20-63413471-C-G

Variant names:

• chr20-63413471-C-G
• rs118192235
• NM_172107.4:c.1742G>C

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5

The NM_172107.4(KCNQ2):​c.1742G>C​(p.Arg581Pro) 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. 13/22 in silico tools predict a damaging 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. R581G) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 7.75
• Publications: 11 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

LOC105372724 (HGNC:):

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PM1: In a hotspot region, there are 13 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 3 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 chr20-63413472-G-C is described in ClinVar as Pathogenic. ClinVar VariationId is 265380.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 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.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.984
• PP5: Variant 20-63413471-C-G is Pathogenic according to our data. Variant chr20-63413471-C-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 804957.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.1742G>C	p.Arg581Pro	missense_variant	Exon 15 of 17	ENST00000359125.7	NP_742105.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNQ2	ENST00000359125.7	c.1742G>C	p.Arg581Pro	missense_variant	Exon 15 of 17	1	NM_172107.4	ENSP00000352035.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Pathogenic:1

Jun 05, 2019

Athena Diagnostics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not found in the total gnomAD dataset, and the data is high quality (0/279694 chr). Predicted to have a damaging effect on the protein. Located in potentially critical domain of the protein. Moderate co-segregation with disease in affected and unaffected individuals, but from a single family. -

Developmental and epileptic encephalopathy Uncertain:1

Jun 15, 2020

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant disrupts the p.Arg581 amino acid residue in KCNQ2. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 25262651, 29186148, 25262651). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with KCNQ2-related conditions. This variant is not present in population databases (ExAC no frequency). This sequence change replaces arginine with proline at codon 581 of the KCNQ2 protein (p.Arg581Pro). The arginine residue is highly conserved and there is a moderate physicochemical difference between arginine and proline. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	33
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.61	.;.;D;D;D;T;D;D;.;.;D
Eigen	Pathogenic	0.85
Eigen_PC	Pathogenic	0.78
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.97	D;D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.96	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.92	D
MutationAssessor	Pathogenic	3.3	.;.;.;.;.;.;M;.;.;.;.
PhyloP100		7.7
PrimateAI	Pathogenic	0.87	D
PROVEAN	Pathogenic	-6.4	.;.;.;.;D;.;D;.;D;.;.
REVEL	Pathogenic	0.95
Sift	Pathogenic	0.0	.;.;.;.;D;.;D;.;D;.;.
Sift4G	Pathogenic	0.0010	D;D;D;D;D;.;D;D;D;D;D
Polyphen		1.0	D;.;.;.;.;.;D;.;D;D;.
Vest4		0.99
MutPred		0.89		.;.;.;.;.;.;Loss of MoRF binding (P = 0.001);.;.;.;.;
MVP		1.0
MPC		2.0
ClinPred		1.0	D
GERP RS		5.0
Varity_R		0.99
gMVP		1.0
Mutation Taster		=2/98	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.040		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: rs118192235; hg19: chr20-62044824;