rs121434470
Variant summary
Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PS4_ModeratePP1_ModeratePP3PM2_Supporting
This summary comes from the ClinGen Evidence Repository: The m.4300A>G variant in MT-TI has been reported in at least 17 individuals from eight families with hypertrophic cardiomyopathy. Affected individuals had variable ages of onset (11 months old to 40s). All cases developed hypertrophic cardiomyopathy. Muscle biopsy revealed COX negative fibers in cardiac tissue and one case had ragged red fibers in skeletal muscle. Heteroplasmy levels were predominantly the same in all affected probands as the variant was present at homoplasmy or > 97% in all tissues. Other affected family members did harbor the variant at 60-100%. Of note, some healthy family members had the variant ranging from 40-100% (PS4_moderate; PMIDs: 10065021, 7646516, 12767666, 12711217, 23847141). This variant segregated with disease in a family with LVH with diffuse hypertrophy as the proband's heteroplasmy was 98% in heart, 85% in muscle, and 95% in blood. His seven affected maternal relatives had heteroplasmy levels ranging from 60-92% in blood. His 12 unaffected relatives available for testing heteroplasmy ranged 50-78% in blood (PP1_moderate, PMID:1006502). There are no reported de novo occurrences of this variant to our knowledge. There are three occurrences of this variant in Helix dataset (frequency of 0.001%) that includes two homoplasmic and one heteroplasmic individuals. This variant is absent in gnomAD v3.1.2 and in GenBank dataset therefore the frequency is still low enough to meet criteria for PM2_supporting. There are no cybrids, single fiber studies, or other functional assays reported on this variant. The computational predictor MitoTIP suggests this variant is pathogenic (79.3 percentile) and HmtVAR predicts it to be pathogenic score of 0.75 (PP3). In summary, this variant meets criteria to be classified as likely pathogenic for primary mitochondrial disease inherited in a mitochondrial manner. This classification was approved by the NICHD/NINDS U24 ClinGen Mitochondrial Disease Variant Curation Expert Panel on September 12, 2022. Mitochondrial DNA-specific ACMG/AMP criteria applied: PS4_moderate, PM2_supporting, PP3, PP1_moderate. LINK:https://erepo.genome.network/evrepo/ui/classification/CA254842/MONDO:0044970/014
Frequency
Consequence
unassigned_transcript_4790 stop_lost
Scores
Clinical Significance
Conservation
Publications
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ACMG classification
Our verdict: Likely_pathogenic. The variant received 6 ACMG points.
Transcripts
RefSeq
| Gene | Transcript | HGVSc | HGVSp | Effect | Exon rank | MANE | Protein | UniProt |
|---|---|---|---|---|---|---|---|---|
| TRNI | unassigned_transcript_4790 | c.38A>G | p.Ter13Trpext*? | stop_lost | Exon 1 of 1 | |||
| ND2 | unassigned_transcript_4793 | c.-170A>G | upstream_gene_variant | |||||
| TRNM | unassigned_transcript_4792 | c.-102A>G | upstream_gene_variant |
Ensembl
Frequencies
Mitomap
ClinVar
Submissions by phenotype
MERRF syndrome Pathogenic:1
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Mitochondrial disease Pathogenic:1
The m.4300A>G variant in MT-TI has been reported in at least 17 individuals from eight families with hypertrophic cardiomyopathy. Affected individuals had variable ages of onset (11 months old to 40s). All cases developed hypertrophic cardiomyopathy. Muscle biopsy revealed COX negative fibers in cardiac tissue and one case had ragged red fibers in skeletal muscle. Heteroplasmy levels were predominantly the same in all affected probands as the variant was present at homoplasmy or > 97% in all tissues. Other affected family members did harbor the variant at 60-100%. Of note, some healthy family members had the variant ranging from 40-100% (PS4_moderate; PMIDs: 10065021, 7646516, 12767666, 12711217, 23847141). This variant segregated with disease in a family with LVH with diffuse hypertrophy as the proband's heteroplasmy was 98% in heart, 85% in muscle, and 95% in blood. His seven affected maternal relatives had heteroplasmy levels ranging from 60-92% in blood. His 12 unaffected relatives available for testing heteroplasmy ranged 50-78% in blood (PP1_moderate, PMID: 1006502). There are no reported de novo occurrences of this variant to our knowledge. There are three occurrences of this variant in Helix dataset (frequency of 0.001%) that includes two homoplasmic and one heteroplasmic individuals. This variant is absent in gnomAD v3.1.2 and in GenBank dataset therefore the frequency is still low enough to meet criteria for PM2_supporting. There are no cybrids, single fiber studies, or other functional assays reported on this variant. The computational predictor MitoTIP suggests this variant is pathogenic (79.3 percentile) and HmtVAR predicts it to be pathogenic score of 0.75 (PP3). In summary, this variant meets criteria to be classified as likely pathogenic for primary mitochondrial disease inherited in a mitochondrial manner. This classification was approved by the NICHD/NINDS U24 ClinGen Mitochondrial Disease Variant Curation Expert Panel on September 12, 2022. Mitochondrial DNA-specific ACMG/AMP criteria applied: PS4_moderate, PM2_supporting, PP3, PP1_moderate. -
Primary dilated cardiomyopathy;C0205700:Asymmetric septal hypertrophy Pathogenic:1
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Primary familial hypertrophic cardiomyopathy Pathogenic:1
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Hypomagnesemia, hypertension, and hypercholesterolemia, mitochondrial Pathogenic:1
The variant is not observed in the gnomAD v3.1.2 dataset. Predicted Consequence/Location: Mitochondrial variant In silico tool predictions suggest damaging effect of the variant on gene or gene product (mitoTIP: 79.3>=50; HmtVAR: 0.75>0.35). Therefore, this variant is classified as Likely pathogenic according to the recommendation of ACMG/AMP guideline. -
Computational scores
Source: