MT-TK

Chr MT

tRNA-Lys

Also known as: MTTK

NCBI Gene: 4566 ENSG00000210156 OMIM: 590060

This gene encodes mitochondrial tRNA-Lysine, which is required for translation of all 13 mitochondrial DNA-encoded proteins involved in oxidative phosphorylation. Mutations cause MERRF syndrome (myoclonic epilepsy with ragged-red fibers), with the m.8344A>G variant accounting for approximately 80% of cases, as well as cardiomyopathy and lipomatosis. Inheritance is maternal, and clinical severity depends on the degree of heteroplasmy.

GeneReviews OMIM ResearchSummary from Curated mito context

GeneReviews OMIM ResearchGenerating clinical summary…

Clinical highlights

Gene–disease validity (ClinGen)

Active trials

Pubs (1 yr)

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P/LP submissions

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P/LP missense

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LOEUF

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Mechanism

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GeneReview available — MT-TK

Authoritative clinical overview · Recommended first read

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Nuclear-gene analyses omitted

MT-TK is a mitochondrial tRNA gene. gnomAD constraint, carrier burden and exome coverage, the ClinVar type breakdown, the protein lollipop, AlphaFold and transcript-architecture views are built for nuclear genes and are not shown. Population data for mtDNA variants (gnomAD v3.1, homoplasmy and heteroplasmy) is on each variant page.

Where it sits in the mitochondrial genome

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proteinrRNAtRNAouter ring H-strand · inner L-strandMITOMAP confirmedreported (as of 2026-10-07)

37 genes from Ensembl (rCRS numbering, matched to MITOMAP’s Gene Loci); landmarks and disease alleles from MITOMAP (CC BY 3.0). Circular layout after MitoWheel.

ClinVar Variant Classifications

0 submitted variants in ClinVar

ClinVar

MITOMAP Disease Variants — MT-TK

Live table ↗

Variant	Disease	Status	GenBank seqs
m.8296A>G	DMDF / MERRF / HCM / epilepsy / hearing loss	Uncertain significance · reported	38
m.8299G>A	PEO + respiratory impairment	Uncertain significance · reported	0
m.8302A>T	Encephalopathy	Unclear	0
m.8304G>A	Epilepsy+ataxia+visual disturbance+deafness	Reported	0
m.8305C>T	Mitochondrial myopathy	Reported	0
m.8306T>C	Severe adult-onset multisymptom myopathy / Myoclonic epilepsy	Uncertain significance · confirmed	0
m.8311T>C	Poss. hypertension factor	Reported	134
m.8313G>A	MNGIE-like / Progressive mito cytopathy	Likely pathogenic · confirmed	1
m.8315A>C	MERRF	Reported	0
m.8316T>C	MELAS	Reported	0
m.8319A>G	Kearns-Sayre syndrome	Uncertain significance · reported	0
m.8326A>G	Mitochondrial Cytopathy	Reported	0
m.8328G>A	Encephalopathy / EXIT with myopathy and ptosis; multi-symptom pt	Reported	0
m.8332A>G	Dystonia and stroke-like episodes	Reported	0
m.8337T>C	Poss. hypertension factor	Reported	175
m.8339A>G	Hearing loss patient	Reported	1
m.8340G>A	Myopathy, Exercise Intolerance, CPEO-like /childhood epilepsy with SNHL & eye disease	Likely pathogenic · confirmed	0
m.8342G>A	PEO and Myoclonus	Uncertain significance · reported	0
m.8343A>G	Metabolic syndrome and polycystic ovary syndrome / possible PD risk factor / deafness	Reported	70
m.8344A>G	MERRF; Other - LD / depressive mood disorder / leukoencephalopathy / HiCM / lipomas	Pathogenic · confirmed	4
m.8346C>-	Rett Syndrome	Reported	7
m.8347A>G	Poss. hypertension factor	Reported	24
m.8348A>G	Cardiomyopathy / SNHL / poss. hypertension factor	Reported	148
m.8355T>C	Myopathy	Reported	0
m.8356T>C	MERRF	Likely pathogenic · confirmed	0
m.8357T>C	Multiple symmetric lipomatosis / multiorgan disease	Reported	1
m.8361G>A	MERRF	Uncertain significance · reported	0
m.8362T>G	Myopathy / ataxia deafness diabetes mellitus	Uncertain significance · reported	0
m.8363G>A	MICM+DEAF / MERRF / Autism / Leigh Syndrome / Ataxia / Lipomatosis	Likely pathogenic · confirmed	0