20-63406665-GC-G

Position:

• chr20-63406665-GC-G

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM2 PM4 PP5_Moderate

The NM_172107.4(KCNQ2):​c.2597del​(p.Gly866AlafsTer64) variant causes a frameshift 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 Pathogenic (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: KCNQ2 NM_172107.4 frameshift
• Clinical Significance: Pathogenic criteria provided, single submitter P:1 O:1
• Conservation: PhyloP100: 3.07

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]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM4: Frameshift in the end of transcript resulting in stoplost. Downstream stopcodon found after 873 codons.
• PP5: Variant 20-63406665-GC-G is Pathogenic according to our data. Variant chr20-63406665-GC-G is described in ClinVar as [Pathogenic]. Clinvar id is 21781.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.2597del	p.Gly866AlafsTer64	frameshift_variant	17/17	ENST00000359125.7	NP_742105.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
KCNQ2	ENST00000359125.7	c.2597del	p.Gly866AlafsTer64	frameshift_variant	17/17	1	NM_172107.4	ENSP00000352035	A1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 30

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

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Mar 08, 2019

The c.2597delG pathogenic variant in the KCNQ2 gene, reported as c.2513delG due to use of alternative nomenclature, has been identified in multiple individuals in a single family with benign familial neonatal seizures (Lerche et al., 1999). The deletion causes a frameshift starting with codon Glycine 866, changes this amino acid to an Alanine residue and creates a premature Stop codon at position 64 of the new reading frame, denoted p.Gly866AlafsX64. This pathogenic variant is predicted to cause loss of normal protein function either through protein truncation or nonsense-mediated mRNA decay. Functional studies suggest that c.2597delG has a damaging effect on the protein (Lerche et al., 1999; Su et al., 2011). -

Seizures, benign familial neonatal, 1 Other:1

not provided, no classification provided

literature only

GeneReviews

-

BFNE (benign familial neonatal epilepsy) -

Computational scores

Source: dbNSFP v4.3

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

Publications

LitVar

Other links and lift over

dbSNP: rs118192245; hg19: chr20-62038018;