20-63356390-G-C

Variant names:

• chr20-63356390-G-C
• rs199699339
• NM_000744.7:c.254C>G

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM2 PP3_Strong

The NM_000744.7(CHRNA4):​c.254C>G​(p.Thr85Arg) variant causes a missense change. The variant allele was found at a frequency of 0.00000658 in 151,962 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T85M) has been classified as Likely benign.

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
• Consequence: CHRNA4 NM_000744.7 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 6.64
• Publications: 1 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: Likely_pathogenic. The variant received 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.975

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.254C>G	p.Thr85Arg	missense	Exon 3 of 6	NP_000735.1
	CHRNA4	NR_046317.2		n.438C>G		non_coding_transcript_exon	Exon 3 of 6
	CHRNA4	NM_001256573.2		c.-293C>G		5_prime_UTR	Exon 3 of 6	NP_001243502.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CHRNA4	ENST00000370263.9	TSL:1 MANE Select	c.254C>G	p.Thr85Arg	missense	Exon 3 of 6	ENSP00000359285.4
	CHRNA4	ENST00000467563.3	TSL:1	n.306C>G		non_coding_transcript_exon	Exon 3 of 6
	CHRNA4	ENST00000627000.1	TSL:1	n.254C>G		non_coding_transcript_exon	Exon 3 of 6	ENSP00000486914.1

Frequencies

GnomAD3 genomes AF: 0.00000658 AC: 1 AN: 151962 Hom.: 0 Cov.: 32

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: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD4 exome Cov.: 32

GnomAD4 genome AF: 0.00000658 AC: 1 AN: 151962 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74218

African (AFR) AF: 0.00 AC: 0 AN: 41336

American (AMR) AF: 0.00 AC: 0 AN: 15264

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: 4814

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10622

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

European-Non Finnish (NFE) AF: 0.0000147 AC: 1 AN: 67966

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

Alfa AF: 0.00 Hom.: 0

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.43	D
BayesDel_noAF	Pathogenic	0.38
CADD	Uncertain	25
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.87	D
Eigen	Pathogenic	0.85
Eigen_PC	Pathogenic	0.72
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D
M_CAP	Pathogenic	0.84	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	0.91	D
MutationAssessor	Pathogenic	4.0	H
PhyloP100		6.6
PrimateAI	Pathogenic	0.84	D
PROVEAN	Pathogenic	-5.2	D
REVEL	Pathogenic	0.92
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0010	D
Polyphen		1.0	D
Vest4		0.90
MutPred		0.84		Gain of MoRF binding (P = 0.0244)
MVP		0.94
MPC		1.3
ClinPred		1.0	D
GERP RS		4.3
Varity_R		0.87
gMVP		0.92
Mutation Taster		=17/83	disease causing

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: rs199699339; hg19: chr20-61987742;