NM_172107.4:c.1347C>T

Variant names:

• chr20-63415081-G-A
• rs771845478
• NM_172107.4:c.1347C>T

Variant summary

Our verdict is Benign. Variant got -10 ACMG points: 0P and 10B. BP4_Strong BP7 BS1_Supporting BS2

The NM_172107.4(KCNQ2):​c.1347C>T​(p.Gly449Gly) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000735 in 1,605,116 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.000053 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000076 (0 hom.)
• Consequence: KCNQ2 NM_172107.4 synonymous
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:3 B:1
• Conservation: PhyloP100: -0.698

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 Benign. Variant got -10 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.54).
• BP7: Synonymous conserved (PhyloP=-0.698 with no splicing effect.
• BS1: Variant frequency is greater than expected in population eas. gnomad4_exome allele frequency = 0.0000757 (110/1452814) while in subpopulation EAS AF= 0.000202 (8/39696). AF 95% confidence interval is 0.0000993. There are 0 homozygotes in gnomad4_exome. There are 59 alleles in male gnomad4_exome subpopulation. Median coverage is 35. This position pass quality control queck. Existence of Clinvar submissions makes me limit the strength of this signal to Supporting
• BS2: High AC in GnomAd4 at 8 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.1347C>T	p.Gly449Gly	synonymous_variant	Exon 13 of 17	ENST00000359125.7	NP_742105.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNQ2	ENST00000359125.7	c.1347C>T	p.Gly449Gly	synonymous_variant	Exon 13 of 17	1	NM_172107.4	ENSP00000352035.2

Frequencies

GnomAD3 genomes AF: 0.0000526 AC: 8 AN: 152184 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.0000654

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000193

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000735

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000500 AC: 12 AN: 239998 Hom.: 0 AF XY: 0.0000457 AC XY: 6 AN XY: 131256

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.000274

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000640

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000757 AC: 110 AN: 1452814 Hom.: 0 Cov.: 35 AF XY: 0.0000816 AC XY: 59 AN XY: 723184

Gnomad4 AFR exome AF: 0.000149

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.000202

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000845

Gnomad4 OTH exome AF: 0.0000497

GnomAD4 genome AF: 0.0000525 AC: 8 AN: 152302 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74464

Gnomad4 AFR AF: 0.0000241

Gnomad4 AMR AF: 0.0000653

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.000194

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000735

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000285 Hom.: 0

Bravo AF: 0.0000567

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:3 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:2

Apr 12, 2018

Eurofins Ntd Llc (ga)

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Jun 26, 2017

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

A variant of uncertain significance has been identified in the KCNQ2 gene. The c.1347 C>T variant has not been published as a pathogenic variant, nor has it been reported as a benign variant to our knowledge. The c.1347 C>T variant is observed in 1/8434 (0.01%) alleles from individuals of East Asian background (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). Several in-silico splice prediction models predict that c.1347 C>T creates a cryptic donor site which may supplant the natural donor site and lead to abnormal gene splicing. However, in the absence of RNA/functional studies, the actual effect of this sequence change in this individual is unknown. Therefore, based on the currently available information, it is unclear whether this variant is a pathogenic variant or a rare benign variant. -

Seizures, benign familial neonatal, 1;C3150986:Developmental and epileptic encephalopathy, 7 Uncertain:1

Oct 31, 2018

Fulgent Genetics, Fulgent Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Early infantile epileptic encephalopathy with suppression bursts Benign:1

Dec 16, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.54
CADD	Benign	12
DANN	Benign	0.76

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.11		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: rs771845478; hg19: chr20-62046434;