rs121434453

Variant names:

• chrM-14709-T-C
• rs121434453
• unassigned_transcript_4817:c.34A>G

Variant summary

Our verdict is Likely pathogenic. The variant received 9 ACMG points: 9P and 0B. PS4 PP1_Moderate PS3_Supporting PP3 PM2_Supporting

This summary comes from the ClinGen Evidence Repository: The m.14709T>C variant in MT-TE has been reported in at least 39 affected individuals from 20 kindreds (PMIDs: 7726155, 7726154, 9353617, 10392369, 11437868, 15048886, 15880407, 15607216, 17161635, 17891417, 20045353, 26469001, 26885883, 29941710, 32313153, 33304817, 32948797; web story: https://www.chop.edu/stories/mitochondrial-disease-noras-story; PS4). Age of onset ranged from shortly after birth to 50s, although there are some reports of decreased fetal movements and hydrops fetalis. Features in affected individuals include myopathy, diabetes, pulmonary hypertension, ataxia, neuropathy, global developmental delay, dysarthria, hearing loss, hypertrophic cardiomyopathy, and dilated cardiomyopathy. Furthermore, this variant has been reported in some individuals with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS)/Leigh syndrome spectrum overlap and myoclonic epilepsy with ragged red fibers (MERRF). Muscle biopsies in affected individuals showed ragged red fibers, COX deficiency, and reduced respiratory chain enzyme activities. The variant was present at variable levels in affected and unaffected individuals. Some healthy family members had the variant present at homoplasmy, however heteroplasmy levels were generally higher in more severely affected individuals. The variant was present at 78% to homoplasmy in muscle and was variable among tissues from the same individual. There are no reported de novo occurrences to our knowledge. The variant segregates with manifestations in several families (PMIDs: 7726155, 7726154, 9353617, 10392369, 11437868, 15607216, 17161635, 17891417, 20045353; PP1_moderate). The computational predictor MitoTIP suggests this variant is pathogenic (56.2 percentile) and HmtVAR predicts it to be pathogenic score of 0.9 (PP3). There is one occurrence in the GenBank population database, and the variant is absent in the Helix dataset and gnomAD v.3.1.2. Although there is one occurrence, the frequency is still low (PM2_supporting). Single fiber testing showed higher levels of heteroplasmy in COX-negative fibers (97.4 ± 3.5%; n=16) than in COX-positive fibers (89.6 ± 9.3%; n=15; P<0.004; PMID:7726154), and cybrid studies, Northern blot analyses, and protein synthesis assays further support the functional impact of this variant (PMIDs: 15048886, 7726155, 12393175; PS3_supporting). 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 January 23, 2023. Mitochondrial DNA-specific ACMG/AMP criteria applied (PMID:32906214): PS4, PP1_moderate, PM2_supporting, PP3, PS3_supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA120580/MONDO:0044970/014

• Frequency: Mitomap GenBank: Absent
• Consequence: TRNE unassigned_transcript_4817 missense
• Scores: Mitotip Uncertain 13
• Clinical Significance: Likely pathogenic reviewed by expert panel P:6 MM+DMDF-/-Encephalomyopathy-/-Dementia+diabetes+ophthalmoplegia
• Conservation: PhyloP100: 0.942
• Publications: 5 publications found

Genes affected

TRNE (HGNC:7479): (mitochondrially encoded tRNA glutamic acid)

MT-CYB (HGNC:7427): (mitochondrially encoded cytochrome b) Predicted to enable metal ion binding activity. Predicted to be involved in several processes, including electron transport coupled proton transport; response to cobalamin; and response to glucagon. Located in mitochondrion. Implicated in ovarian carcinoma and urinary bladder cancer. [provided by Alliance of Genome Resources, Apr 2022]

MT-ND6 (HGNC:7462): (mitochondrially encoded NADH dehydrogenase 6) Enables NADH dehydrogenase (ubiquinone) activity. Involved in mitochondrial electron transport, NADH to ubiquinone and mitochondrial respiratory chain complex I assembly. Predicted to be located in mitochondrial inner membrane. Implicated in Leber hereditary optic neuropathy; Leigh disease; and spinal muscular atrophy with lower extremity predominante 2B. [provided by Alliance of Genome Resources, Apr 2022]

MT-ND6 Gene-Disease associations (from GenCC):

• Leigh syndrome

  Inheritance: Mitochondrial Classification: DEFINITIVE Submitted by: ClinGen
• mitochondrial disease

  Inheritance: Mitochondrial Classification: DEFINITIVE Submitted by: ClinGen
• Leber hereditary optic neuropathy

  Inheritance: Mitochondrial Classification: STRONG, SUPPORTIVE Submitted by: G2P, Orphanet
• Leber plus disease

  Inheritance: Mitochondrial Classification: SUPPORTIVE Submitted by: Orphanet
• maternally-inherited Leigh syndrome

  Inheritance: Mitochondrial Classification: SUPPORTIVE Submitted by: Orphanet
• MELAS syndrome

  Inheritance: Mitochondrial Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 9 ACMG points.

• PS3: For more information check the summary or visit ClinGen Evidence Repository.
• PS4: For more information check the summary or visit ClinGen Evidence Repository.
• PM2: For more information check the summary or visit ClinGen Evidence Repository.
• PP1: For more information check the summary or visit ClinGen Evidence Repository.
• PP3: For more information check the summary or visit ClinGen Evidence Repository.

Variant Effect in Transcripts

ACMG analysis was done for transcript: ENST00000387459.1. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
There are no transcript annotations for this variant.

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	MT-TE	ENST00000387459.1	TSL:6	n.34A>G		non_coding_transcript_exon	Exon 1 of 1
	MT-CYB	ENST00000361789.2	TSL:6	c.-38T>C		upstream_gene	N/A	ENSP00000354554.2	P00156
	MT-ND6	ENST00000361681.2	TSL:6	c.-36A>G		upstream_gene	N/A	ENSP00000354665.2	P03923

Frequencies

Mitomap GenBank The variant is not present, suggesting it is rare .

Alfa AF: 0.00 Hom.: 0

Mitomap

Disease(s): MM+DMDF-/-Encephalomyopathy-/-Dementia+diabetes+ophthalmoplegia

Status: Cfrm-[LP]

ClinVar

ClinVar submissions

Significance: Likely pathogenic

Revision: reviewed by expert panel

Pathogenic	VUS	Benign	Condition
2	-	-	Mitochondrial disease (2)
1	-	-	Diabetes-deafness syndrome maternally transmitted (1)
1	-	-	Inborn mitochondrial myopathy (1)
1	-	-	MELAS syndrome (1)
1	-	-	Myopathy, mitochondrial, with diabetes mellitus (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
Mitotip	Uncertain	13
Hmtvar	Pathogenic	0.90
PhyloP100		0.94

Other links and lift over

dbSNP: rs121434453; hg19: chrM-14710;