rs77345643

chr20-63349744-G-Achr20-63349744-G-C

Variant summary

Our verdict is Likely benign. Variant got -3 ACMG points: 0P and 3B. BP4_Moderate BP6

The NM_000744.7(CHRNA4):c.1667C>T(p.Pro556Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000149 in 1,612,330 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/20 in silico tools predict a benign 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. P556R) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 34)
  • Exomes 𝑓: 0.000015 (0 hom.)
• Consequence: CHRNA4 NM_000744.7 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1 B:1
• Conservation: PhyloP100: -1.17

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 Likely_benign. Variant got -3 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.078847975).
• BP6: Variant 20-63349744-G-A is Benign according to our data. Variant chr20-63349744-G-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 422587.We mark this variant Likely_benign, oryginal submissions are: {Uncertain_significance=1, Likely_benign=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CHRNA4	NM_000744.7	c.1667C>T	p.Pro556Leu	missense_variant	5/6	ENST00000370263.9
CHRNA4	NM_001256573.2	c.1139C>T	p.Pro380Leu	missense_variant	5/6
CHRNA4	NR_046317.2	n.1876C>T		non_coding_transcript_exon_variant	5/6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CHRNA4	ENST00000370263.9	c.1667C>T	p.Pro556Leu	missense_variant	5/6	1	NM_000744.7	P1

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152246 Hom.: 0 Cov.: 34

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: 0.000207

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00316

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000121 AC: 3 AN: 247934 Hom.: 0 AF XY: 0.0000222 AC XY: 3 AN XY: 134844

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 SAS exome AF: 0.0000327

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000180

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000151 AC: 22 AN: 1459966 Hom.: 0 Cov.: 34 AF XY: 0.0000220 AC XY: 16 AN XY: 726258

Gnomad4 AFR exome AF: 0.0000299

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000232

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000135

Gnomad4 OTH exome AF: 0.0000663

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152364 Hom.: 0 Cov.: 34 AF XY: 0.0000134 AC XY: 1 AN XY: 74508

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.000207

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000434 Hom.: 0

ExAC AF: 0.00000827 AC: 1

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Oct 28, 2016

A variant of uncertain significance has been identified in the CHRNA4 gene. The P556L variant has not been published as a pathogenic variant, nor has it been reported as a benign variant 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. The P556L variant is a semi-conservative amino acid substitution, which may impact secondary protein structure as these residues differ in some properties. However, this substitution occurs at a position that is not conserved and in silico analysis predicts this variant likely does not alter the protein structure/function. Additionally, this amino acid substitution is not predicted to occur within the transmembrane region of the protein, where the vast majority of pathogenic missense variants have been identified in association with epilepsy (Steinlein et al., 2010). Therefore, based on the currently available information, it is unclear whether this variant is a pathogenic variant or a rare benign variant. -

Autosomal dominant nocturnal frontal lobe epilepsy Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Invitae

Sep 23, 2022

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.073
BayesDel_addAF	Benign	-0.17	T
BayesDel_noAF	Benign	-0.39
Cadd	Benign	0.23
Dann	Benign	0.74
DEOGEN2	Benign	0.28	T;.
Eigen	Benign	-1.5
Eigen_PC	Benign	-1.5
FATHMM_MKL	Benign	0.015	N
LIST_S2	Benign	0.15	T;T
M_CAP	Uncertain	0.16	D
MetaRNN	Benign	0.079	T;T
MetaSVM	Benign	-0.75	T
MutationAssessor	Benign	0.14	N;.
MutationTaster	Benign	1.0	N
PrimateAI	Benign	0.26	T
PROVEAN	Benign	-0.36	N;.
REVEL	Benign	0.17
Sift	Benign	0.29	T;.
Sift4G	Benign	0.29	T;T
Polyphen		0.059	B;.
Vest4		0.13
MutPred		0.49		Loss of glycosylation at P556 (P = 0.0065);.;
MVP		0.61
MPC		0.46
ClinPred		0.027	T
GERP RS		-0.59
Varity_R		0.024
gMVP		0.24

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: rs77345643; hg19: chr20-61981096;