rs747050726

chr20-63442510-T-Cchr20-63442510-T-G

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM1 PM2 PM5 PP2

The NM_172107.4(KCNQ2):c.712A>G(p.Ile238Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,618 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. I238L) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 29)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1 O:1
• Conservation: PhyloP100: 7.84

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 7 ACMG points.

• PM1: In a hotspot region, there are 14 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 uncertain 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 chr20-63442510-T-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 421609.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Likely_pathogenic=1}.
• PP2: Missense variant where missense usually causes diseases, KCNQ2

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
KCNQ2	NM_172107.4	c.712A>G	p.Ile238Val	missense_variant	5/17	ENST00000359125.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
KCNQ2	ENST00000359125.7	c.712A>G	p.Ile238Val	missense_variant	5/17	1	NM_172107.4	A1

Frequencies

GnomAD3 genomes Cov.: 29

GnomAD3 exomes AF: 0.00000796 AC: 2 AN: 251358 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135856

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000176

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461618 Hom.: 0 Cov.: 33 AF XY: 0.00000138 AC XY: 1 AN XY: 727106

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 29

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1 Other:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Sep 25, 2017

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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site, but this prediction has not been confirmed by published transcriptional studies. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant has not been reported in the literature in individuals with KCNQ2-related disease. This variant is present in population databases (rs747050726, ExAC 0.003%). This sequence change replaces isoleucine with valine at codon 238 of the KCNQ2 protein (p.Ile238Val). The isoleucine residue is highly conserved and there is a small physicochemical difference between isoleucine and valine. -

Complex neurodevelopmental disorder Other:1

not provided, no classification provided

literature only

Channelopathy-Associated Epilepsy Research Center

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Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.72
BayesDel_addAF	Pathogenic	0.35	D
BayesDel_noAF	Pathogenic	0.29
Cadd	Uncertain	24
Dann	Uncertain	1.0
Eigen	Benign	-0.16
Eigen_PC	Benign	-0.077
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	0.98	D;D;D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.40	D
MetaRNN	Uncertain	0.72	D;D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Uncertain	0.77	D
MutationAssessor	Benign	1.7	L;.;.;.;.;.;L;.;L;L;L;.
MutationTaster	Benign	1.0	D;D;D;D;D;D;D;D;D;D;D;D
PrimateAI	Uncertain	0.74	T
Sift4G	Uncertain	0.0040	D;D;D;D;D;.;D;D;D;D;T;D
Polyphen		0.0010	B;.;.;.;.;.;B;.;B;B;.;.
Vest4		0.87
MutPred		0.67		Loss of glycosylation at T234 (P = 0.3595);Loss of glycosylation at T234 (P = 0.3595);Loss of glycosylation at T234 (P = 0.3595);Loss of glycosylation at T234 (P = 0.3595);Loss of glycosylation at T234 (P = 0.3595);.;Loss of glycosylation at T234 (P = 0.3595);.;Loss of glycosylation at T234 (P = 0.3595);Loss of glycosylation at T234 (P = 0.3595);Loss of glycosylation at T234 (P = 0.3595);.;
MVP		0.99
MPC		1.3
ClinPred		0.78	D
GERP RS		3.1
Varity_R		0.57
gMVP		0.95

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs747050726; hg19: chr20-62073863;