Search

The rhythmical nature of the cardiovascular system constantly generates dynamic mechanical forces. At the centre of this system is the heart, which must detect these changes and adjust its performance accordingly. Mechanoelectric feedback provides a rapid mechanism for detecting even subtle changes in the mechanical environment and transducing these signals into electrical responses, which can adjust a variety of cardiac parameters such as heart rate and contractility. However, pathological conditions can disrupt this intricate mechanosensory system and manifest as potentially life-threatening cardiac arrhythmias. Mechanosensitive ion channels are thought to be the main proponents of mechanoelectric feedback as they provide a rapid response to mechanical stimulation and can directly affect cardiac electrical activity. Here, we demonstrate that the mechanosensitive ion channel PIEZO1 is expressed in zebrafish cardiomyocytes. Furthermore, chemically prolonging PIEZO1 activation in zebrafish results in cardiac arrhythmias. indicating that this ion channel plays an important role in mechanoelectric feedback. This also raises the possibility that PIEZO1 gain of function mutations could be linked to heritable cardiac arrhythmias in humans.

The mechanisms underlying cardiac automaticity are still incompletely understood and controversial. Here we report the complete conditional and time-controlled silencing of the 'funny' current (If) by expression of a dominant-negative, non-conductive HCN4-channel subunit (hHCN4-AYA). Heart-specific If silencing caused altered [Ca(2+)]i release and Ca(2+) handling in the sinoatrial node, impaired pacemaker activity and symptoms reminiscent of severe human disease of pacemaking. The effects of If silencing critically depended on the activity of the autonomic nervous system. We were able to rescue the failure of impulse generation and conduction by additional genetic deletion of cardiac muscarinic G-protein-activated (GIRK4) channels in If-deficient mice without impairing heartbeat regulation. Our study establishes the role of f-channels in cardiac automaticity and indicates that arrhythmia related to HCN loss-of-function may be managed by pharmacological or genetic inhibition of GIRK4 channels, thus offering a new therapeutic strategy for the treatment of heart rhythm diseases.