20-63444668-G-T

Variant names:

• chr20-63444668-G-T
• rs1472366685
• NM_172107.4:c.681C>A

Variant summary

Our verdict is Benign. The variant received -13 ACMG points: 0P and 13B. BP4_Strong BP7 BS1 BS2

The NM_172107.4(KCNQ2):​c.681C>A​(p.Ala227Ala) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000709 in 1,411,262 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. A227A) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000071 (0 hom.)
• Consequence: KCNQ2 NM_172107.4 synonymous
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: -1.48
• Publications: 0 publications found

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]

KCNQ2 Gene-Disease associations (from GenCC):

• complex neurodevelopmental disorder

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• developmental and epileptic encephalopathy, 7

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae), G2P
• neonatal encephalopathy with non-epileptic myoclonus

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• neonatal-onset developmental and epileptic encephalopathy

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• seizures, benign familial neonatal, 1

  Inheritance: AD Classification: DEFINITIVE Submitted by: G2P
• seizures, benign familial neonatal, 2

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

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

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

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• malignant migrating partial seizures of infancy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Benign. The variant received -13 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.53).
• BP7: Synonymous conserved (PhyloP=-1.48 with no splicing effect.
• BS1: Variant frequency is greater than expected in population eas. GnomAdExome4 allele frequency = 0.00000709 (10/1411262) while in subpopulation EAS AF = 0.000239 (9/37654). AF 95% confidence interval is 0.000124. There are 0 homozygotes in GnomAdExome4. There are 6 alleles in the male GnomAdExome4 subpopulation. Median coverage is 32. This position passed quality control check.
• BS2: High AC in GnomAdExome4 at 10 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.681C>A	p.Ala227Ala	synonymous_variant	Exon 4 of 17	ENST00000359125.7	NP_742105.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNQ2	ENST00000359125.7	c.681C>A	p.Ala227Ala	synonymous_variant	Exon 4 of 17	1	NM_172107.4	ENSP00000352035.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000709 AC: 10 AN: 1411262 Hom.: 0 Cov.: 32 AF XY: 0.00000862 AC XY: 6 AN XY: 696012

African (AFR) AF: 0.00 AC: 0 AN: 32562

American (AMR) AF: 0.00 AC: 0 AN: 38506

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25170

East Asian (EAS) AF: 0.000239 AC: 9 AN: 37654

South Asian (SAS) AF: 0.00 AC: 0 AN: 80782

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 48790

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5472

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1084034

Other (OTH) AF: 0.0000172 AC: 1 AN: 58292

GnomAD4 genome Cov.: 33

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.53
CADD	Benign	7.8
DANN	Benign	0.85
PhyloP100		-1.5
PromoterAI		-0.019	Neutral

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: rs1472366685; hg19: chr20-62076021;