12-21765780-C-T

Variant summary

Our verdict is Likely benign. Variant got -1 ACMG points: 3P and 4B. PM2 PP2 BP4_Strong

The NM_004982.4(KCNJ8):c.1218G>A(p.Met406Ile) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 16/21 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)
• Consequence: KCNJ8 NM_004982.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -1.89

Genes affected

KCNJ8 (HGNC:6269): (potassium inwardly rectifying channel subfamily J member 8) Potassium channels are present in most mammalian cells, where they participate in a wide range of physiologic responses. The protein encoded by this gene is an integral membrane protein and inward-rectifier type potassium channel. The encoded protein, which has a greater tendency to allow potassium to flow into a cell rather than out of a cell, is controlled by G-proteins. Defects in this gene may be a cause of J-wave syndromes and sudden infant death syndrome (SIDS). [provided by RefSeq, May 2012]

(HGNC:):

ACMG classification

Verdict is Likely_benign. Variant got -1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, KCNJ8
• BP4: Computational evidence support a benign effect (MetaRNN=0.033014596).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
KCNJ8	NM_004982.4	c.1218G>A	p.Met406Ile	missense_variant	3/3	ENST00000240662.3
LOC105369689	XR_007063241.1	n.631+5695C>T		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
KCNJ8	ENST00000240662.3	c.1218G>A	p.Met406Ile	missense_variant	3/3	1	NM_004982.4	P1
	ENST00000542489.1	n.107-576C>T		intron_variant, non_coding_transcript_variant		3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Brugada syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Oct 08, 2018

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 sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site, but this prediction has not been confirmed by published transcriptional studies. Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Tolerated"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The isoleucine amino acid residue is found in multiple mammalian species, suggesting that this missense change does not adversely affect protein function. These predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant has not been reported in the literature in individuals with KCNJ8-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces methionine with isoleucine at codon 406 of the KCNJ8 protein (p.Met406Ile). The methionine residue is moderately conserved and there is a small physicochemical difference between methionine and isoleucine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.083
BayesDel_addAF	Benign	-0.25	T
BayesDel_noAF	Benign	-0.59
Cadd	Benign	0.015
Dann	Benign	0.75
DEOGEN2	Benign	0.25	T
Eigen	Benign	-1.8
Eigen_PC	Benign	-1.9
FATHMM_MKL	Benign	0.052	N
LIST_S2	Benign	0.62	T
M_CAP	Benign	0.016	T
MetaRNN	Benign	0.033	T
MetaSVM	Benign	-0.93	T
MutationAssessor	Benign	0.0	N
MutationTaster	Benign	1.0	N;N
PrimateAI	Benign	0.38	T
PROVEAN	Benign	-0.18	N
REVEL	Benign	0.17
Sift	Benign	1.0	T
Sift4G	Benign	0.23	T
Polyphen		0.0	B
Vest4		0.054
MutPred		0.34		Gain of sheet (P = 0.0266);
MVP		0.43
MPC		1.1
ClinPred		0.047	T
GERP RS		-12
Varity_R		0.087
gMVP		0.34

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

LitVar

Other links and lift over

dbSNP: rs1591882812; hg19: chr12-21918714;