| Domain | Key facts | Suggested ontology IDs | Evidence |
|---|---|---|---|
| Identity / identifiers | MTO1 deficiency is a rare Mendelian mitochondrial disease, commonly described as combined oxidative phosphorylation deficiency-10 (COXPD10) and also as mitochondrial hypertrophic cardiomyopathy with lactic acidosis due to MTO1 deficiency; evidence here is aggregated from published case reports/series rather than EHR-only resources. | MONDO:0013865; OMIM for MTO1 deficiency/COXPD10: not confidently verified here; Orphanet/MeSH/ICD: unavailable or not confidently verified here | (pqac-00000000, pqac-00000003, pqac-00000005) |
| Genetics / inheritance | Cause: biallelic pathogenic variants in **MTO1** (mitochondrial tRNA translation optimization 1), autosomal recessive. Largest compiled cohort: 35 patients from 26 unrelated families, 17 male/18 female, across 11 countries. Variant spectrum in that cohort: 19 pathogenic variants total (15 missense, 3 frameshift, 1 splice-site); no confirmed biallelic truncating genotypes, suggesting complete loss of function may be incompatible with human survival. Consanguinity reported in 34% of cases. | Gene: **MTO1**; inheritance term: autosomal recessive (ontology ID not asserted here); GO process suggestions: mitochondrial translational elongation/translation **GO:0032543** (mitochondrial translation), oxidative phosphorylation **GO:0006119** | (pqac-00000002, pqac-00000004, pqac-00000015, pqac-00000020) |
| Core phenotype frequencies | Frequent clinical features in the 35-patient series: lactic acidosis 100% eventually; hypertrophic cardiomyopathy 79% eventually (44% presenting feature); developmental delay/intellectual disability 97%; hypotonia 63% eventually; feeding difficulties 49%; optic atrophy 52%; seizures 34%; failure to thrive 34%; ataxia 21%. | HP:0003128 lactic acidosis; HP:0001639 hypertrophic cardiomyopathy; HP:0001263 global developmental delay; HP:0001252 hypotonia; HP:0001250 seizures; HP:0000648 optic atrophy; ataxia: HPO ID not confidently asserted here; failure to thrive: HPO ID not confidently asserted here | (pqac-00000002, pqac-00000003, pqac-00000005) |
| Biochemical signature | Peak plasma lactate averaged 13.6 mmol/L (range 3.4-57.8). Elevated plasma alanine in 88% of tested patients. Muscle respiratory-chain enzymology commonly showed combined deficiencies, especially complex IV deficiency in 28/30 muscle samples (93%); combined complex I+IV deficiency was most common (20/30). Fibroblast testing can be falsely normal. | CHEBI lactate/alanine: not asserted here; GO:0006120 mitochondrial electron transport, NADH to ubiquinone; GO:0006123 mitochondrial electron transport, cytochrome c to oxygen; GO:0006119 oxidative phosphorylation | (pqac-00000004, pqac-00000016, pqac-00000018) |
| Mechanism / causal chain | Upstream defect: impaired MTO1-dependent wobble U34 taurine-related modification of specific mt-tRNAs (reported for mt-tRNA\(Glu\), mt-tRNA\(Gln\), mt-tRNA\(Lys\), mt-tRNA\(Trp\), mt-tRNA\(Leu\(UUR\)\)). Intermediate effects: abnormal mt-tRNA structure/stability and aminoacylation, impaired mitochondrial transcript maturation/polyadenylation, reduced mitochondrial translation, defective OXPHOS complex assembly/activity. Downstream effects: bioenergetic failure, increased anaerobic glycolysis/lactic acidosis, altered fatty-acid metabolism with lipid droplet accumulation, cardiomyocyte hypertrophy and multisystem disease. Human fibroblasts further support HIF-1 activation with PPARγ/UCP2/AMPK-axis dysregulation. | GO:0032543 mitochondrial translation; GO:0000959 mitochondrial RNA metabolic process; GO:0006119 oxidative phosphorylation; GO:0006635 fatty acid beta-oxidation; GO:0001666 response to hypoxia; GO:0005739 mitochondrion | (pqac-00000009, pqac-00000010, pqac-00000011, pqac-00000014) |
