15-89319048-GC-GCC

Variant names:

• chr15-89319048-G-GC
• rs1447799185
• NM_002693.3:c.3155dupG

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PVS1 PM2 PP5_Moderate

The NM_002693.3(POLG):​c.3155dupG​(p.Thr1053HisfsTer8) variant causes a frameshift change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,858 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★). Synonymous variant affecting the same amino acid position (i.e. G1052G) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: POLG NM_002693.3 frameshift
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 7.39
• Publications: 1 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]

POLG Gene-Disease associations (from GenCC):

• progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 1

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: G2P, Labcorp Genetics (formerly Invitae), Ambry Genetics
• mitochondrial DNA depletion syndrome 4a

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Ambry Genetics, Laboratory for Molecular Medicine, Labcorp Genetics (formerly Invitae), Orphanet, G2P
• sensory ataxic neuropathy, dysarthria, and ophthalmoparesis

  Inheritance: AR Classification: DEFINITIVE, SUPPORTIVE Submitted by: Ambry Genetics, Orphanet, G2P
• autosomal dominant progressive external ophthalmoplegia

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• autosomal recessive progressive external ophthalmoplegia

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• mitochondrial neurogastrointestinal encephalomyopathy

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• recessive mitochondrial ataxia syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• spinocerebellar ataxia with epilepsy

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• Leigh syndrome

  Inheritance: AR Classification: LIMITED Submitted by: ClinGen

ACMG classification

Our verdict: Pathogenic. The variant received 12 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
• PP5: Variant 15-89319048-G-GC is Pathogenic according to our data. Variant chr15-89319048-G-GC is described in ClinVar as Pathogenic. ClinVar VariationId is 458711.Status of the report is criteria_provided_single_submitter, 1 stars.

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

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	POLG	NM_002693.3	MANE Select	c.3155dupG	p.Thr1053HisfsTer8	frameshift	Exon 20 of 23	NP_002684.1
	POLG	NM_001126131.2		c.3155dupG	p.Thr1053HisfsTer8	frameshift	Exon 20 of 23	NP_001119603.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	POLG	ENST00000268124.11	TSL:1 MANE Select	c.3155dupG	p.Thr1053HisfsTer8	frameshift	Exon 20 of 23	ENSP00000268124.5
	POLG	ENST00000442287.6	TSL:1	c.3155dupG	p.Thr1053HisfsTer8	frameshift	Exon 20 of 23	ENSP00000399851.2
	POLG	ENST00000636937.2	TSL:5	c.3155dupG	p.Thr1053HisfsTer8	frameshift	Exon 20 of 23	ENSP00000516154.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461858 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727232

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53412

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1111984

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Progressive sclerosing poliodystrophy Pathogenic:1

Sep 08, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. ClinVar contains an entry for this variant (Variation ID: 458711). This variant has not been reported in the literature in individuals affected with POLG-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (p.Thr1053Hisfs*8) in the POLG gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in POLG are known to be pathogenic (PMID: 18546365).

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		7.4
Mutation Taster		=0/200	disease causing (ClinVar)

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

Other links and lift over

dbSNP: rs1447799185; hg19: chr15-89862279;