rs747671066

chr9-135771033-C-Gchr9-135771033-C-T

Variant summary

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

The NM_020822.3(KCNT1):c.1946C>G(p.Ser649Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 12/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. S649L) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 33)
• Consequence: KCNT1 NM_020822.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.303

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=0.2808944).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
KCNT1	NM_020822.3	c.1946C>G	p.Ser649Trp	missense_variant	18/31	ENST00000371757.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
KCNT1	ENST00000371757.7	c.1946C>G	p.Ser649Trp	missense_variant	18/31	1	NM_020822.3	A2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

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

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Sep 10, 2023

This variant has not been reported in the literature in individuals affected with KCNT1-related conditions. This sequence change replaces serine, which is neutral and polar, with tryptophan, which is neutral and slightly polar, at codon 649 of the KCNT1 protein (p.Ser649Trp). This variant is not present in population databases (gnomAD no frequency). ClinVar contains an entry for this variant (Variation ID: 1008322). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt KCNT1 protein function. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Benign	-0.18	T
BayesDel_noAF	Benign	-0.49
Cadd	Benign	15
Dann	Uncertain	0.99
Eigen	Benign	-0.51
Eigen_PC	Benign	-0.68
FATHMM_MKL	Benign	0.11	N
LIST_S2	Uncertain	0.89	D;D;D;D;D;D;D;D;D;D
M_CAP	Uncertain	0.20	D
MetaRNN	Benign	0.28	T;T;T;T;T;T;T;T;T;T
MetaSVM	Benign	-1.0	T
MutationTaster	Benign	1.0	N;N;N;N;N;N;N;N
PrimateAI	Benign	0.43	T
REVEL	Benign	0.047
Sift4G	Uncertain	0.038	D;D;D;D;D;D;D;D;D;D
Polyphen		0.86	.;.;.;.;.;.;.;.;P;.
Vest4		0.34
MutPred		0.48		.;.;.;.;.;.;Loss of disorder (P = 1e-04);Loss of disorder (P = 1e-04);Loss of disorder (P = 1e-04);Loss of disorder (P = 1e-04);
MVP		0.51
MPC		1.5
ClinPred		0.50	D
GERP RS		1.6
Varity_R		0.083
gMVP		0.49

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: rs747671066; hg19: chr9-138662879;