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

MT-TH gene

The MT-TH gene provides instructions for a transfer RNA molecule that is critical for the assembly of proteins involved in mitochondrial energy production.

Normal Function

The MT-TH gene provides instructions for making a particular type of RNA called transfer RNA (tRNA), which helps assemble protein building blocks known as amino acids into full-length, functioning proteins. The MT-TH gene provides instructions for a specific form of tRNA designated as tRNAHis. During protein assembly, this molecule attaches to the amino acid histidine (His) and inserts it into the appropriate locations in the growing protein.

The tRNAHis molecule is present in cellular structures called mitochondria. These structures convert energy from food into a form that cells can use. Through a process called oxidative phosphorylation, mitochondria use oxygen, simple sugars, and fatty acids to create adenosine triphosphate (ATP), the cell's main energy source. The tRNAHis molecule is involved in the assembly of proteins that carry out oxidative phosphorylation.

Health Conditions Related to Genetic Changes

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes

A small number of people with the features of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) have a mutation in the MT-TH gene. This condition is characterized by recurrent severe headaches, muscle weakness (myopathy), hearing loss, stroke-like episodes including a loss of consciousness, seizures, and other problems affecting the nervous system. Some people with an MT-TH gene mutation also have features of another mitochondrial disorder called myoclonic epilepsy with ragged-red fibers (MERRF); this combination is called MERRF/MELAS overlap syndrome.

Myoclonic epilepsy with ragged-red fibers

A few individuals with a mutation in the MT-TH gene have features of both myoclonic epilepsy with ragged-red fibers (MERRF) and MELAS. The mutation involved in this overlap syndrome replaces the nucleotide guanine with the nucleotide adenine at gene position 12147 (written as G12147A).

Nonsyndromic hearing loss

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

Other disorders

Another mutation in the MT-TH gene may increase the risk of developing a heart condition called cardiomyopathy, where the heart muscle is weakened and unable to pump blood effectively. This mutation replaces the nucleotide guanine with the nucleotide adenine at gene position 12192 (written as G12192A).

Other Names for This Gene

  • MTTH
  • tRNA histidine

Frequently Asked Questions

Early symptoms often include frequent, severe headaches, muscle weakness that worsens with activity, hearing loss, and episodes of confusion or loss of consciousness. Seizures may appear later, and some patients develop visual disturbances or speech difficulties. These symptoms usually start in childhood or adolescence.
Yes, MT-TH mutations are inherited in a maternal pattern because mitochondria are passed from mother to child. If you carry a pathogenic MT-TH mutation, all of your children will inherit the same mitochondrial DNA variant. Genetic counseling can help you understand the risks and discuss reproductive options.===
Diagnosis usually involves a blood test for mitochondrial DNA sequencing, followed by a muscle biopsy if needed. The test looks for specific point mutations in the MT-TH gene that are known to cause MELAS or MERRF/MELAS overlap. A neurologist or geneticist typically orders these studies.
While there is no cure, certain supplements (such as coenzyme Q10, L‑carnitine, and riboflavin) may help support mitochondrial energy production. Anticonvulsants can manage seizures, and physical therapy can improve muscle strength. Treatment plans are highly individualized and should be coordinated with a mitochondrial disease specialist.
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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