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Reviewed May 2014

What is the official name of the MT-TH gene?

The official name of this gene is “mitochondrially encoded tRNA histidine.”

MT-TH is the gene's official symbol. The MT-TH gene is also known by other names, listed below.

Read more about gene names and symbols on the About page.

What is the normal function of the MT-TH gene?

The MT-TH gene provides instructions for making a particular type of RNA, a molecule that is a chemical cousin of DNA. This type of RNA, called transfer RNA (tRNA), 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 that is designated as tRNAHis. During protein assembly, this molecule attaches to a particular 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.

Does the MT-TH gene share characteristics with other genes?

The MT-TH gene belongs to a family of genes called TRNA (transfer RNAs).

A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? in the Handbook.

How are changes in the MT-TH gene related to health conditions?

mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes - caused by mutations in the MT-TH gene

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); these additional features can include muscle twitches (myoclonus), difficulty coordinating movement (ataxia), and abnormal muscle cells known as ragged-red fibers. This combination of signs and symptoms is called MERRF/MELAS overlap syndrome.

MT-TH gene mutations that cause MELAS and MERRF/MELAS overlap syndrome change single DNA building blocks (nucleotides) in the gene. Researchers have not determined how these genetic changes alter energy production in mitochondria or cause the varied signs and symptoms of MELAS or MERRF/MELAS overlap syndrome.

myoclonic epilepsy with ragged-red fibers - caused by mutations in the MT-TH gene

As mentioned above, 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). It remains unknown why this mutation causes the overlapping features of MERRF and MELAS.

other disorders - associated with the MT-TH gene

Another mutation in the MT-TH gene may increase the risk of developing a heart condition called cardiomyopathy. People with cardiomyopathy have a weakened heart muscle that is unable to pump blood effectively. A particular change in the MT-TH gene has been identified in several adults with cardiomyopathy, but without other common signs of mitochondrial disease such as neurological abnormalities. This mutation replaces the nucleotide guanine with the nucleotide adenine at gene position 12192 (written as G12192A). It is unclear why this alteration in mitochondrial DNA may increase a person's risk of developing heart problems without affecting other parts of the body.

Where is the MT-TH gene located?

The MT-TH gene is located in mitochondrial DNA.

Molecular Location in mitochondrial DNA: base pairs 12,138 to 12,206

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBIThis link leads to a site outside Genetics Home Reference.)

Overview of gene located on mitochondrial DNA Close-up of gene located on mitochondrial DNA

Where can I find additional information about MT-TH?

You and your healthcare professional may find the following resources about MT-TH helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the MT-TH gene or gene products?

  • MTTH
  • tRNA histidine

Where can I find general information about genes?

The Handbook provides basic information about genetics in clear language.

These links provide additional genetics resources that may be useful.

What glossary definitions help with understanding MT-TH?

References (9 links)


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.

Reviewed: May 2014
Published: February 8, 2016