NM_002693.3:c.122_127dupGGCGGC

Variant names:

• chr15-89333626-CT-CTGCCGC
• NM_002693.3:c.123_127dupGCGGC

Variant summary

Our verdict is Pathogenic. The variant received 10 ACMG points: 10P and 0B. PVS1 PM2

The NM_002693.3(POLG):​c.123_127dupGCGGC​(p.Gln43ArgfsTer225) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. Q43Q) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay. The gene POLG is included in the ClinGen Criteria Specification Registry.

• Frequency: Genomes: not found (cov: 33)
• Consequence: POLG NM_002693.3 frameshift
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 0.749
• Publications: 0 publications found

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

Specifications for POLG are available in the ClinGen Criteria Specification Registry and recommended for reference when assigning criteria.

Our verdict: Pathogenic. The variant received 10 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_002693.3. 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
	POLG	NM_002693.3	MANE Select	c.123_127dupGCGGC	p.Gln43ArgfsTer225	frameshift	Exon 2 of 23	NP_002684.1	P54098
	POLGARF	NM_001430120.1	MANE Select	c.178_182dupGCGGC	p.Ala62ArgfsTer201	frameshift	Exon 1 of 2	NP_001417049.1	A0A3B3IS91
	POLG	NM_001126131.2		c.123_127dupGCGGC	p.Gln43ArgfsTer225	frameshift	Exon 2 of 23	NP_001119603.1	P54098

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	POLG	ENST00000268124.11	TSL:1 MANE Select	c.123_127dupGCGGC	p.Gln43ArgfsTer225	frameshift	Exon 2 of 23	ENSP00000268124.5	P54098
	POLGARF	ENST00000706918.1	MANE Select	c.178_182dupGCGGC	p.Ala62ArgfsTer201	frameshift	Exon 1 of 2	ENSP00000516626.1	A0A3B3IS91
	POLG	ENST00000442287.6	TSL:1	c.123_127dupGCGGC	p.Gln43ArgfsTer225	frameshift	Exon 2 of 23	ENSP00000399851.2	P54098

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		0.75

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

MaxEntScan Visualizer can be used to analyze the impact of this mutation on the neighboring sequence.

Other links and lift over

hg19: chr15-89876857;