chr1-110604539-G-A

Variant names:

• chr1-110604539-G-A
• rs1433727837
• NM_004974.4:c.244C>T

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM2 PP3_Strong

The NM_004974.4(KCNA2):​c.244C>T​(p.Arg82Cys) variant causes a missense change. The variant allele was found at a frequency of 0.00000274 in 1,461,890 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. R82H) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: KCNA2 NM_004974.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 5.08
• Publications: 2 publications found

Genes affected

KCNA2 (HGNC:6220): (potassium voltage-gated channel subfamily A member 2) 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. Four sequence-related potassium channel genes - shaker, shaw, shab, and shal - have been identified in Drosophila, and each has been shown to have human homolog(s). This gene encodes a member of the potassium channel, voltage-gated, shaker-related subfamily. This member contains six membrane-spanning domains with a shaker-type repeat in the fourth segment. It belongs to the delayed rectifier class, members of which allow nerve cells to efficiently repolarize following an action potential. The coding region of this gene is intronless, and the gene is clustered with genes KCNA3 and KCNA10 on chromosome 1. [provided by RefSeq, Jul 2008]

KCNA2 Gene-Disease associations (from GenCC):

• developmental and epileptic encephalopathy, 32

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P
• genetic developmental and epileptic encephalopathy

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• undetermined early-onset epileptic encephalopathy

  Inheritance: AD Classification: STRONG, SUPPORTIVE Submitted by: ClinGen, Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.974

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_004974.4. 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
	KCNA2	NM_004974.4	MANE Select	c.244C>T	p.Arg82Cys	missense	Exon 3 of 3	NP_004965.1
	KCNA2	NM_001204269.2		c.244C>T	p.Arg82Cys	missense	Exon 3 of 5	NP_001191198.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	KCNA2	ENST00000316361.10	TSL:2 MANE Select	c.244C>T	p.Arg82Cys	missense	Exon 3 of 3	ENSP00000314520.4
	KCNA2	ENST00000369770.7	TSL:1	c.244C>T	p.Arg82Cys	missense	Exon 3 of 5	ENSP00000358785.3
	KCNA2	ENST00000485317.6	TSL:5	c.244C>T	p.Arg82Cys	missense	Exon 3 of 3	ENSP00000433109.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000398 AC: 1 AN: 251442 AF XY: 0.00000736

Gnomad AFR exome AF: 0.0000616

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461890 Hom.: 0 Cov.: 34 AF XY: 0.00000413 AC XY: 3 AN XY: 727246

African (AFR) AF: 0.0000299 AC: 1 AN: 33478

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.0000187 AC: 1 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1112010

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Developmental and epileptic encephalopathy, 32 Uncertain:1

Jun 13, 2022

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. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. ClinVar contains an entry for this variant (Variation ID: 542665). This variant has not been reported in the literature in individuals affected with KCNA2-related conditions. This variant is present in population databases (no rsID available, gnomAD 0.007%). This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 82 of the KCNA2 protein (p.Arg82Cys).

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.22	D
BayesDel_noAF	Pathogenic	0.26
CADD	Pathogenic	33
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.95	D
Eigen	Pathogenic	0.84
Eigen_PC	Pathogenic	0.75
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Uncertain	0.27	D
MetaRNN	Pathogenic	0.97	D
MetaSVM	Uncertain	0.48	D
MutationAssessor	Pathogenic	4.0	H
PhyloP100		5.1
PrimateAI	Pathogenic	0.92	D
PROVEAN	Pathogenic	-6.9	D
REVEL	Pathogenic	0.79
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.77
MutPred		0.90		Gain of catalytic residue at R80 (P = 0.0618)
MVP		0.94
MPC		2.7
ClinPred		1.0	D
GERP RS		4.8
Varity_R		0.69
gMVP		0.92
Mutation Taster		=34/66	disease causing

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

Other links and lift over

dbSNP: rs1433727837; hg19: chr1-111147161; COSMIC: COSV60369380;