16-66531432-G-C

Variant names:

• chr16-66531432-G-C
• rs137854431
• NM_004614.5:c.323C>G

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 7P and 0B. PM1 PM2 PM5 PP3

The NM_004614.5(TK2):​c.323C>G​(p.Thr108Arg) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T108M) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: TK2 NM_004614.5 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 5.48
• Publications: 0 publications found

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 Gene-Disease associations (from GenCC):

• mitochondrial disease

  Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
• mitochondrial DNA depletion syndrome, myopathic form

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: PanelApp Australia, Orphanet, Labcorp Genetics (formerly Invitae), G2P
• autosomal recessive progressive external ophthalmoplegia

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 7 ACMG points.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 6 uncertain in NM_004614.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr16-66531432-G-A is described in ClinVar as Pathogenic. ClinVar VariationId is 12710.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.826

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_004614.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TK2	NM_004614.5	MANE Select	c.323C>G	p.Thr108Arg	missense	Exon 5 of 10	NP_004605.4
	TK2	NM_001172645.2		c.269C>G	p.Thr90Arg	missense	Exon 4 of 9	NP_001166116.1	O00142-4
	TK2	NM_001172644.2		c.248C>G	p.Thr83Arg	missense	Exon 4 of 9	NP_001166115.1	O00142-3

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TK2	ENST00000544898.6	TSL:1 MANE Select	c.323C>G	p.Thr108Arg	missense	Exon 5 of 10	ENSP00000440898.2	O00142-1
	TK2	ENST00000451102.7	TSL:1	c.230C>G	p.Thr77Arg	missense	Exon 5 of 10	ENSP00000414334.4	O00142-2
	TK2	ENST00000527284.6	TSL:1	c.266C>G	p.Thr89Arg	missense	Exon 5 of 9	ENSP00000435312.2	A0A7P0PE46

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.86
BayesDel_addAF	Pathogenic	0.46	D
BayesDel_noAF	Pathogenic	0.42
CADD	Pathogenic	29
DANN	Uncertain	0.98
DEOGEN2	Pathogenic	0.94	D
Eigen	Uncertain	0.37
Eigen_PC	Uncertain	0.37
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Uncertain	0.96	D
M_CAP	Pathogenic	0.53	D
MetaRNN	Pathogenic	0.83	D
MetaSVM	Pathogenic	0.87	D
MutationAssessor	Pathogenic	3.0	M
PhyloP100		5.5
PrimateAI	Uncertain	0.63	T
PROVEAN	Uncertain	-4.0	D
REVEL	Pathogenic	0.83
Sift	Benign	0.059	T
Sift4G	Uncertain	0.034	D
Polyphen		0.99	D
Vest4		0.89
MutPred		0.58		Gain of MoRF binding (P = 0.0054)
MVP		0.96
MPC		1.2
ClinPred		0.99	D
GERP RS		5.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.86
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

Other links and lift over

dbSNP: rs137854431; hg19: chr16-66565335;