7-124863547-G-A

Position:

• chr7-124863547-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM2 PP3_Moderate PP5

The NM_015450.3(POT1):​c.349C>T​(p.Arg117Cys) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,461,660 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. R117H) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: POT1 NM_015450.3 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:1 O:1
• Conservation: PhyloP100: 5.86

Genes affected

POT1 (HGNC:17284): (protection of telomeres 1) This gene is a member of the telombin family and encodes a nuclear protein involved in telomere maintenance. Specifically, this protein functions as a member of a multi-protein complex that binds to the TTAGGG repeats of telomeres, regulating telomere length and protecting chromosome ends from illegitimate recombination, catastrophic chromosome instability, and abnormal chromosome segregation. Increased transcriptional expression of this gene is associated with stomach carcinogenesis and its progression. Alternatively spliced transcript variants have been described. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Uncertain_significance. Variant got 5 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.911
• PP5: Variant 7-124863547-G-A is Pathogenic according to our data. Variant chr7-124863547-G-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 475082.We mark this variant Likely_pathogenic, oryginal submissions are: {not_provided=1, Likely_pathogenic=1, Pathogenic=1, Uncertain_significance=1}. Variant chr7-124863547-G-A is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
POT1	NM_015450.3	c.349C>T	p.Arg117Cys	missense_variant	8/19	ENST00000357628.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
POT1	ENST00000357628.8	c.349C>T	p.Arg117Cys	missense_variant	8/19	2	NM_015450.3	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251098 Hom.: 0 AF XY: 0.00000737 AC XY: 1 AN XY: 135690

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000881

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461660 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727132

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:1 Other:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Tumor predisposition syndrome 3 Pathogenic:2 Other:1

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Dec 08, 2023	This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 117 of the POT1 protein (p.Arg117Cys). This variant is present in population databases (rs780936436, gnomAD 0.0009%). This missense change has been observed in individuals with clinical features of POT1 tumor predisposition syndrome (PMID: 26403419; Invitae). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 475082). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt POT1 protein function with a negative predictive value of 80%. Experimental studies have shown that this missense change affects POT1 function (PMID: 26403419). For these reasons, this variant has been classified as Pathogenic. -
Likely pathogenic, no assertion criteria provided	clinical testing	Center of Human Genetics, Hôpital Erasme	-	The variant is rare in gnomADv4 (2/1461660 alleles, frequency : 0.00014%). Arginine at position 117 is an amino acid that appears to be highly conserved in evolution. The variant is located in the Telomeric single stranded DNA binding domain. The variant has been describred in 3 “Li-Fraumeni-like” families with multiple cancers including cardiosarcomas but also melanomas or lung cancers. In silico, in vitro and in vivo studies in cells showed that the variant reduces POT1 binding to telomeres and increases telomere length and fragility (PMID:26403419_2015). Another study by the same author showed the presence of a POT1 mutation in 20% of families with angiosarcomas and 10% of individuals with sporadic angio or cardiosarcoma (PMID:28853721_2017). The patient's phenotype and family history are compatible with the pathology associated with POT1 gene. -
not provided, no classification provided	literature only	GeneReviews	-	Reported in 3 families with Li-Fraumeni-like and familial cardiac angiosarcoma -

Hereditary cancer-predisposing syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 02, 2023

The p.R117C variant (also known as c.349C>T), located in coding exon 4 of the POT1 gene, results from a C to T substitution at nucleotide position 349. The arginine at codon 117 is replaced by cysteine, an amino acid with highly dissimilar properties. This alteration segregated in three Li-Fraumeni like families, including members affected with cardiac angiosarcomas, and other soft tissue sarcomas. Individuals in these families were shown to have reduced telomere bound POT1 levels, abnormally long telomeres, and increased telomere fragility (Calvete O et al. Nat Commun, 2015 Sep;6:8383). Mouse modeling using both embryonic fibroblasts and tissues with the R117C alteration showed longer telomeres than wild-type controls and complementation assays showed that R117C exerts dominant-negative effects at telomeres (Martínez P et al. PLoS Genet, 2022 06;18:e1010260). This amino acid position is highly conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Dec 17, 2020

Identified in Spanish families with angiosarcoma and other cancers (Calvete 2015); Published functional studies demonstrate reduced recruitment of POT1 protein to telomeres and increased DNA damage markers, but no impact on telomerase activity in patient cells (Calvete 2015, Calvete 2019); Not observed at a significant frequency in large population cohorts (Lek 2016); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 26403419, 28853721, 32033110, 28389767, 31510873) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.30
BayesDel_addAF	Uncertain	0.12	D
BayesDel_noAF	Uncertain	-0.060
CADD	Pathogenic	32
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.95	D
Eigen	Uncertain	0.67
Eigen_PC	Uncertain	0.61
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Uncertain	0.89	D
M_CAP	Uncertain	0.11	D
MetaRNN	Pathogenic	0.91	D
MetaSVM	Benign	-0.61	T
MutationAssessor	Uncertain	2.6	M
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.57	T
PROVEAN	Pathogenic	-4.5	D
REVEL	Uncertain	0.39
Sift	Uncertain	0.0010	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.81
MutPred		0.73		Loss of solvent accessibility (P = 0.0404);
MVP		0.67
MPC		2.3
ClinPred		0.99	D
GERP RS		4.6
Varity_R		0.40
gMVP		0.91

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: rs780936436; hg19: chr7-124503601; COSMIC: COSV105268145; COSMIC: COSV105268145;