13-32363534-G-A

Position:

• chr13-32363534-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.8331+1G>A variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000686 in 1,458,766 control chromosomes in the GnomAD database, with no homozygous occurrence. 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)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: BRCA2 NM_000059.4 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:8
• Conservation: PhyloP100: 9.60

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 0.034513015 fraction of the gene. Cryptic splice site detected, with MaxEntScore 3.2, offset of 21, new splice context is: ttgGTaaaa. 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 13-32363534-G-A is Pathogenic according to our data. Variant chr13-32363534-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 38154.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr13-32363534-G-A is described in Lovd as [Pathogenic]. Variant chr13-32363534-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.8331+1G>A		splice_donor_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.8331+1G>A		splice_donor_variant, intron_variant		5	NM_000059.4	ENSP00000369497.3
BRCA2	ENST00000530893.7	c.7962+1G>A		splice_donor_variant, intron_variant		1		ENSP00000499438.2
BRCA2	ENST00000614259.2	n.*389+1G>A		splice_donor_variant, intron_variant		2		ENSP00000506251.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.86e-7 AC: 1 AN: 1458766 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 725908

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: 9.01e-7

Gnomad4 OTH exome AF: 0.00

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:2

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, no assertion criteria provided	clinical testing	Sharing Clinical Reports Project (SCRP)	Jan 07, 2013	- -

Familial cancer of breast Pathogenic:2

Likely pathogenic, no assertion criteria provided	literature only	Center for Precision Medicine, Meizhou People's Hospital	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Oct 14, 2022	- -

Medulloblastoma;C0346153:Familial cancer of breast;C1838457:Fanconi anemia complementation group D1;C2675520:Breast-ovarian cancer, familial, susceptibility to, 2;C2751641:Glioma susceptibility 3;C2931456:Familial prostate cancer;C3150546:Pancreatic cancer, susceptibility to, 2;CN033288:Wilms tumor 1 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Juno Genomics, Hangzhou Juno Genomics, Inc

-

PVS1+PM2_Supporting+PS4_Supporting -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Jul 26, 2018

This pathogenic variant is denoted BRCA2 IVS18+1G>A or c.8331+1G>A and consists of a G>A nucleotide substitution at the +1 position of intron 18 of the BRCA2 gene. The variant destroys a canonical splice donor site and is predicted to cause abnormal gene splicing, leading to either an abnormal message that is subject to nonsense-mediated mRNA decay or to an abnormal protein product. This variant has been observed in men and women with breast cancer (Zhang 2012, Pritzlaff 2017). Based on the current evidence, we consider this variant to be pathogenic. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Mar 18, 2022

The c.8331+1G>A intronic variant (also known as IVS18+1G>A) results from a G to A one nucleotide after coding exon 17 of the BRCA2 gene. This alteration was previously reported in 1/409 Chinese breast cancer patients with at least one first or second degree relatives with breast and/or ovarian cancer or with bilateral breast cancer diagnosed under the age of 50 (Zhang J, Breast Cancer Res. Treat. 2012 Apr; 132(2):421-8). This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice donor site. RNA studies have demonstrated that this alteration results in substantial, but incomplete splice defects as ascertained by multiple quantitative analyses (Ambry internal data; Gelli E et al. Cancers (Basel), 2019 Mar;11; Nix P et al. Fam Cancer, 2021 Jan;). Furthermore, the close match alteration BRCA2 c.8331+2T>C was observed in individuals who collectively do not present with a clinical history seen in typical high-risk hereditary breast and ovarian cancer (HBOC) variant carriers (Nix P et al. Fam Cancer, 2021 Jan;). However, these data cannot rule out the possibility of a hypomorphic variant with atypical risks. Based on the majority of available evidence to date, this variant is likely to be pathogenic. However, carriers of this variant and their families may present with reduced risks, and not with the typical clinical characteristics of a high-risk pathogenic BRCA2 alteration. As risk estimates are unknown at this time, clinical correlation is advised. -

Hereditary breast ovarian cancer syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 12, 2022

For these reasons, this variant has been classified as Pathogenic. This variant disrupts the c.8331+1G nucleotide in the BRCA2 gene. Other variant(s) that disrupt this nucleotide have been determined to be pathogenic (PMID: 19619314, 28339459). This suggests that this nucleotide is clinically significant, and that variants that disrupt this position are likely to be disease-causing. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. ClinVar contains an entry for this variant (Variation ID: 38154). Disruption of this splice site has been observed in individual(s) with breast cancer (PMID: 21614564, 26681312, 28008555). This variant is not present in population databases (gnomAD no frequency). This sequence change affects a donor splice site in intron 18 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). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.45	D
BayesDel_noAF	Pathogenic	0.42
CADD	Pathogenic	33
DANN	Uncertain	1.0
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.1
FATHMM_MKL	Pathogenic	1.0	D
GERP RS		5.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.93		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.93		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: rs81002837; hg19: chr13-32937671;