How to control cyclic nucleotide signaling by light.
Optogenetics allows to non-invasively manipulate cellular functions with spatio-temporal precision by combining genetic engineering with the control of protein function by light. Since the discovery of channelrhodopsin has pioneered the field, the optogenetic toolkit has been ever expanding and allows now not only to control neuronal activity by light, but rather a multitude of other cellular functions. One important application that has been established in recent years is the light-dependent control of second messenger signaling. The optogenetic toolkit now allows to control cyclic nucleotide-dependent signaling by light in vitro and in vivo.
Controlling fertilization and cAMP signaling in sperm by optogenetics.
Optogenetics is a powerful technique to control cellular activity by light. The light-gated Channelrhodopsin has been widely used to study and manipulate neuronal activity in vivo, whereas optogenetic control of second messengers in vivo has not been examined in depth. In this study, we present a transgenic mouse model expressing a photoactivated adenylyl cyclase (bPAC) in sperm. In transgenic sperm, bPAC mimics the action of the endogenous soluble adenylyl cyclase (SACY) that is required for motility and fertilization: light-stimulation rapidly elevates cAMP, accelerates the flagellar beat, and, thereby, changes swimming behavior of sperm. Furthermore, bPAC replaces endogenous adenylyl cyclase activity. In mutant sperm lacking the bicarbonate-stimulated SACY activity, bPAC restored motility after light-stimulation and, thereby, enabled sperm to fertilize oocytes in vitro. We show that optogenetic control of cAMP in vivo allows to non-invasively study cAMP signaling, to control behaviors of single cells, and to restore a fundamental biological process such as fertilization.