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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed May 2014

What is the official name of the MT-TS1 gene?

The official name of this gene is “mitochondrially encoded tRNA serine 1 (UCN).”

MT-TS1 is the gene's official symbol. The MT-TS1 gene is also known by other names, listed below.

What is the normal function of the MT-TS1 gene?

The MT-TS1 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-TS1 gene provides instructions for a specific form of tRNA that is designated as tRNASer(UCN). During protein assembly, this molecule attaches to a particular amino acid, serine (Ser), and inserts it into the appropriate locations in the growing protein.

The tRNASer(UCN) 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 tRNASer(UCN) molecule is involved in the assembly of proteins that carry out oxidative phosphorylation.

Does the MT-TS1 gene share characteristics with other genes?

The MT-TS1 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-TS1 gene related to health conditions?

myoclonic epilepsy with ragged-red fibers - caused by mutations in the MT-TS1 gene

Mutations in the MT-TS1 gene have been found in a few people with variant forms of myoclonic epilepsy with ragged-red fibers (MERRF). In these cases, affected individuals typically have muscle twitches (myoclonus), muscle weakness (myopathy), difficulty coordinating movement (ataxia), hearing loss, seizures, and intellectual impairment. Two mutations in the MT-TS1 gene have been found to cause these symptoms. One mutation replaces the DNA building block (nucleotide) thymine with the nucleotide cytosine at gene position 7512 (written as T7512C). The other mutation inserts an extra cytosine at position 7472 (written as 7472insC). Researchers have not determined how these genetic changes cause variant forms of MERRF.

palmoplantar keratoderma with deafness - caused by mutations in the MT-TS1 gene

Some of the MT-TS1 gene mutations responsible for hearing loss can cause additional signs and symptoms in affected individuals. For example, one mutation causes a skin condition called palmoplantar keratoderma with deafness. In addition to hearing loss, this condition causes skin on the palms of the hands and the soles of the feet to become thick, scaly, and calloused.

The genetic change that results in this combination of features replaces the nucleotide adenine with the nucleotide guanine at position 7445 in the MT-TS1 gene (written as A7445G). This mutation likely disrupts the normal production of the tRNASer(UCN) molecule. As a result, less tRNASer(UCN) is available to assemble proteins within mitochondria. These changes reduce the production of proteins needed for oxidative phosphorylation, which may impair the ability of mitochondria to make ATP. It is unclear why the effects of the mutation are limited to cells in the inner ear and the skin in this condition.

other disorders - caused by mutations in the MT-TS1 gene

In some families, mutations in the MT-TS1 gene cause health problems unrelated to hearing loss. For example, one mutation has been identified in people with muscle pain, weakness, and extreme fatigue associated with exercise (exercise intolerance). The genetic change that causes these symptoms replaces the nucleotide adenine with the nucleotide guanine at position 7497 in the MT-TS1 gene (written as A7497G).

It is unclear why changes in the MT-TS1 gene can cause such a large variety of signs and symptoms. Even within a single family, affected individuals may have different health problems caused by the same genetic change. Researchers believe that other genetic and environmental factors help determine whether a MT-TS1 gene mutation leads to isolated hearing loss, hearing loss associated with other signs and symptoms, or features unrelated to hearing.

Where is the MT-TS1 gene located?

The MT-TS1 gene is located in mitochondrial DNA.

Molecular Location in mitochondrial DNA: base pairs 7,446 to 7,514

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

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

Where can I find additional information about MT-TS1?

You and your healthcare professional may find the following resources about MT-TS1 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-TS1 gene or gene products?

  • MTTS1
  • tRNA serine 1 (UCN)
  • TRNS1 tRNA

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding MT-TS1?

acids ; adenine ; adenosine triphosphate ; amino acid ; ataxia ; ATP ; cell ; cytosine ; deficiency ; DNA ; epilepsy ; fatty acids ; gene ; guanine ; keratoderma ; mitochondria ; molecule ; mutation ; myoclonus ; nucleotide ; oxidase ; oxidative phosphorylation ; oxygen ; palmoplantar keratoderma ; phosphorylation ; protein ; reactive oxygen species ; RNA ; ser ; serine ; thymine ; transfer RNA ; tRNA

