chr20-63350733-A-C

Position:

• chr20-63350733-A-C

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM2 PP3_Strong

The NM_000744.7(CHRNA4):​c.678T>G​(p.Cys226Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. C226C) has been classified as Benign.

• Frequency: Genomes: not found (cov: 27)
• Consequence: CHRNA4 NM_000744.7 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: -0.186

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 (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.985

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CHRNA4	NM_000744.7	c.678T>G	p.Cys226Trp	missense_variant	5/6	ENST00000370263.9	NP_000735.1
CHRNA4	NM_001256573.2	c.150T>G	p.Cys50Trp	missense_variant	5/6		NP_001243502.1
CHRNA4	NR_046317.2	n.887T>G		non_coding_transcript_exon_variant	5/6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CHRNA4	ENST00000370263.9	c.678T>G	p.Cys226Trp	missense_variant	5/6	1	NM_000744.7	ENSP00000359285.4

Frequencies

GnomAD3 genomes Cov.: 27

GnomAD4 exome Cov.: 86

GnomAD4 genome Cov.: 27

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.35	D
BayesDel_noAF	Pathogenic	0.26
CADD	Benign	3.1
DANN	Benign	0.90
DEOGEN2	Pathogenic	0.88	D;.
Eigen	Benign	-0.91
Eigen_PC	Benign	-1.2
FATHMM_MKL	Benign	0.31	N
LIST_S2	Pathogenic	0.98	D;D
M_CAP	Pathogenic	0.94	D
MetaRNN	Pathogenic	0.98	D;D
MetaSVM	Uncertain	0.54	D
MutationAssessor	Pathogenic	4.0	H;.
PrimateAI	Pathogenic	0.88	D
PROVEAN	Pathogenic	-11	D;.
REVEL	Uncertain	0.58
Sift	Pathogenic	0.0	D;.
Sift4G	Pathogenic	0.0	D;D
Polyphen		1.0	D;.
Vest4		0.93
MutPred		0.72		Gain of catalytic residue at C226 (P = 0.0057);.;
MVP		0.65
MPC		1.4
ClinPred		1.0	D
GERP RS		-5.0
Varity_R		0.86
gMVP		0.96

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

LitVar

Other links and lift over

dbSNP: rs1044394; hg19: chr20-61982085;