chr15-89333654-T-C

Position:

• chr15-89333654-T-C

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_002693.3(POLG):​c.101A>G​(p.Asp34Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 14/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: POLG NM_002693.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: -1.20

Genes affected

POLG (HGNC:9179): (DNA polymerase gamma, catalytic subunit) Mitochondrial DNA polymerase is heterotrimeric, consisting of a homodimer of accessory subunits plus a catalytic subunit. The protein encoded by this gene is the catalytic subunit of mitochondrial DNA polymerase. The encoded protein contains a polyglutamine tract near its N-terminus that may be polymorphic. Defects in this gene are a cause of progressive external ophthalmoplegia with mitochondrial DNA deletions 1 (PEOA1), sensory ataxic neuropathy dysarthria and ophthalmoparesis (SANDO), Alpers-Huttenlocher syndrome (AHS), and mitochondrial neurogastrointestinal encephalopathy syndrome (MNGIE). Two transcript variants encoding the same protein have been found for this gene. [provided by RefSeq, Jul 2008]

POLGARF (HGNC:56246): (POLG alternative reading frame) This gene uses the same transcript as the POLG gene but has a CUG start codon and an alternate reading frame that makes a 260 aa protein. This protein is distinct from POLG isoforms and may interact with P32 (also known as C1QBP), a mitochondrial matrix protein thought to be involved in the expression of mitochondrial genome-encoded proteins. POLGARF protein may bind P32 and sequester it in the nucleolus. Interestingly, some disease-causing mutations thought to be in POLG may instead be associated with POLGARF. [provided by RefSeq, May 2022]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.06211564).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
POLG	NM_002693.3	c.101A>G	p.Asp34Gly	missense_variant	2/23	ENST00000268124.11	NP_002684.1
POLGARF	NM_001406557.1	c.156A>G	p.Arg52=	synonymous_variant	2/23		NP_001393486.1
POLG	NM_001126131.2	c.101A>G	p.Asp34Gly	missense_variant	2/23		NP_001119603.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
POLG	ENST00000268124.11	c.101A>G	p.Asp34Gly	missense_variant	2/23	1	NM_002693.3	ENSP00000268124	P1
POLGARF	ENST00000706918.1	c.156A>G	p.Arg52=	synonymous_variant	1/2			ENSP00000516626	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

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	Revvity Omics, Revvity	Jan 20, 2022	- -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Mar 18, 2017	A variant of uncertain significance has been identified in the POLG gene. The D34G variant has not been published as a pathogenic variant, nor has it been reported as a benign variant to our knowledge. The D34G variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The D34G 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. However, this substitution occurs at a position that is not conserved. In silico analysis predicts this variant likely does not alter the protein structure/function. Therefore, based on the currently available information, it is unclear whether this variant is a pathogenic variant or a rare benign variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.073
BayesDel_addAF	Benign	-0.24	T
BayesDel_noAF	Benign	-0.58
CADD	Benign	6.0
DANN	Benign	0.55
DEOGEN2	Benign	0.21	T;T
Eigen	Benign	-1.2
Eigen_PC	Benign	-1.1
FATHMM_MKL	Benign	0.091	N
LIST_S2	Benign	0.66	.;T
M_CAP	Uncertain	0.15	D
MetaRNN	Benign	0.062	T;T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	0.0	N;N
MutationTaster	Benign	1.0	N;N
PrimateAI	Uncertain	0.59	T
PROVEAN	Benign	-0.050	N;N
REVEL	Benign	0.18
Sift	Benign	0.63	T;T
Sift4G	Benign	0.36	T;T
Polyphen		0.0	B;B
Vest4		0.042
MutPred		0.22		Gain of catalytic residue at D34 (P = 0.0103);Gain of catalytic residue at D34 (P = 0.0103);
MVP		0.47
MPC		0.20
ClinPred		0.027	T
GERP RS		-2.7
Varity_R		0.051
gMVP		0.22

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: rs779409525; hg19: chr15-89876885;