M-4295-A-G

Position:

• chrM-4295-A-G

Variant summary

Our verdict is Likely benign. Variant got -4 ACMG points: 0P and 4B. BS2

The ENST00000387365.1(MT-TI):​n.33A>G variant causes a non coding transcript exon change involving the alteration of a non-conserved nucleotide. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency: Mitomap GenBank: 𝑓 0.0018 (AC: 113)
• Consequence: MT-TI ENST00000387365.1 non_coding_transcript_exon
• Scores: Mitotip Uncertain 12
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:4 B:1 MHCM-/-Maternally-inherited-hypertension-/-Maternally-inherited-deafness
• Conservation: PhyloP100: 3.44

Genes affected

MT-TI (HGNC:7488): (mitochondrially encoded tRNA isoleucine)

TRNI (HGNC:):

MT-ND1 (HGNC:7455): (mitochondrially encoded NADH dehydrogenase 1) Enables NADH dehydrogenase (ubiquinone) activity. Involved in mitochondrial electron transport, NADH to ubiquinone and mitochondrial respiratory chain complex I assembly. Located in mitochondrial membrane. Part of mitochondrial respiratory chain complex I. Implicated in several diseases, including MELAS syndrome; neurodegenerative disease (multiple); optic nerve disease (multiple); toxic shock syndrome; and type 2 diabetes mellitus. Biomarker of Alzheimer's disease; Parkinson's disease; and multiple sclerosis. [provided by Alliance of Genome Resources, Apr 2022]

MT-TQ (HGNC:7495): (mitochondrially encoded tRNA glutamine)

ACMG classification

Verdict is Likely_benign. Variant got -4 ACMG points.

• BS2: High AC in GnomadMitoHomoplasmic at 167

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TRNI	TRNI.1	n.33A>G		non_coding_transcript_exon_variant	1/1
TRNQ	TRNQ.1			downstream_gene_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MT-TI	ENST00000387365.1	n.33A>G		non_coding_transcript_exon_variant	1/1
MT-ND1	ENST00000361390.2			downstream_gene_variant				ENSP00000354687	P1
MT-TQ	ENST00000387372.1			downstream_gene_variant

Frequencies

GnomAD4 exome Cov.: 0

We have no GnomAD4 genomes data on this position. Probably position not covered by the project.

Mitomap GenBank AF: 0.0018 AC: 113

Gnomad homoplasmic AF: 0.0030 AC: 167 AN: 56431

Gnomad heteroplasmic AF: 0.0 AC: 0 AN: 56431

Alfa AF: 0.00156 Hom.: 7

Mitomap

MHCM-/-Maternally-inherited-hypertension-/-Maternally-inherited-deafness

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:4 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:3

Uncertain significance, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Dec 22, 2017	The m.4295A>G variant (rs121434467) is located at position 33 of the tRNA-isoleucine gene. Although this variant has been reported in patients with diverse symptoms including hypertrophic cardiomyopathy, encephalopathy, non-syndromic hearing loss, occipital stroke and essential hypertension, a consistent clinical presentation has not been identified (Finnila 2001, Gutierrez Cortes 2012, Li 2008, Merante 1996, Zhu 2009). Functional characterization of the variant tRNA indicates a defect in 3' processing (Levinger 2003), resulting in reduced activity of complex III in oxidative phosphorylation; however, the clinical relevance of these observations in not known (Gutierrez Cortes 2012, Merante 1996). Furthermore, the m.4295A>G variant is observed in 10 percent of individuals with the mitochondrial haplogroup K1a (87 out of 916 individual in the MITOMAP database). Therefore, based on the available information, the clinical significance of the m.4295A>G variant cannot be determined with certainty. -
Uncertain significance, criteria provided, single submitter	clinical testing	Center for Pediatric Genomic Medicine, Children's Mercy Hospital and Clinics	Jan 19, 2015	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Athena Diagnostics	Mar 22, 2019	- -

Mitochondrial non-syndromic sensorineural hearing loss Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Apr 01, 2012

- -

Primary familial hypertrophic cardiomyopathy Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Apr 01, 2012

- -

not specified Uncertain:1

Uncertain significance, no assertion criteria provided

clinical testing

Stanford Center for Inherited Cardiovascular Disease, Stanford University

-

Note this variant was found in clinical genetic testing performed by one or more labs who may also submit to ClinVar. Thus any internal case data may overlap with the internal case data of other labs. The interpretation reviewed below is that of the Stanford Center for Inherited Cardiovascular Disease. MTTI m.4295A>G Merante et al (1996) report the variant in two siblings with severe HCM and their mother who was phenotype negative. The proband presented at 7 months of age with cyanosis and died due to complications of HCM. Autopsy revealed proliferation of mitochondria in the heart, so the authors looked for mitochondrial variants. Notably, they did only a limited analysis of mitochondrial DNA; they sequenced tRNA genes and looked for gross deletions and duplications. The proband, who had the most severe presentation, had a >90 % heteroplasmic load in the heart, her brother had 89% variant load in the heart and developed HCM at age 4 while their mother who had a variant load of 79% in the cardiac muscle was phenotype negative for HCM but did have reduced respiratory chain activity levels. Adenosine is highly conserved at position 4295 across species. This variant has been reported in individuals from the general population: 5/2704 individuals in mtDB (www.genpath.uu.se/mtDB); 2/3735 individuals in MitoWheel (http://mitowheel.org/mitowheel.html ). -

Juvenile myopathy, encephalopathy, lactic acidosis AND stroke Benign:1

Benign, criteria provided, single submitter

clinical testing

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

Jul 12, 2019

The NC_012920.1:m.4295A>G variant in MT-TI gene is interpreted to be a Benign variant based on the modified ACMG guidelines (unpublished). This variant meets the following evidence codes reported in the guidelines: BS1, BS4 -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
Mitotip	Uncertain	12
Hmtvar	Pathogenic	0.75

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs121434467; hg19: chrM-4296;