rs772971971

Variant names:

• chr20-63407378-G-A
• rs772971971
• NM_172107.4:c.1888-3C>T

Variant summary

Our verdict is Benign. Variant got -8 ACMG points: 0P and 8B. BP4_Strong BS2

The NM_172107.4(KCNQ2):​c.1888-3C>T variant causes a splice region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000288 in 1,597,662 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 2/2 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: 𝑓 0.000039 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000028 (0 hom.)
• Consequence: KCNQ2 NM_172107.4 splice_region, intron
• Scores: Splicing: ADA: 0.3551
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 0.766

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 Benign. Variant got -8 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.79).
• BS2: High AC in GnomAd4 at 6 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNQ2	NM_172107.4	c.1888-3C>T		splice_region_variant, intron_variant	Intron 16 of 16	ENST00000359125.7	NP_742105.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNQ2	ENST00000359125.7	c.1888-3C>T		splice_region_variant, intron_variant	Intron 16 of 16	1	NM_172107.4	ENSP00000352035.2

Frequencies

GnomAD3 genomes AF: 0.0000394 AC: 6 AN: 152254 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000482

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000588

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000213 AC: 5 AN: 234416 Hom.: 0 AF XY: 0.0000233 AC XY: 3 AN XY: 128804

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000458

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000277 AC: 40 AN: 1445408 Hom.: 0 Cov.: 36 AF XY: 0.0000278 AC XY: 20 AN XY: 719296

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000342

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome AF: 0.0000394 AC: 6 AN: 152254 Hom.: 0 Cov.: 33 AF XY: 0.0000269 AC XY: 2 AN XY: 74388

Gnomad4 AFR AF: 0.0000482

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000588

Gnomad4 OTH AF: 0.00

Bravo AF: 0.0000264

EpiCase AF: 0.0000545

EpiControl AF: 0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Uncertain:1

Jan 05, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change falls in intron 16 of the KCNQ2 gene. It does not directly change the encoded amino acid sequence of the KCNQ2 protein. It affects a nucleotide within the consensus splice site. This variant is present in population databases (rs772971971, gnomAD 0.006%). This variant has not been reported in the literature in individuals affected with KCNQ2-related conditions. ClinVar contains an entry for this variant (Variation ID: 283738). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant is not likely to affect RNA splicing. 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. -

not provided Uncertain:1

Oct 12, 2015

Eurofins Ntd Llc (ga)

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Seizures, benign familial neonatal, 1;C3150986:Developmental and epileptic encephalopathy, 7 Uncertain:1

Oct 31, 2018

Fulgent Genetics, Fulgent Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.79
CADD	Benign	11
DANN	Benign	0.57

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.36
SpliceAI score (max)		0.060		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: rs772971971; hg19: chr20-62038731;