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MT-TS1 gene

mitochondrially encoded tRNA serine 1 (UCN)

Normal Function

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.

Health Conditions Related to Genetic Changes

Myoclonic epilepsy with ragged-red fibers

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.

More About This Health Condition

Nonsyndromic hearing loss

MedlinePlus Genetics provides information about Nonsyndromic hearing loss

More About This Health Condition

Palmoplantar keratoderma with deafness

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.

More About This Health Condition

Other disorders

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.

Other Names for This Gene

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

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


  • 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. doi: 10.1111/j.1468-3083.2005.01087.x. Citation on PubMed
  • Finsterer J, Harbo HF, Baets J, Van Broeckhoven C, Di Donato S, Fontaine B, De Jonghe P, Lossos A, Lynch T, Mariotti C, Schols 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. doi: 10.1111/j.1468-1331.2009.02811.x. Citation on PubMed
  • Fischel-Ghodsian N, Kopke RD, Ge X. Mitochondrial dysfunction in hearing loss. Mitochondrion. 2004 Sep;4(5-6):675-94. doi: 10.1016/j.mito.2004.07.040. Epub 2004 Nov 6. Citation on PubMed
  • 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. doi: 10.1023/a:1025960300710. Citation on PubMed
  • Jaksch M, Klopstock T, Kurlemann G, Dorner M, Hofmann S, Kleinle S, Hegemann S, Weissert M, Muller-Hocker 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. doi: 10.1002/ana.410440409. Citation on PubMed
  • Komlosi K, Maasz A, Kisfali P, Hadzsiev K, Bene J, Melegh BI, Melegh B, Ablonczy M, Nemeth 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;9:105-111. doi: 10.1007/8904_2012_187. Epub 2012 Nov 2. Erratum In: JIMD Rep. 2013;9:E1. doi: 10.1007/978-3-642-35518-9_195. Citation on PubMed or Free article on PubMed Central
  • Maasz A, Komlosi K, Hadzsiev K, Szabo Z, Willems PJ, Gerlinger I, Kosztolanyi G, Mehes K, Melegh B. Phenotypic variants of the deafness-associated mitochondrial DNA A7445G mutation. Curr Med Chem. 2008;15(13):1257-62. doi: 10.2174/092986708784534910. Citation on PubMed
  • 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. doi: 10.1006/bbrc.1995.2260. Citation on PubMed
  • 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. doi: 10.1016/j.nmd.2005.01.006. Citation on PubMed
  • 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. Citation on PubMed
  • 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. doi: 10.1074/jbc.M200338200. Epub 2002 Mar 27. Citation on PubMed
  • Usami SI, Nishio SY. Nonsyndromic Hearing Loss and Deafness, Mitochondrial. 2004 Oct 22 [updated 2018 Jun 14]. In: Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Bean LJH, Gripp KW, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from Citation on PubMed
  • 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. Citation on PubMed

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