8-132129843-A-C

Position:

• chr8-132129843-A-C

Variant summary

Our verdict is Benign. Variant got -8 ACMG points: 0P and 8B. BP4_Strong BS2

The ENST00000388996.10(KCNQ3):​c.2038T>G​(p.Leu680Val) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000103 in 1,461,890 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 16/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.000010 (0 hom.)
• Consequence: KCNQ3 ENST00000388996.10 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.198

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]

ACMG classification

Verdict is Benign. Variant got -8 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.046398252).
• BS2: High AC in GnomAdExome4 at 15 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
KCNQ3	NM_004519.4	c.2038T>G	p.Leu680Val	missense_variant	15/15	ENST00000388996.10	NP_004510.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
KCNQ3	ENST00000388996.10	c.2038T>G	p.Leu680Val	missense_variant	15/15	1	NM_004519.4	ENSP00000373648	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.0000103 AC: 15 AN: 1461890 Hom.: 0 Cov.: 32 AF XY: 0.0000110 AC XY: 8 AN XY: 727246

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: 0.0000126

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Benign neonatal seizures Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 04, 2023

ClinVar contains an entry for this variant (Variation ID: 478607). This sequence change replaces leucine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 680 of the KCNQ3 protein (p.Leu680Val). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with KCNQ3-related conditions. 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 not expected to disrupt 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.088
BayesDel_addAF	Benign	-0.0033	T
BayesDel_noAF	Benign	-0.24
CADD	Benign	4.0
DANN	Benign	0.85
DEOGEN2	Benign	0.23	T;.;.;.;.
Eigen	Benign	-1.1
Eigen_PC	Benign	-1.1
FATHMM_MKL	Benign	0.10	N
LIST_S2	Benign	0.80	T;T;T;T;T
M_CAP	Benign	0.046	D
MetaRNN	Benign	0.046	T;T;T;T;T
MetaSVM	Uncertain	0.15	D
MutationAssessor	Benign	0.69	N;.;.;.;.
MutationTaster	Benign	1.0	N;N;N
PrimateAI	Benign	0.42	T
PROVEAN	Benign	-0.050	N;.;N;N;.
REVEL	Benign	0.20
Sift	Benign	0.16	T;.;T;T;.
Sift4G	Benign	0.55	T;T;T;T;.
Polyphen		0.0	B;.;.;B;.
Vest4		0.075
MutPred		0.27		Loss of stability (P = 0.027);.;.;.;.;
MVP		0.45
MPC		0.10
ClinPred		0.12	T
GERP RS		-3.2
Varity_R		0.042
gMVP		0.26

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: rs1223253841; hg19: chr8-133142090;