rs1554622023

Positions:

• chr8-132134290-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_004519.4(KCNQ3):​c.1799G>A​(p.Arg600Lys) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,460,582 control chromosomes in the GnomAD database, with no homozygous occurrence. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: KCNQ3 NM_004519.4 missense, splice_region
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.35

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 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
KCNQ3	NM_004519.4	c.1799G>A	p.Arg600Lys	missense_variant, splice_region_variant	13/15	ENST00000388996.10	NP_004510.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
KCNQ3	ENST00000388996.10	c.1799G>A	p.Arg600Lys	missense_variant, splice_region_variant	13/15	1	NM_004519.4	ENSP00000373648.3

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1460582 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 726746

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: 9.00e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 31

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

Sep 13, 2018

Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may alter RNA splicing, 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 do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a KCNQ3-related disease. This sequence change replaces arginine with lysine at codon 600 of the KCNQ3 protein (p.Arg600Lys). The arginine residue is moderately conserved and there is a small physicochemical difference between arginine and lysine. This variant also falls at the last nucleotide of exon 13 of the KCNQ3 coding sequence, which is part of the consensus splice site for this exon. In summary, this variant is a novel missense change with uncertain impact on mRNA splicing and protein function. It has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.13
BayesDel_addAF	Pathogenic	0.28	D
BayesDel_noAF	Pathogenic	0.16
CADD	Pathogenic	33
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.60	D;.;.;.
Eigen	Pathogenic	0.75
Eigen_PC	Pathogenic	0.76
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Benign	0.77	T;T;T;T
M_CAP	Pathogenic	0.52	D
MetaRNN	Uncertain	0.62	D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Benign	1.6	L;.;.;.
PrimateAI	Uncertain	0.64	T
PROVEAN	Benign	-0.30	N;.;N;.
REVEL	Uncertain	0.55
Sift	Benign	0.35	T;.;T;.
Sift4G	Benign	0.38	T;T;T;.
Polyphen		0.99	D;.;.;.
Vest4		0.72
MutPred		0.41		Gain of ubiquitination at R600 (P = 0.0014);.;.;.;
MVP		0.83
MPC		0.50
ClinPred		0.87	D
GERP RS		5.5
Varity_R		0.18
gMVP		0.53

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	1.0
SpliceAI score (max)		0.84		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.84		Position offset: 0

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs1554622023; hg19: chr8-133146537;