rs142291440

Positions:

chr16-66536971-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM1PM2

The NM_004614.5(TK2):c.278A>G(p.Asn93Ser) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000868 in 1,613,752 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★★).

Frequency

Genomes: 𝑓 0.000033 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000062 ( 0 hom. )

Consequence

TK2
NM_004614.5 missense

Scores

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:3

Conservation

PhyloP100: 2.74

Variant links:

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]

TK2 links:

TK2 (HGNC:):

TK2 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Uncertain_significance. Variant got 4 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;

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TK2	NM_004614.5 linkuse as main transcript	c.278A>G	p.Asn93Ser	missense_variant	4/10	ENST00000544898.6	NP_004605.4	O00142-1Q8IZR3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TK2	ENST00000544898.6 linkuse as main transcript	c.278A>G	p.Asn93Ser	missense_variant	4/10	1	NM_004614.5	ENSP00000440898.2		O00142-1

Frequencies

GnomAD3 genomes

AF:

0.0000329

AC:

AN:

151884

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.000121

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000119

AC:

AN:

251488

Hom.:

AF XY:

0.0000221

AC XY:

AN XY:

135918

show subpopulations

Gnomad AFR exome

AF:

0.0000615

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.0000653

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000616

AC:

AN:

1461868

Hom.:

Cov.:

AF XY:

0.00000963

AC XY:

AN XY:

727236

show subpopulations

Gnomad4 AFR exome

AF:

0.000119

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.0000348

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

8.99e-7

Gnomad4 OTH exome

AF:

0.0000166

GnomAD4 genome

AF:

0.0000329

AC:

AN:

151884

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74170

show subpopulations

Gnomad4 AFR

AF:

0.000121

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.00

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000538

Hom.:

Bravo

AF:

0.0000302

ESP6500AA

AF:

0.000454

AC:

ESP6500EA

AF:

0.00

AC:

ExAC

AF:

0.0000330

AC:

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not provided

Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jul 12, 2022	This sequence change replaces asparagine, which is neutral and polar, with serine, which is neutral and polar, at codon 93 of the TK2 protein (p.Asn93Ser). This variant is present in population databases (rs142291440, gnomAD 0.007%). This missense change has been observed in individual(s) with TK2-related conditions (PMID: 16908738). ClinVar contains an entry for this variant (Variation ID: 38983). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C0"). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Oct 14, 2020	Reported in a patient with mitochondrial DNA depletion syndrome who also harbored a frameshift variant in the TK2 gene in published literature (Oskoui et al., 2006), although it is not known whether these variants were present on the same allele (in cis) or on opposite alleles (in trans); Not observed at a significant frequency in large population cohorts (Lek et al., 2016); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 25215937, 22571666, 23230576, 23932787, 16908738) -

not specified

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Sep 20, 2023

Variant summary: TK2 c.278A>G (p.Asn93Ser) results in a conservative amino acid change in the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 1.2e-05 in 251488 control chromosomes. c.278A>G has been reported in the literature in at-least two individuals affected with Mitochondrial DNA Depletion Syndrome or childhood-onset mitochondrial myopathy, along with two apparently pathogenic frame-shifting variants, respectively (examples, Oskoui_2006, Manini_2022). These data indicate that the variant may be associated with TK2 Related Mitochondrial DNA Depletion Syndrome. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 35280287, 16908738). Two submitters have cited clinical-significance assessments for this variant to ClinVar after 2014. Both submitters classified the variant as uncertain significance. Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.26

BayesDel_addAF

Benign

-0.046

BayesDel_noAF

Benign

-0.12

CADD

Benign

DANN

Uncertain

1.0

DEOGEN2

Pathogenic

0.96

D;D;.;.;.;D

Eigen

Benign

0.16

Eigen_PC

Uncertain

0.22

FATHMM_MKL

Uncertain

0.91

LIST_S2

Uncertain

0.91

D;.;D;D;D;D

M_CAP

Uncertain

0.29

MetaRNN

Uncertain

0.50

T;T;T;T;T;T

MetaSVM

Uncertain

0.57

MutationAssessor

Pathogenic

3.5

H;H;.;.;.;.

PrimateAI

Uncertain

0.48

PROVEAN

Uncertain

-4.3

.;.;.;D;D;D

REVEL

Uncertain

0.50

Sift

Uncertain

0.013

.;.;.;D;D;D

Sift4G

Uncertain

0.028

D;D;D;D;D;D

Polyphen

0.065

.;.;.;B;.;.

Vest4

0.47

MVP

0.95

MPC

0.55

ClinPred

0.95

GERP RS

4.2

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Varity_R

0.42

gMVP

0.91

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over