rs757781708

chr17-43095923-C-Achr17-43095923-C-Gchr17-43095923-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PVS1_Moderate PM2 PP3_Strong

The NM_007294.4(BRCA1):c.594-1G>T variant causes a splice acceptor change. The variant allele was found at a frequency of 0.000000686 in 1,458,188 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 Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: BRCA1 NM_007294.4 splice_acceptor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:4
• Conservation: PhyloP100: 3.67

Genes affected

BRCA1 (HGNC:1100): (BRCA1 DNA repair associated) This gene encodes a 190 kD nuclear phosphoprotein that plays a role in maintaining genomic stability, and it also acts as a tumor suppressor. The BRCA1 gene contains 22 exons spanning about 110 kb of DNA. The encoded protein combines with other tumor suppressors, DNA damage sensors, and signal transducers to form a large multi-subunit protein complex known as the BRCA1-associated genome surveillance complex (BASC). This gene product associates with RNA polymerase II, and through the C-terminal domain, also interacts with histone deacetylase complexes. This protein thus plays a role in transcription, DNA repair of double-stranded breaks, and recombination. Mutations in this gene are responsible for approximately 40% of inherited breast cancers and more than 80% of inherited breast and ovarian cancers. Alternative splicing plays a role in modulating the subcellular localization and physiological function of this gene. Many alternatively spliced transcript variants, some of which are disease-associated mutations, have been described for this gene, but the full-length natures of only some of these variants has been described. A related pseudogene, which is also located on chromosome 17, has been identified. [provided by RefSeq, May 2020]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PVS1: Splicing variant, NOT destroyed by nmd, known LOF gene, truncates exone, which is 0.013590844 fraction of the gene. Cryptic splice site detected, with MaxEntScore 6.7, offset of -21, new splice context is: taactagtgtttcttattAGgac. 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
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BRCA1	NM_007294.4	c.594-1G>T		splice_acceptor_variant		ENST00000357654.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BRCA1	ENST00000357654.9	c.594-1G>T		splice_acceptor_variant		1	NM_007294.4	P4

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD3 exomes AF: 0.00000400 AC: 1 AN: 249902 Hom.: 0 AF XY: 0.00000740 AC XY: 1 AN XY: 135068

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000329

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.86e-7 AC: 1 AN: 1458188 Hom.: 0 Cov.: 30 AF XY: 0.00000138 AC XY: 1 AN XY: 725552

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: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 31

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary cancer-predisposing syndrome Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Dec 16, 2019	This variant causes a G>T nucleotide substitution at the -1 position of intron 8 of the BRCA1 gene. While this variant is expected to disrupt the intron 8 splice acceptor site, another canonical splice site variant c.594-2A>C at this splice site was found not to segregate with breast or ovarian cancer (PMID: 25639900, 27008870) and it has been observed in trans with a pathogenic BRCA1 co-variant in an individual who did not have early-developmental phenotype (PMID: 26884819). The naturally-occurring and functional alternative BRCA1 transcript lacking exons 8 and 9 is thought to ameliorate canonical splice site variants in exons 8 and 9 (PMID: 19892845, 27008870). To our knowledge, functional studies have not been performed for this variant nor has it been reported in individuals affected with hereditary cancer in the literature. This variant has been identified in 1/249902 chromosomes in the general population by the Genome Aggregation Database (gnomAD). The available evidence is insufficient 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	Ambry Genetics	Jan 15, 2016	The c.594-1G>T intronic variant results from a G to T substitution one nucleotide upstream from coding exon 8 of the BRCA1 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; however, this alteration occurs at a splice junction that is located at a naturally occurring, alternatively spliced exon and, thus, the degree and effects of abnormal splicing cannot be predicted (Colombo M et al. Hum. Mol. Genet., 2014 Jul;23:3666-80). Using the BDGP and ESEfinder splice site prediction tools, this alteration is predicted to abolish the native splice acceptor site; however, direct evidence is unavailable. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Sep 01, 2017

The c.594-1G>T variant in BRCA1 has not been previously reported in individuals with BRCA1-associated cancers, but has been identified in 1/14982 South Asian ch romosomes by the Exome Aggregation Consortium (ExAC, http://exac.broadinstitute. org; dbSNP rs757781708). This variant occurs in the invariant region (+/- 1,2) o f the splice consensus sequence and is predicted to cause altered splicing leadi ng to skipping of exon 9; however, a BRCA1 isoform that lacks exons 9 and 10 is normally expressed in breast tissue, suggesting that the c.594-1G>T variant may not cause disease (Tesoriero 2005, Rosenthal 2015, de la Hoya 2016, Wong-Brown 2 016). In summary, the clinical significance of the c.594-1G>T variant is uncerta in. -

Hereditary breast ovarian cancer syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jun 02, 2023

In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Studies have shown that disruption of this splice site is associated with altered splicing resulting in skipping of exon 8 and 9 (also known as exon 9 and 10). However, an in-frame BRCA1 isoform that skips exons 8 and 9 is expressed in normal blood and breast tissue, suggesting that this isoform may not be deleterious (PMID: 24569164). ClinVar contains an entry for this variant (Variation ID: 440453). Disruption of this splice site has been observed in individual(s) with breast cancer (PMID: 33151324). This variant is present in population databases (rs757781708, gnomAD 0.003%). This sequence change affects an acceptor splice site in intron 8 of the BRCA1 gene. Loss-of-function variants in BRCA1 are expected to be pathogenic (PMID: 20104584). However, an in-frame BRCA1 isoform lacking exons 8 and 9 (also known as exons 9 and 10) is highly expressed in blood from unaffected individuals and in normal breast tissue; this isoform may retain protein function and could functionally rescue loss-of-function variants within exons 8-9 (PMID: 24569164). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.29	D
BayesDel_noAF	Pathogenic	0.28
Cadd	Pathogenic	27
Dann	Uncertain	0.99
Eigen	Pathogenic	0.97
Eigen_PC	Pathogenic	0.78
FATHMM_MKL	Uncertain	0.90	D
MutationTaster	Benign	1.0	D;D;D;D;D;D;D;D;D;D;D;D;D;D
GERP RS		4.6
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	0.92
SpliceAI score (max)		0.83		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.83		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: rs757781708; hg19: chr17-41247940;