rs199759055
Variant summary
Our verdict is Uncertain significance. The variant received 3 ACMG points: 7P and 4B. PM5PP3_StrongPP5BS2
The NM_002693.3(POLG):c.1156C>T(p.Arg386Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000026 in 1,613,962 control chromosomes in the GnomAD database, including 2 homozygotes. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R386H) has been classified as Uncertain significance.
Frequency
Consequence
NM_002693.3 missense
Scores
Clinical Significance
Conservation
Publications
- progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 1Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: G2P, Labcorp Genetics (formerly Invitae), Ambry Genetics
- mitochondrial DNA depletion syndrome 4aInheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Ambry Genetics, Laboratory for Molecular Medicine, Labcorp Genetics (formerly Invitae), Orphanet, G2P
- sensory ataxic neuropathy, dysarthria, and ophthalmoparesisInheritance: AR Classification: DEFINITIVE, SUPPORTIVE Submitted by: Ambry Genetics, Orphanet, G2P
- autosomal dominant progressive external ophthalmoplegiaInheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
- autosomal recessive progressive external ophthalmoplegiaInheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
- mitochondrial neurogastrointestinal encephalomyopathyInheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
- recessive mitochondrial ataxia syndromeInheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
- spinocerebellar ataxia with epilepsyInheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
- Leigh syndromeInheritance: AR Classification: LIMITED Submitted by: ClinGen
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ACMG classification
Our verdict: Uncertain_significance. The variant received 3 ACMG points.
Transcripts
RefSeq
Ensembl
Frequencies
GnomAD3 genomes AF: 0.0000197 AC: 3AN: 152176Hom.: 0 Cov.: 33 show subpopulations
GnomAD2 exomes AF: 0.0000358 AC: 9AN: 251406 AF XY: 0.0000442 show subpopulations
GnomAD4 exome AF: 0.0000267 AC: 39AN: 1461786Hom.: 2 Cov.: 33 AF XY: 0.0000275 AC XY: 20AN XY: 727188 show subpopulations
Age Distribution
GnomAD4 genome AF: 0.0000197 AC: 3AN: 152176Hom.: 0 Cov.: 33 AF XY: 0.0000135 AC XY: 1AN XY: 74344 show subpopulations
Age Distribution
ClinVar
Submissions by phenotype
not provided Pathogenic:2Uncertain:2
In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 32347949, 20837862) -
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Progressive sclerosing poliodystrophy Pathogenic:2Uncertain:1
The NM_002693.2:c.1156C>T (NP_002684.1:p.Arg386Cys) [GRCH38: NC_000015.10:g.89328699G>A] variant in POLG gene is interpretated to be a Pathogenic based on ACMG guidelines (PMID: 25741868). This variant has been reported in PMID:20837862 . This variant meets the following evidence codes reported in the ACMG-guideline. PS3:Well established functional studies show a deleterious effect on POLG. PM2:This variant is absent in key population databases. PM3:Detected in trans with a pathogenic variant for Mitochondrial DNA depletion syndrome 4A (Alpers type) which is a recessive disorder. PP1:This variant is co-segregated with Mitochondrial DNA depletion syndrome 4A (Alpers type) in multiple affected family members. PP2:This is a missense variant in POLG with a low rate of benign and high rate of pathogenic missense variations. PP4:Patient's phenotype or family history is highly specific for POLG. Based on the evidence criteria codes applied, the variant is suggested to be Pathogenic. -
This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 386 of the POLG protein (p.Arg386Cys). This variant is present in population databases (rs199759055, gnomAD 0.01%). This missense change has been observed in individual(s) with autosomal recessive POLG-related conditions (PMID: 20837862). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 206589). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) indicates that this missense variant is expected to disrupt POLG protein function with a positive predictive value of 95%. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -
This variant was determined to be of uncertain significance according to ACMG Guidelines, 2015 [PMID:25741868]. -
Mitochondrial DNA depletion syndrome 4b Uncertain:2
Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as 3A-VUS. Following criteria are met: 0102 - Loss of function is a known mechanism of disease in this gene and is associated with POLG-related disorders. (I) 0108 - This gene is associated with both recessive and dominant disease (OMIM). (I) 0112 - The condition associated with this gene has incomplete penetrance (OMIM). (I) 0200 - Variant is predicted to result in a missense amino acid change from arginine to cysteine. (I) 0251 - This variant is heterozygous. (I) 0304 - Variant is present in gnomAD <0.01 for a recessive condition (9 heterozygotes, 0 homozygotes). (P) 0309 - An alternative amino acid change at the same position has been observed in gnomAD (1 heterozygotes, 0 homozygotes). (I) 0501 - Missense variant consistently predicted to be damaging by multiple in silico tools or highly conserved with a major amino acid change. (SP) 0600 - Variant is located in an annotated domain or motif DNA mitochondrial polymerase exonuclease domain; PDB). (I) 0704 - Another missense variant comparable to the one identified in this case has limited previous evidence for pathogenicity. A variant in the same codon resulting in a change to histidine has been reported in patients with Alpers syndrome as VUS (ClinVar, PMID: 20883824). Another change to proline has also been reported in patient with early onset epilepsy (PMID: 31164858). (P). (SP) 0808 - Previous reports of pathogenicity for this variant are conflicting. The variant has been previously reported as VUS (4x), likely pathogenic (1x) and pathogenic (1x) (ClinVar, PMID: 20837862). (I) 0905 - No published segregation evidence has been identified for this variant. (I) 1007 - No published functional evidence has been identified for this variant. (I) 1201 - Heterozygous variant detected in trans with a second pathogenic heterozygous variant (p.P587L/p.T25aI) in a recessive disease. (SP) 1206 - This variant has been shown to be paternally inherited (by trio analysis). (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -
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POLG-related disorder Pathogenic:1
The POLG c.1156C>T variant is predicted to result in the amino acid substitution p.Arg386Cys. This variant was previously reported in the compound heterozygous state with a pathogenic variant in a patient with isolated distal myopathy of the upper limbs and the variant was segregating with the disease in the family (Giordano et al. 2010. PubMed ID: 20837862). This variant is reported in 0.013% of alleles in individuals of South Asian descent in gnomAD. Alternative variants at the same codon p.Arg386Pro and p.Arg386His were observed in POLG related disorders (Demos et al. 2019. PubMed ID: 31164858, Table 2; Baruffini et al. 2010. PubMed ID: 20883824) and p.Arg386His variant was confirmed by functional study in yeast to be damaging (Baruffini et al. 2010. PubMed ID: 20883824). In summary, we interpret the c.Arg386Cys variant as likely pathogenic. -
Progressive sclerosing poliodystrophy;C1834846:Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 1;C1843851:Sensory ataxic neuropathy, dysarthria, and ophthalmoparesis;C3150914:Mitochondrial DNA depletion syndrome 4b;C4225153:Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal recessive 1 Pathogenic:1
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Progressive sclerosing poliodystrophy;C1843851:Sensory ataxic neuropathy, dysarthria, and ophthalmoparesis;C3150914:Mitochondrial DNA depletion syndrome 4b Uncertain:1
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Computational scores
Source:
Splicing
Find out detailed SpliceAI scores and Pangolin per-transcript scores at