a Phase I clinical trial, it is usually not possible to give an answer about whether or not the drug is effective, as this is not what this phase of trial is designed to discover.

Phase II clinical trial: Also written as phase 2 clinical trial. Phase II clinical trials are designed to test how well the drug or treatment works as well as to continue safety assessments on a larger group of people. Only one third of experimental drugs successfully complete both phase I and phase II clinical trials.

Phase IIa and Phase IIb clinical trial: Also written as phase 2a and 2b clinical trial. Phase II clinical trials are sometimes divided into Phase IIa and Phase IIb. Phase IIa is designed to assess how much drug should be given. Phase IIb is designed to study how well the drug works when different amounts are given.

Phase III clinical trial: Also written as phase 3 clinical trial. A Phase III clinical trial is designed to test a new drug on a larger number of people after it has been shown to be effective in a phase II clinical trial. Phase III trials allow researchers to gain a more in-depth understanding of the effectiveness of the drug and to further assess the benefits / risks of the drug.

Phase IV clinical trial: Also written as phase 4 clinical trial. Phase IV clinical trials evaluate the long term risks and benefits of a drug or treatment after it has become available on the market. They are designed to detect any rare or long-term effects in a much larger number of people and over a longer time period than was possible during the Phase I, II and III clinical trials.

Phenotype: The observable characteristics of an organism resulting from its genetic makeup (genotype) and environmental influences.

Physiotherapy: Physical techniques used to promote, maintain and restore physical function of the body.

Placebo: A harmless substance that should have no effect on the progression of a disease. A placebo is used instead of a drug in clinical trials to help rule out any benefits a drug might appear to have because the patient believes it will have an effect.

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 something that has an effect and to eliminate any bias on the part of the researchers measuring the benefit of the treatment.

Pneumonia: A condition where the lung tissue becomes inflamed. This can be caused by infection or injury to the lungs. It causes symptoms of coughing, chest pain, and difficulty breathing.

PNS: Peripheral nervous system. Consists of the nerve cell extensions found outside of the central nervous system (CNS). The PNS acts to connect the CNS with the muscles and internal organs. The lower motor neuron axons and their connections with the muscle (neuromuscular junctions) are found within the PNS.

Point mutation: A type of genetic mutation that causes a single building block of DNA (nucleotide) to be replaced with a different one.

Polysomnography: Also known as sleep study. A test to assess the quality of a person's sleep. For people affected by SMA it is done specifically to look at breathing patterns during sleep. The test usually involves wearing lightweight equipment overnight. Often the study will require a single night's stay in a specialist hospital although portable equipment for use at home may sometimes be available.

Positive End Expiration Pressure: PEEP. The pressure given at the end of a breath by a machine such as a ventilator.

Pre-implantation genetic diagnosis: PGD. The technique used to test very early embryos for a specific genetic disorder 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 have grown into a ball of cells. A small sample of these cells is then removed for genetic testing.

Preclinical research: Research done in the laboratory, on cells or on animals. This kind of research is done before research on humans, which is called clinical research.

Prenatal testing: The genetic testing for diseases or conditions in a foetus or embryo. This is done by removing a sample of fluid or tissue by procedures such as amniocentesis or chorionic villus sampling (CVS).

Presymptomatic diagnosis: The diagnosis of a genetic disorder before the appearance of any symptoms.

Prognosis: The predicted course and outcome of a medical condition.

Promoter region: A section of DNA that "switches on" a particular gene.

Prone: Lying on the stomach.

Protein: Proteins consist of chains of amino acids arranged in very specific orders. The order of amino acids within a chain is determined by the genetic code (DNA). Different genes have the "instructions" for making different proteins. Proteins are the building blocks of our bodies and are essential for the structure, function, and regulation of cells, tissues and organs. Examples of different proteins include enzymes, hormones, antibodies and the survival motor neuron (SMN) protein.

Protein complex: A protein complex is the name given to a group of proteins that 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: Anatomical term meaning situated close to the centre of the body. Proximal muscles, such as those found in the hips, shoulders and neck, are more affected than distal muscles in most forms of SMA.

Pulmonary: Relating to the lungs. Clinicians measure pulmonary (lung) function to assess how well a patient is able to breathe.

Pulse oximetry: Pulse oximetry is a simple, non-invasive technique to monitor the amount of oxygen in the blood (oxygen saturation). This most commonly involves a small red light and sensor being worn over a finger or earlobe.

R

Randomised controlled trial: A clinical trial where the treatment and the placebo are allocated randomly to the participants rather than by the conscious decisions of the doctor or the patient. See also placebo-controlled clinical trial.

Rare Disease: The European Union (EU) considers diseases to be rare when they affect not more than 5 per 10,000 persons in the EU.

