chr20-63433905-T-C

Variant names:

• chr20-63433905-T-C
• rs1057516104
• NM_172107.4:c.1024-2A>G

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PVS1 PM2

The NM_172107.4(KCNQ2):​c.1024-2A>G variant causes a splice acceptor, intron change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as not provided (no stars).

• Frequency: Genomes: not found (cov: 33)
• Consequence: KCNQ2 NM_172107.4 splice_acceptor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: not provided no classification provided O:1
• Conservation: PhyloP100: 5.59

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 Pathogenic. Variant got 10 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 6.5, offset of 40, new splice context is: caccaacctctcgcgcacAGacc. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.1024-2A>G		splice_acceptor_variant, intron_variant	Intron 7 of 16	ENST00000359125.7	NP_742105.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNQ2	ENST00000359125.7	c.1024-2A>G		splice_acceptor_variant, intron_variant	Intron 7 of 16	1	NM_172107.4	ENSP00000352035.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: not provided

Submissions summary: Other:1

Revision: no classification provided

Submissions by phenotype

Developmental and epileptic encephalopathy, 7 Other:1

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GeneReviews

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

Sequenced in a proband with epileptic encephalopathy. Parental sequencing was not reported (therefore unknown if de novo or inherited). However, splicing defects are associated with Benign Familial Neonatal Epilepsy, therefore the contribution to the observed phenotype is likely to be partial. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Uncertain	0.060
CADD	Pathogenic	28
DANN	Uncertain	0.99
Eigen	Pathogenic	0.90
Eigen_PC	Pathogenic	0.69
FATHMM_MKL	Pathogenic	0.99	D
GERP RS		4.9

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.99		Position offset: -2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs1057516104; hg19: chr20-62065258;