20-63442495-G-C

Position:

• chr20-63442495-G-C

Variant summary

Our verdict is Pathogenic. Variant got 17 ACMG points: 17P and 0B. PM1 PM2 PM5 PP2 PP3_Moderate PP5_Very_Strong

The NM_172107.4(KCNQ2):​c.727C>G​(p.Leu243Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. L243F) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 29)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 9.77

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 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 17 ACMG points.

• PM1: In a region_of_interest Mediates interaction with SLC5A3 (size 101) in uniprot entity KCNQ2_HUMAN there are 33 pathogenic changes around while only 0 benign (100%) in NM_172107.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr20-63442495-G-A is described in Lovd as [Pathogenic].
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), KCNQ2. . Gene score misZ 4.0411 (greater than the threshold 3.09). Trascript score misZ 3.6968 (greater than threshold 3.09). GenCC has associacion of gene with seizures, benign familial neonatal, 1, neonatal-onset developmental and epileptic encephalopathy, benign familial neonatal-infantile seizures, benign neonatal seizures, malignant migrating partial seizures of infancy, neonatal encephalopathy with non-epileptic myoclonus, complex neurodevelopmental disorder, seizures, benign familial neonatal, 2, developmental and epileptic encephalopathy, 7, benign familial infantile epilepsy.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.882
• PP5: Variant 20-63442495-G-C is Pathogenic according to our data. Variant chr20-63442495-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 692002.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.727C>G	p.Leu243Val	missense_variant	5/17	ENST00000359125.7	NP_742105.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
KCNQ2	ENST00000359125.7	c.727C>G	p.Leu243Val	missense_variant	5/17	1	NM_172107.4	ENSP00000352035.2

Frequencies

GnomAD3 genomes Cov.: 29

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 29

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 13, 2023

This sequence change replaces leucine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 243 of the KCNQ2 protein (p.Leu243Val). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with early infantile epileptic encephalopathy (PMID: 31564432). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 692002). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt KCNQ2 protein function. This variant disrupts the p.Leu243 amino acid residue in KCNQ2. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 14534157, 30478917). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -

Developmental and epileptic encephalopathy, 7 Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Rady Children's Institute for Genomic Medicine, Rady Children's Hospital San Diego

Jan 06, 2018

This c.727C>G (p.Leu243Val) variant has not been reported in the literature to our knowledge. However, a variant affecting the same nucleotide position but resulting in a different amino acid change (p.Leu243Phe) was detected in multiple individuals with neonatal seizures from a single family (PMID: 14534157). Additionally, studies have shown that the p.Leu243Phe variant is functionally consequential (PMID: 14534157, 11278406). This variant is absent from the gnomAD population database, thus it is presumed to be rare. This variant affects a highly conserved amino acid and is predicted by multiple in silico tools to have a deleterious effect on protein function. Based on the available evidence, the c.727C>G (p.Leu243Val) variant is classified as likely pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.38	D
BayesDel_noAF	Pathogenic	0.30
CADD	Uncertain	25
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.45	.;.;T;T;D;T;D;T;.;.;.;.
Eigen	Benign	-0.13
Eigen_PC	Benign	-0.041
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	0.99	D;D;D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.49	D
MetaRNN	Pathogenic	0.88	D;D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.84	D
MutationAssessor	Benign	1.4	L;.;.;.;.;.;L;.;L;L;L;.
PrimateAI	Pathogenic	0.86	D
PROVEAN	Uncertain	-2.7	.;.;.;.;D;.;D;N;D;D;D;.
REVEL	Pathogenic	0.75
Sift	Uncertain	0.0010	.;.;.;.;D;.;D;D;D;D;D;.
Sift4G	Uncertain	0.0020	D;D;D;D;D;.;D;D;D;D;D;D
Polyphen		0.0040	B;.;.;.;.;.;B;.;B;B;.;.
Vest4		0.82
MutPred		0.72		Loss of helix (P = 0.079);Loss of helix (P = 0.079);Loss of helix (P = 0.079);Loss of helix (P = 0.079);Loss of helix (P = 0.079);.;Loss of helix (P = 0.079);.;Loss of helix (P = 0.079);Loss of helix (P = 0.079);Loss of helix (P = 0.079);.;
MVP		1.0
MPC		1.6
ClinPred		0.93	D
GERP RS		3.1
Varity_R		0.81
gMVP		0.98

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: rs118192205; hg19: chr20-62073848;