chrM-3271-T-C

Position:

• chrM-3271-T-C

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM2 PP5_Very_Strong

Variant has been reported in ClinVar as Pathogenic (★★★).

• Frequency: Mitomap GenBank: Absent
• Consequence: TRNL1 synonymous
• Scores: Mitotip Pathogenic 17
• Clinical Significance: Pathogenic reviewed by expert panel P:6 O:1 MELAS-/-DM-/-MERRF-like
• Conservation: PhyloP100: 2.98

Genes affected

TRNL1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 10 ACMG points.

• PM2: No frequency data in Mitomap. Probably very rare.
• PP5: Variant M-3271-T-C is Pathogenic according to our data. Variant chrM-3271-T-C is described in ClinVar as [Pathogenic]. Clinvar id is 9590.Status of the report is reviewed_by_expert_panel, 3 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TRNL1	unassigned_transcript_4789	c.42T>C	p.Thr14Thr	synonymous_variant	1/1
ND1	unassigned_transcript_4790	c.-36T>C		upstream_gene_variant
RNR2	unassigned_transcript_4788	n.*42T>C		downstream_gene_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt

Frequencies

GnomAD4 exome Cov.: 0

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

Mitomap

MELAS-/-DM-/-MERRF-like

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:6 Other:1

Revision: reviewed by expert panel

Submissions by phenotype

MELAS syndrome Pathogenic:3 Other:1

Pathogenic, criteria provided, single submitter	clinical testing	Mendelics	May 04, 2022	- -
Pathogenic, 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.3271T>C variant in MT-TL1 gene is interpreted to be a Pathogenic variant based on the modified ACMG guidelines (unpublished). This variant meets the following evidence codes reported in the guidelines: PS3, PS5, PM7 -
not provided, no classification provided	literature only	GeneReviews	-	- -
Pathogenic, no assertion criteria provided	literature only	OMIM	Aug 01, 2005	- -

not specified Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Mar 17, 2017

- -

Mitochondrial disease Pathogenic:1

Pathogenic, reviewed by expert panel

curation

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

Apr 25, 2023

The m.3271T>C variant in MT-TL1 gene has been reported in more than 40 affected individuals from 20 kindreds (PS4; PMIDs: 1932147, 8482977, 7993661, 8908402, 9766710, 9427220, 11404119, 11828557, 10214753, 12609508, 16006433, 15794182, 16353243, 18206799, 20972245, 25680467, 33951347). The age of onset ranged from early childhood to the late 30s. This variant has been seen in individuals with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS; accounts for approximately 10% of cases of MELAS and is the second most common cause) as well as in one individual with myoclonic epilepsy with ragged red fibers (MERRF). Other features seen in affected individual include muscle weakness, exercise intolerance, fatigue, developmental delay, axonal neuropathy, dementia, migraines, seizures, diabetes, growth hormone deficiency, lipoma, sensorineural hearing loss, hypertrophic cardiomyopathy, Wolff-Parkinson-White arrhythmia, optic atrophy, and short stature. Muscle biopsies showed ragged red fibers, COX-negative fibers, paracrystalline inclusions, hypertrophic/atrophic fibers, enlarged mitochondria, abnormal cristae, increased fat droplets, and variable respiratory chain enzyme activities. Heteroplasmy levels were variable but were highest in muscle and urine, and levels were as high as homoplasmic in muscle. This variant segregated with disease in multiple affected members across several families and several healthy family members had lower levels of the variant (PP1_moderate; PMIDs: 9427220, 16006433, 15794182, 18206799, 25680467). There is one report of a de novo occurrence, however technology at the time could have missed low level variants and the tissue(s) tested was not specified (PMID: 11828557). This variant is absent in the GenBank dataset, Helix dataset, and gnomAD v3.1.2 (PM2_supporting). The computational predictor MitoTIP suggests this variant is pathogenic (78.3 percentile) and HmtVAR predicts it to be pathogenic score of 0.85 (PP3). Cybrid studies and other assays supported the functional impact of this variant (PS3_moderate; PMIDs: 12527767, 12729737, 15870203, 16120315, 10660592, 9744809, 7603512, 8280119). In summary, this variant meets criteria to be classified as 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 April 25, 2023. Mitochondrial DNA-specific ACMG/AMP criteria applied (PMID: 32906214): PS4, PP1_moderate, PM2_supporting, PP3, PS3_moderate. -

MELAS syndrome;C0162672:MERRF syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Oct 31, 2018

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
Mitotip	Pathogenic	17
Hmtvar	Pathogenic	0.85

Splicing

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

Publications

LitVar

Other links and lift over

dbSNP: rs199474658; hg19: chrM-3272;