9-135784058-T-C

Position:

• chr9-135784058-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_020822.3(KCNT1):​c.2876T>C​(p.Met959Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000206 in 1,453,632 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 (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: KCNT1 NM_020822.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:4
• Conservation: PhyloP100: 7.76

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 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.826

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
KCNT1	NM_020822.3	c.2876T>C	p.Met959Thr	missense_variant	25/31	ENST00000371757.7	NP_065873.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
KCNT1	ENST00000371757.7	c.2876T>C	p.Met959Thr	missense_variant	25/31	1	NM_020822.3	ENSP00000360822	A2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000411 AC: 1 AN: 243558 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 132680

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: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000887

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000206 AC: 3 AN: 1453632 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 723504

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Athena Diagnostics

Feb 24, 2017

- -

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

Dec 31, 2022

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. 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 expected to disrupt KCNT1 protein function. ClinVar contains an entry for this variant (Variation ID: 447647). This missense change has been observed in at least one individual who was not affected with KCNT1-related conditions (Invitae). This variant has not been reported in the literature in individuals affected with KCNT1-related conditions. This variant is present in population databases (no rsID available, gnomAD 0.0009%). This sequence change replaces methionine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 959 of the KCNT1 protein (p.Met959Thr). -

Developmental and epileptic encephalopathy, 14 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Genome-Nilou Lab

Mar 15, 2022

- -

Autosomal dominant nocturnal frontal lobe epilepsy 5 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Genome-Nilou Lab

Mar 15, 2022

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.37	D
BayesDel_noAF	Pathogenic	0.30
CADD	Uncertain	24
DANN	Uncertain	0.98
DEOGEN2	Benign	0.40	.;.;.;.;.;.;.;.;T;.
Eigen	Benign	0.14
Eigen_PC	Uncertain	0.24
FATHMM_MKL	Uncertain	0.92	D
LIST_S2	Pathogenic	0.98	D;D;D;D;D;D;D;D;D;D
M_CAP	Uncertain	0.17	D
MetaRNN	Pathogenic	0.83	D;D;D;D;D;D;D;D;D;D
MetaSVM	Benign	-0.36	T
MutationAssessor	Uncertain	2.4	.;.;.;.;.;.;.;.;M;.
MutationTaster	Benign	1.0	D;D;D;D;D;D;D;D
PrimateAI	Pathogenic	0.92	D
PROVEAN	Pathogenic	-5.2	.;.;D;.;.;.;.;.;D;D
REVEL	Pathogenic	0.80
Sift	Uncertain	0.0010	.;.;D;.;.;.;.;.;D;D
Sift4G	Pathogenic	0.0010	D;D;D;D;D;D;D;D;D;D
Polyphen		0.14	.;.;.;.;.;.;.;.;B;.
Vest4		0.96
MutPred		0.54		.;.;.;.;.;.;Gain of sheet (P = 0.0028);Gain of sheet (P = 0.0028);Gain of sheet (P = 0.0028);.;
MVP		0.66
MPC		1.1
ClinPred		0.96	D
GERP RS		4.5
Varity_R		0.85
gMVP		0.99

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: rs1318262895; hg19: chr9-138675904;