chr7-117535341-T-C

Variant names:

• chr7-117535341-T-C
• rs397508780
• NM_000492.4:c.673T>C

Variant summary

Our verdict is Likely pathogenic. The variant received 9 ACMG points: 9P and 0B. PM1 PM2 PP2 PP3_Strong

The NM_000492.4(CFTR):​c.673T>C​(p.Cys225Arg) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,872 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 Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C225Y) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: CFTR NM_000492.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1 O:1
• Conservation: PhyloP100: 3.88
• Publications: 4 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: Likely_pathogenic. The variant received 9 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 10 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

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CFTR	NM_000492.4	c.673T>C	p.Cys225Arg	missense_variant	Exon 6 of 27	ENST00000003084.11	NP_000483.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CFTR	ENST00000003084.11	c.673T>C	p.Cys225Arg	missense_variant	Exon 6 of 27	1	NM_000492.4	ENSP00000003084.6

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461872 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727240

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

African (AFR) AF: 0.0000299 AC: 1 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39696

South Asian (SAS) AF: 0.00 AC: 0 AN: 86256

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5766

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1112000

Other (OTH) AF: 0.00 AC: 0 AN: 60396

⚠️ 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.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1 Other:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Mar 04, 2025

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

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: CFTR c.673T>C (p.Cys225Arg) results in a non-conservative amino acid change in the encoded protein sequence. Four of four in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251420 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.673T>C has been reported in the literature in at-least one individual affected with Cystic Fibrosis (Fanen_1992). These data do not allow any conclusion about variant significance. At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect resulted in approximately (Gt channel conductance) 70% of normal chloride channel conductance relative to wild type (e.g., Bihler_2024) and the expression of this variant was moderately reduced in HeLa cells (Fanen_1997). The following publications have been ascertained in the context of this evaluation (PMID: 38388235, 1379210, 9374552). ClinVar contains an entry for this variant (Variation ID: 54038). Based on the evidence outlined above, the variant was classified as uncertain significance. -

Cystic fibrosis Other:1

-

ClinVar Staff, National Center for Biotechnology Information (NCBI)

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.91
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.35
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.87	D;.;.;D;.
Eigen	Uncertain	0.28
Eigen_PC	Uncertain	0.32
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Benign	0.85	T;D;D;T;D
M_CAP	Pathogenic	0.44	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D
MetaSVM	Uncertain	0.30	D
MutationAssessor	Benign	1.9	M;.;.;.;M
PhyloP100		3.9
PrimateAI	Uncertain	0.54	T
PROVEAN	Pathogenic	-4.4	D;.;.;D;.
REVEL	Pathogenic	0.81
Sift	Uncertain	0.0020	D;.;.;D;.
Sift4G	Pathogenic	0.0010	D;.;.;D;.
Polyphen		0.59	P;.;.;.;.
Vest4		0.91
MutPred		0.94		Gain of methylation at C225 (P = 0.002);Gain of methylation at C225 (P = 0.002);Gain of methylation at C225 (P = 0.002);.;Gain of methylation at C225 (P = 0.002);
MVP		0.99
MPC		0.0032
ClinPred		0.98	D
GERP RS		4.3
Varity_R		0.98
gMVP		0.92
Mutation Taster		=12/88	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: rs397508780; hg19: chr7-117175395;