Genetic Variant KCNT1:p.Ala897Ala (chr9-135778784-G-A) – ACMG Classification: Benign (-21 pts)

Variant summary

Our verdict is Benign. The variant received -21 ACMG points: 0P and 21B. BP4_StrongBP6_Very_StrongBP7BS1BS2

The NM_020822.3(KCNT1):c.2691G>A(p.Ala897Ala) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000632 in 1,613,736 control chromosomes in the GnomAD database, including 2 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Likely benign (★★).

Frequency

Genomes: 𝑓 0.00038 ( 0 hom., cov: 33)

Exomes 𝑓: 0.00066 ( 2 hom. )

Consequence

KCNT1
NM_020822.3 synonymous

Scores

Clinical Significance

Benign/Likely benign criteria provided, multiple submitters, no conflicts B:6

Conservation

PhyloP100: -2.27

Publications

1 publications found

Variant links:

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 Gene-Disease associations (from GenCC):

childhood-onset epilepsy syndrome
Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
developmental and epileptic encephalopathy, 14
Inheritance: AD Classification: DEFINITIVE, STRONG, MODERATE Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics, G2P
malignant migrating partial seizures of infancy
Inheritance: AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: G2P, Orphanet
autosomal dominant nocturnal frontal lobe epilepsy 5
Inheritance: AD Classification: STRONG, MODERATE Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)
autosomal dominant nocturnal frontal lobe epilepsy
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

KCNT1 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Benign. The variant received -21 ACMG points.

BP4

Computational evidence support a benign effect (BayesDel_noAF=-0.61).

BP6

Variant 9-135778784-G-A is Benign according to our data. Variant chr9-135778784-G-A is described in ClinVar as Benign/Likely_benign. ClinVar VariationId is 383085.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

BP7

Synonymous conserved (PhyloP=-2.27 with no splicing effect.

BS1

Variant frequency is greater than expected in population sas. GnomAd4 allele frequency = 0.000381 (58/152286) while in subpopulation SAS AF = 0.000827 (4/4834). AF 95% confidence interval is 0.000495. There are 0 homozygotes in GnomAd4. There are 20 alleles in the male GnomAd4 subpopulation. Median coverage is 33. This position passed quality control check.

BS2

High AC in GnomAd4 at 58 AD gene.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_020822.3. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNT1	NM_020822.3	MANE Select	c.2691G>A	p.Ala897Ala	synonymous	Exon 23 of 31	NP_065873.2
	KCNT1	NM_001272003.2		c.2556G>A	p.Ala852Ala	synonymous	Exon 22 of 31	NP_001258932.1

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
KCNT1	ENST00000371757.7	TSL:1 MANE Select	c.2691G>A	p.Ala897Ala	synonymous	Exon 23 of 31	ENSP00000360822.2
KCNT1	ENST00000460750.5	TSL:1	n.*2301G>A		non_coding_transcript_exon	Exon 23 of 32	ENSP00000418777.1
KCNT1	ENST00000460750.5	TSL:1	n.*2301G>A		3_prime_UTR	Exon 23 of 32	ENSP00000418777.1

Frequencies

GnomAD3 genomes

AF:

0.000368

AC:

AN:

152168

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000966

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.000770

Gnomad SAS

AF:

0.000827

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.000647

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.000319

AC:

AN:

250948

AF XY:

0.000383

show subpopulations

Gnomad AFR exome

AF:

0.0000616

Gnomad AMR exome

AF:

0.0000579

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00131

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.000335

Gnomad OTH exome

AF:

0.000163

GnomAD4 exome

AF:

0.000658

AC:

962

AN:

1461450

Hom.:

Cov.:

AF XY:

0.000641

AC XY:

466

AN XY:

727058

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33474

American (AMR)

AF:

0.000157

AC:

AN:

44714

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26116

East Asian (EAS)

AF:

0.000605

AC:

AN:

39682

South Asian (SAS)

AF:

0.000557

AC:

AN:

86248

European-Finnish (FIN)

AF:

0.0000188

AC:

AN:

53288

Middle Eastern (MID)

AF:

0.000347

AC:

AN:

5766

European-Non Finnish (NFE)

AF:

0.000721

AC:

802

AN:

1111790

Other (OTH)

AF:

0.00129

AC:

AN:

60372

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.468

Heterozygous variant carriers

121

182

242

303

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Exome Hom

Variant carriers

114

152

190

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.000381

AC:

AN:

152286

Hom.:

Cov.:

AF XY:

0.000269

AC XY:

AN XY:

74462

show subpopulations

African (AFR)

AF:

0.000144

AC:

AN:

41546

American (AMR)

AF:

0.00

AC:

AN:

15306

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.000772

AC:

AN:

5184

South Asian (SAS)

AF:

0.000827

AC:

AN:

4834

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10622

Middle Eastern (MID)

AF:

0.00

AC:

AN:

294

European-Non Finnish (NFE)

AF:

0.000647

AC:

AN:

68008

Other (OTH)

AF:

0.00

AC:

AN:

2110

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.501

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.000458

Hom.:

Bravo

AF:

0.000389

Asia WGS

AF:

0.000289

AC:

AN:

3478

EpiCase

AF:

0.000763

EpiControl

AF:

0.000356

ClinVar

Significance: Benign/Likely benign

Submissions summary: Benign:6

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not provided

Benign:2

Oct 11, 2021

GeneDx

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Jun 01, 2025

CeGaT Center for Human Genetics Tuebingen

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

KCNT1: BP4, BP7

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

Benign:1

Feb 02, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Inborn genetic diseases

Benign:1

Aug 30, 2017

Ambry Genetics

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity.

Developmental and epileptic encephalopathy, 14

Benign:1

Mar 15, 2022

Genome-Nilou Lab

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Autosomal dominant nocturnal frontal lobe epilepsy 5

Benign:1

Mar 15, 2022

Genome-Nilou Lab

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Computational scores

Source: dbNSFP v4.9

Name

Calibrated prediction

Score

Prediction

BayesDel_noAF

Benign

-0.61

CADD

Benign

9.1

(source)

DANN

Benign

0.86

PhyloP100

-2.3

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over