15-89330218-A-G

Position:

• chr15-89330218-A-G

Variant summary

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

The NM_002693.3(POLG):​c.718T>C​(p.Ser240Pro) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: POLG NM_002693.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.42

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 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	Protein	UniProt
POLG	NM_002693.3	c.718T>C	p.Ser240Pro	missense_variant	3/23	ENST00000268124.11	NP_002684.1
POLGARF	NM_001406557.1	c.773T>C	p.Val258Ala	missense_variant	3/23		NP_001393486.1
POLG	NM_001126131.2	c.718T>C	p.Ser240Pro	missense_variant	3/23		NP_001119603.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
POLG	ENST00000268124.11	c.718T>C	p.Ser240Pro	missense_variant	3/23	1	NM_002693.3	ENSP00000268124	P1
POLGARF	ENST00000706918.1	c.773T>C	p.Val258Ala	missense_variant	2/2			ENSP00000516626	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Progressive sclerosing poliodystrophy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Mar 10, 2021

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 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: "Possibly Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with POLG-related conditions. This variant is not present in population databases (ExAC no frequency). This sequence change replaces serine with proline at codon 240 of the POLG protein (p.Ser240Pro). The serine residue is moderately conserved and there is a moderate physicochemical difference between serine and proline. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.41
BayesDel_addAF	Uncertain	0.15	D
BayesDel_noAF	Uncertain	-0.030
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Benign	0.40	T;T
Eigen	Uncertain	0.39
Eigen_PC	Uncertain	0.45
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.87	.;D
M_CAP	Uncertain	0.085	D
MetaRNN	Uncertain	0.45	T;T
MetaSVM	Uncertain	0.36	D
MutationAssessor	Benign	2.0	M;M
MutationTaster	Benign	1.0	D;D
PrimateAI	Benign	0.44	T
PROVEAN	Benign	-1.7	N;N
REVEL	Uncertain	0.45
Sift	Benign	0.14	T;T
Sift4G	Benign	0.26	T;T
Polyphen		0.93	P;P
Vest4		0.41
MutPred		0.38		Gain of catalytic residue at S240 (P = 0.0025);Gain of catalytic residue at S240 (P = 0.0025);
MVP		0.94
MPC		0.48
ClinPred		0.72	D
GERP RS		5.7
Varity_R		0.57
gMVP		0.78

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

No publications associated with this variant yet.

Other links and lift over

hg19: chr15-89873449;