15-73323309-CG-C

Position:

• chr15-73323309-CG-C

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PVS1_Strong PM2

The NM_005477.3(HCN4):​c.2783del​(p.Pro928ArgfsTer57) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000659 in 151,800 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. P928P) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 33)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: HCN4 NM_005477.3 frameshift
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.52

Genes affected

HCN4 (HGNC:16882): (hyperpolarization activated cyclic nucleotide gated potassium channel 4) This gene encodes a member of the hyperpolarization-activated cyclic nucleotide-gated potassium channels. The encoded protein shows slow kinetics of activation and inactivation, and is necessary for the cardiac pacemaking process. This channel may also mediate responses to sour stimuli. Mutations in this gene have been linked to sick sinus syndrome 2, also known as atrial fibrillation with bradyarrhythmia or familial sinus bradycardia. Two pseudogenes have been identified on chromosome 15. [provided by RefSeq, Oct 2008]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.23 CDS is truncated, and there are 0 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
HCN4	NM_005477.3	c.2783del	p.Pro928ArgfsTer57	frameshift_variant	8/8	ENST00000261917.4
HCN4	XM_011521148.3	c.1565del	p.Pro522ArgfsTer57	frameshift_variant	7/7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
HCN4	ENST00000261917.4	c.2783del	p.Pro928ArgfsTer57	frameshift_variant	8/8	1	NM_005477.3	P1

Frequencies

GnomAD3 genomes AF: 0.00000659 AC: 1 AN: 151800 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000242

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1395940 Hom.: 0 Cov.: 35 AF XY: 0.00 AC XY: 0 AN XY: 686516

Gnomad4 AFR exome AF: 0.00

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000659 AC: 1 AN: 151800 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 74140

Gnomad4 AFR AF: 0.0000242

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Cardiovascular phenotype Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 05, 2016

The c.2783delC variant, located in coding exon 8 of the HCN4 gene, results from a deletion of one nucleotide at nucleotide position 2783, causing a translational frameshift with a predicted alternate stop codon (p.P928Rfs*57). This frameshift occurs in the 3' terminal exon of HCN4, and is not expected to trigger nonsense-mediated mRNA decay. Rather, this deletion results in truncation and loss of the C-terminal 277 amino acids of the HCN4 channel. The exact functional impact of the loss of these amino acids is unknown at this time. Frameshift variants are typically deleterious in nature. However, loss of function through HCN4 protein truncation has not been clearly established as a mechanism of disease. Prior studies reporting HCN4 frameshift and splice alterations did not demonstrate that channel truncation was truly pathogenic in the patients in whom the sequence alterations were identified (Ueda K et al. J Hum Genet. 2009;54(2):115-21; Schweizer PA et al. Circ Arrhythm Electrophysiol. 2010;3(5):542-52; Verkerk AO et al. Europace. 2014;16(3):384-95). In addition, this variant was not reported in population-based cohorts in the following databases: Database of Single Nucleotide Polymorphisms (dbSNP), Exome Aggregation Consortium (ExAC), NHLBI Exome Sequencing Project (ESP), and 1000 Genomes Project. In the ESP, this variant was not observed in 5877 samples (11754 alleles) with coverage at this position. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		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: rs1277827477; hg19: chr15-73615650;