Recessive: Autosomal recessive describes a form of inheritance in which two faulty copies of a gene are required in order for a person to be affected by a genetic disorder. This means that a faulty copy of a gene is inherited from each parent. Survival Motor Neuron 1-associated SMA is an autosomal recessive condition. In X-linked recessive conditions, two faulty copies of the gene are needed for the genetic disorder to show in females, but only one faulty copy in males. This is because X-linked recessive conditions are caused by mutations in genes found on the X chromosome, but that are missing from the Y chromosome. Males have one X and one Y chromosome, while females have two X chromosomes.

Reflexes: Involuntary / unconscious movement caused by a response to a stimulus. For example, blinking when something comes very near to your eye.

Reflux: When liquid goes back up into the oesophagus (food pipe) from the stomach.

Respirator: A machine that provides artificial breathing.

Respiratory: Relating to breathing.

Ribonucleic acid : RNA. RNA is very similar to DNA in that it carries genetic information. It plays an important role in the creation of proteins. There are different types of RNA that have different roles, for example messenger RNA (mRNA).

Ribosome: Ribosomes read messenger RNA (mRNA) and use it as a template to build proteins within a cell by connecting amino acids together.

RNA: Ribonucleic acid. RNA is very similar to DNA in that it carries genetic information. It plays an important role in the creation of proteins. There are different types of RNA that have different roles, for example messenger RNA (mRNA).

S

Sacral spine: The lowermost part of the spine.

Satellite cells: Cells that repair damaged muscle fibres. Also called muscle stem cells. They produce large numbers of myoblasts that fuse together with surviving parts of the damaged muscle fibre to fill any gaps.

Schwann cells: The main kind of nervous system support cells, glial cells, that are found in the peripheral nervous system.

Scoliosis: Sideways curvature of the spine.

Secretions: Substances like mucus that are produced by certain cells. Secretions perform useful functions in the body, for example, trapping foreign particles in the airways. They can be a problem though if they can't be removed from the body, for example, if a person has a weak cough.

Sensory nerves: Also known as sensory neurons. Nerve cells responsible for converting external stimuli, for example sound, light and smell into internal signals. This is how we feel, see, smell and hear.

Sensory neurons: Also known as sensory nerves. Nerve cells responsible for converting external stimuli, for example sound, light and smell into internal signals. This is how we feel, see, smell and hear.

Sex chromosomes: The X and Y chromosomes determine the sex of an individual. Females have two X chromosomes; males have an X and a Y chromosome.

Signalling pathway: A series of chemical signals through which cells communicate internally and with their surroundings.

Single-blind clinical trial: A clinical trial in which the patient does not know what treatment they are receiving. This helps eliminate potential bias caused by the patient's opinion on whether or not a particular treatment will be effective.

Six minute walk test: A standardised way of measuring a patient's mobility. It involves measuring how far a person can walk in six minutes.

Skeletal muscle: Consciously controlled muscle that attaches to bones allowing movement. Examples include the biceps, triceps, and thigh muscles.

Sleep study: Also known as polysomnography. A test to assess the quality of a person's sleep. For people affected by SMA it is done specifically to look at breathing patterns during sleep. The test usually involves wearing lightweight equipment overnight. Often the study will require a single night's stay in a specialist hospital although portable equipment for use at home may sometimes be available.

SMN gene: Survival Motor Neuron gene. A gene that produces the Survival Motor Neuron protein. Mutations in the SMN1 gene are the cause of some forms of SMA. There are two types of SMN genes - SMN1 and SMN2.

SMN protein: Survival Motor Neuron protein. Produced from both the SMN1 and SMN2 genes, the SMN protein is required for the survival of lower motor neurons. If there is no SMN protein in a cell, the cell will die. Of all the different cell types, the lower motor neurons seem to be most affected by low levels of SMN protein.

SMN1: Survival Motor Neuron 1. The gene that when mutated or deleted can lead to the development of SMA. For our lower motor neurons to survive and thrive we need a certain amount of the full-length SMN protein produced by the SMN1 gene.

SMN2: Survival Motor Neuron 2. The gene that can have an impact on the severity of SMA because it is able to produce a small amount of functional SMN protein. In people with a fault in the SMN1 gene, this can be important because the more copies of SMN2 that someone has, the more functional SMN protein they can produce. Individuals with more severe forms of SMA, for examples Types 1 and 2, usually have fewer copies of the SMN2 gene than those with SMA Type 3.

Spinal: Relating to the spine.

Spinal cord: The bundle of nervous tissue within the spine. It includes nerve cells and extends out from the brain. The brain and spinal cord make up the central nervous system (CNS).

Spirometry: The measurement of lung volume and function using specialist equipment. This will usually be carried out at a hospital outpatient appointment. A "peg" is placed on the nose and the patient is asked to perform a series of breathing exercises, such as breathing out as quickly as they can, into a mouthpiece. A typical assessment may last 20-30 minutes.

