A synaptopathy is a disease of the

brain The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head ( cephalization), usually near organs for special ...

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spin ...

peripheral nervous system The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain a ...

relating to the dysfunction of

synapses In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to the transmission of nervous impulses from ...

. This can arise as a result of a mutation in a gene encoding a synaptic protein such as an

ion channel Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ...

neurotransmitter receptor A neurotransmitter receptor (also known as a neuroreceptor) is a membrane receptor protein that is activated by a neurotransmitter. Chemicals on the outside of the cell, such as a neurotransmitter, can bump into the cell's membrane, in which the ...

, or a protein involved in neurotransmitter release. It can also arise as a result of an

autoantibody An autoantibody is an antibody (a type of protein) produced by the immune system that is directed against one or more of the individual's own proteins. Many autoimmune diseases (notably lupus erythematosus) are associated with such antibodies. Pr ...

targeting a synaptic protein. Synaptopathies caused by

mutations are also known as synaptic channelopathies. An example is episodic ataxia.

Myasthenia gravis Myasthenia gravis (MG) is a long-term neuromuscular junction disease that leads to varying degrees of skeletal muscle weakness. The most commonly affected muscles are those of the eyes, face, and swallowing. It can result in double vision, ...

is an example of an

autoimmune In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an " autoimmune disease" ...

synaptopathy. Some toxins also affect synaptic function. Tetanus toxin and

botulinum toxin Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromu ...

affect neurotransmitter release. Tetanus toxin can enter the body via a wound, and botulinum toxin can be ingested or administered therapeutically to alleviate dystonia or as cosmetic treatment. Another example of synaptopathy occurs in the auditory system. This cochlear synaptopathy has been seen after prolonged noise exposure in both primate and non-primate models. Two possible reasons for this neuronal death are both glutamate-mediated

excitotoxicity In excitotoxicity, nerve cells suffer damage or death when the levels of otherwise necessary and safe neurotransmitters such as glutamate become pathologically high, resulting in excessive stimulation of receptors. For example, when glutamate ...

in the postsynaptic terminal, and presynaptic ribbon damage which occurs by an unknown mechanism. Synaptopathies are attracting research interest because they provide an insight into fundamental mechanisms of

synaptic transmission Neurotransmission (Latin: ''transmissio'' "passage, crossing" from ''transmittere'' "send, let through") is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron (the presynaptic neuron) ...

and because an improved understanding of disease mechanisms may lead to new treatments. Some diseases of unknown etiology have been proposed to be synaptopathies. Examples include

autism spectrum disorder The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...

and

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social wi ...

. Synaptic dysfunction can also occur in

neurodegenerative A neurodegenerative disease is caused by the progressive loss of structure or function of neurons, in the process known as neurodegeneration. Such neuronal damage may ultimately involve cell death. Neurodegenerative diseases include amyotrophic ...

disorders such as

Alzheimer's Alzheimer's disease (AD) is a neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As ...

. Immune-mediated cerebellar ataxias represent a group of disorders causing cerebellar ataxia induced by a dysfunction of synapses. Increasing knowledge of the genetic basis of these diseases has linked proteins to the function of the synapse. Age-related cochlear synaptic and neural degeneration has also been demonstrated in mice. Molecules such as FMRP1 act as translational repressor thus when ablated such as in FXS result in varying degrees of cellular and behavioural abnormalities. Additional molecules thought to be involved include SynGAP and SHANK1.

References

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External links

* https://www.ucl.ac.uk/ion/synaptopathies Neurological disorders