20-63346763-G-C

Position:

• chr20-63346763-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_000744.7(CHRNA4):​c.1859C>G​(p.Pro620Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: CHRNA4 NM_000744.7 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 9.74

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CHRNA4	NM_000744.7	c.1859C>G	p.Pro620Arg	missense_variant	6/6	ENST00000370263.9	NP_000735.1
CHRNA4	NM_001256573.2	c.1331C>G	p.Pro444Arg	missense_variant	6/6		NP_001243502.1
CHRNA4	NR_046317.2	n.2068C>G		non_coding_transcript_exon_variant	6/6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CHRNA4	ENST00000370263.9	c.1859C>G	p.Pro620Arg	missense_variant	6/6	1	NM_000744.7	ENSP00000359285	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Autosomal dominant nocturnal frontal lobe epilepsy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 14, 2022

ClinVar contains an entry for this variant (Variation ID: 1017487). This variant has not been reported in the literature in individuals affected with CHRNA4-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces proline, which is neutral and non-polar, with arginine, which is basic and polar, at codon 620 of the CHRNA4 protein (p.Pro620Arg). Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.82
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.11
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.54	D;.
Eigen	Uncertain	0.61
Eigen_PC	Uncertain	0.61
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Uncertain	0.90	D;D
M_CAP	Uncertain	0.25	D
MetaRNN	Uncertain	0.71	D;D
MetaSVM	Benign	-0.44	T
MutationAssessor	Benign	0.53	N;.
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.78	T
PROVEAN	Uncertain	-2.6	D;.
REVEL	Uncertain	0.56
Sift	Benign	0.12	T;.
Sift4G	Benign	0.38	T;T
Polyphen		1.0	D;.
Vest4		0.80
MutPred		0.53		Loss of glycosylation at P620 (P = 0.1022);.;
MVP		0.82
MPC		1.3
ClinPred		0.98	D
GERP RS		4.4
Varity_R		0.39
gMVP		0.88

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: rs754340834; hg19: chr20-61978115;