20-63444826-C-G

Variant names:

• chr20-63444826-C-G
• rs1057516082
• NM_172107.4:c.523G>C

Variant summary

Our verdict is Pathogenic. The variant received 13 ACMG points: 13P and 0B. PS1 PM1 PM2 PP2 PP3_Moderate PP5_Moderate

The NM_172107.4(KCNQ2):​c.523G>C​(p.Val175Leu) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Pathogenic in ClinVar.

• Frequency: Genomes: not found (cov: 33)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1 O:1
• Conservation: PhyloP100: 7.66
• Publications: 7 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: Pathogenic. The variant received 13 ACMG points.

• PS1: Transcript NM_172107.4 (KCNQ2) is affected with MISSENSE_VARIANT having same AA change as one Pathogenic present in ClinVar as 2138369
• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 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.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.897
• PP5: Variant 20-63444826-C-G is Pathogenic according to our data. Variant chr20-63444826-C-G is described in ClinVar as [Pathogenic]. Clinvar id is 369748.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.523G>C	p.Val175Leu	missense_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.523G>C	p.Val175Leu	missense_variant	Exon 4 of 17	1	NM_172107.4	ENSP00000352035.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1 Other:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Pathogenic:1

May 29, 2018

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This V175L variant in this individual has been reported as a de novo change in association with myoclonic epilepsy which progressed to West syndrome (Samanta et al., 2015). The V175L variant is not observed in large population cohorts (Lek et al., 2016). This variant is a conservative amino acid substitution, which is not likely to impact secondary protein structure as these residues share similar properties. However, in-silico analyses, including protein predictors and evolutionary conservation, support a deleterious effect. A different nucleotide substitution resulting in the same amino acid change (c.523 G>T) has been reported as a de novo variant in an individual with early onset epileptic encephalopathy (Milh et al., 2013). The V175L variant is predicted to be within the transmembrane segment S3. -

Developmental and epileptic encephalopathy, 7 Other:1

-

GeneReviews

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

Infantile spasms -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.35
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Benign	0.41	.;.;T;T;D;T;D;T;.;.;.
Eigen	Uncertain	0.56
Eigen_PC	Uncertain	0.50
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.96	D;D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.92	D
MetaRNN	Pathogenic	0.90	D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.1	M;.;.;.;.;.;M;.;M;M;M
PhyloP100		7.7
PrimateAI	Pathogenic	0.87	D
PROVEAN	Uncertain	-2.7	.;.;.;.;D;.;D;.;D;D;D
REVEL	Pathogenic	0.97
Sift	Uncertain	0.0040	.;.;.;.;D;.;D;.;D;D;D
Sift4G	Uncertain	0.0070	D;D;D;D;D;.;D;D;D;D;D
Polyphen		0.89	P;.;.;.;.;.;D;.;P;P;.
Vest4		0.91
MutPred		0.66		Gain of catalytic residue at V175 (P = 0.12);Gain of catalytic residue at V175 (P = 0.12);Gain of catalytic residue at V175 (P = 0.12);Gain of catalytic residue at V175 (P = 0.12);Gain of catalytic residue at V175 (P = 0.12);.;Gain of catalytic residue at V175 (P = 0.12);.;Gain of catalytic residue at V175 (P = 0.12);Gain of catalytic residue at V175 (P = 0.12);Gain of catalytic residue at V175 (P = 0.12);
MVP		0.97
MPC		2.3
ClinPred		0.99	D
GERP RS		3.9
PromoterAI		-0.049	Neutral
Varity_R		0.94
gMVP		0.99
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: rs1057516082; hg19: chr20-62076179;