20-63442447-C-T

Variant names:

• chr20-63442447-C-T
• rs777257591
• NM_172107.4:c.775G>A

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 8P and 1B. PM1 PM2 PM5 PP2 PP5 BP4

The NM_172107.4(KCNQ2):​c.775G>A​(p.Asp259Asn) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000658 in 151,960 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D259Y) has been classified as Pathogenic.

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 29)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:2
• Conservation: PhyloP100: 2.20
• Publications: 6 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: Likely_pathogenic. The variant received 7 ACMG points.

• PM1: In a hotspot region, there are 28 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 12 uncertain in NM_172107.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr20-63442447-C-A is described in ClinVar as Pathogenic. ClinVar VariationId is 219240.Status of the report is no_assertion_criteria_provided, 0 stars.
• 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.
• PP5: Variant 20-63442447-C-T is Pathogenic according to our data. Variant chr20-63442447-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 692196.
• BP4: Computational evidence support a benign effect (MetaRNN=0.2526705). . Strength limited to SUPPORTING due to the PP5.

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.775G>A	p.Asp259Asn	missense	Exon 5 of 17	NP_742105.1	O43526-1
	KCNQ2	NM_001382235.1		c.775G>A	p.Asp259Asn	missense	Exon 5 of 17	NP_001369164.1	A0A9L9PXL0
	KCNQ2	NM_172106.3		c.775G>A	p.Asp259Asn	missense	Exon 5 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.775G>A	p.Asp259Asn	missense	Exon 5 of 17	ENSP00000352035.2	O43526-1
	KCNQ2	ENST00000626839.2	TSL:1	c.775G>A	p.Asp259Asn	missense	Exon 5 of 16	ENSP00000486706.1	O43526-2
	KCNQ2	ENST00000344462.8	TSL:1	c.775G>A	p.Asp259Asn	missense	Exon 5 of 16	ENSP00000339611.4	O43526-4

Frequencies

GnomAD3 genomes AF: 0.00000658 AC: 1 AN: 151960 Hom.: 0 Cov.: 29

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.0000943

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.00 AC: 0 AN: 251414 AF XY: 0.00

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome Cov.: 32

GnomAD4 genome AF: 0.00000658 AC: 1 AN: 151960 Hom.: 0 Cov.: 29 AF XY: 0.0000135 AC XY: 1 AN XY: 74210

African (AFR) AF: 0.00 AC: 0 AN: 41334

American (AMR) AF: 0.00 AC: 0 AN: 15262

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3468

East Asian (EAS) AF: 0.00 AC: 0 AN: 5186

South Asian (SAS) AF: 0.00 AC: 0 AN: 4822

European-Finnish (FIN) AF: 0.0000943 AC: 1 AN: 10604

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 67966

Other (OTH) AF: 0.00 AC: 0 AN: 2092

Alfa AF: 0.00 Hom.: 0

ExAC AF: 0.00000824 AC: 1

ClinVar

ClinVar submissions

Significance: Conflicting classifications of pathogenicity

Revision: criteria provided, conflicting classifications

Pathogenic	VUS	Benign	Condition
-	1	-	Developmental and epileptic encephalopathy (1)
-	1	-	not provided (1)
1	-	-	Seizures, benign familial neonatal, 1 (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.11
BayesDel_addAF	Benign	-0.0043	T
BayesDel_noAF	Benign	-0.24
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Benign	0.31	T
Eigen	Benign	-0.40
Eigen_PC	Benign	-0.25
FATHMM_MKL	Uncertain	0.78	D
LIST_S2	Uncertain	0.94	D
M_CAP	Uncertain	0.22	D
MetaRNN	Benign	0.25	T
MetaSVM	Uncertain	0.56	D
MutationAssessor	Benign	1.5	L
PhyloP100		2.2
PrimateAI	Uncertain	0.68	T
PROVEAN	Benign	-0.90	N
REVEL	Benign	0.27
Sift	Benign	0.065	T
Sift4G	Benign	0.085	T
Polyphen		0.0050	B
Vest4		0.27
MutPred		0.28		Loss of catalytic residue at D259 (P = 0.1193)
MVP		0.78
MPC		1.5
ClinPred		0.59	D
GERP RS		3.4
Varity_R		0.12
gMVP		0.90
Mutation Taster		=0/100	disease causing (ClinVar)

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: rs777257591; hg19: chr20-62073800; COSMIC: COSV105235307; COSMIC: COSV105235307;