chr20-63439625-G-C

Variant names:

• chr20-63439625-G-C
• rs764404303
• NM_172107.4:c.900C>G

Variant summary

Our verdict is Uncertain significance. The variant received 5 ACMG points: 5P and 0B. PM1 PM2 PP2

The NM_172107.4(KCNQ2):​c.900C>G​(p.Ile300Met) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,144 control chromosomes in the GnomAD database, with no homozygous occurrence. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. I300I) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: -3.08
• 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: G2P, Orphanet, Labcorp Genetics (formerly Invitae)
• 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
• undetermined early-onset epileptic encephalopathy

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• 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 5 ACMG points.

• PM1: In a hotspot region, there are 29 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 8 uncertain in NM_172107.4
• PM2: Very rare variant in population databases, with high coverage
• 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.

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

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNQ2	NM_172107.4	MANE Select	c.900C>G	p.Ile300Met	missense	Exon 6 of 17	NP_742105.1	O43526-1
	KCNQ2	NM_001382235.1		c.900C>G	p.Ile300Met	missense	Exon 6 of 17	NP_001369164.1	A0A9L9PXL0
	KCNQ2	NM_172106.3		c.900C>G	p.Ile300Met	missense	Exon 6 of 16	NP_742104.1	O43526-2

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNQ2	ENST00000359125.7	TSL:1 MANE Select	c.900C>G	p.Ile300Met	missense	Exon 6 of 17	ENSP00000352035.2	O43526-1
	KCNQ2	ENST00000626839.2	TSL:1	c.900C>G	p.Ile300Met	missense	Exon 6 of 16	ENSP00000486706.1	O43526-2
	KCNQ2	ENST00000344462.8	TSL:1	c.900C>G	p.Ile300Met	missense	Exon 6 of 16	ENSP00000339611.4	O43526-4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461144 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 726896

African (AFR) AF: 0.00 AC: 0 AN: 33478

American (AMR) AF: 0.00 AC: 0 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86256

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 52880

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1111838

Other (OTH) AF: 0.00 AC: 0 AN: 60368

GnomAD4 genome Cov.: 33

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.39
BayesDel_addAF	Pathogenic	0.30	D
BayesDel_noAF	Pathogenic	0.19
CADD	Benign	7.2
DANN	Uncertain	0.99
DEOGEN2	Benign	0.32	T
Eigen	Benign	-0.55
Eigen_PC	Benign	-0.76
FATHMM_MKL	Benign	0.13	N
LIST_S2	Uncertain	0.90	D
M_CAP	Pathogenic	0.74	D
MetaRNN	Uncertain	0.67	D
MetaSVM	Pathogenic	0.81	D
MutationAssessor	Benign	0.65	N
PhyloP100		-3.1
PrimateAI	Uncertain	0.76	T
PROVEAN	Benign	-1.6	N
REVEL	Pathogenic	0.68
Sift	Uncertain	0.0040	D
Sift4G	Uncertain	0.013	D
Polyphen		1.0	D
Vest4		0.65
MutPred		0.53		Gain of catalytic residue at I300 (P = 0.1194)
MVP		0.98
MPC		2.8
ClinPred		0.77	D
GERP RS		-3.2
PromoterAI		-0.050	Neutral
Varity_R		0.73
gMVP		0.97
Mutation Taster		=25/75	disease causing

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: rs764404303; hg19: chr20-62070978;