20-63406948-G-T

Variant names:

• chr20-63406948-G-T
• rs774206764
• NM_172107.4:c.2315C>A

Variant summary

Our verdict is Uncertain significance. The variant received 3 ACMG points: 5P and 2B. PM2 PM5 PP2 BP4_Moderate

The NM_172107.4(KCNQ2):​c.2315C>A​(p.Pro772Gln) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000699 in 1,431,436 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. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. P772L) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 34)
  • Exomes 𝑓: 7.0e-7 (0 hom.)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 1.49
• 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: Uncertain_significance. The variant received 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr20-63406948-G-A is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 530457.
• PP2: Missense variant in the KCNQ2 gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 319 curated pathogenic missense variants (we use a threshold of 10). The gene has 78 curated benign missense variants. Gene score misZ: 4.0411 (above the threshold of 3.09). Trascript score misZ: 3.6968 (above the threshold of 3.09). GenCC associations: The gene is linked to benign familial infantile epilepsy, malignant migrating partial seizures of infancy, developmental and epileptic encephalopathy, 7, benign familial neonatal-infantile seizures, benign neonatal seizures, neonatal-onset developmental and epileptic encephalopathy, complex neurodevelopmental disorder, seizures, benign familial neonatal, 2, seizures, benign familial neonatal, 1, neonatal encephalopathy with non-epileptic myoclonus.
• BP4: Computational evidence support a benign effect (MetaRNN=0.11501327).

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_172107.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNQ2	NM_172107.4	MANE Select	c.2315C>A	p.Pro772Gln	missense	Exon 17 of 17	NP_742105.1
	KCNQ2	NM_001382235.1		c.2369C>A	p.Pro790Gln	missense	Exon 17 of 17	NP_001369164.1
	KCNQ2	NM_172106.3		c.2261C>A	p.Pro754Gln	missense	Exon 16 of 16	NP_742104.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNQ2	ENST00000359125.7	TSL:1 MANE Select	c.2315C>A	p.Pro772Gln	missense	Exon 17 of 17	ENSP00000352035.2
	KCNQ2	ENST00000626839.2	TSL:1	c.2261C>A	p.Pro754Gln	missense	Exon 16 of 16	ENSP00000486706.1
	KCNQ2	ENST00000344462.8	TSL:1	c.2222C>A	p.Pro741Gln	missense	Exon 16 of 16	ENSP00000339611.4

Frequencies

GnomAD3 genomes Cov.: 34

GnomAD4 exome AF: 6.99e-7 AC: 1 AN: 1431436 Hom.: 0 Cov.: 36 AF XY: 0.00000141 AC XY: 1 AN XY: 710218

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33068

American (AMR) AF: 0.00 AC: 0 AN: 41866

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25700

East Asian (EAS) AF: 0.00 AC: 0 AN: 38438

South Asian (SAS) AF: 0.00 AC: 0 AN: 83606

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 43088

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5730

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1100632

Other (OTH) AF: 0.0000169 AC: 1 AN: 59308

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 34

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.075
BayesDel_addAF	Uncertain	0.057	T
BayesDel_noAF	Benign	-0.16
CADD	Benign	10
DANN	Benign	0.83
DEOGEN2	Benign	0.0070	T
Eigen	Benign	-1.1
Eigen_PC	Benign	-1.1
FATHMM_MKL	Benign	0.25	N
LIST_S2	Uncertain	0.86	D
M_CAP	Uncertain	0.14	D
MetaRNN	Benign	0.12	T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	0.69	N
PhyloP100		1.5
PrimateAI	Uncertain	0.59	T
PROVEAN	Benign	-0.77	N
REVEL	Benign	0.045
Sift	Benign	0.51	T
Sift4G	Benign	0.40	T
Polyphen		0.30	B
Vest4		0.061
MVP		0.78
MPC		1.1
ClinPred		0.11	T
GERP RS		1.6
Varity_R		0.021
gMVP		0.19
Mutation Taster		=94/6	polymorphism

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: rs774206764; hg19: chr20-62038301;