HCN4 (Hyperpolarization Activated Cyclic Nucleotide Gated Potassium Channel 4): HCN4 is a key component of the cardiac pacemaker channels responsible for regulating heart rhythm. It contributes to the generation and modulation of the pacemaker current in the heart, influencing heart rate and cardiac output. Mutations in HCN4 are associated with a variety of cardiac arrhythmias, including bradycardia and heart block, making it a critical gene for understanding cardiac function and its disorders....