Optogenetic manipulation of neuronal and cardiomyocyte functions in zebrafish using microbial rhodopsins and adenylyl cyclases.

Abstract

Even though microbial photosensitive proteins have been used for optogenetics, their use should be optimized to precisely control cell and tissue functions in vivo. We exploited <i>Gt</i>CCR4 and <i>Kn</i>ChR, cation channelrhodopsins from algae, <i>Be</i>GC1, a guanylyl cyclase rhodopsin from a fungus, and photoactivated adenylyl cyclases (PACs) from cyanobacteria (<i>Oa</i>PAC) or bacteria (<i>b</i>PAC), to control cell functions in zebrafish. Optical activation of <i>Gt</i>CCR4 and <i>Kn</i>ChR in the hindbrain reticulospinal V2a neurons, which are involved in locomotion, induced swimming behavior at relatively short latencies, whereas activation of <i>Be</i>GC1 or PACs achieved it at long latencies. Activation of <i>Gt</i>CCR4 and <i>Kn</i>ChR in cardiomyocytes induced cardiac arrest, whereas activation of <i>b</i>PAC gradually induced bradycardia. <i>Kn</i>ChR activation led to an increase in intracellular Ca²⁺ in the heart, suggesting that depolarization caused cardiac arrest. These data suggest that these optogenetic tools can be used to reveal the function and regulation of zebrafish neurons and cardiomyocytes.