chr8-27463391-T-G

Variant names:

• chr8-27463391-T-G
• rs770305730
• NM_000742.4:c.1052A>C

Variant summary

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

The NM_000742.4(CHRNA2):​c.1052A>C​(p.Asn351Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,836 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. N351S) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: CHRNA2 NM_000742.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.02
• Publications: 0 publications found

Genes affected

CHRNA2 (HGNC:1956): (cholinergic receptor nicotinic alpha 2 subunit) Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels formed by a pentameric arrangement of alpha and beta subunits to create distinct muscle and neuronal receptors. Neuronal receptors are found throughout the peripheral and central nervous system where they are involved in fast synaptic transmission. This gene encodes an alpha subunit that is widely expressed in the brain. The proposed structure for nAChR subunits is a conserved N-terminal extracellular domain followed by three conserved transmembrane domains, a variable cytoplasmic loop, a fourth conserved transmembrane domain, and a short C-terminal extracellular region. Mutations in this gene cause autosomal dominant nocturnal frontal lobe epilepsy type 4. Single nucleotide polymorphisms (SNPs) in this gene have been associated with nicotine dependence. [provided by RefSeq, Nov 2009]

CHRNA2 Gene-Disease associations (from GenCC):

• autosomal dominant nocturnal frontal lobe epilepsy 4

  Inheritance: AD Classification: STRONG, LIMITED Submitted by: G2P, Illumina, Labcorp Genetics (formerly Invitae)
• autosomal dominant nocturnal frontal lobe epilepsy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• familial sleep-related hypermotor epilepsy

  Inheritance: AD Classification: LIMITED Submitted by: ClinGen
• benign familial infantile epilepsy

  Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen
• epilepsy

  Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen

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, 0.946

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000742.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CHRNA2	NM_000742.4	MANE Select	c.1052A>C	p.Asn351Thr	missense	Exon 6 of 7	NP_000733.2	Q15822-1
	CHRNA2	NM_001282455.2		c.1007A>C	p.Asn336Thr	missense	Exon 6 of 7	NP_001269384.1	Q15822-2
	CHRNA2	NM_001347705.2		c.575A>C	p.Asn192Thr	missense	Exon 6 of 7	NP_001334634.1

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CHRNA2	ENST00000407991.3	TSL:5 MANE Select	c.1052A>C	p.Asn351Thr	missense	Exon 6 of 7	ENSP00000385026.1	Q15822-1
	CHRNA2	ENST00000523695.5	TSL:1	n.*454A>C		non_coding_transcript_exon	Exon 6 of 7	ENSP00000430612.1	E5RJ54
	CHRNA2	ENST00000523695.5	TSL:1	n.*454A>C		3_prime_UTR	Exon 6 of 7	ENSP00000430612.1	E5RJ54

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461836 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727210

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53364

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1112012

Other (OTH) AF: 0.00 AC: 0 AN: 60394

GnomAD4 genome Cov.: 33

ClinVar

ClinVar submissions

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
AlphaMissense	Pathogenic	0.81
BayesDel_addAF	Uncertain	0.12	D
BayesDel_noAF	Uncertain	-0.060
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.89	D
Eigen	Pathogenic	0.93
Eigen_PC	Pathogenic	0.82
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Uncertain	0.95	D
M_CAP	Uncertain	0.27	D
MetaRNN	Pathogenic	0.95	D
MetaSVM	Uncertain	0.62	D
MutationAssessor	Pathogenic	4.2	H
PhyloP100		8.0
PrimateAI	Uncertain	0.73	T
PROVEAN	Pathogenic	-6.0	D
REVEL	Pathogenic	0.81
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.87
MutPred		0.81		Gain of glycosylation at N351 (P = 0.0423)
MVP		0.95
MPC		0.74
ClinPred		1.0	D
GERP RS		4.9
Varity_R		0.96
gMVP		0.84
Mutation Taster		=29/71	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: rs770305730; hg19: chr8-27320908;