rs81002820

Positions:

• chr13-32329442-G-A
• chr13-32329442-G-C
• chr13-32329442-G-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000059.4(BRCA2):​c.632-1G>A variant causes a splice acceptor change. 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 Pathogenic (★★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: BRCA2 NM_000059.4 splice_acceptor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic reviewed by expert panel P:6
• Conservation: PhyloP100: 4.40

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 Pathogenic. Variant got 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 5.4, offset of 4, new splice context is: aatttttatcttacaatcAGaaa. Cryptic site results in frameshift 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 13-32329442-G-A is Pathogenic according to our data. Variant chr13-32329442-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 52060.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr13-32329442-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.632-1G>A		splice_acceptor_variant		ENST00000380152.8	NP_000050.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BRCA2	ENST00000380152.8	c.632-1G>A		splice_acceptor_variant		5	NM_000059.4	ENSP00000369497	A2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 28

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:6

Revision: reviewed by expert panel

Submissions by phenotype

Breast-ovarian cancer, familial, susceptibility to, 2 Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA), c/o University of Cambridge	Oct 02, 2015	- -
Pathogenic, reviewed by expert panel	curation	Evidence-based Network for the Interpretation of Germline Mutant Alleles (ENIGMA)	Jun 18, 2019	IARC class based on posterior probability from multifactorial likelihood analysis, thresholds for class as per Plon et al. 2008 (PMID: 18951446). Class 5 based on posterior probability = 0.999853 -
Pathogenic, criteria provided, single submitter	clinical testing	Biomedical Genomics and Oncogenetics Laboratory, Institut Pasteur de Tunis, University Tunis El Manar	-	- -

not provided Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

Department of Pathology and Laboratory Medicine, Sinai Health System

-

The BRCA2 c.632-1G>A variant was identified in 7 of 74942 proband chromosomes (frequency: 0.000093) from Japanese, Caucasian, Asian and U.K. individuals or families with familial breast cancer or prostate cancer and was not identified in 22482 control chromosomes from healthy individuals (Tesoriero 2005, Rebbeck 2018, Momozawa 2018). The variant was also identified in dbSNP (ID: rs81002820) as "With Likely pathogenic, Pathogenic allele ", ClinVar (classified as pathogenic by the University of Cambridge and Mount Sinai Hospital (Toronto), and LOVD 3.0 (classified as pathogenic by 4 submitters). The variant was not identified in UMD-LSDB. The variant was also identified by our laboratory in 1 individual with breast cancer. The variant was not identified in the following control databases: the Exome Aggregation Consortium (August 8th 2016), or the Genome Aggregation Database (Feb 27, 2017). In a study of 720 familial breast cancer families, this variant was identified in 3 families (Tesoriero 2005). In this paper this variant was predicted to result in the deletion of exon 8 by disrupting the intron 7 acceptor site. RT-PCR of BRCA2, c.632-1G>A RNA was undertaken and the entire RT-PCR reaction was cloned and sequenced. Of the fifty clones sequenced, only the wildtype transcript and a transcript lacking exon 8 (BRCA2, c.860_909del) were identified. No other alternative transcripts were found. The resulting BRCA2 c.860-909del introduces a frameshift that is predicted to create a stop at codon 220, and the authors therefore considered this variant to be pathogenic. The c.632-1G>A variant is predicted to cause abnormal splicing because the nucleotide substitution occurs in the invariant region of the splice consensus sequence and 4 of 4 in silico or computational prediction software programs (SpliceSiteFinder, MaxEntScan, NNSPLICE, GeneSplicer) predict a greater than 10% difference in splicing. In summary, based on the above information this variant meets our laboratory’s criteria to be classified as pathogenic. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 03, 2019

The c.632-1G>A intronic variant results from a G to A substitution one nucleotide upstream from coding exon 7 of the BRCA2 gene. This alteration has been reported in several BRCA1/2 positive cohorts (Al-Mulla F et al. J. Clin. Pathol., 2009 Apr;62:350-6; Edwards SM et al. Br. J. Cancer, 2010 Sep;103:918-24; Rebbeck TR et al. Hum. Mutat., 2018 05;39:593-620). This alteration is also reported as c.860-1G>A in the literature. 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. As such, this alteration is classified as likely pathogenic. -

Hereditary breast ovarian cancer syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 28, 2022

Disruption of this splice site has been observed in individual(s) with breast, ovarian or prostate cancer (PMID: 20736950, 29371908, 29446198). For these reasons, this variant has been classified as Pathogenic. Studies have shown that disruption of this splice site results in skipping of exon 8 and introduces a premature termination codon (PMID: 18819001). The resulting mRNA is expected to undergo nonsense-mediated decay. Based on a multifactorial likelihood algorithm using genetic, in silico, and/or statistical data, this variant has been determined to have a high probability of being pathogenic (PMID: 31131967). ClinVar contains an entry for this variant (Variation ID: 52060). This variant is also known as c.860-1G>A. This variant is not present in population databases (gnomAD no frequency). This sequence change affects an acceptor splice site in intron 7 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.23	D
BayesDel_noAF	Uncertain	0.10
CADD	Pathogenic	33
DANN	Uncertain	0.99
Eigen	Pathogenic	0.98
Eigen_PC	Pathogenic	0.80
FATHMM_MKL	Uncertain	0.97	D
MutationTaster	Benign	1.0	D;D
GERP RS		5.5

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.91
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.55		Position offset: 5
DS_AL_spliceai		0.99		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: rs81002820; hg19: chr13-32903579;