20-63433862-G-T

Variant names:

• chr20-63433862-G-T
• rs200395340
• NM_172107.4:c.1065C>A

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PS1 PM2 PP2 PP5_Moderate

The NM_172107.4(KCNQ2):​c.1065C>A​(p.Asp355Glu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (★). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Pathogenic in Lovd.

• Frequency: Genomes: not found (cov: 33)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 1.57

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]

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PS1: Transcript NM_172107.4 (KCNQ2) is affected with MISSENSE_VARIANT having same AA change as one Pathogenic present in Lovd
• PM2: Very rare variant in population databases, with high coverage
• 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 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.
• PP5: Variant 20-63433862-G-T is Pathogenic according to our data. Variant chr20-63433862-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 963965.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.1065C>A	p.Asp355Glu	missense_variant	Exon 8 of 17	ENST00000359125.7	NP_742105.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNQ2	ENST00000359125.7	c.1065C>A	p.Asp355Glu	missense_variant	Exon 8 of 17	1	NM_172107.4	ENSP00000352035.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Jan 08, 2020

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces aspartic acid with glutamic acid at codon 355 of the KCNQ2 protein (p.Asp355Glu). The aspartic acid residue is highly conserved and there is a small physicochemical difference between aspartic acid and glutamic acid. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C0"). This variant has been observed in individual(s) with neonatal seizures (PMID: 28926830, Invitae). In at least one individual the variant was observed to be de novo. This variant is not present in population databases (ExAC no frequency). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.33	D
BayesDel_noAF	Pathogenic	0.23
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Benign	0.33	.;.;T;T;T;T;T;T;.;.;.
Eigen	Benign	0.13
Eigen_PC	Benign	0.084
FATHMM_MKL	Uncertain	0.91	D
LIST_S2	Uncertain	0.87	D;D;D;D;D;D;D;T;D;T;D
M_CAP	Pathogenic	0.74	D
MetaRNN	Uncertain	0.69	D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Uncertain	2.5	M;.;.;.;.;.;M;.;M;M;M
PrimateAI	Pathogenic	0.82	D
PROVEAN	Benign	-2.0	.;.;.;.;N;.;N;.;N;N;N
REVEL	Pathogenic	0.79
Sift	Uncertain	0.011	.;.;.;.;D;.;D;.;D;T;D
Sift4G	Benign	0.064	T;T;T;T;T;.;T;T;D;T;T
Polyphen		1.0	D;.;.;.;.;.;D;.;D;D;.
Vest4		0.94
MutPred		0.44		Gain of helix (P = 0.0325);Gain of helix (P = 0.0325);Gain of helix (P = 0.0325);Gain of helix (P = 0.0325);Gain of helix (P = 0.0325);.;Gain of helix (P = 0.0325);.;Gain of helix (P = 0.0325);Gain of helix (P = 0.0325);Gain of helix (P = 0.0325);
MVP		0.98
MPC		2.4
ClinPred		0.93	D
GERP RS		1.9
Varity_R		0.30
gMVP		0.93

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: rs200395340; hg19: chr20-62065215;