Genetic Variant KCNN1:p.Ala218Val (chr19-17981863-C-T) – ACMG Classification: Likely_benign (-2 pts)

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2BP4_Strong

The NM_001386974.1(KCNN1):c.653C>T(p.Ala218Val) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000616 in 1,460,260 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/18 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 0.0000062 ( 0 hom. )

Consequence

KCNN1
NM_001386974.1 missense

Scores

Clinical Significance

Uncertain significance criteria provided, single submitter U:1

Conservation

PhyloP100: 3.14

Variant links:

Genes affected

KCNN1 (HGNC:6290): (potassium calcium-activated channel subfamily N member 1) Action potentials in vertebrate neurons are followed by an afterhyperpolarization (AHP) that may persist for several seconds and may have profound consequences for the firing pattern of the neuron. Each component of the AHP is kinetically distinct and is mediated by different calcium-activated potassium channels. The protein encoded by this gene is activated before membrane hyperpolarization and is thought to regulate neuronal excitability by contributing to the slow component of synaptic AHP. The encoded protein is an integral membrane protein that forms a voltage-independent calcium-activated channel with three other calmodulin-binding subunits. This gene is a member of the KCNN family of potassium channel genes. [provided by RefSeq, Jul 2008]

KCNN1 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Likely_benign. Variant got -2 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (MetaRNN=0.06272116).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KCNN1	NM_001386974.1 link	c.653C>T	p.Ala218Val	missense_variant	Exon 4 of 10	ENST00000684775.1	NP_001373903.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KCNN1	ENST00000684775.1 link	c.653C>T	p.Ala218Val	missense_variant	Exon 4 of 10		NM_001386974.1	ENSP00000507021.1		Q92952-1

Frequencies

GnomAD3 genomes

Cov.:

GnomAD3 exomes

AF:

0.00000407

AC:

AN:

245986

Hom.:

AF XY:

0.00000747

AC XY:

AN XY:

133878

show subpopulations

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:

0.00000901

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000616

AC:

AN:

1460260

Hom.:

Cov.:

AF XY:

0.00000275

AC XY:

AN XY:

726334

show subpopulations

Gnomad4 AFR exome

AF:

0.0000299

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:

0.00000450

Gnomad4 OTH exome

AF:

0.0000332

GnomAD4 genome

Cov.:

Bravo

AF:

0.0000113

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

LINK: link

Submissions by phenotype

not specified

Uncertain:1

Mar 14, 2025

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.653C>T (p.A218V) alteration is located in exon 5 (coding exon 3) of the KCNN1 gene. This alteration results from a C to T substitution at nucleotide position 653, causing the alanine (A) at amino acid position 218 to be replaced by a valine (V). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.064

BayesDel_addAF

Benign

-0.12

BayesDel_noAF

Benign

-0.42

CADD

Benign

DANN

Uncertain

0.99

DEOGEN2

Benign

0.19

T;.

Eigen

Benign

-0.60

Eigen_PC

Benign

-0.44

FATHMM_MKL

Benign

0.49

LIST_S2

Benign

0.83

T;T

M_CAP

Benign

0.0088

MetaRNN

Benign

0.063

T;T

MetaSVM

Benign

-1.0

MutationAssessor

Benign

-0.29

N;.

PrimateAI

Benign

0.39

REVEL

Benign

0.091

Sift4G

Benign

0.53

T;T

Polyphen

0.0010

B;.

Vest4

0.16

MutPred

0.34

Gain of helix (P = 0.0325);Gain of helix (P = 0.0325);

MVP

0.043

MPC

1.6

ClinPred

0.90

GERP RS

3.7

Varity_R

0.033

gMVP

0.69

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.060

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over