20-63406886-C-T

Variant names:

• chr20-63406886-C-T
• rs377227909
• NM_172107.4:c.2377G>A

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 1P and 4B. PP2 BS2

The NM_172107.4(KCNQ2):​c.2377G>A​(p.Val793Met) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000891 in 1,459,480 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. V793L) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000089 (0 hom.)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 7.68
• Publications: 2 publications found

Genes affected

KCNQ2 (HGNC:6296): (potassium voltage-gated channel subfamily Q member 2) The M channel is a slowly activating and deactivating potassium channel that plays a critical role in the regulation of neuronal excitability. The M channel is formed by the association of the protein encoded by this gene and a related protein encoded by the KCNQ3 gene, both integral membrane proteins. M channel currents are inhibited by M1 muscarinic acetylcholine receptors and activated by retigabine, a novel anti-convulsant drug. Defects in this gene are a cause of benign familial neonatal convulsions type 1 (BFNC), also known as epilepsy, benign neonatal type 1 (EBN1). At least five transcript variants encoding five different isoforms have been found for this gene. [provided by RefSeq, Jul 2008]

KCNQ2 Gene-Disease associations (from GenCC):

• complex neurodevelopmental disorder

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• developmental and epileptic encephalopathy, 7

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae), G2P
• neonatal encephalopathy with non-epileptic myoclonus

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• neonatal-onset developmental and epileptic encephalopathy

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• seizures, benign familial neonatal, 1

  Inheritance: AD Classification: DEFINITIVE Submitted by: G2P
• seizures, benign familial neonatal, 2

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• benign familial infantile epilepsy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• benign familial neonatal-infantile seizures

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• benign neonatal seizures

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• malignant migrating partial seizures of infancy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_benign. The variant received -3 ACMG points.

• PP2: Missense variant in the KCNQ2 gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 319 curated pathogenic missense variants (we use a threshold of 10). The gene has 78 curated benign missense variants. Gene score misZ: 4.0411 (above the threshold of 3.09). Trascript score misZ: 3.6968 (above the threshold of 3.09). GenCC associations: The gene is linked to benign familial infantile epilepsy, malignant migrating partial seizures of infancy, developmental and epileptic encephalopathy, 7, benign familial neonatal-infantile seizures, benign neonatal seizures, neonatal-onset developmental and epileptic encephalopathy, complex neurodevelopmental disorder, seizures, benign familial neonatal, 2, seizures, benign familial neonatal, 1, neonatal encephalopathy with non-epileptic myoclonus.
• BS2: High AC in GnomAdExome4 at 13 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.2377G>A	p.Val793Met	missense_variant	Exon 17 of 17	ENST00000359125.7	NP_742105.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNQ2	ENST00000359125.7	c.2377G>A	p.Val793Met	missense_variant	Exon 17 of 17	1	NM_172107.4	ENSP00000352035.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.0000244 AC: 6 AN: 245912 AF XY: 0.0000299

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000291

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000452

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000891 AC: 13 AN: 1459480 Hom.: 0 Cov.: 30 AF XY: 0.0000124 AC XY: 9 AN XY: 725954

African (AFR) AF: 0.00 AC: 0 AN: 33466

American (AMR) AF: 0.00 AC: 0 AN: 44654

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26090

East Asian (EAS) AF: 0.0000252 AC: 1 AN: 39672

South Asian (SAS) AF: 0.00 AC: 0 AN: 86082

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 51816

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

European-Non Finnish (NFE) AF: 0.00000900 AC: 10 AN: 1111614

Other (OTH) AF: 0.0000332 AC: 2 AN: 60318

GnomAD4 genome Cov.: 33

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000756

ExAC AF: 0.0000579 AC: 7

Asia WGS AF: 0.000289 AC: 1 AN: 3478

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Developmental and epileptic encephalopathy Uncertain:1

Jan 16, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces valine, which is neutral and non-polar, with methionine, which is neutral and non-polar, at codon 793 of the KCNQ2 protein (p.Val793Met). This variant is present in population databases (rs377227909, gnomAD 0.005%). This missense change has been observed in individuals with clinical features of developmental and epileptic encephalopathy (Invitae). ClinVar contains an entry for this variant (Variation ID: 1025174). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests 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. -

not provided Uncertain:1

Aug 11, 2020

Athena Diagnostics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This observation is not an independent occurrence and has been identified in the same individual by RCIGM, the other laboratory participating in the GEMINI study. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.92
BayesDel_addAF	Uncertain	0.072	D
BayesDel_noAF	Uncertain	0.0
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Benign	0.033	.;T;T;T;.;.
Eigen	Uncertain	0.47
Eigen_PC	Uncertain	0.51
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Uncertain	0.96	D;D;D;D;D;D
M_CAP	Uncertain	0.090	D
MetaRNN	Uncertain	0.43	T;T;T;T;T;T
MetaSVM	Benign	-0.60	T
MutationAssessor	Benign	1.9	.;.;L;.;.;.
PhyloP100		7.7
PrimateAI	Pathogenic	0.90	D
PROVEAN	Benign	-1.1	.;.;N;.;N;.
REVEL	Benign	0.18
Sift	Pathogenic	0.0	.;.;D;.;D;.
Sift4G	Uncertain	0.0050	D;.;D;D;D;D
Polyphen		0.96	D;.;D;.;D;D
Vest4		0.50
MutPred		0.39		.;.;Loss of sheet (P = 0.1907);.;.;.;
MVP		0.80
MPC		1.4
ClinPred		0.66	D
GERP RS		5.0
Varity_R		0.27
gMVP		0.72
Mutation Taster		=41/59	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: rs377227909; hg19: chr20-62038239; COSMIC: COSV60549003; COSMIC: COSV60549003;