chr17-43124023-G-A

Variant names:

• chr17-43124023-G-A
• rs876660096
• NM_007294.4:c.74C>T

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PS3 PP3 PM2_Supporting

This summary comes from the ClinGen Evidence Repository: The c.74C>T variant in BRCA1 is a missense variant predicted to cause substitution of proline by leucine at amino acid 25 (p.Pro25Leu). This variant is absent from gnomAD v2.1 (exomes only, non-cancer subset, read depth ≥25) and gnomAD v3.1 (non-cancer subset, read depth ≥25) (PM2_Supporting met). This BRCA1 missense variant is within a key functional domain and the computational predictor BayesDel (noAF) gives a score of 0.35, above the recommended threshold of 0.28 for prediction of impact on BRCA1 function via protein change. A SpliceAI score of 0.02 predicts no impact on splicing (score threshold ≤0.1) (PP3 met). Reported by two calibrated studies to exhibit protein function similar to pathogenic control variants (PMIDs:30209399, 35659930) (PS3 met). In summary, this variant meets the criteria to be classified as a likely pathogenic variant for BRCA1-related cancer predisposition based on the ACMG/AMP criteria applied as specified by the ENIGMA BRCA1/2 VCEP (PM2_Supporting, PP3, PS3). LINK:https://erepo.genome.network/evrepo/ui/classification/CA10580713/MONDO:0700268/092

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: BRCA1 NM_007294.4 missense
• Clinical Significance: Likely pathogenic reviewed by expert panel P:2 U:4
• Conservation: PhyloP100: 4.47
• Publications: 13 publications found

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]

BRCA1 Gene-Disease associations (from GenCC):

• breast-ovarian cancer, familial, susceptibility to, 1

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Ambry Genetics, ClinGen, Labcorp Genetics (formerly Invitae), Genomics England PanelApp
• Fanconi anemia, complementation group S

  Inheritance: AR Classification: DEFINITIVE, STRONG, MODERATE, LIMITED Submitted by: G2P, Labcorp Genetics (formerly Invitae), ClinGen, Ambry Genetics
• pancreatic cancer, susceptibility to, 4

  Inheritance: AD Classification: MODERATE Submitted by: Genomics England PanelApp
• hereditary breast ovarian cancer syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Fanconi anemia

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 6 ACMG points.

• PS3: For more information check the summary or visit ClinGen Evidence Repository.
• PM2: For more information check the summary or visit ClinGen Evidence Repository.
• PP3: For more information check the summary or visit ClinGen Evidence Repository.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
BRCA1	NM_007294.4	c.74C>T	p.Pro25Leu	missense_variant	Exon 2 of 23	ENST00000357654.9	NP_009225.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
BRCA1	ENST00000357654.9	c.74C>T	p.Pro25Leu	missense_variant	Exon 2 of 23	1	NM_007294.4	ENSP00000350283.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1459166 Hom.: 0 Cov.: 30 AF XY: 0.00000138 AC XY: 1 AN XY: 726114

African (AFR) AF: 0.0000299 AC: 1 AN: 33408

American (AMR) AF: 0.00 AC: 0 AN: 44718

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26110

East Asian (EAS) AF: 0.00 AC: 0 AN: 39638

South Asian (SAS) AF: 0.00 AC: 0 AN: 86196

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53408

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5752

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1109658

Other (OTH) AF: 0.00 AC: 0 AN: 60278

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2 Uncertain:4

Revision: reviewed by expert panel

Submissions by phenotype

not provided Uncertain:2

Feb 09, 2016

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is denoted BRCA1 c.74C>T at the cDNA level, p.Pro25Leu (P25L) at the protein level, and results in the change of a Proline to a Leucine (CCC>CTC). Using alternate nomenclature, this variant would be defined as BRCA1 193C>T. This variant has not, to our knowledge, been published in the literature as pathogenic or benign. BRCA1 Pro25Leu was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, suggesting it is not a common benign variant in these populations. Since Proline and Leucine differ in some properties, this is considered a semi-conservative amino acid substitution. BRCA1 Pro25Leu occurs at a position that is conserved across species and is located in the RING finger domain as well as a region known to interact with multiple other proteins (Narod 2004, Paul 2014). In silico analyses predict that this variant is probably damaging to protein structure and function. Based on currently available evidence, it is unclear whether BRCA1 Pro25Leu is a pathogenic or benign variant. We consider it to be a variant of uncertain significance. -

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Department of Pathology and Laboratory Medicine, Sinai Health System

