rs778647834

Positions:

• chr9-135778788-G-A

Variant summary

Our verdict is Likely benign. Variant got -1 ACMG points: 3P and 4B. PM1 PP3 BS2

The NM_020822.3(KCNT1):​c.2695G>A​(p.Ala899Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000753 in 1,461,602 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic 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. A899S) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000075 (0 hom.)
• Consequence: KCNT1 NM_020822.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 9.65

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 Likely_benign. Variant got -1 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_020822.3
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.749
• BS2: High AC in GnomAdExome4 at 11 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
KCNT1	NM_020822.3	c.2695G>A	p.Ala899Thr	missense_variant	23/31	ENST00000371757.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
KCNT1	ENST00000371757.7	c.2695G>A	p.Ala899Thr	missense_variant	23/31	1	NM_020822.3	A2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000399 AC: 1 AN: 250940 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135758

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: 0.0000327

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000753 AC: 11 AN: 1461602 Hom.: 0 Cov.: 33 AF XY: 0.00000688 AC XY: 5 AN XY: 727134

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: 0.0000232

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000809

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

Bravo AF: 0.00000378

ExAC AF: 0.00000824 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

Invitae

Jul 07, 2023

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. ClinVar contains an entry for this variant (Variation ID: 412309). This variant has not been reported in the literature in individuals affected with KCNT1-related conditions. This variant is present in population databases (rs778647834, gnomAD 0.003%). This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 899 of the KCNT1 protein (p.Ala899Thr). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.93
BayesDel_addAF	Uncertain	0.12	D
BayesDel_noAF	Uncertain	0.040
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Benign	0.28	.;.;.;.;.;.;.;.;T;.
Eigen	Uncertain	0.52
Eigen_PC	Uncertain	0.55
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	1.0	D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.35	D
MetaRNN	Pathogenic	0.75	D;D;D;D;D;D;D;D;D;D
MetaSVM	Uncertain	-0.011	T
MutationAssessor	Uncertain	2.5	.;.;.;.;.;.;.;.;M;.
MutationTaster	Benign	1.0	D;D;D;D;D;D;D;D
PrimateAI	Pathogenic	0.82	D
PROVEAN	Uncertain	-2.4	.;.;N;.;.;.;.;.;N;N
REVEL	Uncertain	0.57
Sift	Uncertain	0.016	.;.;D;.;.;.;.;.;D;D
Sift4G	Uncertain	0.015	D;D;D;D;D;D;D;D;D;D
Polyphen		0.53	.;.;.;.;.;.;.;.;P;.
Vest4		0.84
MutPred		0.29		.;.;.;.;.;.;Loss of helix (P = 0.079);Loss of helix (P = 0.079);Loss of helix (P = 0.079);.;
MVP		0.84
MPC		0.72
ClinPred		0.93	D
GERP RS		4.5
Varity_R		0.27
gMVP		0.94

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: rs778647834; hg19: chr9-138670634; COSMIC: COSV53702134;