chr20-63350969-G-A

Variant names:

Variant summary

Our verdict is Likely benign. The variant received -4 ACMG points: 1P and 5B. PP3BP6BS2

The NM_000744.7(CHRNA4):c.442C>T(p.Arg148Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000242 in 1,613,700 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. R148Q) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000039 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000023 ( 0 hom. )

Consequence

CHRNA4
NM_000744.7 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:3B:2O:1

Conservation

PhyloP100: 2.47

Publications

8 publications found

Variant links:

Genes affected

CHRNA4 (HGNC:1958): (cholinergic receptor nicotinic alpha 4 subunit) This gene encodes a nicotinic acetylcholine receptor, which belongs to a superfamily of ligand-gated ion channels that play a role in fast signal transmission at synapses. These pentameric receptors can bind acetylcholine, which causes an extensive change in conformation that leads to the opening of an ion-conducting channel across the plasma membrane. This protein is an integral membrane receptor subunit that can interact with either nAChR beta-2 or nAChR beta-4 to form a functional receptor. Mutations in this gene cause nocturnal frontal lobe epilepsy type 1. Polymorphisms in this gene that provide protection against nicotine addiction have been described. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Feb 2012]

CHRNA4 Gene-Disease associations (from GenCC):

autosomal dominant nocturnal frontal lobe epilepsy 1
Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P
familial sleep-related hypermotor epilepsy
Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
autosomal dominant nocturnal frontal lobe epilepsy
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

CHRNA4 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -4 ACMG points.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.768

BP6

Variant 20-63350969-G-A is Benign according to our data. Variant chr20-63350969-G-A is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 98324.

BS2

High AC in GnomAd4 at 6 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein
CHRNA4	NM_000744.7 link	c.442C>T	p.Arg148Trp	missense_variant	Exon 5 of 6	ENST00000370263.9	NP_000735.1
CHRNA4	NR_046317.2 link	n.651C>T		non_coding_transcript_exon_variant	Exon 5 of 6
CHRNA4	NM_001256573.2 link	c.-87C>T		5_prime_UTR_variant	Exon 5 of 6		NP_001243502.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CHRNA4	ENST00000370263.9 link	c.442C>T	p.Arg148Trp	missense_variant	Exon 5 of 6	1	NM_000744.7	ENSP00000359285.4

Frequencies

GnomAD3 genomes

AF:

0.0000395

AC:

AN:

152084

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.0000943

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000735

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.0000399

AC:

AN:

250556

AF XY:

0.0000368

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000619

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000226

AC:

AN:

1461498

Hom.:

Cov.:

AF XY:

0.0000261

AC XY:

AN XY:

727016

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33480

American (AMR)

AF:

0.0000224

AC:

AN:

44718

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26136

East Asian (EAS)

AF:

0.00

AC:

AN:

39700

South Asian (SAS)

AF:

0.0000464

AC:

AN:

86258

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53040

Middle Eastern (MID)

AF:

0.000693

AC:

AN:

5768

European-Non Finnish (NFE)

AF:

0.0000207

AC:

AN:

1112006

Other (OTH)

AF:

0.0000166

AC:

AN:

60392

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.480

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.0000394

AC:

AN:

152202

Hom.:

Cov.:

AF XY:

0.0000538

AC XY:

AN XY:

74410

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

41504

American (AMR)

AF:

0.00

AC:

AN:

15294

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3470

East Asian (EAS)

AF:

0.00

AC:

AN:

5184

South Asian (SAS)

AF:

0.00

AC:

AN:

4824

European-Finnish (FIN)

AF:

0.0000943

AC:

AN:

10604

Middle Eastern (MID)

AF:

0.00

AC:

AN:

294

European-Non Finnish (NFE)

AF:

0.0000735

AC:

AN:

68008

Other (OTH)

AF:

0.00

AC:

AN:

2108

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.508

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.0000473

Hom.:

Bravo

AF:

0.00000756

ExAC

AF:

