NM_020822.3:c.968A>G

Variant names:

• chr9-135759792-A-G
• rs978227077
• NM_020822.3:c.968A>G

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2 BP4

The NM_020822.3(KCNT1):​c.968A>G​(p.Lys323Arg) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,461,154 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 34)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: KCNT1 NM_020822.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:4
• Conservation: PhyloP100: 4.76

Genes affected

KCNT1 (HGNC:18865): (potassium sodium-activated channel subfamily T member 1) Potassium channels represent the most complex class of voltage-gated ion channels from both functional and structural standpoints. Their diverse functions include regulating neurotransmitter release, heart rate, insulin secretion, neuronal excitability, epithelial electrolyte transport, smooth muscle contraction, and cell volume. This gene encodes a sodium-activated potassium channel subunit which is thought to function in ion conductance and developmental signaling pathways. Mutations in this gene cause the early-onset epileptic disorders, malignant migrating partial seizures of infancy and autosomal dominant nocturnal frontal lobe epilepsy. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Dec 2012]

ACMG classification

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.40301666).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNT1	NM_020822.3	c.968A>G	p.Lys323Arg	missense_variant	Exon 11 of 31	ENST00000371757.7	NP_065873.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNT1	ENST00000371757.7	c.968A>G	p.Lys323Arg	missense_variant	Exon 11 of 31	1	NM_020822.3	ENSP00000360822.2

Frequencies

GnomAD3 genomes Cov.: 34

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461154 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 726924

Gnomad4 AFR exome AF: 0.0000598

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 34

Alfa AF: 0.0000712 Hom.: 0

Bravo AF: 0.0000151

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Developmental and epileptic encephalopathy, 14;C3554306:Autosomal dominant nocturnal frontal lobe epilepsy 5 Uncertain:1

Jul 06, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces lysine, which is basic and polar, with arginine, which is basic and polar, at codon 323 of the KCNT1 protein (p.Lys323Arg). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with KCNT1-related conditions. ClinVar contains an entry for this variant (Variation ID: 578621). Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. 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. -

Developmental and epileptic encephalopathy, 14 Uncertain:1

Mar 15, 2022

Genome-Nilou Lab

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not provided Uncertain:1

Dec 03, 2019

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed in large population cohorts (Lek et al., 2016); In silico analysis, which includes protein predictors and evolutionary conservation, supports that this variant does not alter protein structure/function; Has not been previously published as pathogenic or benign to our knowledge -

Autosomal dominant nocturnal frontal lobe epilepsy 5 Uncertain:1

Mar 15, 2022

Genome-Nilou Lab

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.080
BayesDel_addAF	Uncertain	0.15	D
BayesDel_noAF	Uncertain	-0.020
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Benign	0.23	.;.;.;.;.;.;.;.;.;T;.
Eigen	Benign	-0.11
Eigen_PC	Benign	0.083
FATHMM_MKL	Uncertain	0.84	D
LIST_S2	Uncertain	0.90	D;D;D;D;D;D;D;D;D;D;D
M_CAP	Benign	0.068	D
MetaRNN	Benign	0.40	T;T;T;T;T;T;T;T;T;T;T
MetaSVM	Uncertain	0.43	D
MutationAssessor	Benign	0.30	.;.;.;.;.;.;.;.;.;N;.
PrimateAI	Uncertain	0.55	T
PROVEAN	Benign	-1.0	.;.;N;N;N;.;.;.;.;N;N
REVEL	Benign	0.043
Sift	Benign	0.11	.;.;T;T;T;.;.;.;.;T;T
Sift4G	Benign	0.20	T;T;T;T;T;T;T;T;T;T;T
Polyphen		0.0010	.;.;.;.;.;.;.;.;.;B;.
Vest4		0.26
MutPred		0.43		.;.;.;.;.;.;.;Loss of methylation at K304 (P = 0.0177);Loss of methylation at K304 (P = 0.0177);Loss of methylation at K304 (P = 0.0177);Loss of methylation at K304 (P = 0.0177);
MVP		0.80
MPC		0.52
ClinPred		0.79	D
GERP RS		5.0
Varity_R		0.34
gMVP		0.82

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.15		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: rs978227077; hg19: chr9-138651638;