| Affected anatomy / cells / compartments | Organs/systems: heart, brain/CNS, skeletal muscle, eye/optic nerve; multisystem disease with high-energy tissues preferentially affected. Imaging abnormalities reported in >70% with involvement of claustrum, thalami, white matter, cerebellar peduncles, and corpus callosum. Cell types implicated include cardiomyocytes and fibroblasts; subcellular localization centers on mitochondria/mitochondrial matrix and inner-membrane respiratory-chain machinery. | UBERON heart/brain/skeletal muscle/eye terms: not confidently asserted here; CL: cardiomyocyte and fibroblast IDs not confidently asserted here; GO:0005739 mitochondrion; GO:0005759 mitochondrial matrix; GO:0005743 mitochondrial inner membrane | (pqac-00000006, pqac-00000013) |
| Diagnosis | Best-confirming test strategy is genomic: WES or comprehensive mitochondrial/nuclear gene sequencing, because phenotype is nonspecific and fibroblast respiratory-chain testing may miss cases. Supportive findings: elevated lactate/alanine, urinary mitochondrial markers, brain MRI abnormalities, and reduced muscle complex I/III/IV activities. Muscle biopsy with respiratory-chain enzyme analysis is more sensitive than fibroblasts but not specific. Differential diagnosis includes other nuclear mitochondrial-translation disorders causing infantile cardiomyopathy/lactic acidosis (for example GTPBP3, TRMU/MTU1, MTFMT, MRPL44, FARS2, RARS2-related disease). | Diagnostic ontology IDs: not asserted here; GO terms as above may support annotation of functional assays | (pqac-00000015, pqac-00000017, pqac-00000018) |
| Treatment evidence | No evidence-based disease-specific therapy established. Supportive regimens used include L-carnitine, coenzyme Q10, riboflavin, vitamins, dichloroacetate, and antiseizure therapies; most had little or no appreciable objective benefit. Ketogenic diet showed subjective or seizure-related benefit in a minority (2/5 cases in one summary; 1/5 improved in another extract), so evidence remains limited and individualized. Experimental mechanistic suggestions from cell work include PPARγ agonism/AMPK activation and N-acetyl-cysteine, but these are not established clinical therapies for MTO1 deficiency. No disease-specific interventional clinical trial was retrieved in the tool search. | NCIT intervention IDs: not confidently asserted here; diet/drug ontologies not asserted here | (pqac-00000004, pqac-00000015, pqac-00000018, pqac-00000019) |
| Prognosis / natural history | Onset ranged from day 1 of life to 8 years (average ~10.2 months); 44% presented within first 2 days of life. Mortality in the 35-patient series was 34% overall, mean age at death 2.67 years; early neonatal presentation predicted worse outcome, and patients with one truncating plus one missense allele had particularly severe disease. Cardiomyopathy is common but not obligatory, and a minority survive into adolescence/adulthood, demonstrating variable expressivity. | Natural-history ontology IDs: not asserted here | (pqac-00000002, pqac-00000006, pqac-00000015, pqac-00000016) |
| Models | **Zebrafish mto1 knockout** recapitulates human hypertrophic cardiomyopathy, showing heart-looping defects, cardiomyocyte hypertrophy, myofiber disarray, mitochondrial fragmentation/cristae loss, impaired mt-tRNA maturation, altered mRNA polyadenylation, and reduced OXPHOS activity. **Mouse models:** partial knockdown yields mild cardiac phenotype with reduced mitochondrial translation/respiration; complete knockout causes >80% loss of mitochondrial translation and embryonic lethality around E8. **Yeast models:** conserved MTO1 ortholog supports pathogenicity testing and links U34 hypomodification to mitochondrial translation defects. No clearly established naturally occurring veterinary disease was identified here. | NCBI Taxon suggestions: Danio rerio 7955; Mus musculus 10090; Saccharomyces cerevisiae 4932 | (pqac-00000009, pqac-00000012, pqac-00000013, pqac-00000014) |


*Table: This compact table summarizes high-value knowledge-base facts for MTO1 deficiency, including identifiers, genetics, phenotype frequencies, mechanism, diagnosis, treatment evidence, prognosis, and model systems. It also suggests ontology mappings where the identifier is confidently supported and flags unavailable or uncertain IDs rather than inventing them.*