rs1555479000

Positions:

• chr15-73367903-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_005477.3(HCN4):​c.368A>G​(p.His123Arg) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000323 in 1,238,918 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/21 in silico tools predict a benign 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. H123P) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000032 (0 hom.)
• Consequence: HCN4 NM_005477.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 0.584

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 Uncertain_significance. Variant got 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.21485516).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
HCN4	NM_005477.3	c.368A>G	p.His123Arg	missense_variant	1/8	ENST00000261917.4	NP_005468.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
HCN4	ENST00000261917.4	c.368A>G	p.His123Arg	missense_variant	1/8	1	NM_005477.3	ENSP00000261917	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000323 AC: 4 AN: 1238918 Hom.: 0 Cov.: 31 AF XY: 0.00000165 AC XY: 1 AN XY: 607634

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: 0.00000398

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Brugada syndrome 8 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 31, 2023

This sequence change replaces histidine, which is basic and polar, with arginine, which is basic and polar, at codon 123 of the HCN4 protein (p.His123Arg). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with HCN4-related conditions. ClinVar contains an entry for this variant (Variation ID: 470672). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt HCN4 protein function. 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. -

Cardiovascular phenotype Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 18, 2021

The p.H123R variant (also known as c.368A>G), located in coding exon 1 of the HCN4 gene, results from an A to G substitution at nucleotide position 368. The histidine at codon 123 is replaced by arginine, an amino acid with highly similar properties. This amino acid position is well conserved in available vertebrate species; however, arginine is the reference amino acid in other vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.082
BayesDel_addAF	Benign	-0.073	T
BayesDel_noAF	Benign	-0.34
CADD	Benign	18
DANN	Benign	0.62
DEOGEN2	Benign	0.24	T
Eigen	Benign	-0.82
Eigen_PC	Benign	-0.69
FATHMM_MKL	Benign	0.55	D
LIST_S2	Benign	0.62	T
M_CAP	Pathogenic	0.98	D
MetaRNN	Benign	0.21	T
MetaSVM	Uncertain	-0.047	T
MutationAssessor	Benign	0.63	N
MutationTaster	Benign	0.75	N
PrimateAI	Pathogenic	0.94	D
PROVEAN	Benign	-0.31	N
REVEL	Benign	0.19
Sift	Benign	0.21	T
Sift4G	Benign	0.48	T
Polyphen		0.0	B
Vest4		0.093
MutPred		0.20		Gain of methylation at H123 (P = 0.0433);
MVP		0.83
MPC		1.3
ClinPred		0.049	T
GERP RS		0.47
Varity_R		0.11
gMVP		0.30

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: rs1555479000; hg19: chr15-73660244;