20-63439639-T-G

Variant names:

• chr20-63439639-T-G
• rs756921902
• NM_172107.4:c.886A>C

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM1 PM2 PP2 PP5

The NM_172107.4(KCNQ2):​c.886A>C​(p.Thr296Pro) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T296N) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 33)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Likely pathogenic no assertion criteria provided P:1 O:1
• Conservation: PhyloP100: 3.31
• Publications: 4 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: Likely_pathogenic. The variant received 6 ACMG points.

• PM1: In a hotspot region, there are 23 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.
• PP5: Variant 20-63439639-T-G is Pathogenic according to our data. Variant chr20-63439639-T-G is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 369769.Status of the report is no_assertion_criteria_provided, 0 stars.

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.886A>C	p.Thr296Pro	missense	Exon 6 of 17	NP_742105.1
	KCNQ2	NM_001382235.1		c.886A>C	p.Thr296Pro	missense	Exon 6 of 17	NP_001369164.1
	KCNQ2	NM_172106.3		c.886A>C	p.Thr296Pro	missense	Exon 6 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.886A>C	p.Thr296Pro	missense	Exon 6 of 17	ENSP00000352035.2
	KCNQ2	ENST00000626839.2	TSL:1	c.886A>C	p.Thr296Pro	missense	Exon 6 of 16	ENSP00000486706.1
	KCNQ2	ENST00000344462.8	TSL:1	c.886A>C	p.Thr296Pro	missense	Exon 6 of 16	ENSP00000339611.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1 Other:1

Revision: no assertion criteria provided

Submissions by phenotype

Seizure Pathogenic:1

Diagnostic Laboratory, Strasbourg University Hospital

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

Developmental and epileptic encephalopathy, 7 Other:1

GeneReviews

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

EE (epileptic encephalopathy)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Benign	0.0040	T
BayesDel_noAF	Pathogenic	0.20
CADD	Uncertain	25
DANN	Benign	0.97
Eigen	Benign	0.15
Eigen_PC	Benign	0.083
FATHMM_MKL	Uncertain	0.80	D
LIST_S2	Benign	0.19	T
M_CAP	Pathogenic	0.91	D
MetaRNN	Uncertain	0.73	D
PhyloP100		3.3
Sift4G	Benign	1.0	T
MVP		0.65
ClinPred		0.93	D
GERP RS		4.0
PromoterAI		-0.035	Neutral
Varity_R		0.92
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: rs756921902; hg19: chr20-62070992;