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.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TRNE	unassigned_transcript_4817	c.34A>G	p.Met12Val	missense_variant	Exon 1 of 1
CYTB	unassigned_transcript_4818	c.-38T>C		upstream_gene_variant
ND6	unassigned_transcript_4816	c.-36A>G		upstream_gene_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MT-TE	ENST00000387459.1	n.34A>G		non_coding_transcript_exon_variant	Exon 1 of 1	6
MT-CYB	ENST00000361789.2	c.-38T>C		upstream_gene_variant		6		ENSP00000354554.2
MT-ND6	ENST00000361681.2	c.-36A>G		upstream_gene_variant		6		ENSP00000354665.2

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

Significance: Likely pathogenic

Submissions summary: Pathogenic:6

Revision: reviewed by expert panel

Submissions by phenotype

Mitochondrial disease Pathogenic:2

Jan 23, 2023

ClinGen Mitochondrial Disease Nuclear and Mitochondrial Variant Curation Expert Panel, ClinGen

Significance: Likely pathogenic

Review Status: reviewed by expert panel

Collection Method: curation

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. -

May 22, 2017

Wellcome Centre for Mitochondrial Research, Newcastle University

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Myopathy, mitochondrial, with diabetes mellitus Pathogenic:1

Apr 01, 2004

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

- -

MELAS syndrome Pathogenic:1

Jul 12, 2019

Wong Mito Lab, Molecular and Human Genetics, Baylor College of Medicine

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The NC_012920.1:m.14709T>C variant in MT-TE gene is interpreted to be a Likely Pathogenic variant based on the modified ACMG guidelines (unpublished). This variant meets the following evidence codes reported in the guidelines: PS5, PP3, PP4, PP6 -

Inborn mitochondrial myopathy Pathogenic:1

-

Kids Research, The Children's Hospital at Westmead

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: research

- -

Diabetes-deafness syndrome maternally transmitted Pathogenic:1

Apr 01, 2004

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

- -

Computational scores

Source: dbNSFP v4.3

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;