13-32370448-G-T

Position:

• chr13-32370448-G-T

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM2 PM5 PP3_Strong PP5

The NM_000059.4(BRCA2):​c.8378G>T​(p.Gly2793Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 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. G2793E?) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: BRCA2 NM_000059.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:4
• Conservation: PhyloP100: 9.94

Genes affected

BRCA2 (HGNC:1101): (BRCA2 DNA repair associated) Inherited mutations in BRCA1 and this gene, BRCA2, confer increased lifetime risk of developing breast or ovarian cancer. Both BRCA1 and BRCA2 are involved in maintenance of genome stability, specifically the homologous recombination pathway for double-strand DNA repair. The largest exon in both genes is exon 11, which harbors the most important and frequent mutations in breast cancer patients. The BRCA2 gene was found on chromosome 13q12.3 in human. The BRCA2 protein contains several copies of a 70 aa motif called the BRC motif, and these motifs mediate binding to the RAD51 recombinase which functions in DNA repair. BRCA2 is considered a tumor suppressor gene, as tumors with BRCA2 mutations generally exhibit loss of heterozygosity (LOH) of the wild-type allele. [provided by RefSeq, May 2020]

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr13-32370447-GG-GAA is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.978
• PP5: Variant 13-32370448-G-T is Pathogenic according to our data. Variant chr13-32370448-G-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 38158.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=2, Pathogenic=2}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BRCA2	NM_000059.4	c.8378G>T	p.Gly2793Val	missense_variant	19/27	ENST00000380152.8	NP_000050.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BRCA2	ENST00000380152.8	c.8378G>T	p.Gly2793Val	missense_variant	19/27	5	NM_000059.4	ENSP00000369497	A2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:4

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Breast-ovarian cancer, familial, susceptibility to, 2 Uncertain:4

Uncertain significance, no assertion criteria provided	clinical testing	Sharing Clinical Reports Project (SCRP)	Jan 04, 2013	- -
Uncertain significance, criteria provided, single submitter	clinical testing	All of Us Research Program, National Institutes of Health	Feb 05, 2024	This missense variant replaces glycine with valine at codon 2793 of the BRCA2 protein. Computational prediction suggests that this variant may have deleterious impact on protein structure and function. Functional studies have shown that this variant impacts homology-directed DNA repair activity and increases sensitivity to PARP inhibitors (PMID: 32444794, 33609447). A multifactorial analysis has reported an inconclusive likelihood ratio for pathogenicity based on personal and family history for this variant (PMID: 31853058). This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). Different variants affecting the same codon, c.8377G>A (p.Gly2793Arg) and c.8378G>A (p.Gly2793Glu), are considered pathogenic (ClinVar Variation ID: 52569, 38157), suggesting that Gly at this position is important for BRCA2 protein function. Although there is a suspicion that this variant may be associated with disease, additional clinical studies are necessary to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance. -
Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	Mar 23, 2018	- -
Uncertain significance, no assertion criteria provided	clinical testing	Department of Medical and Surgical Sciences, University of Bologna	Sep 01, 2023	PM2(Supporting)+PP3(Supporting) according to ACMG/AMP classification guidelines specified for BRCA1 & BRCA2 (Classification Criteria V1.0.0 2023-09-08 - https://cspec.genome.network/cspec/ui/svi/affiliation/50087) (PMID: 38160042) -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jan 24, 2020

The p.G2793V pathogenic mutation (also known as c.8378G>T), located in coding exon 18 of the BRCA2 gene, results from a G to T substitution at nucleotide position 8378. The glycine at codon 2793 is replaced by valine, an amino acid with dissimilar properties. Several other alterations at this same codon are considered pathogenic including p.G2793E and p.G2793R (Ambry internal data). This alteration was non-functional in a homology-directed DNA repair (HDR) assay (Ambry internal data). This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD) (Lek M et al. Nature, 2016 08;536:285-91). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the majority of available evidence to date, this variant is considered a disease-causing mutation. -

Hereditary breast ovarian cancer syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Feb 09, 2024

Variant summary: BRCA2 c.8378G>T (p.Gly2793Val) results in a non-conservative amino acid change located in the BRCA2, OB1 domain (IPR015187) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. Consensus agreement among computational tools predict no significant impact on normal splicing. However, at least one publication reports experimental evidence that this variant affects mRNA splicing, resulting in skipping of exon 19, which is expected to cause an in-frame deletion (Wai_2020). The variant was absent in 251422 control chromosomes (gnomAD). c.8378G>T has been reported in the literature in at least one individual affected with Hereditary Breast And Ovarian Cancer Syndrome (Innella_2023). At least one publication reports experimental evidence evaluating an impact on protein function, finding that the variant is non-functional in an HDR assay (Richardson_2021). HDR assays qualify as a recognized gold standard on the basis of updated guidance provided by the ClinGen Sequence Variant Interpretation (SVI) working group. This working group has recommended strong functional evidence (ACMG PS3) as sufficient weightage for categorization as likely pathogenic (Tavtigian_2018). In addition, this variant alters a highly conserved amino acid (HGMD) in which another missense variant (p.Gly2793Arg) has been classified as pathogenic, suggesting this is a functionally important residue. The following publications have been ascertained in the context of this evaluation (PMID: 32123317, 33609447, 36561320, 38160042). ClinVar contains an entry for this variant (Variation ID: 38158). Based on the evidence outlined above, the variant was classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.95
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.59
CADD	Pathogenic	33
DANN	Uncertain	1.0
Eigen	Pathogenic	0.99
Eigen_PC	Pathogenic	0.92
FATHMM_MKL	Pathogenic	0.99	D
M_CAP	Pathogenic	0.85	D
MetaRNN	Pathogenic	0.98	D;D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.62	T
PROVEAN	Uncertain	-2.7	D;D
REVEL	Pathogenic	0.91
Sift	Pathogenic	0.0	D;D
Sift4G	Pathogenic	0.0	D;D
Vest4		0.84
MutPred		0.86		Loss of loop (P = 0.0512);Loss of loop (P = 0.0512);
MVP		0.99
MPC		0.18
ClinPred		1.0	D
GERP RS		5.2
gMVP		0.93

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.36		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.36		Position offset: 19

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

Publications

LitVar

Other links and lift over

dbSNP: rs80359083; hg19: chr13-32944585;