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Caria H, Matos T, Oliveira-Soares R, Santos AR, Galhardo I, Soares-Almeida L, Dias O, Andrea M, Correia C, Fialho G. A7445G mtDNA mutation present in a Portuguese family exhibiting hereditary deafness and palmoplantar keratoderma. J Eur Acad Dermatol Venereol. 2005 Jul;19(4):455-8. (
  • Finsterer J, Harbo HF, Baets J, Van Broeckhoven C, Di Donato S, Fontaine B, De Jonghe P, Lossos A, Lynch T, Mariotti C, Schöls L, Spinazzola A, Szolnoki Z, Tabrizi SJ, Tallaksen CM, Zeviani M, Burgunder JM, Gasser T; European Federation of Neurological Sciences. EFNS guidelines on the molecular diagnosis of mitochondrial disorders. Eur J Neurol. 2009 Dec;16(12):1255-64. (
  • Fischel-Ghodsian N, Kopke RD, Ge X. Mitochondrial dysfunction in hearing loss. Mitochondrion. 2004 Sep;4(5-6):675-94. Epub 2004 Nov 6. (
  • Gene Review: Nonsyndromic Hearing Loss and Deafness, Mitochondrial (
  • Grafakou O, Hol FA, Otfried Schwab K, Siers MH, ter Laak H, Trijbels F, Ensenauer R, Boelen C, Smeitink J. Exercise intolerance, muscle pain and lactic acidaemia associated with a 7497G>A mutation in the tRNASer(UCN) gene. J Inherit Metab Dis. 2003;26(6):593-600. (
  • Jaksch M, Klopstock T, Kurlemann G, Dörner M, Hofmann S, Kleinle S, Hegemann S, Weissert M, Müller-Höcker J, Pongratz D, Gerbitz KD. Progressive myoclonus epilepsy and mitochondrial myopathy associated with mutations in the tRNA(Ser(UCN)) gene. Ann Neurol. 1998 Oct;44(4):635-40. (
  • Komlósi K, Maász A, Kisfali P, Hadzsiev K, Bene J, Melegh BI, Melegh B, Ablonczy M, Németh K, Fekete G. Non-syndromic Hearing Impairment in a Hungarian Family with the m.7510T>C Mutation of Mitochondrial tRNA(Ser(UCN)) and Review of Published Cases. JIMD Rep. 2013;9:105-11. doi: 10.1007/8904_2012_187. Epub 2012 Nov 2. (
  • Maász A, Komlósi K, Hadzsiev K, Szabó Z, Willems PJ, Gerlinger I, Kosztolányi G, Méhes K, Melegh B. Phenotypic variants of the deafness-associated mitochondrial DNA A7445G mutation. Curr Med Chem. 2008;15(13):1257-62. Review. (
  • Nakamura M, Nakano S, Goto Y, Ozawa M, Nagahama Y, Fukuyama H, Akiguchi I, Kaji R, Kimura J. A novel point mutation in the mitochondrial tRNA(Ser(UCN)) gene detected in a family with MERRF/MELAS overlap syndrome. Biochem Biophys Res Commun. 1995 Sep 5;214(1):86-93. (
  • NCBI Gene (
  • Pulkes T, Liolitsa D, Eunson LH, Rose M, Nelson IP, Rahman S, Poulton J, Marchington DR, Landon DN, Debono AG, Morgan-Hughes JA, Hanna MG. New phenotypic diversity associated with the mitochondrial tRNA(SerUCN) gene mutation. Neuromuscul Disord. 2005 May;15(5):364-71. (
  • Sevior KB, Hatamochi A, Stewart IA, Bykhovskaya Y, Allen-Powell DR, Fischel-Ghodsian N, Maw MA. Mitochondrial A7445G mutation in two pedigrees with palmoplantar keratoderma and deafness. Am J Med Genet. 1998 Jan 13;75(2):179-85. (
  • Toompuu M, Yasukawa T, Suzuki T, Hakkinen T, Spelbrink JN, Watanabe K, Jacobs HT. The 7472insC mitochondrial DNA mutation impairs the synthesis and extent of aminoacylation of tRNASer(UCN) but not its structure or rate of turnover. J Biol Chem. 2002 Jun 21;277(25):22240-50. Epub 2002 Mar 27. (
  • Zheng J, Ji Y, Guan MX. Mitochondrial tRNA mutations associated with deafness. Mitochondrion. 2012 May;12(3):406-13. doi: 10.1016/j.mito.2012.04.001. Epub 2012 Apr 16. (


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 1, 2016