8-132129498-C-T

Variant names:

• chr8-132129498-C-T
• rs764544537
• NM_004519.4:c.2383G>A

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 0P and 2B. BP4_Moderate

The NM_004519.4(KCNQ3):​c.2383G>A​(p.Val795Ile) variant causes a missense change. The variant allele was found at a frequency of 0.0000123 in 1,461,880 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.000012 (0 hom.)
• Consequence: KCNQ3 NM_004519.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 5.65
• Publications: 0 publications found

Genes affected

KCNQ3 (HGNC:6297): (potassium voltage-gated channel subfamily Q member 3) This gene encodes a protein that functions in the regulation of neuronal excitability. The encoded protein forms an M-channel by associating with the products of the related KCNQ2 or KCNQ5 genes, which both encode integral membrane proteins. M-channel currents are inhibited by M1 muscarinic acetylcholine receptors and are activated by retigabine, a novel anti-convulsant drug. Defects in this gene are a cause of benign familial neonatal convulsions type 2 (BFNC2), also known as epilepsy, benign neonatal type 2 (EBN2). Alternative splicing of this gene results in multiple transcript variants. [provided by RefSeq, May 2014]

KCNQ3 Gene-Disease associations (from GenCC):

• seizures, benign familial neonatal, 2

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

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

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• genetic developmental and epileptic encephalopathy

  Inheritance: AR Classification: LIMITED Submitted by: Ambry Genetics

ACMG classification

Our verdict: Likely_benign. The variant received -2 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.25231287).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNQ3	NM_004519.4	c.2383G>A	p.Val795Ile	missense_variant	Exon 15 of 15	ENST00000388996.10	NP_004510.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNQ3	ENST00000388996.10	c.2383G>A	p.Val795Ile	missense_variant	Exon 15 of 15	1	NM_004519.4	ENSP00000373648.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.0000199 AC: 5 AN: 251304 AF XY: 0.0000221

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 FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000123 AC: 18 AN: 1461880 Hom.: 0 Cov.: 32 AF XY: 0.0000179 AC XY: 13 AN XY: 727238

African (AFR) AF: 0.0000299 AC: 1 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: 39696

South Asian (SAS) AF: 0.000174 AC: 15 AN: 86254

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53418

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

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1112010

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

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000756

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Benign neonatal seizures Uncertain:1

Dec 02, 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 isoleucine, which is neutral and non-polar, at codon 795 of the KCNQ3 protein (p.Val795Ile). This variant is present in population databases (rs764544537, gnomAD 0.02%). This variant has not been reported in the literature in individuals affected with KCNQ3-related conditions. ClinVar contains an entry for this variant (Variation ID: 205993). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed for this missense variant. However, the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on KCNQ3 protein function. 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

Apr 10, 2017

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

p.Val795Ile (GTC>ATC): c.2383 G>A in exon 15 of the KCNQ3 gene (NM_004519.2) The Val795Ile missense change has not been published as a mutation, nor has it been reported as a benign polymorphism to our knowledge. It was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. The amino acid substitution is conservative as both Valine and Isoleucine are uncharged, non-polar amino acid residues. However, Val795Ile alters a conserved position in the C-terminal region of the KCNQ3 protein and in silico analysis is inconsistent with regard to the effect this variant may have on the protein structure/function. Therefore, based on the currently available information, it is unclear whether Val795Ile is a disease-causing mutation or a rare benign variant. The variant is found in EPILEPSY panel(s). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Benign	-0.23	T
BayesDel_noAF	Benign	-0.30
CADD	Benign	23
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.45	T;.;.;.;.
Eigen	Uncertain	0.31
Eigen_PC	Uncertain	0.37
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.90	D;D;D;D;D
M_CAP	Benign	0.011	T
MetaRNN	Benign	0.25	T;T;T;T;T
MetaSVM	Benign	-0.82	T
MutationAssessor	Benign	2.0	M;.;.;.;.
PhyloP100		5.6
PrimateAI	Uncertain	0.54	T
PROVEAN	Benign	-0.42	N;.;N;N;.
REVEL	Benign	0.10
Sift	Uncertain	0.0020	D;.;D;D;.
Sift4G	Uncertain	0.024	D;D;D;D;.
Polyphen		0.73	P;.;.;P;.
Vest4		0.29
MutPred		0.34		Gain of sheet (P = 0.0221);.;.;.;.;
MVP		0.36
MPC		0.26
ClinPred		0.71	D
GERP RS		4.8
Varity_R		0.25
gMVP		0.30
Mutation Taster		=71/29	polymorphism

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: rs764544537; hg19: chr8-133141745;