rs554833870

Positions:

• chr8-132129923-T-A
• chr8-132129923-T-C
• chr8-132129923-T-G

Variant summary

Our verdict is Likely benign. Variant got -5 ACMG points: 0P and 5B. BP4 BS2

The NM_004519.4(KCNQ3):​c.1958A>T​(p.Gln653Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000116 in 1,461,884 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 12/21 in silico tools predict a benign outcome for this variant. 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. Q653R) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.000012 (0 hom.)
• Consequence: KCNQ3 NM_004519.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.66

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 Likely_benign. Variant got -5 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.2714369).
• BS2: High AC in GnomAdExome4 at 17 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
KCNQ3	NM_004519.4	c.1958A>T	p.Gln653Leu	missense_variant	15/15	ENST00000388996.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
KCNQ3	ENST00000388996.10	c.1958A>T	p.Gln653Leu	missense_variant	15/15	1	NM_004519.4	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.0000116 AC: 17 AN: 1461884 Hom.: 0 Cov.: 32 AF XY: 0.0000110 AC XY: 8 AN XY: 727244

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000224

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: 0.0000144

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

Bravo AF: 0.00000378

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

Invitae

Mar 27, 2022

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. 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. This variant has not been reported in the literature in individuals affected with KCNQ3-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces glutamine, which is neutral and polar, with leucine, which is neutral and non-polar, at codon 653 of the KCNQ3 protein (p.Gln653Leu). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Uncertain	0.15	D
BayesDel_noAF	Uncertain	-0.020
CADD	Benign	16
DANN	Benign	0.96
DEOGEN2	Benign	0.40	T;.;.;.;.
Eigen	Benign	-0.49
Eigen_PC	Benign	-0.33
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Benign	0.74	T;T;T;T;T
M_CAP	Uncertain	0.25	D
MetaRNN	Benign	0.27	T;T;T;T;T
MetaSVM	Uncertain	0.73	D
MutationAssessor	Benign	1.6	L;.;.;.;.
MutationTaster	Benign	0.96	N;N;N
PrimateAI	Benign	0.26	T
PROVEAN	Benign	-2.2	N;.;N;N;.
REVEL	Uncertain	0.47
Sift	Uncertain	0.023	D;.;D;D;.
Sift4G	Benign	0.14	T;T;T;T;.
Polyphen		0.022	B;.;.;B;.
Vest4		0.16
MutPred		0.40		Loss of disorder (P = 0.039);.;.;.;.;
MVP		0.64
MPC		0.11
ClinPred		0.27	T
GERP RS		4.6
Varity_R		0.12
gMVP		0.33

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: rs554833870; hg19: chr8-133142170;