MT-TI

Mitochondrially encoded tRNA isoleucine also known as MT-TI is a transfer RNA which in humans is encoded by the mitochondrial MT-TI gene.^[1]

mitochondrially encoded tRNA isoleucine
Identifiers
Symbol	MT-TI
Alt. symbols	MTTI
NCBI gene	4565
HGNC	7488
RefSeq	NC_001807
Other data
Locus	Chr. MT

Structure

The MT-TI gene is located on the p arm of the mitochondrial DNA at position 12 and it spans 69 base pairs.^[2] The structure of a tRNA molecule is a distinctive folded structure which contains three hairpin loops and resembles a three-leafed clover.^[3]

Function

MT-TI is a small 69 nucleotide RNA (human mitochondrial map position 4263-4331) that transfers the amino acid isoleucine to a growing polypeptide chain at the ribosome site of protein synthesis during translation.

Clinical significance

Mutations in MT-TI can result in multiple mitochondrial deficiencies and associated disorders.

Myoclonic epilepsy with ragged-red fibers (MERRF)

Mutations in the MT-TI gene have been associated with myoclonic epilepsy with ragged-red fibers (MERRF). Myoclonic epilepsy with ragged-red fibers (MERRF) is a disorder that affects many parts of the body, particularly the muscles and nervous system. In most cases, the signs and symptoms of this disorder appear during childhood or adolescence. The features of MERRF vary widely among affected individuals, even among members of the same family. Common symptoms include, myoclonus, myopathy, spasticity, epilepsy, peripheral neuropathy, dementia, ataxia, atrophy, and more.^[4]

Cardiomyopathy

Mutations in the MT-TI gene may also cause cardiomyopathy, a disorder of the heart characterized by the thickening of the heart, usually in the interventricular septum, which results in a weakened heart muscle that is unable to pump blood effectively. It is unclear why such mutations result in the symptoms of isolated cardiomyopathy.^[5] Mutations of 4300A>G, 4295A>G, 4269A>G, and 4317A>G in the MT-TI gene have been found in patients with cardiomyopathy in varying severities and onset.^[6][7][8][9]

Complex IV Deficiency

MT-TI mutations have been associated with complex IV deficiency of the mitochondrial respiratory chain, also known as the cytochrome c oxidase deficiency. Cytochrome c oxidase deficiency is a rare genetic condition that can affect multiple parts of the body, including skeletal muscles, the heart, the brain, or the liver. Common clinical manifestations include myopathy, hypotonia, and encephalomyopathy, lactic acidosis, and hypertrophic cardiomyopathy.^[10] A patient with a 4269A>G mutation in MT-TI was found with the deficiency.^[11]

References

1. Anderson S, Bankier AT, Barrell BG, de Bruijn MH, Coulson AR, Drouin J, et al. (April 1981). "Sequence and organization of the human mitochondrial genome". Nature. 290 (5806): 457–65. Bibcode:1981Natur.290..457A. doi:10.1038/290457a0. PMID 7219534. S2CID 4355527.
2. "MT-TI mitochondrially encoded tRNA isoleucine [Homo sapiens (human)] - Gene - NCBI". www.ncbi.nlm.nih.gov.
3. "tRNA / transfer RNA". Learn Science at Scitable.
4. "Myoclonic epilepsy with ragged-red fibers". Genetics Home Reference. U.S. National Library of Medicine. This article incorporates text from this source, which is in the public domain.
5. "Familial hypertrophic cardiomyopathy". Genetics Home Reference. U.S. National Library of Medicine. This article incorporates text from this source, which is in the public domain.
6. Tanaka M, Ino H, Ohno K, Hattori K, Sato W, Ozawa T, et al. (December 1990). "Mitochondrial mutation in fatal infantile cardiomyopathy". Lancet. 336 (8728): 1452. doi:10.1016/0140-6736(90)93162-I. PMID 1978914. S2CID 27652968.
7. Taniike M, Fukushima H, Yanagihara I, Tsukamoto H, Tanaka J, Fujimura H, et al. (July 1992). "Mitochondrial tRNA(Ile) mutation in fatal cardiomyopathy". Biochemical and Biophysical Research Communications. 186 (1): 47–53. doi:10.1016/S0006-291X(05)80773-9. PMID 1632786.
8. Merante F, Myint T, Tein I, Benson L, Robinson BH (1996). "An additional mitochondrial tRNA(Ile) point mutation (A-to-G at nucleotide 4295) causing hypertrophic cardiomyopathy". Human Mutation. 8 (3): 216–22. doi:10.1002/(SICI)1098-1004(1996)8:3<216::AID-HUMU4>3.0.CO;2-7. PMID 8889580. S2CID 34527275.
9. Taylor RW, Giordano C, Davidson MM, d'Amati G, Bain H, Hayes CM, et al. (May 2003). "A homoplasmic mitochondrial transfer ribonucleic acid mutation as a cause of maternally inherited hypertrophic cardiomyopathy". Journal of the American College of Cardiology. 41 (10): 1786–96. doi:10.1016/S0735-1097(03)00300-0. PMID 12767666.
10. Reference, Genetics Home. "Cytochrome c oxidase deficiency". Genetics Home Reference. This article incorporates text from this source, which is in the public domain.
11. Kaido M, Fujimura H, Taniike M, Yoshikawa H, Toyooka K, Yorifuji S, Inui K, Okada S, Sparaco M, Yanagihara T (August 1995). "Focal cytochrome c oxidase deficiency in the brain and dorsal root ganglia in a case with mitochondrial encephalomyopathy (tRNA(Ile) 4269 mutation): histochemical, immunohistochemical, and ultrastructural study". Journal of the Neurological Sciences. 131 (2): 170–6. doi:10.1016/0022-510X(95)00111-E. PMID 7595643. S2CID 41493869.

Further reading

Finsterer, J (January 2003). "Mitochondriopathy mimicking amyotrophic lateral sclerosis". The Neurologist. 9 (1): 45–8. doi:10.1097/01.nrl.0000038589.58012.a8. PMID 12801431. S2CID 43440359.

This article incorporates text from the United States National Library of Medicine, which is in the public domain.