17-64477962-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_007215.4(POLG2):c.1319C>T(p.Thr440Ile) variant causes a missense change. The variant allele was found at a frequency of 0.00000496 in 1,613,798 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000048 (0 hom.)
• Consequence: POLG2 NM_007215.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 4.50

Genes affected

POLG2 (HGNC:9180): (DNA polymerase gamma 2, accessory subunit) This gene encodes the processivity subunit of the mitochondrial DNA polymerase gamma. The encoded protein forms a heterotrimer containing one catalytic subunit and two processivity subunits. This protein enhances DNA binding and promotes processive DNA synthesis. Mutations in this gene result in autosomal dominant progressive external ophthalmoplegia with mitochondrial DNA deletions.[provided by RefSeq, Sep 2009]

MILR1 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
POLG2	NM_007215.4	c.1319C>T	p.Thr440Ile	missense_variant	8/8	ENST00000539111.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
POLG2	ENST00000539111.7	c.1319C>T	p.Thr440Ile	missense_variant	8/8	1	NM_007215.4	P1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152108 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

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: 0.0000147

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251156 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135754

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: 0.00000881

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000479 AC: 7 AN: 1461572 Hom.: 0 Cov.: 30 AF XY: 0.00000413 AC XY: 3 AN XY: 727076

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: 0.00000630

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152226 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74422

Gnomad4 AFR AF: 0.00

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: 0.0000147

Gnomad4 OTH AF: 0.00

TwinsUK AF: 0.00 AC: 0

ALSPAC AF: 0.000259 AC: 1

EpiCase AF: 0.0000546

EpiControl AF: 0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	Nov 09, 2022	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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. 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: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). ClinVar contains an entry for this variant (Variation ID: 546474). This variant has not been reported in the literature in individuals affected with POLG2-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces threonine, which is neutral and polar, with isoleucine, which is neutral and non-polar, at codon 440 of the POLG2 protein (p.Thr440Ile). -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	May 21, 2018	The T440I variant in the POLG2 gene has not been reported previously as a pathogenic variant, nor as a benign variant, to our knowledge. The T440I variant is not observed at a significant frequency in large population cohorts (Lek et al., 2016). The T440I variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. In-silico analyses, including protein predictors and evolutionary conservation, support that this variant does not alter protein structure/function. We interpret T440I as a variant of uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.26
BayesDel_addAF	Uncertain	0.11	D
BayesDel_noAF	Uncertain	-0.070
Cadd	Uncertain	25
Dann	Uncertain	1.0
DEOGEN2	Benign	0.041	T
Eigen	Uncertain	0.59
Eigen_PC	Uncertain	0.53
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Benign	0.83	T
M_CAP	Uncertain	0.21	D
MetaRNN	Uncertain	0.65	D
MetaSVM	Uncertain	0.39	D
MutationAssessor	Uncertain	2.5	M
MutationTaster	Benign	0.99	D
PrimateAI	Uncertain	0.56	T
PROVEAN	Benign	-2.4	N
REVEL	Uncertain	0.52
Sift	Uncertain	0.014	D
Sift4G	Uncertain	0.0080	D
Polyphen		0.99	D
Vest4		0.63
MVP		0.95
MPC		0.57
ClinPred		0.96	D
GERP RS		5.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.6
Varity_R		0.44
gMVP		0.72

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: rs200118292; hg19: chr17-62474079;