chr9-135757376-A-C

Variant names:

• chr9-135757376-A-C
• rs755782470
• NM_020822.3:c.754A>C

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_020822.3(KCNT1):​c.754A>C​(p.Met252Leu) variant causes a missense change. The variant allele was found at a frequency of 0.00000249 in 1,607,974 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: 31)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: KCNT1 NM_020822.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.77

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 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNT1	NM_020822.3	c.754A>C	p.Met252Leu	missense_variant	Exon 9 of 31	ENST00000371757.7	NP_065873.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNT1	ENST00000371757.7	c.754A>C	p.Met252Leu	missense_variant	Exon 9 of 31	1	NM_020822.3	ENSP00000360822.2

Frequencies

GnomAD3 genomes AF: 0.0000132 AC: 2 AN: 151754 Hom.: 0 Cov.: 31

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000294

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.00000406 AC: 1 AN: 246126 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 133894

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: 0.00000137 AC: 2 AN: 1456220 Hom.: 0 Cov.: 36 AF XY: 0.00000138 AC XY: 1 AN XY: 724720

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: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0000132 AC: 2 AN: 151754 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 74078

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000294

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000756

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

Mar 09, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. This sequence change replaces methionine, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 252 of the KCNT1 protein (p.Met252Leu). 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: 1513535). 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.36
BayesDel_addAF	Pathogenic	0.39	D
BayesDel_noAF	Pathogenic	0.33
CADD	Uncertain	24
DANN	Benign	0.96
DEOGEN2	Benign	0.28	.;.;.;.;.;.;.;.;.;T;.
Eigen	Benign	0.0027
Eigen_PC	Benign	0.13
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.96	D;D;D;D;D;D;D;D;D;D;D
M_CAP	Uncertain	0.13	D
MetaRNN	Uncertain	0.63	D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Uncertain	0.61	D
MutationAssessor	Uncertain	2.2	.;.;.;.;.;.;.;.;.;M;.
PrimateAI	Pathogenic	0.85	D
PROVEAN	Uncertain	-2.4	.;.;N;D;N;.;.;.;.;N;N
REVEL	Uncertain	0.29
Sift	Benign	0.056	.;.;T;T;T;.;.;.;.;T;T
Sift4G	Uncertain	0.031	D;D;D;T;D;D;D;D;D;D;D
Polyphen		0.0	.;.;.;.;.;.;.;.;.;B;.
Vest4		0.64
MutPred		0.48		.;.;.;.;.;.;.;Loss of stability (P = 0.2237);Loss of stability (P = 0.2237);Loss of stability (P = 0.2237);Loss of stability (P = 0.2237);
MVP		0.81
MPC		0.61
ClinPred		0.95	D
GERP RS		4.6
Varity_R		0.59
gMVP		0.91

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: rs755782470; hg19: chr9-138649222;