Genetic Variant CFTR:c.1680-1G>T (chr7-117590352-G-T) – ACMG Classification: Uncertain_significance (4 pts)

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 4P and 0B. PVS1_ModeratePM2

The NM_000492.4(CFTR):c.1680-1G>T variant causes a splice acceptor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000138 in 1,450,042 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 0.0000014 ( 0 hom. )

Consequence

CFTR
NM_000492.4 splice_acceptor, intron

Scores

Splicing: ADA: 1.000

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 9.27

Publications

0 publications found

Variant links:

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)

CFTR links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 4 ACMG points.

PVS1

Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.019581364 fraction of the gene. Cryptic splice site detected, with MaxEntScore 9.4, offset of 2, new splice context is: tttccattttctttttatAGcag. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.

PM2

Very rare variant in population databases, with high coverage;

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CFTR	NM_000492.4 link	c.1680-1G>T		splice_acceptor_variant, intron_variant	Intron 12 of 26	ENST00000003084.11	NP_000483.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CFTR	ENST00000003084.11 link	c.1680-1G>T		splice_acceptor_variant, intron_variant	Intron 12 of 26	1	NM_000492.4	ENSP00000003084.6

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

AF:

0.00000138

AC:

AN:

1450042

Hom.:

Cov.:

AF XY:

0.00000139

AC XY:

AN XY:

721128

show subpopulations

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

African (AFR)

AF:

0.00

AC:

AN:

33220

American (AMR)

AF:

0.00

AC:

AN:

44366

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

25592

East Asian (EAS)

AF:

0.00

AC:

AN:

39334

South Asian (SAS)

AF:

0.0000232

AC:

AN:

86032

European-Finnish (FIN)

AF:

0.00

AC:

AN:

52460

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5678

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

1103728

Other (OTH)

AF:

0.00

AC:

AN:

59632

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.250

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

GnomAD4 genome

Cov.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.63

BayesDel_noAF

Pathogenic

0.34

CADD

Pathogenic

(source)

DANN

Uncertain

1.0

DEOGEN2

Benign

0.0

.;.;.;.

Eigen

Pathogenic

1.2

Eigen_PC

Pathogenic

1.0

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Benign

0.0

.;.;.;.

MetaRNN

Benign

0.0

.;.;.;.

MutationAssessor

Benign

0.0

.;.;.;.

PhyloP100

9.3

PROVEAN

Benign

0.0

.;.;.;.

REVEL

Benign

0.0

Sift

Pathogenic

0.0

.;.;.;.

Sift4G

Pathogenic

0.0

.;.;.;.

Vest4

0.0

GERP RS

4.8

Mutation Taster

=4/96

disease causing

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

1.0

dbscSNV1_RF

Pathogenic

0.94

SpliceAI score (max)

0.92

Details are displayed if max score is > 0.2

DS_AG_spliceai

0.82

Position offset: 3

DS_AL_spliceai

0.92

Position offset: 1

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Computational scores

Splicing

Publications

Other links and lift over