Optogenetic Control of Cardiac Function

A Steady Beat A regular heartbeat depends on steady function of the cardiac pacemaker. The early embryonic heart is neither as steady nor as organized as the mature heart. Arrenberg et al. (p. 971 ) used zebrafish engineered to express light-sensitive proteins to locate and manipulate the function of the cardiac pacemaker. By controlling the activity of small patches of cells with light beams, the authors monitored the development of the young heart, showing how the cardiac pacemaker develops during embryogenesis.