rs121908809

Variant names:

• chr7-117592140-GA-G
• rs121908809
• NM_000492.4:c.1976delA

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000492.4(CFTR):​c.1976delA​(p.Asn659IlefsTer4) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 32)
• Consequence: CFTR NM_000492.4 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2 O:1
• Conservation: PhyloP100: 1.20
• Publications: 0 publications found

Genes affected

CFTR (HGNC:1884): (CF transmembrane conductance regulator) This gene encodes a member of the ATP-binding cassette (ABC) transporter superfamily. The encoded protein functions as a chloride channel, making it unique among members of this protein family, and controls ion and water secretion and absorption in epithelial tissues. Channel activation is mediated by cycles of regulatory domain phosphorylation, ATP-binding by the nucleotide-binding domains, and ATP hydrolysis. Mutations in this gene cause cystic fibrosis, the most common lethal genetic disorder in populations of Northern European descent. The most frequently occurring mutation in cystic fibrosis, DeltaF508, results in impaired folding and trafficking of the encoded protein. Multiple pseudogenes have been identified in the human genome. [provided by RefSeq, Aug 2017]

CFTR Gene-Disease associations (from GenCC):

• cystic fibrosis

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Laboratory for Molecular Medicine, Labcorp Genetics (formerly Invitae), Myriad Women’s Health, Orphanet
• congenital bilateral absence of vas deferens

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• hereditary chronic pancreatitis

  Inheritance: AD Classification: LIMITED Submitted by: Labcorp Genetics (formerly Invitae)

ACMG classification

Our verdict: Pathogenic. The variant received 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 7-117592140-GA-G is Pathogenic according to our data. Variant chr7-117592140-GA-G is described in ClinVar as Pathogenic. ClinVar VariationId is 53418.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CFTR	NM_000492.4	c.1976delA	p.Asn659IlefsTer4	frameshift_variant	Exon 14 of 27	ENST00000003084.11	NP_000483.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CFTR	ENST00000003084.11	c.1976delA	p.Asn659IlefsTer4	frameshift_variant	Exon 14 of 27	1	NM_000492.4	ENSP00000003084.6

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Cystic fibrosis Pathogenic:2 Other:1

Jul 19, 2017

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.1976delA pathogenic mutation (also known as 2108delA), located in coding exon 14 of the CFTR gene, results from a deletion of one nucleotide at nucleotide position 1976, causing a translational frameshift with a predicted alternate stop codon (p.N659Ifs*4). This mutation was identified in one Hispanic individual with cystic fibrosis; however, additional genotype and phenotype information were not provided (Wong LJ et al. Hum. Mutat., 2001 Oct;18:296-307). An in vitro functional study suggested that this mutation may interrupt the correct splicing of the exon due to disruption of a predicted ESE sequence (Aznarez I et al. Hum. Mol. Genet., 2003 Aug;12:2031-40). In addition to the clinical data presented in the literature, this alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. As such, this alteration is interpreted as a disease-causing mutation.

ClinVar Staff, National Center for Biotechnology Information (NCBI)

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

Dec 24, 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 this premature translational stop signal is associated with altered splicing resulting in multiple RNA products (PMID: 12913074). ClinVar contains an entry for this variant (Variation ID: 53418). This variant is also known as 2108delA. This premature translational stop signal has been observed in individual(s) with cystic fibrosis (PMID: 15300780). This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (p.Asn659Ilefs*4) in the CFTR gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in CFTR are known to be pathogenic (PMID: 1695717, 7691345, 9725922).

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		1.2
Mutation Taster		=0/200	disease causing (fs/PTC)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.16		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: rs121908809; hg19: chr7-117232194;