13-32376669-G-A

Position:

• chr13-32376669-G-A

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1_Moderate PM2 PP5_Very_Strong

The NM_000059.4(BRCA2):​c.8633-1G>A variant causes a splice acceptor, intron change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: BRCA2 NM_000059.4 splice_acceptor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:8
• Conservation: PhyloP100: 3.56

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]

BRCA2 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.011796822 fraction of the gene. Cryptic splice site detected, with MaxEntScore 6.3, offset of -33, new splice context is: agttgcttttgaatttacAGttt. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 13-32376669-G-A is Pathogenic according to our data. Variant chr13-32376669-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 91731.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr13-32376669-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BRCA2	NM_000059.4	c.8633-1G>A		splice_acceptor_variant, intron_variant		ENST00000380152.8	NP_000050.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BRCA2	ENST00000380152.8	c.8633-1G>A		splice_acceptor_variant, intron_variant		5	NM_000059.4	ENSP00000369497.3
BRCA2	ENST00000530893.7	c.8264-1G>A		splice_acceptor_variant, intron_variant		1		ENSP00000499438.2
BRCA2	ENST00000614259.2	n.*691-1G>A		splice_acceptor_variant, intron_variant		2		ENSP00000506251.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:8

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

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

Pathogenic, criteria provided, single submitter	clinical testing	Human Genome Sequencing Center Clinical Lab, Baylor College of Medicine	May 25, 2017	This c.8633-1G>A variant in the BRCA2 gene has not been observed in our cohort database nor has been detected in the ExAC database. This variant was however reported in ClinVar but the clinical presentation of the patients was not available (https://www.ncbi.nlm.nih.gov/clinvar/variation/91731/). This variant affects the invariant acceptor splice site of intron 20 of the BRCA2 gene. While not validated for clinical use, computer-based algorithms predict this c.8633-1G>A variant change to disrupt the splice site. This variant is classified as pathogenic -
Pathogenic, criteria provided, single submitter	clinical testing	Quest Diagnostics Nichols Institute San Juan Capistrano	Jul 30, 2015	- -
Likely pathogenic, no assertion criteria provided	clinical testing	Sharing Clinical Reports Project (SCRP)	Mar 15, 2010	- -
Pathogenic, criteria provided, single submitter	clinical testing	Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA), c/o University of Cambridge	Oct 02, 2015	- -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Apr 23, 2021

Canonical splice site variant predicted to result in a null allele in a gene for which loss-of-function is a known mechanism of disease; Not observed in large population cohorts (Lek 2016); Also known as 8861-1G>A; Observed in individuals undergoing hereditary breast and/or ovarian cancer testing (Rebbeck 2018); This variant is associated with the following publications: (PMID: 31447099, 31131967, 29446198) -

Familial cancer of breast Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Apr 30, 2021

- -

Hereditary cancer-predisposing syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 29, 2024

The c.8633-1G>A intronic variant results from a G to A substitution one nucleotide upstream from coding exon 20 of the BRCA2 gene. Alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. This alteration was identified in a large, worldwide study of BRCA1/2 mutation positive families (Rebbeck TR et al. Hum Mutat, 2018 May;39:593-620). In addition, this variant was reported in 1/60,466 breast cancer cases and in 0/53,461 controls (Dorling et al. N Engl J Med 2021 02;384:428-439). One functional study based in mouse embryonic stem cells reported this variant as non-functional (Biswas K et al. Cell Rep Methods. 2023 Nov;3(11):100628). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice acceptor site and may result in the creation or strengthening of a novel splice acceptor site; however direct evidence is insufficient (Ambry internal data). Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Hereditary breast ovarian cancer syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Sep 27, 2022

This sequence change affects an acceptor splice site in intron 20 of the BRCA2 gene. RNA analysis indicates that disruption of this splice site induces altered splicing and may result in an absent or disrupted protein product. For these reasons, this variant has been classified as Pathogenic. Studies have shown that disruption of this splice site results in a 43 bp deletion at the beginning of exon 21 or a 93 bp insertion from intron 20 and introduces a premature termination codon (PMID: 16619214). The resulting mRNA is expected to undergo nonsense-mediated decay. ClinVar contains an entry for this variant (Variation ID: 91731). Disruption of this splice site has been observed in individual(s) with increased risk of breast and/or ovarian cancers (PMID: 29446198). This variant is not present in population databases (gnomAD no frequency). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.21	D
BayesDel_noAF	Uncertain	0.060
CADD	Pathogenic	31
DANN	Uncertain	0.99
Eigen	Pathogenic	0.91
Eigen_PC	Pathogenic	0.70
FATHMM_MKL	Uncertain	0.97	D
GERP RS		5.3

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.98		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.47		Position offset: 48
DS_AL_spliceai		0.98		Position offset: 1

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

Publications

LitVar

Other links and lift over

dbSNP: rs398122711; hg19: chr13-32950806;