NM_000492.4:c.3257C>T

Variant names:

• chr7-117611698-C-T
• rs77958296
• NM_000492.4:c.3257C>T

Variant summary

Our verdict is Pathogenic. The variant received 10 ACMG points: 10P and 0B. PM1 PM2 PP2 PP3_Strong PP5

The NM_000492.4(CFTR):​c.3257C>T​(p.Thr1086Ile) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 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. T1086A) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 31)
• Consequence: CFTR NM_000492.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:3
• Conservation: PhyloP100: 7.82
• Publications: 3 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)

ENSG00000083622 (HGNC:40145):

ACMG classification

Our verdict: Pathogenic. The variant received 10 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 20 uncertain in NM_000492.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 197 curated pathogenic missense variants (we use a threshold of 10). The gene has 46 curated benign missense variants. Gene score misZ: -3.1397 (below the threshold of 3.09). Trascript score misZ: -1.0868 (below the threshold of 3.09). GenCC associations: The gene is linked to hereditary chronic pancreatitis, cystic fibrosis, congenital bilateral absence of vas deferens.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.977
• PP5: Variant 7-117611698-C-T is Pathogenic according to our data. Variant chr7-117611698-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 53694.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CFTR	NM_000492.4	c.3257C>T	p.Thr1086Ile	missense_variant	Exon 20 of 27	ENST00000003084.11	NP_000483.3
CFTR-AS2	NR_199597.1	n.177+4531G>A		intron_variant	Intron 2 of 2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CFTR	ENST00000003084.11	c.3257C>T	p.Thr1086Ile	missense_variant	Exon 20 of 27	1	NM_000492.4	ENSP00000003084.6

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 31

Alfa AF: 0.0000318 Hom.: 0

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Cystic fibrosis Pathogenic:1 Uncertain:3

Mar 18, 2025

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

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: CFTR c.3257C>T (p.Thr1086Ile) results in a non-conservative amino acid change in the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251126 control chromosomes. c.3257C>T has been reported in the literature in at-least one individual affected with Cystic Fibrosis, who carries a second pathogenic CFTR variant (example: Alibakhshi_2008). At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect resulted in approximately 5.66% of normal chloride channel conductance relative to wild type (e.g., Bihler_2024). The following publications have been ascertained in the context of this evaluation (PMID: 17662673, 38388235, 36796836, 10923036, 27086061). ClinVar contains an entry for this variant (Variation ID: 53694). Based on the evidence outlined above, the variant was classified as likely pathogenic. -

Feb 02, 2017

Counsyl

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com. -

Nov 05, 2018

Mendelics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Sep 05, 2021

Genome-Nilou Lab

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.92
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.33
CADD	Pathogenic	26
DANN	Pathogenic	1.0
DEOGEN2	Uncertain	0.70	D;.;.;D;.
Eigen	Pathogenic	0.85
Eigen_PC	Pathogenic	0.84
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.98	D;D;D;D;D
M_CAP	Pathogenic	0.79	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D
MetaSVM	Uncertain	0.70	D
MutationAssessor	Benign	2.0	M;.;.;.;.
PhyloP100		7.8
PrimateAI	Pathogenic	0.85	D
PROVEAN	Benign	-1.5	N;.;.;N;.
REVEL	Pathogenic	0.80
Sift	Benign	0.38	T;.;.;T;.
Sift4G	Pathogenic	0.0	D;.;.;D;.
Polyphen		1.0	D;.;.;.;.
Vest4		0.92
MutPred		0.91		Gain of MoRF binding (P = 0.086);.;.;.;.;
MVP		1.0
MPC		0.011
ClinPred		0.96	D
GERP RS		5.7
PromoterAI		0.0029	Neutral
Varity_R		0.80
gMVP		0.95
Mutation Taster		=0/100	disease causing

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: rs77958296; hg19: chr7-117251752;