Splicing: Before messenger RNA (mRNA) can be read by ribosomes to produce protein, it must first be modified by the sticking, or “splicing”, together of important regions of the mRNA called exons. Introns are removed by the process of splicing.

Stem cells: Cells that have not yet specialised to form a particular cell type, and can still develop and mature into other types of cell, for example a lower motor neuron.

Stop codon: A section of DNA code that signals the end of protein production.

Suctioning: The mechanical removal of a substance. In SMA this term generally refers to the removal of mucus from the airway using a small tube.

Supine: Lying on back.

Survival Motor Neuron 1 : SMN1. The gene that when mutated or deleted can lead to the development of SMA. For our lower motor neurons to survive and thrive we need a certain amount of the full-length SMN protein produced by the SMN1 gene.

Survival Motor Neuron 2 : SMN2. The gene that can have an impact on the severity of SMA because it is able to produce a small amount of functional SMN protein. In people with a fault in the SMN1 gene, this can be important because the more copies of SMN2 that someone has, the more functional SMN protein they can produce. Individuals with more severe forms of SMA, for examples Types 1 and 2, usually have fewer copies of the SMN2 gene than those with SMA Type 3.

Survival Motor Neuron gene: SMN gene. A gene that produces the Survival Motor Neuron protein. Mutations in the SMN1 gene are the cause of some forms of SMA. There are two types of SMN genes - SMN1 and SMN2.

Survival Motor Neuron protein: SMN protein. Produced from both the SMN1 and SMN2 genes, the SMN protein is required for the survival of lower motor neurons. If there is no SMN protein in a cell, the cell will die. Of all the different cell types, the lower motor neurons seem to be most affected by low levels of SMN protein.

Symmetrical: The same on both sides of a central point.

Synapse: The connection between a nerve cell and another cell that enables the passage of electrical or chemical signals.

Systemic: Spread throughout the body and affecting many or all body systems or organs.

T

T cell: A type of white blood cell also known as T lymphocytes. T cells are important as they seek out and destroy foreign substances in the body such as bacteria and viruses.

Thoracic spine: Middle part of the spine, associated with the rib cage.

Tissue: A collection of cells that work together to perform a common function. For example, organs are formed from multiple tissues.

Trachea: Windpipe.

Tracheostomy: Surgical operation to create an opening into the windpipe (trachea) to allow breathing through a tube, rather than through the mouth.

Transcription: The first stage in the production of proteins. Information in the DNA sequence is converted to messenger RNA (mRNA) before being translated into protein by ribosomes.

Transgene: A gene or genetic material transferred from one species to another. This can occur naturally or through genetic engineering. It is usually integrated into the germ line (reproductive cells) of the organism to create a strain of the organism that has this particular gene.

Transgenic: An organism that has had genes from another species added into its genome. This is sometimes done so that researchers can study a particular human gene in an animal model.

Translation: The process that takes place after transcription, when proteins are made from messenger RNA (mRNA) by ribosomes.

Tremor: Involuntary shaking of the muscles or parts of the body.

Trial: An experimental test. For example, testing certain therapies on animals or humans. See also clinical trial.

U

Ultrasound: The use of reflected sound waves to "see" a hidden object. Now widely used in medicine as a non-invasive way to obtain images of muscle structure, internal organs or an unborn child.

V

Vasculature: The network of blood vessels, including the arteries, veins and capillaries, found within a particular organ or part of the body.

Vector: 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 healthy human DNA.

Ventilator: A machine that provides artificial breathing.

Vertebrae: Individual bones that make up the spine.

Vesicles: 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 material (DNA or RNA) surrounded by a protective coat of protein. They are capable of latching onto cells and getting inside them. Some viruses (like the cold virus or flu virus) cause people to become ill. But, their ability to get inside cells also means that certain viruses can be used to deliver treatments into the cell. See also adeno-associated virus (AAV) and gene therapy.

Vital capacity: The maximum volume of air that a person can inhale and exhale. See also forced vital capacity (FVC).

W

Werdnig Hoffman Disease: Also known as SMA Type 1 or Type I SMA.

White blood cells: Cells of the immune system that defend the body against both infectious disease and foreign substances.

Wild-type: In genetics, wild-type refers to the most common form of an allele as it occurs in nature. You may hear this term used when referring to animal models, where it refers to an animal that has the normal genetic make-up occurring in nature. These animals do not have the genetic condition being studied and are used as a comparison with the animals that have been bred to have a particular genetic disorder.

Z

Zebrafish: An animal model used to investigate human disease. Zebrafish are small, tropical freshwater fish. Like mice, zebrafish can be used to study a specific gene's function, disease processes, and to test potential treatments.