chr20-63350232-AG-A

Variant names:

• chr20-63350232-AG-A
• rs1435638963
• NM_000744.7:c.1178delC

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PM2

The NM_000744.7(CHRNA4):​c.1178delC​(p.Pro393LeufsTer172) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000186 in 1,608,996 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: CHRNA4 NM_000744.7 frameshift
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.158
• Publications: 0 publications found

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

ACMG classification

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

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

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000744.7. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CHRNA4	NM_000744.7	MANE Select	c.1178delC	p.Pro393LeufsTer172	frameshift	Exon 5 of 6	NP_000735.1
	CHRNA4	NM_001256573.2		c.650delC	p.Pro217LeufsTer172	frameshift	Exon 5 of 6	NP_001243502.1
	CHRNA4	NR_046317.2		n.1387delC		non_coding_transcript_exon	Exon 5 of 6

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CHRNA4	ENST00000370263.9	TSL:1 MANE Select	c.1178delC	p.Pro393LeufsTer172	frameshift	Exon 5 of 6	ENSP00000359285.4
	CHRNA4	ENST00000463705.5	TSL:1	n.1826delC		non_coding_transcript_exon	Exon 4 of 5
	CHRNA4	ENST00000467563.3	TSL:1	n.1248delC		non_coding_transcript_exon	Exon 5 of 6

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152120 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000241

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: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.00000840 AC: 2 AN: 238042 AF XY: 0.00000768

Gnomad AFR exome AF: 0.0000687

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: 0.00000940

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.86e-7 AC: 1 AN: 1456876 Hom.: 0 Cov.: 99 AF XY: 0.00000138 AC XY: 1 AN XY: 724482

African (AFR) AF: 0.00 AC: 0 AN: 33430

American (AMR) AF: 0.00 AC: 0 AN: 44318

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25974

East Asian (EAS) AF: 0.00 AC: 0 AN: 39574

South Asian (SAS) AF: 0.00 AC: 0 AN: 85900

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 51644

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5762

European-Non Finnish (NFE) AF: 9.01e-7 AC: 1 AN: 1110126

Other (OTH) AF: 0.00 AC: 0 AN: 60148

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152120 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74316

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

African (AFR) AF: 0.0000241 AC: 1 AN: 41424

American (AMR) AF: 0.00 AC: 0 AN: 15284

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3470

East Asian (EAS) AF: 0.00 AC: 0 AN: 5174

South Asian (SAS) AF: 0.00 AC: 0 AN: 4832

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10616

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000147 AC: 1 AN: 68006

Other (OTH) AF: 0.00 AC: 0 AN: 2088

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.0000151

ClinVar

ClinVar submissions as Germline

Significance: Uncertain significance

Revision: criteria provided, single submitter

Pathogenic	VUS	Benign	Condition
-	1	-	Autosomal dominant nocturnal frontal lobe epilepsy (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		-0.16
Mutation Taster		=55/145	disease causing (fs/PTC)

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

Other links and lift over

dbSNP: rs1435638963; hg19: chr20-61981584; COSMIC: COSV64721419; COSMIC: COSV64721419;