rs756921902

chr20-63439639-T-Cchr20-63439639-T-G

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 7P and 1B. PM1 PM2 PM5 PP2 BP4

The NM_172107.4(KCNQ2):c.886A>G(p.Thr296Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,360 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 8/13 in silico tools predict a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T296P) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 3.31

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.

• PM1: In a hotspot region, there are 9 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
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr20-63439639-T-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 369769.Status of the report is no_assertion_criteria_provided, 0 stars.
• PP2: Missense variant where missense usually causes diseases, KCNQ2
• BP4: Computational evidence support a benign effect (MetaRNN=0.33319694).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
KCNQ2	NM_172107.4	c.886A>G	p.Thr296Ala	missense_variant	6/17	ENST00000359125.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
KCNQ2	ENST00000359125.7	c.886A>G	p.Thr296Ala	missense_variant	6/17	1	NM_172107.4	A1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 250950 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135872

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: 0.00000882

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461360 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 726998

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000824 AC: 1

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Benign	-0.22	T
BayesDel_noAF	Uncertain	-0.040
Cadd	Benign	22
Dann	Benign	0.26
Eigen	Benign	-0.51
Eigen_PC	Benign	-0.38
FATHMM_MKL	Uncertain	0.80	D
LIST_S2	Benign	0.28	T
M_CAP	Pathogenic	0.60	D
MetaRNN	Benign	0.33	T
MutationTaster	Benign	0.99	D;D;D;D;D;D;D;D;D;D;D;D
Sift4G	Benign	0.083	T
MVP		0.40
ClinPred		0.16	T
GERP RS		4.0

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: rs756921902; hg19: chr20-62070992;