0.0000577

AC:

EpiCase

AF:

0.000109

EpiControl

AF:

0.0000593

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:3Benign:2Other:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not specified

Uncertain:1

Aug 19, 2024

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: CHRNA4 c.442C>T (p.Arg148Trp) results in a non-conservative amino acid change located in the Neurotransmitter-gated ion-channel ligand-binding domain (IPR006202) 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 4e-05 in 250556 control chromosomes. This frequency is not significantly higher than estimated for a pathogenic variant in CHRNA4 causing Epilepsy, Nocturnal Frontal Lobe, Type 1, allowing no conclusion about variant significance. c.442C>T has been reported in the literature as a heterozygous de-novo variant classified as "uncertain" in one individual affected with a combined co-occurring neurological manifestation of multifocal dystonia undergoing diagnostic exome sequencing (DES) (example, Powis_2020). However, this individual also harbored a second de-novo heterozygous variant in the NACC1 gene, c.892C>T (p.R298W) that the authors report as "likely pathogenic" without evidence for independent evaluation. Due to this finding of potentially relevant findings in multiple genes, this report does not provide unequivocal conclusions about association of the variant with Epilepsy, Nocturnal Frontal Lobe, Type 1. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 31628766, 32579787). ClinVar contains an entry for this variant (Variation ID: 98324). Based on the evidence outlined above, the variant was classified as uncertain significance. -

Inborn genetic diseases

Uncertain:1

Feb 06, 2017

Ambry Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

not provided

Uncertain:1

Sep 25, 2013

GeneDx

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

p.Arg148Trp (CGG>TGG): c.442 C>T: The Arg148Trp missense change has not been published as a mutation, nor has it been reported as a benign polymorphism to our knowledge. It was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. This variant is a non-conservative amino acid substitution of a positively charged Arginine residue with an uncharged Tryptophan residue at a position that is conserved across species. In silico analysis predicts this variant may be damaging to the protein structure/function. However, this amino acid substitution does not occur within the transmembrane region of the protein, where the vast majority of pathogenic missense mutations have been identified in association with epilepsy (Steinlein et al., 2010). The Arg148Trp variant may be a benign variant or a disease-associated mutation, as mutations in CHRNA4 demonstrate incomplete penetrance (Hirose and Kurahashi, 2012). This variant has been observed to be paternally inherited. The variant is found in EPILEPSY panel(s). -

Autosomal dominant nocturnal frontal lobe epilepsy

Benign:1

Aug 21, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Amyotrophic lateral sclerosis

Benign:1

Mar 31, 2020

Suna and Inan Kirac Foundation Neurodegeneration Research Laboratory, Koc University

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:research

- -

Tobacco use disorder

Other:1

Psychiatry Genetics Yale University

Significance:not provided

Review Status:no classification provided

Collection Method:literature only

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.13

BayesDel_addAF

Uncertain

0.065

BayesDel_noAF

Uncertain

0.060

CADD

Pathogenic

(source)

DANN

Pathogenic

1.0

DEOGEN2

Uncertain

0.65

D;.

Eigen

Uncertain

0.52

Eigen_PC

Uncertain

0.43

FATHMM_MKL

Uncertain

0.78

LIST_S2

Uncertain

0.94

D;D

M_CAP

Pathogenic

0.47

MetaRNN

Pathogenic

0.77

D;D

MetaSVM

Uncertain

0.43

MutationAssessor

Benign

1.9

L;.

PhyloP100

2.5

PrimateAI

Uncertain

0.56

PROVEAN

Uncertain

-3.1

D;.

REVEL

Uncertain

0.56

Sift

Uncertain

0.0080

D;.

Sift4G

Uncertain

0.013

D;D

Polyphen

1.0

D;.

Vest4

0.68

MVP

0.90

MPC

1.2

ClinPred

0.74

GERP RS

2.7

Varity_R

0.25

gMVP

0.73

Mutation Taster

=43/57

disease causing

(source)

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over