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

The BRCA1 p.Pro25Leu variant was not identified in the literature nor was it identified in the LOVD 3.0 or UMD-LSDB databases. The variant was identified in dbSNP (ID: rs876660096) as "With Uncertain significance allele", ClinVar (classified as uncertain significance by Ambry Genetics, Invitae, GeneDx and Foulkes Cancer Genetics).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).A homology directed recombination efficiency assay indicated this variant has deficient homologous recombination (Yi 2018, Ambry Genetics ACMG poster). The p.Pro25 residue is conserved in mammals and computational analyses (PolyPhen-2, SIFT, AlignGVGD, BLOSUM, MutationTaster) provide inconsistent predictions regarding the impact to the protein; this information is not very predictive of pathogenicity. The variant occurs outside of the splicing consensus sequence and in silico or computational prediction software programs (SpliceSiteFinder, MaxEntScan, NNSPLICE, GeneSplicer) do not predict a difference in splicing. In summary, based on the above information the clinical significance of this variant cannot be determined with certainty at this time. This variant is classified as a variant of uncertain significance. -

BRCA1-related cancer predisposition Pathogenic:1

May 23, 2025

ClinGen ENIGMA BRCA1 and BRCA2 Variant Curation Expert Panel, ClinGen

Significance: Likely pathogenic

Review Status: reviewed by expert panel

Collection Method: curation

The c.74C>T variant in BRCA1 is a missense variant predicted to cause substitution of proline by leucine at amino acid 25 (p.Pro25Leu). This variant is absent from gnomAD v2.1 (exomes only, non-cancer subset, read depth ≥25) and gnomAD v3.1 (non-cancer subset, read depth ≥25) (PM2_Supporting met). This BRCA1 missense variant is within a key functional domain and the computational predictor BayesDel (noAF) gives a score of 0.35, above the recommended threshold of 0.28 for prediction of impact on BRCA1 function via protein change. A SpliceAI score of 0.02 predicts no impact on splicing (score threshold ≤0.1) (PP3 met). Reported by two calibrated studies to exhibit protein function similar to pathogenic control variants (PMIDs:30209399, 35659930) (PS3 met). In summary, this variant meets the criteria to be classified as a likely pathogenic variant for BRCA1-related cancer predisposition based on the ACMG/AMP criteria applied as specified by the ENIGMA BRCA1/2 VCEP (PM2_Supporting, PP3, PS3). -

Hereditary cancer-predisposing syndrome Pathogenic:1

Jun 06, 2025

Ambry Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.P25L variant (also known as c.74C>T), located in coding exon 1 of the BRCA1 gene, results from a C to T substitution at nucleotide position 74. The proline at codon 25 is replaced by leucine, an amino acid with similar properties. One functional study found that this nucleotide substitution is non-functional in a high-throughput, genome editing, haploid cell survival assay (Findlay GM et al. Nature, 2018 10;562:217-222). This alteration has been identified in 1/7400 Czech families with suspected hereditary predisposition to breast and/or ovarian cancer (Machackova E et al. Klin Onkol, 2019;32:51-71). Based on internal structural analysis, this variant is anticipated to result in a significant decrease in structural stability (Brzovic PS et al. Nat Struct Biol, 2001 Oct;8:833-7; Ambry internal data). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Breast and/or ovarian cancer Uncertain:1

Jan 28, 2016

Foulkes Cancer Genetics LDI, Lady Davis Institute for Medical Research

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Hereditary breast ovarian cancer syndrome Uncertain:1

Apr 15, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces proline, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 25 of the BRCA1 protein (p.Pro25Leu). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with BRCA1-related conditions. ClinVar contains an entry for this variant (Variation ID: 232955). Advanced modeling performed at Invitae incorporating data from internal and/or published experimental studies (PMID: 30209399) indicates that this missense variant is expected to disrupt BRCA1 function with a positive predictive value of 95%. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.35
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.47	.;T;.;.;.;D;.;T;T;.;T;D;.
Eigen	Uncertain	0.41
Eigen_PC	Uncertain	0.37
FATHMM_MKL	Uncertain	0.85	D
LIST_S2	Pathogenic	0.97	D;D;D;D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.82	D
MetaRNN	Pathogenic	0.93	D;D;D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Uncertain	0.77	D
MutationAssessor	Uncertain	2.5	M;M;M;M;M;.;.;.;.;.;.;.;.
PhyloP100		4.5
PrimateAI	Uncertain	0.74	T
PROVEAN	Benign	-1.8	N;N;N;D;N;D;N;.;N;N;N;D;D
REVEL	Pathogenic	0.84
Sift	Uncertain	0.0020	D;D;D;D;D;D;D;.;D;D;D;D;D
Sift4G	Pathogenic	0.0	D;D;D;T;T;.;D;.;D;.;D;.;.
Polyphen		0.24, 1.0, 1.0	.;B;.;.;D;.;D;.;.;.;.;.;.
Vest4		0.88
MutPred		0.72		Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);Loss of loop (P = 0.0235);
MVP		0.95
MPC		0.43
ClinPred		0.97	D
GERP RS		3.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.77
gMVP		0.75

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

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

Other links and lift over

dbSNP: rs876660096; hg19: chr17-41276040;