7-150947386-G-GACCC

Position:

• chr7-150947386-G-GACCC

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000238.4(KCNH2):​c.3093_3094insGGGT​(p.Arg1032GlyfsTer88) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 33)
• Consequence: KCNH2 NM_000238.4 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 0.608

Genes affected

KCNH2 (HGNC:6251): (potassium voltage-gated channel subfamily H member 2) This gene encodes a component of a voltage-activated potassium channel found in cardiac muscle, nerve cells, and microglia. Four copies of this protein interact with one copy of the KCNE2 protein to form a functional potassium channel. Mutations in this gene can cause long QT syndrome type 2 (LQT2). Transcript variants encoding distinct isoforms have been identified. [provided by RefSeq, May 2022]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 7-150947386-G-GACCC is Pathogenic according to our data. Variant chr7-150947386-G-GACCC is described in ClinVar as [Likely_pathogenic]. Clinvar id is 519348.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
KCNH2	NM_000238.4	c.3093_3094insGGGT	p.Arg1032GlyfsTer88	frameshift_variant	13/15	ENST00000262186.10	NP_000229.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
KCNH2	ENST00000262186.10	c.3093_3094insGGGT	p.Arg1032GlyfsTer88	frameshift_variant	13/15	1	NM_000238.4	ENSP00000262186	P1
KCNH2	ENST00000330883.9	c.2073_2074insGGGT	p.Arg692GlyfsTer88	frameshift_variant	9/11	1		ENSP00000328531
KCNH2	ENST00000684241.1	n.3926_3927insGGGT		non_coding_transcript_exon_variant	11/13

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 36

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Aug 01, 2023

Reported in a patient referred for Long QT syndrome genetic testing (Kapplinger et al., 2009); Not observed at significant frequency in large population cohorts (gnomAD); Frameshift variant predicted to result in protein truncation, as the last 128 amino acids are replaced with 87 different amino acids, and other loss-of-function variants have been reported downstream in HGMD; This variant is associated with the following publications: (PMID: 19716085) -

Long QT syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 31, 2021

This variant disrupts the C-terminus of the KCNH2 protein. Other variant(s) that disrupt this region (p.Pro1086Alafs*33) have been determined to be pathogenic (Invitae). This suggests that variants that disrupt this region of the protein are likely to be causative of disease. For these reasons, this variant has been classified as Pathogenic. This variant has been observed in individual(s) with clinical features of long QT syndrome (PMID: 19716085). ClinVar contains an entry for this variant (Variation ID: 519348). This variant is also described as 3093dupGGGT (G1031fs+87X*) in the literature. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate insufficient coverage at this position in the ExAC database. This sequence change creates a premature translational stop signal (p.Arg1032Glyfs*88) in the KCNH2 gene. While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 128 amino acid(s) of the KCNH2 protein. -

Cardiovascular phenotype Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Dec 20, 2017

The c.3090_3093dupGGGT pathogenic mutation, located in coding exon 13 of the KCNH2 gene, results from a duplication of GGGT at nucleotide position 3090, causing a translational frameshift with a predicted alternate stop codon (p.R1032Gfs*88). In a study of long QT syndrome clinical genetic testing, this alteration was reported in one patient, though clinical details were limited (Kapplinger JD et al. Heart Rhythm. 2009;6:1297-303). In addition, similar C-terminal frameshift alterations have been reported in association with long QT syndrome (LQTS) in the literature, and functional studies have indicated that several of those alterations result in truncated proteins with deficient function (e.g., Sasano T et al. J. Mol. Cell. Cardiol. 2004;37:1205-11; Mihic A et al. PLoS ONE. 2011;6:e18273). This alteration is therefore expected to result in loss of function by premature protein truncation. As such, this alteration is interpreted as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs1554424091; hg19: chr7-150644474;