9-135772825-C-T

Position:

• chr9-135772825-C-T

Variant summary

Our verdict is Likely benign. Variant got -4 ACMG points: 0P and 4B. BS2

The NM_020822.3(KCNT1):​c.2119C>T​(p.Arg707Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000919 in 1,524,018 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 33)
  • Exomes 𝑓: 0.0000087 (0 hom.)
• Consequence: KCNT1 NM_020822.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.24

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]

KCNT1 (HGNC:):

ACMG classification

Verdict is Likely_benign. Variant got -4 ACMG points.

• BS2: High AC in GnomAdExome4 at 12 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
KCNT1	NM_020822.3	c.2119C>T	p.Arg707Trp	missense_variant	19/31	ENST00000371757.7	NP_065873.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
KCNT1	ENST00000371757.7	c.2119C>T	p.Arg707Trp	missense_variant	19/31	1	NM_020822.3	ENSP00000360822.2

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152214 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000386

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000875 AC: 12 AN: 1371686 Hom.: 0 Cov.: 31 AF XY: 0.0000119 AC XY: 8 AN XY: 674222

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000862

Gnomad4 SAS exome AF: 0.0000133

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000750

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152332 Hom.: 0 Cov.: 33 AF XY: 0.0000269 AC XY: 2 AN XY: 74486

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.000387

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000378

ExAC AF: 0.0000105 AC: 1

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

Labcorp Genetics (formerly Invitae), Labcorp

Oct 17, 2023

This sequence change replaces arginine, which is basic and polar, with tryptophan, which is neutral and slightly polar, at codon 707 of the KCNT1 protein (p.Arg707Trp). The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. 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: 412315). 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) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on 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	Pathogenic	0.83
BayesDel_addAF	Uncertain	0.15	D
BayesDel_noAF	Uncertain	-0.020
CADD	Pathogenic	26
DANN	Pathogenic	1.0
DEOGEN2	Benign	0.42	.;.;.;.;.;.;.;.;T;.
Eigen	Uncertain	0.38
Eigen_PC	Uncertain	0.23
FATHMM_MKL	Benign	0.55	D
LIST_S2	Pathogenic	1.0	D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.33	D
MetaRNN	Uncertain	0.67	D;D;D;D;D;D;D;D;D;D
MetaSVM	Benign	-0.42	T
MutationAssessor	Uncertain	2.9	.;.;.;.;.;.;.;.;M;.
PrimateAI	Pathogenic	0.89	D
PROVEAN	Pathogenic	-6.7	.;.;D;.;.;.;.;.;D;D
REVEL	Uncertain	0.32
Sift	Pathogenic	0.0	.;.;D;.;.;.;.;.;D;D
Sift4G	Pathogenic	0.0	D;D;D;D;D;D;D;D;D;D
Polyphen		1.0	.;.;.;.;.;.;.;.;D;.
Vest4		0.82
MutPred		0.38		.;.;.;.;.;.;Loss of glycosylation at P689 (P = 0.0591);Loss of glycosylation at P689 (P = 0.0591);Loss of glycosylation at P689 (P = 0.0591);.;
MVP		0.69
MPC		1.6
ClinPred		0.87	D
GERP RS		2.9
Varity_R		0.87
gMVP		0.69

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs568144711; hg19: chr9-138664671;