13-32329442-G-T

Variant names:

• chr13-32329442-G-T
• rs81002820
• NM_000059.4:c.632-1G>T

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PVS1 PM2 PP5

The NM_000059.4(BRCA2):​c.632-1G>T variant causes a splice acceptor, intron 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 Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 32)
• Consequence: BRCA2 NM_000059.4 splice_acceptor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• 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 11 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 6.6, offset of 4, new splice context is: aatttttatcttacattcAGaaa. 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-T is Pathogenic according to our data. Variant chr13-32329442-G-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 52062.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Pathogenic=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
BRCA2	NM_000059.4	c.632-1G>T		splice_acceptor_variant, intron_variant	Intron 7 of 26	ENST00000380152.8	NP_000050.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
BRCA2	ENST00000380152.8	c.632-1G>T		splice_acceptor_variant, intron_variant	Intron 7 of 26	5	NM_000059.4	ENSP00000369497.3
BRCA2	ENST00000530893.7	c.263-1G>T		splice_acceptor_variant, intron_variant	Intron 7 of 26	1		ENSP00000499438.2
BRCA2	ENST00000614259.2	n.632-1G>T		splice_acceptor_variant, intron_variant	Intron 6 of 25	2		ENSP00000506251.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 28

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hereditary breast ovarian cancer syndrome Pathogenic:1

Nov 15, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. Studies have shown that disruption of this splice site alters mRNA splicing and is expected to lead to the loss of protein expression (PMID: 18819001, 30883759, 32393813). 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: 52062). Disruption of this splice site has been observed in individual(s) with BRCA2-related conditions (PMID: 19656164, 22798144, 29446198, 30613976). 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. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in BRCA2 are known to be pathogenic (PMID: 20104584). -

Hereditary cancer-predisposing syndrome Uncertain:1

Apr 08, 2024

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.632-1G>T intronic variant results from a G to T substitution one nucleotide upstream from coding exon 7 of the BRCA2 gene. This variant has been detected in multiple breast cancer cohorts (Seong MW et al. Clin Genet, 2009 Aug;76:152-60; Kim H et al. Breast Cancer Res Treat, 2012 Aug;134:1315-26; Dorling et al. N Engl J Med. 2021 02;384:428-439), as well as an individual with prostate cancer (Edwards SM et al. Br J Cancer, 2010 Sep;103:918-24). 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 will result in the creation or strengthening of a novel splice acceptor site. RNA experiments have shown coding exon 7 splicing alterations to express an in-frame transcript, known as 6q39_8 in the literature (Ambry internal data). This transcript has been shown to be able to perform homology directed repair in protein functional studies at a near wild-type level (Mesman, RLS et al. Genet Med 2020 08;22(8):1355-1365). Since supporting evidence is conflicting at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.22	D
BayesDel_noAF	Uncertain	0.070
CADD	Pathogenic	33
DANN	Uncertain	0.99
Eigen	Pathogenic	0.98
Eigen_PC	Pathogenic	0.80
FATHMM_MKL	Pathogenic	0.97	D
GERP RS		5.5

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.91
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.62		Position offset: 5
DS_AL_spliceai		1.0		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;