16-66509670-G-A

Variant summary

Our verdict is Benign. Variant got -14 ACMG points: 0P and 14B. BP4_Strong BP6_Moderate BS1 BS2

The NM_004614.5(TK2):c.*2298C>T variant causes a 3 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00662 in 152,320 control chromosomes in the GnomAD database, including 4 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Likely benign (★).

• Frequency:
  • Genomes: 𝑓 0.0066 (4 hom., cov: 33)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: TK2 NM_004614.5 3_prime_UTR
• Clinical Significance: Likely benign criteria provided, single submitter B:1
• Conservation: PhyloP100: 0.0290

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]

(HGNC:):

ACMG classification

Verdict is Benign. Variant got -14 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.88).
• BP6: Variant 16-66509670-G-A is Benign according to our data. Variant chr16-66509670-G-A is described in ClinVar as [Likely_benign]. Clinvar id is 320126.Status of the report is criteria_provided_single_submitter, 1 stars.
• BS1: Variant frequency is greater than expected in population nfe. gnomad4 allele frequency = 0.00662 (1009/152320) while in subpopulation NFE AF= 0.0096 (653/68030). AF 95% confidence interval is 0.00899. There are 4 homozygotes in gnomad4. There are 522 alleles in male gnomad4 subpopulation. Median coverage is 33. This position pass quality control queck.
• BS2: High Homozygotes in GnomAd at 4 AR gene

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TK2	NM_004614.5	c.*2298C>T		3_prime_UTR_variant	10/10	ENST00000544898.6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TK2	ENST00000544898.6	c.*2298C>T		3_prime_UTR_variant	10/10	1	NM_004614.5	P1
	ENST00000568560.1	n.234G>A		non_coding_transcript_exon_variant	1/2	5

Frequencies

GnomAD3 genomes AF: 0.00664 AC: 1010 AN: 152202 Hom.: 4 Cov.: 33

Gnomad AFR AF: 0.00169

Gnomad AMI AF: 0.00987

Gnomad AMR AF: 0.00294

Gnomad ASJ AF: 0.000288

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.000621

Gnomad FIN AF: 0.0210

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00961

Gnomad OTH AF: 0.00239

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 194 Hom.: 0 Cov.: 0 AF XY: 0.00 AC XY: 0 AN XY: 146

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00662 AC: 1009 AN: 152320 Hom.: 4 Cov.: 33 AF XY: 0.00701 AC XY: 522 AN XY: 74478

Gnomad4 AFR AF: 0.00168

Gnomad4 AMR AF: 0.00294

Gnomad4 ASJ AF: 0.000288

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.000622

Gnomad4 FIN AF: 0.0210

Gnomad4 NFE AF: 0.00960

Gnomad4 OTH AF: 0.00236

Alfa AF: 0.0101 Hom.: 4

Bravo AF: 0.00506

Asia WGS AF: 0.000866 AC: 3 AN: 3478

ClinVar

Significance: Likely benign

Submissions summary: Benign:1

Revision: criteria provided, single submitter

Submissions by phenotype

Mitochondrial DNA depletion syndrome, myopathic form Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 12, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as likely benign is not then subjected to further curation. The score for this variant resulted in a classification of likely benign for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.88
Cadd	Benign	1.9
Dann	Benign	0.39

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		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: rs139593959; hg19: chr16-66543573;