rs281865497

Positions:

• chr16-66513786-A-G

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PP3_Moderate PP5_Moderate

The NM_004614.5(TK2):​c.644T>C​(p.Leu215Pro) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,461,814 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TK2 NM_004614.5 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 4.82

Genes affected

TK2 (HGNC:11831): (thymidine kinase 2) This gene encodes a deoxyribonucleoside kinase that specifically phosphorylates thymidine, deoxycytidine, and deoxyuridine. The encoded enzyme localizes to the mitochondria and is required for mitochondrial DNA synthesis. Mutations in this gene are associated with a myopathic form of mitochondrial DNA depletion syndrome. Alternate splicing results in multiple transcript variants encoding distinct isoforms, some of which lack transit peptide, so are not localized to mitochondria. [provided by RefSeq, Dec 2012]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a chain Thymidine kinase 2, mitochondrial (size 231) in uniprot entity KITM_HUMAN there are 9 pathogenic changes around while only 1 benign (90%) in NM_004614.5
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.917
• PP5: Variant 16-66513786-A-G is Pathogenic according to our data. Variant chr16-66513786-A-G is described in ClinVar as [Pathogenic]. Clinvar id is 2736362.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TK2	NM_004614.5	c.644T>C	p.Leu215Pro	missense_variant	9/10	ENST00000544898.6	NP_004605.4

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TK2	ENST00000544898.6	c.644T>C	p.Leu215Pro	missense_variant	9/10	1	NM_004614.5	ENSP00000440898	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000796 AC: 2 AN: 251252 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135792

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000176

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461814 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 727206

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 14, 2023

This sequence change replaces leucine, which is neutral and non-polar, with proline, which is neutral and non-polar, at codon 215 of the TK2 protein (p.Leu215Pro). This variant is present in population databases (rs281865497, gnomAD 0.0009%). This missense change has been observed in individual(s) with mitochondrial DNA depletion syndrome (PMID: 16504786). It has also been observed to segregate with disease in related individuals. This variant is also known as p.Leu257Pro. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt TK2 protein function with a positive predictive value of 80%. For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.54	D
BayesDel_noAF	Pathogenic	0.54
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	D;.;D;.;.;.;.;D;.;.;.;D
Eigen	Uncertain	0.61
Eigen_PC	Uncertain	0.50
FATHMM_MKL	Uncertain	0.85	D
LIST_S2	Uncertain	0.96	D;D;.;D;.;D;D;D;.;D;D;D
M_CAP	Pathogenic	0.59	D
MetaRNN	Pathogenic	0.92	D;D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.94	D
MutationAssessor	Pathogenic	3.4	M;.;M;.;.;.;.;.;.;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D;D;D;D;D
PrimateAI	Uncertain	0.55	T
PROVEAN	Pathogenic	-6.2	.;.;.;.;D;D;D;D;D;.;.;.
REVEL	Pathogenic	0.89
Sift	Uncertain	0.0020	.;.;.;.;D;D;D;D;D;.;.;.
Sift4G	Uncertain	0.025	D;D;D;D;D;T;D;D;D;D;D;.
Polyphen		1.0	D;.;D;.;.;D;.;.;.;.;.;.
Vest4		0.91
MutPred		0.67		.;.;.;Loss of stability (P = 0.0272);.;.;.;.;.;.;.;.;
MVP		1.0
MPC		1.4
ClinPred		0.98	D
GERP RS		4.9
Varity_R		0.99
gMVP		0.87

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs281865497; hg19: chr16-66547689;