HCN4 Gene: Structure, Function, and Clinical Significance
A comprehensive guide to the HCN4 gene, its role in cardiac pacemaking, associated diseases, and mutation spectrum.
Gene Information Card
| Symbol | HCN4 |
|---|---|
| Full Name | Hyperpolarization Activated Cyclic Nucleotide Gated Potassium Channel 4 |
| Gene Type | Protein coding |
| Chromosomal Location | 15q24.1 |
| NCBI Gene ID | 10021 ncbi.nlm.nih.gov/gene/10021 |
| Ensembl ID | ENSG00000138622 |
| UniProt ID | Q9Y3Q4 |
| OMIM ID | 605206 |
| HGNC ID | 16870 |
| Aliases | HCN4, SSS2, I(f) channel, HCN4b |
Description
The HCN4 gene encodes the hyperpolarization-activated cyclic nucleotide-gated potassium channel 4, a key component of the cardiac pacemaker 'funny' current (I(f)). This channel is activated by hyperpolarization and modulated by cyclic nucleotides, playing a critical role in the generation and regulation of spontaneous rhythmic activity in the sinoatrial node. HCN4 is also expressed in other tissues, including the brain, where it contributes to neuronal excitability. Mutations in HCN4 are associated with various cardiac arrhythmias, including sick sinus syndrome and bradycardia.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Sick Sinus Syndrome 2 (SSS2) | Loss-of-function mutations reduce the I(f) current, impairing sinoatrial node automaticity and leading to bradycardia and sinus pauses. | ClinVar, OMIM (605206) |
| Bradycardia | Both loss-of-function and gain-of-function mutations can disrupt heart rate regulation; loss-of-function reduces pacemaker activity, while gain-of-function may cause inappropriate tachycardia or atrial fibrillation. | ClinVar, OMIM |
| Atrial Fibrillation | Gain-of-function mutations in HCN4 have been linked to familial atrial fibrillation, possibly by increasing automaticity in atrial tissue. | ClinVar, OMIM |
| Left Ventricular Noncompaction (LVNC) | Some HCN4 mutations are associated with LVNC, a cardiomyopathy, though the mechanism is less clear; may involve altered calcium handling or developmental defects. | ClinVar, OMIM |
| Ventricular Tachycardia | Rare variants may predispose to ventricular arrhythmias, but evidence is limited. | ClinVar |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Heart | High (nTPM ~ 100) | High |
| Brain | Moderate (nTPM ~ 20-30) | Moderate |
| Skeletal Muscle | Low (nTPM ~ 5) | Low |
| Liver | Not detected | Not detected |
| Kidney | Low (nTPM ~ 2) | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| Sinoatrial node cells | High | Primary site of expression; critical for pacemaking. |
| Ventricular cardiomyocytes | Low | Low expression in adult ventricles; may be upregulated in disease. |
| Neurons (hippocampus) | Moderate | Contributes to rhythmic firing. |
| HEK293 (overexpression) | High | Used for functional studies. |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.451C>T (p.Arg151Trp) | Missense | Rare | Loss-of-function; associated with sick sinus syndrome. |
| c.1441G>A (p.Gly481Arg) | Missense | Rare | Gain-of-function; linked to atrial fibrillation. |
| c.1748T>C (p.Ile583Thr) | Missense | Rare | Loss-of-function; causes bradycardia. |
| c.2148G>A (p.Met716Ile) | Missense | Rare | Loss-of-function; associated with LVNC. |
| c.1000C>T (p.Arg334Trp) | Missense | Rare | Loss-of-function; reduces I(f) current. |
Mutation functional classification
Loss of Function (LOF)
Most HCN4 mutations are loss-of-function, reducing the I(f) current amplitude or shifting activation to more negative voltages, leading to bradycardia and sick sinus syndrome.
Gain of Function (GOF)
Gain-of-function mutations increase the I(f) current or shift activation to more positive voltages, potentially causing atrial fibrillation or inappropriate tachycardia.
Dominant Negative (DN)
Some loss-of-function mutations may exert a dominant-negative effect, where the mutant subunit co-assembles with wild-type subunits and impairs the function of the tetrameric channel.
View complete mutation data：
Gene Ontology (GO)
| • Ion channel activity | • Voltage-gated potassium channel activity |
| • cAMP binding | • Hyperpolarization-activated ion channel activity |
| • Plasma membrane | • Integral component of membrane |
| • Regulation of heart contraction | • Cardiac conduction |
| • Cellular response to cAMP |
Pathways
• Cardiac pacemaker pathway (I(f) current)
• cAMP signaling pathway
• Ion channel transport
Protein Summary
The HCN4 protein is a member of the hyperpolarization-activated cyclic nucleotide-gated channel family. It forms tetrameric channels that conduct a mixed Na+/K+ inward current, activated by hyperpolarization and enhanced by cAMP binding. The protein has six transmembrane domains, a pore-forming loop, and a cyclic nucleotide-binding domain in the C-terminus. It is essential for the spontaneous diastolic depolarization of sinoatrial node cells, thus controlling heart rate. Mutations affecting its function lead to arrhythmias.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| HCN4 Knockout HEK293 Cell Line | EDJ-KQ1798 | Human | 10021 | Details Get a Quote |
| HCN4 Knockout HCT 116 Cell Line | EDJ-KQ20325 | Human | 10021 | Details Get a Quote |
| HCN4 Knockout HeLa Cell Line | EDJ-KQ55302 | Human | 10021 | Details Get a Quote |
| HCN4 Knockout A-549 Cell Line | EDJ-KQ63784 | Human | 10021 | Details Get a Quote |
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