M-616-T-C

Position:

• chrM-616-T-C

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PP3 PS4_Moderate PP1_Moderate PM2_Supporting

This summary comes from the ClinGen Evidence Repository: The m.616T>C variant in MT-TF has been reported in at least 12 individuals from six families with features of a primary mitochondrial disease. Affected individuals had variable ages of onset (first few months of life with delays or seizures at 10 months old to late teenage years with renal disease or epilepsy). Several individuals had chronic kidney disease or renal failure; some even had transplants with non-recurrence of disease post-transplant. Other symptoms reported include developmental delay, epilepsy, status epilepticus (EPC), and myoclonus. Muscle biopsy revealed COX negative fibers. Heteroplasmy levels were the same in all affected probands as the variant was present at homoplasmy or > 97% in all tissues. Of note, some healthy family members had the variant at lower heteroplasmy levels but in at least one healthy family member, the variant was present at a heteroplasmy level as high as 92% (PS4_moderate; PMIDs: 31722346, 28267784, 20142618). There are no reports of de novo occurrence of this variant. This variant segregated with disease in multiple affected members in multiple families and several healthy family members had lower or undetectable levels of the variant (PP1_moderate; PMIDs: 31722346, 28267784, 20142618). This variant is absent in the GenBank dataset, Helix dataset, and gnomAD v3.1.2 (PM2_supporting). There is one cybrid study for this variant however the cybrid also had another mtDNA variant precluding scoring for PS3. There are no single fiber studies or other functional assays reported for this variant. The computational predictor MitoTIP suggests this variant is pathogenic (83.3 percentile) and HmtVAR predicts it to be pathogenic score of 0.5 (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 Mitochondrial Disease Variant Curation Expert Panel on June 13, 2022. Mitochondrial DNA-specific ACMG/AMP criteria applied (PMID:32906214): PS4_moderate, PP1_moderate, PP3, PM2_supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA120552/MONDO:0044970/014

• Frequency: Mitomap GenBank: Absent
• Consequence: MT-TF ENST00000387314.1 non_coding_transcript_exon
• Scores: Mitotip Pathogenic 17
• Clinical Significance: Likely pathogenic reviewed by expert panel P:5 Maternally-inherited-epilepsy-/-mito-tubulointerstitial-kidney-disease-(MITKD)-/-Gitelman-like-syndrome,Maternally-inherited-epilepsy
• Conservation: PhyloP100: 3.71

Genes affected

MT-TF (HGNC:7481): (mitochondrially encoded tRNA phenylalanine)

TRNF (HGNC:):

MT-RNR1 (HGNC:7470): (mitochondrially encoded 12S RNA) Enables DNA binding activity and DNA-binding transcription factor binding activity. Involved in several processes, including osteoblast proliferation; regulation of carbohydrate utilization; and regulation of phosphate metabolic process. Located in extracellular space; mitochondrion; and nucleus. [provided by Alliance of Genome Resources, Apr 2022]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TRNF	TRNF.1	n.40T>C		non_coding_transcript_exon_variant	1/1
RNR1	RNR1.1			upstream_gene_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MT-TF	ENST00000387314.1	n.40T>C		non_coding_transcript_exon_variant	1/1
MT-RNR1	ENST00000389680.2			upstream_gene_variant

Frequencies

GnomAD4 exome Cov.: 0

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

Mitomap

Maternally-inherited-epilepsy-/-mito-tubulointerstitial-kidney-disease-(MITKD)-/-Gitelman-like-syndrome,Maternally-inherited-epilepsy

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:5

Revision: reviewed by expert panel

Submissions by phenotype

Mitochondrial disease Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Mendelics	May 04, 2022	- -
Likely pathogenic, reviewed by expert panel	curation	ClinGen Mitochondrial Disease Nuclear and Mitochondrial Variant Curation Expert Panel, ClinGen	Jun 30, 2022	The m.616T>C variant in MT-TF has been reported in at least 12 individuals from six families with features of a primary mitochondrial disease. Affected individuals had variable ages of onset (first few months of life with delays or seizures at 10 months old to late teenage years with renal disease or epilepsy). Several individuals had chronic kidney disease or renal failure; some even had transplants with non-recurrence of disease post-transplant. Other symptoms reported include developmental delay, epilepsy, status epilepticus (EPC), and myoclonus. Muscle biopsy revealed COX negative fibers. Heteroplasmy levels were the same in all affected probands as the variant was present at homoplasmy or > 97% in all tissues. Of note, some healthy family members had the variant at lower heteroplasmy levels but in at least one healthy family member, the variant was present at a heteroplasmy level as high as 92% (PS4_moderate; PMIDs: 31722346, 28267784, 20142618). There are no reports of de novo occurrence of this variant. This variant segregated with disease in multiple affected members in multiple families and several healthy family members had lower or undetectable levels of the variant (PP1_moderate; PMIDs: 31722346, 28267784, 20142618). This variant is absent in the GenBank dataset, Helix dataset, and gnomAD v3.1.2 (PM2_supporting). There is one cybrid study for this variant however the cybrid also had another mtDNA variant precluding scoring for PS3. There are no single fiber studies or other functional assays reported for this variant. The computational predictor MitoTIP suggests this variant is pathogenic (83.3 percentile) and HmtVAR predicts it to be pathogenic score of 0.5 (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 Mitochondrial Disease Variant Curation Expert Panel on June 13, 2022. Mitochondrial DNA-specific ACMG/AMP criteria applied (PMID: 32906214): PS4_moderate, PP1_moderate, PP3, PM2_supporting. -

Interstitial nephritis Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+

Jul 07, 2021

The m.616T>C variant was observed in 1 family affected by tubulo-interstitial kidney disease (Connor et al. 2017). At least two members of this family were later found to additionally suffer from hypomagnesemia and hypokalemia.(Viering et al. 2021) The homoplasmic variant cosegregated with disease. The variant was scored as pathogenic based on the system published by Wong et al. (2020): PS5, PM7, PM9, PM10. -

Epilepsy, mitochondrial Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Feb 09, 2010

- -

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

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.616T>C variant in MT-TF 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: PS5, PM7, PM9, PM10 -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
Mitotip	Pathogenic	17
Hmtvar	Pathogenic	0.50

Splicing

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

Publications

LitVar

Other links and lift over

dbSNP: rs387906420; hg19: chrM-618;