5-112780904-G-A

Variant names:

• chr5-112780904-G-A
• rs863225370
• NM_000038.6:c.645+1G>A

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 7P and 0B. PM2_Supporting PS4 PVS1_Moderate

This summary comes from the ClinGen Evidence Repository: The c.645+1G>A variant in APC occurs within the canonical splice donor site +1 of intron 6. It is predicted to result in an inframe skipping of exon 6 (PVS1_Moderate). The results from ≥2 in silico splicing predictors (SpliceAI, MaxEntScan, VarSeak) indicate that this variant may affect splicing by disrupting the donor splice site of intron 6 (PP3 supplanted by PVS1_Moderate). RT-PCR of patient blood demonstrated that the variant impacts splicing by removing exon 6 from the transcript, resulting in an NMD-escaping in-frame event with uncertain impact (PMID:22987206, PS3 supplanted by PVS1_Moderate). This variant has been reported in 9 families with FAP with a total phenotype score of 6 points (PS4; Ambry, Invitae, GeneDX, Barcelona, Edinburgh and Leiden internal data; PMID 22987206; PMID 17411426; PMID 20685668; PMID 8381580). This variant is absent from gnomAD v2.1.1 (PM2_supporting). In summary, this variant meets the criteria to be classified as Likely Pathogenic for FAP based on the ACMG/AMP criteria applied, as specified by the ClinGen InSiGHT Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel: PVS1_Moderate, PS4, and PM2_Supporting; (VCEP specifications version 1; date of approval: 12/12/2022). LINK:https://erepo.genome.network/evrepo/ui/classification/CA279701/MONDO:0021056/089

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 7.0e-7 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: APC NM_000038.6 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Likely pathogenic reviewed by expert panel P:6 U:1
• Conservation: PhyloP100: 8.99
• Publications: 2 publications found

Genes affected

APC (HGNC:583): (APC regulator of WNT signaling pathway) This gene encodes a tumor suppressor protein that acts as an antagonist of the Wnt signaling pathway. It is also involved in other processes including cell migration and adhesion, transcriptional activation, and apoptosis. Defects in this gene cause familial adenomatous polyposis (FAP), an autosomal dominant pre-malignant disease that usually progresses to malignancy. Mutations in the APC gene have been found to occur in most colorectal cancers, where disease-associated mutations tend to be clustered in a small region designated the mutation cluster region (MCR) and result in a truncated protein product. [provided by RefSeq, Jun 2022]

APC Gene-Disease associations (from GenCC):

• classic or attenuated familial adenomatous polyposis

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• desmoid tumor

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: G2P, Genomics England PanelApp
• familial adenomatous polyposis 1

  Inheritance: AD Classification: DEFINITIVE, STRONG, MODERATE Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), Ambry Genetics
• gastric adenocarcinoma and proximal polyposis of the stomach

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae), ClinGen, Orphanet
• sarcoma

  Inheritance: AD Classification: MODERATE Submitted by: Genomics England PanelApp
• APC-related attenuated familial adenomatous polyposis

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Turcot syndrome with polyposis

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Cenani-Lenz syndactyly syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 7 ACMG points.

• PVS1: For more information check the summary or visit ClinGen Evidence Repository.
• PS4: For more information check the summary or visit ClinGen Evidence Repository.
• PM2: For more information check the summary or visit ClinGen Evidence Repository.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
APC	NM_000038.6	c.645+1G>A		splice_donor_variant, intron_variant	Intron 6 of 15	ENST00000257430.9	NP_000029.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
APC	ENST00000257430.9	c.645+1G>A		splice_donor_variant, intron_variant	Intron 6 of 15	5	NM_000038.6	ENSP00000257430.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Data not reliable, filtered out with message: AS_VQSR AF: 6.96e-7 AC: 1 AN: 1437060 Hom.: 0 Cov.: 27 AF XY: 0.00 AC XY: 0 AN XY: 716202

