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MT-TK gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

MT-TK gene

The MT-TK gene provides instructions for a transfer RNA molecule necessary for protein assembly and energy production within mitochondria.

Normal Function

The MT-TK gene provides instructions for making a molecule called a transfer RNA (tRNA), which helps assemble protein building blocks (amino acids) into functioning proteins. The MT-TK gene provides instructions for a specific form of tRNA designated as tRNALys. During protein assembly, this molecule attaches to the amino acid lysine (Lys) and inserts it into the growing protein.

The tRNALys molecule is present in mitochondria, which convert energy from food into adenosine triphosphate (ATP) through oxidative phosphorylation. In pancreatic beta cells, mitochondria also help trigger the release of insulin in response to high glucose levels, regulating blood sugar.

Health Conditions Related to Genetic Changes

Maternally inherited diabetes and deafness

A mutation in the MT-TK gene (A8296G) has been found in a small number of people with maternally inherited diabetes and deafness (MIDD). This mutation impairs the ability of mitochondria to help trigger insulin release, leading to diabetes.

Myoclonic epilepsy with ragged-red fibers

Several mutations in the MT-TK gene have been identified in people with myoclonic epilepsy with ragged-red fibers (MERRF). This condition is characterized by muscle twitches (myoclonus), recurrent seizures (epilepsy), and abnormal muscle cells known as ragged-red fibers. The most common mutation, A8344G, impairs the ability of mitochondria to make proteins and produce energy. Some individuals with a T8356C mutation exhibit MERRF/MELAS overlap syndrome, which includes features of both MERRF and mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS).

Leigh syndrome

The A8344G mutation can also cause Leigh syndrome, a progressive brain disorder. Signs and symptoms, which usually begin in infancy or early childhood, include vomiting, seizures, delayed development, myopathy, and problems with movement.

Nonsyndromic hearing loss

MT-TK gene mutations are associated with nonsyndromic hearing loss.

Other disorders

A condition characterized by cardiomyopathy and hearing loss is caused by the G8363A mutation in the MT-TK gene. Affected individuals may also experience myopathy and ataxia.

Other Names for This Gene

  • mitochondrial tRNA-Lys
  • MTTK
  • trnK

Frequently Asked Questions

Diabetes resulting from an MT-TK mutation, such as the A8296G variant, is a mitochondrial disorder that impairs the pancreas's ability to release insulin in response to glucose. Unlike Type 1 diabetes, which is autoimmune, or Type 2, which is often linked to insulin resistance, this condition stems from defective mitochondrial function in beta cells. Treatment may still involve insulin therapy, but the progression can be more variable, and patients often require monitoring for associated symptoms like hearing loss, which is not a feature of standard diabetes types.
You should request targeted mitochondrial DNA sequencing specifically looking for the A8296G mutation in the MT-TK gene. Since this mutation is maternally inherited, it is passed from mother to all children, but only daughters can pass it on. Standard nuclear genetic panels often miss mitochondrial variants, so it is crucial to specify that you are looking for mitochondrial tRNA mutations associated with MIDD.
The hearing loss associated with MT-TK mutations is due to the high energy demands of the inner ear hair cells, which rely heavily on mitochondrial function. When the tRNALys molecule is defective, these cells cannot produce enough ATP, leading to their gradual death. Currently, there is no cure to prevent the hearing loss, but early detection through audiometry allows for the timely use of hearing aids or cochlear implants to maintain communication abilities.
Yes, certain MT-TK mutations, particularly the A8344G variant, can cause severe neurological conditions such as myoclonic epilepsy with ragged-red fibers (MERRF) or Leigh syndrome. These conditions involve muscle twitches, seizures, and progressive brain dysfunction. Monitoring typically involves regular neurological exams, EEGs for seizure activity, and MRI scans to detect brain changes, especially if a patient presents with unexplained muscle weakness or cognitive decline.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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