NM_172107.4:c.829A>G

Variant names:

• chr20-63439696-T-C
• rs1555870554
• NM_172107.4:c.829A>G

Variant summary

Our verdict is Pathogenic. The variant received 15 ACMG points: 15P and 0B. PS3 PM1 PM2 PM5 PP2 PP3_Moderate PP5_Moderate

The NM_172107.4(KCNQ2):​c.829A>G​(p.Thr277Ala) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★). ClinVar reports functional evidence for this variant: "SCV003921867: "Moderate functional evidence supporting abnormal protein function. Transfected cells expressing this variant have been shown to have abolished channel function (PMID 17435769)."". Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T277S) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: KCNQ2 NM_172107.4 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 6.10
• Publications: 2 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: G2P, Orphanet, Labcorp Genetics (formerly Invitae)
• 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
• undetermined early-onset epileptic encephalopathy

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• 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

ACMG classification

Our verdict: Pathogenic. The variant received 15 ACMG points.

• PS3: PS3 evidence extracted from ClinVar submissions: SCV003921867: "Moderate functional evidence supporting abnormal protein function. Transfected cells expressing this variant have been shown to have abolished channel function (PMID 17435769)."
• PM1: In a hotspot region, there are 43 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 chr20-63439696-T-A is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 495250.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 complex neurodevelopmental disorder, developmental and epileptic encephalopathy, 7, neonatal encephalopathy with non-epileptic myoclonus, benign familial infantile epilepsy, malignant migrating partial seizures of infancy, seizures, benign familial neonatal, 1, benign familial neonatal-infantile seizures, benign neonatal seizures, seizures, benign familial neonatal, 2, undetermined early-onset epileptic encephalopathy, neonatal-onset developmental and epileptic encephalopathy.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.88
• PP5: Variant 20-63439696-T-C is Pathogenic according to our data. Variant chr20-63439696-T-C is described in ClinVar as Pathogenic. ClinVar VariationId is 2500737.Status of the report is criteria_provided_single_submitter, 1 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_172107.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNQ2	NM_172107.4	MANE Select	c.829A>G	p.Thr277Ala	missense	Exon 6 of 17	NP_742105.1	O43526-1
	KCNQ2	NM_001382235.1		c.829A>G	p.Thr277Ala	missense	Exon 6 of 17	NP_001369164.1	A0A9L9PXL0
	KCNQ2	NM_172106.3		c.829A>G	p.Thr277Ala	missense	Exon 6 of 16	NP_742104.1	O43526-2

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNQ2	ENST00000359125.7	TSL:1 MANE Select	c.829A>G	p.Thr277Ala	missense	Exon 6 of 17	ENSP00000352035.2	O43526-1
	KCNQ2	ENST00000626839.2	TSL:1	c.829A>G	p.Thr277Ala	missense	Exon 6 of 16	ENSP00000486706.1	O43526-2
	KCNQ2	ENST00000344462.8	TSL:1	c.829A>G	p.Thr277Ala	missense	Exon 6 of 16	ENSP00000339611.4	O43526-4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

ClinVar submissions

Significance: Pathogenic

Revision: criteria provided, single submitter

Pathogenic	VUS	Benign	Condition
1	-	-	Developmental and epileptic encephalopathy, 7 (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.57
CADD	Pathogenic	27
DANN	Uncertain	1.0
Eigen	Uncertain	0.64
Eigen_PC	Uncertain	0.51
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Benign	0.20	T
M_CAP	Pathogenic	0.94	D
MetaRNN	Pathogenic	0.88	D
PhyloP100		6.1
Sift4G	Benign	0.14	T
MVP		0.71
ClinPred		1.0	D
GERP RS		4.0
PromoterAI		0.056	Neutral
Varity_R		0.93
Mutation Taster		=0/100	disease causing

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

Other links and lift over

dbSNP: rs1555870554; hg19: chr20-62071049;