rs397508462

chr7-117606701-A-Cchr7-117606701-A-Gchr7-117606701-A-T

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP3_Strong PP5

The NM_000492.4(CFTR):c.2936A>C(p.Asp979Ala) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000879 in 1,591,906 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D979V) has been classified as Pathogenic.

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000083 (0 hom.)
• Consequence: CFTR NM_000492.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:3 O:1
• Conservation: PhyloP100: 8.62

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]

(HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 11 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 12 uncertain in NM_000492.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr7-117606701-A-T is described in ClinVar as [Pathogenic]. Clinvar id is 53603.Status of the report is reviewed_by_expert_panel, 3 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.984
• PP5: Variant 7-117606701-A-C is Pathogenic according to our data. Variant chr7-117606701-A-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 53602.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=3, Uncertain_significance=3, not_provided=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CFTR	NM_000492.4	c.2936A>C	p.Asp979Ala	missense_variant	18/27	ENST00000003084.11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CFTR	ENST00000003084.11	c.2936A>C	p.Asp979Ala	missense_variant	18/27	1	NM_000492.4	P2
	ENST00000456270.1	n.178-1712T>G		intron_variant, non_coding_transcript_variant		3

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152144 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000386

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000358 AC: 9 AN: 251154 Hom.: 0 AF XY: 0.0000295 AC XY: 4 AN XY: 135772

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.000489

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000834 AC: 12 AN: 1439644 Hom.: 0 Cov.: 27 AF XY: 0.00000836 AC XY: 6 AN XY: 717908

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.000279

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.16e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152262 Hom.: 0 Cov.: 32 AF XY: 0.0000134 AC XY: 1 AN XY: 74454

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.000386

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

ExAC AF: 0.0000247 AC: 3

Asia WGS AF: 0.000289 AC: 1 AN: 3478

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:3 Other:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Cystic fibrosis Pathogenic:1 Uncertain:2 Other:1

Likely pathogenic, criteria provided, single submitter	clinical testing	Invitae	Jan 04, 2024	This sequence change replaces aspartic acid, which is acidic and polar, with alanine, which is neutral and non-polar, at codon 979 of the CFTR protein (p.Asp979Ala). This variant is present in population databases (rs397508462, gnomAD 0.05%). This missense change has been observed in individuals with clinical features of CFTR-related conditions (PMID: 9493456, 10376575, 32020786, 34782259). ClinVar contains an entry for this variant (Variation ID: 53602). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt CFTR protein function with a positive predictive value of 80%. Experimental studies have shown that this missense change affects CFTR function (PMID: 11118444). This variant disrupts the p.Asp979 amino acid residue in CFTR. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 9401110, 29805046). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -
not provided, no classification provided	literature only	ClinVar Staff, National Center for Biotechnology Information (NCBI)	-	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	Mar 12, 2018	The c.2936A>C (p.D979A) alteration is located in exon 18 (coding exon 18) of the CFTR gene. This alteration results from a A to C substitution at nucleotide position 2936, causing the aspartic acid (D) at amino acid position 979 to be replaced by an alanine (A). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -
Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	May 18, 2018	- -

Bronchiectasis with or without elevated sweat chloride 1 Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Oct 15, 2023

- -

Congenital bilateral aplasia of vas deferens from CFTR mutation Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Jan 20, 2023

Variant summary: CFTR c.2936A>C (p.Asp979Ala) results in a non-conservative amino acid change located in the ABC transporter type 1, transmembrane domain (IPR011527) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 3.5e-05 in 253874 control chromosomes (gnomAD and publications). c.2936A>C has been reported in the literature in multiple individuals affected with Congenital Bilateral Absence Of The Vas Deferens (CBAVD) who carry the variant in trans with the pathogenic 5T allele (e.g. Dork_1997, Mak_1999, Luo_2021). In addition, the variant was found in two twin siblings with CF who carried another pathogenic mutation (p.R347H) in cis and the common disease variant p.F508del on the other allele (Hojo_1998). It was speculated that the p.D979A variant may contribute to more severe disease in these individuals, however the contributions of the individual variants to the phenotype could not be determined. The variant was also detected in several individuals with pancreatitis, however co-occurred with variants in SPINK1 and PRSS1 (e.g. Zou_2018). At least one publication reports experimental evidence evaluating an impact on protein function, suggesting that the variant results in a partial reduction of CFTR processing and moderate effects on chloride channel dynamics, consistent with the milder CFTR-related phenotype (CBAVD) that has been observed in most patients with the variant (e.g. Clain_2001). Four other clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. Both laboratories cited the variant as uncertain significance (VUS, n=3, LP, n=1). Based on the evidence outlined above, the variant was classified as likely pathogenic in association with CBAVD. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Feb 05, 2020