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 32718

American (AMR) AF: 0.00 AC: 0 AN: 44540

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26012

East Asian (EAS) AF: 0.00 AC: 0 AN: 39288

South Asian (SAS) AF: 0.00 AC: 0 AN: 85106

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53250

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5730

European-Non Finnish (NFE) AF: 9.17e-7 AC: 1 AN: 1090902

Other (OTH) AF: 0.00 AC: 0 AN: 59514

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 33

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:6 Uncertain:1

Revision: reviewed by expert panel

Submissions by phenotype

Familial adenomatous polyposis 1 Pathogenic:3

Nov 27, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects a donor splice site in intron 6 of the APC 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 APC are known to be pathogenic (PMID: 17963004, 20685668). This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individuals with familial adenomatous polyposis (PMID: 8381580, 17411426, 20685668, 22987206). ClinVar contains an entry for this variant (Variation ID: 218000). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -

Feb 18, 2023

ClinGen InSiGHT Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel

Significance: Likely pathogenic

Review Status: reviewed by expert panel

Collection Method: curation

The c.645+1G>A variant in APC occurs within the canonical splice donor site +1 of intron 6. It is predicted to result in an inframe skipping of exon 6 (PVS1_Moderate). The results from more than 2 in silico splicing predictors (SpliceAI, MaxEntScan, VarSeak) indicate that this variant may affect splicing by disrupting the donor splice site of intron 6 (PP3 supplanted by PVS1_Moderate). RT-PCR of patient blood demonstrated that the variant impacts splicing by removing exon 6 from the transcript, resulting in an NMD-escaping in-frame event with uncertain impact (PMID: 22987206, PS3 supplanted by PVS1_Moderate). This variant has been reported in 9 families with FAP with a total phenotype score of 6 points (PS4; Ambry, Invitae, GeneDX, Barcelona, Edinburgh and Leiden internal data; PMID 22987206; PMID 17411426; PMID 20685668; PMID 8381580). This variant is absent from gnomAD v2.1.1 (PM2_supporting). In summary, this variant meets the criteria to be classified as Likely Pathogenic for FAP based on the ACMG/AMP criteria applied, as specified by the ClinGen InSiGHT Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel: PVS1_Moderate, PS4, and PM2_Supporting; (VCEP specifications version 1; date of approval: 12/12/2022). -

Apr 27, 2023

Myriad Genetics, Inc.

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is considered likely pathogenic. This variant occurs within a consensus splice junction and is predicted to result in abnormal mRNA splicing of either an out-of-frame exon or an in-frame exon necessary for protein stability and/or normal function. -

not provided Pathogenic:2 Uncertain:1

-

Department of Pathology and Laboratory Medicine, Sinai Health System

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

-

Mayo Clinic Laboratories, Mayo Clinic

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: research

- -

Apr 27, 2017

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is denoted APC c.645+1G>A or IVS6+1G>A and consists of a G>A nucleotide substitution at the +1 position of intron 6 of the APC gene. This 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 reported in individuals with a history of familial adenomatous polyposis (Olschwang 1993, Lagarde 2010). Based on the currently available information, we consider APC c.645+1G>A to be a likely pathogenic variant. -

Hereditary cancer-predisposing syndrome Pathogenic:1

May 06, 2025

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.645+1G>A intronic pathogenic mutation results from a G to A substitution one nucleotide after coding exon 5 of the APC gene. Alterations that disrupt the canonical splice site are expected to result in aberrant splicing. In silico splice site analysis predicts that this alteration will weaken the native splice donor site and may result in the creation or strengthening of a novel splice donor site; however, direct evidence is insufficient at this time (Ambry internal data). A resulting transcript is predicted to be in-frame and is not expected to trigger nonsense-mediated mRNA decay; although, direct evidence is unavailable. This alteration was identified in 1/934 French patients with familial adenomatous polyposis (FAP) (Lagarde A et al. J. Med. Genet., 2010 Oct;47:721-2), and in a cohort of 160 unrelated patients with FAP (Olschwang S et al. Am. J. Hum. Genet., 1993 Feb;52:273-9). 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. Based on the supporting evidence, this variant is interpreted as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.42
CADD	Pathogenic	35
DANN	Uncertain	1.0
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.1
FATHMM_MKL	Pathogenic	1.0	D
PhyloP100		9.0
GERP RS		5.6
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Mutation Taster		=0/100	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.97		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.39		Position offset: -33
DS_DL_spliceai		0.97		Position offset: -1

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

Other links and lift over

dbSNP: rs863225370; hg19: chr5-112116601; COSMIC: COSV57341437; COSMIC: COSV57341437;