The CFTR c.2936A>C; p.Asp979Ala variant (rs397508462) is reported in the literature in individuals affected with congenital absence of vas deferens who carry a mildly pathogenic variant in CFTR (Dork 1997, Mak 1999, Wilschanski 2006), but is also reported in individuals with pancreatitis who carry variants in other pancreatitis-associated genes (Zou 2018), and in a pair of twins with cystic fibrosis who carry two pathogenic CFTR variants on opposite chromosomes (Hojo 1997). Functional assays show that the p.Asp979Ala variant result in a mild defect (Clain 2001). The p.Asp979Ala variant is reported in the ClinVar database (Variation ID: 53602), and is found in the East Asian population with an allele frequency of 0.05% (9/18394 alleles) in the Genome Aggregation Database. The asparagine at codon 979 is highly conserved, and computational analyses (SIFT, PolyPhen-2) predict that this variant is deleterious. A different variant at this codon, p.Asp979Val, is reported as a CF-causing variant in the CFTR2 database (see CFTR2 database link). While the p.Asp979Ala variant is not predicted to cause classic cystic fibrosis, based on available information, the clinical significance is uncertain for CFTR-related disorders. References: CFTR2 database: https://cftr2.org/ Clain J et al. Two mild cystic fibrosis-associated mutations result in severe cystic fibrosis when combined in cis and reveal a residue important for cystic fibrosis transmembrane conductance regulator processing and function. J Biol Chem. 2001 Mar 23;276(12):9045-9. Dork T et al. Distinct spectrum of CFTR gene mutations in congenital absence of vas deferens. Hum Genet. 1997 Sep;100(3-4):365-77. Hojo S et al. (Two cases of cystic fibrosis in Japanese/German twins). Nihon Kyobu Shikkan Gakkai Zasshi. 1997 Nov;35(11):1259-64. Mak V et al. Proportion of cystic fibrosis gene mutations not detected by routine testing in men with obstructive azoospermia. JAMA. 1999 Jun 16;281(23):2217-24. Wilschanski M et al. Mutations in the cystic fibrosis transmembrane regulator gene and in vivo transepithelial potentials. Am J Respir Crit Care Med. 2006 Oct 1;174(7):787-94. Zou WB et al. SPINK1, PRSS1, CTRC, and CFTR Genotypes Influence Disease Onset and Clinical Outcomes in Chronic Pancreatitis. Clin Transl Gastroenterol. 2018 Nov 12;9(11):204. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.34	D
BayesDel_noAF	Pathogenic	0.58
Cadd	Pathogenic	28
Dann	Uncertain	1.0
DEOGEN2	Pathogenic	0.91	D;.;.;D;.
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.92
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.96	D;D;D;D;D
M_CAP	Pathogenic	0.78	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.3	H;.;.;.;.
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.62	T
PROVEAN	Pathogenic	-6.5	D;.;.;D;.
REVEL	Pathogenic	0.99
Sift	Pathogenic	0.0	D;.;.;D;.
Sift4G	Pathogenic	0.0	D;.;.;D;.
Polyphen		1.0	D;.;.;.;.
Vest4		0.98
MutPred		0.98		Loss of ubiquitination at K978 (P = 0.1601);.;.;.;.;
MVP		1.0
MPC		0.015
ClinPred		0.99	D
GERP RS		5.4
Varity_R		0.99
gMVP		0.99

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs397508462; hg19: chr7-117246755;