Optogenetic actuators have had a stunning impact on the understanding of complex neural circuits. Combined with cell lineage specific promoters, optogenetic tools enable the activation of discrete cells to initiate biological events. These light gated channel proteins depolarize and activate cells and have proved to be a major advantage in the study of neural circuits.[1, 2, 3] Recent advancements in the field have resulted in a palette of color-tuned tools that can initiate cellular processes through the activation of second messengers.
Channelrhodopsin-2 (ChR2) is a 489nm activated cation channel that depolarizes and activates excitable cells.  A mutated form of ChR2 (L132C) results in an increase in photocurrents and light sensitivity.  This mutated form is named CatCh and is used in our transgenes. Opto-α1AR and opto-β2AR are fusion proteins that have the transmembrane and light-sensitive domains of the G protein-coupled protein rhodopsin with the intracellular domains of the α1 and β2 adrenergic receptors, generating diacylglycerol/IP3 and cAMP, respectively, allowing dynamic regulation of the production of these key secondary messengers, and the investigation of the functional consequences of their activation in vivo. Rhodopsin–based tools are particularly well suited to pairing with red-shifted detectors such as RCaMP1.07, as excitation of the effectors occurs in the range of 480-500nm and RCaMP1.07 or R-GECO1 are not excited by the effector stimulus.
All of the rhodopsin based optogenetic tools have been developed with a lacZ tag attached via an IRES. This will allow for easy detection of the expressed proteins. Mice created expressing these tools will enable localized, subcellular activation to evaluate the extent to which local activation of signaling pathways regulate processes such as contraction, transcription, and secretion.
- Fenno L, Yizhar O, Deisseroth K. The development and application of optogenetics. Annu.Rev.Neurosci. 2011;34:389-412
- Boyden ES, Zhang F, Bamberg E, Nagel G, Deisseroth K. Millisecond-timescale, genetically targeted optical control of neural activity. Nat.Neurosci. 2005 Sep;8(9):1263-8
- Zhang F, Wang LP, Boyden ES, Deisseroth K. Channelrhodopsin-2 and optical control of excitable cells. Nat.Methods 2006 Oct;3(10):785-92
- Prigge M, Schneider F, Tsunoda SP, Shilyansky C, Wietek J, Deisseroth K, Hegemann P. Color-tuned channelrhodopsins for multiwavelength optogenetics. J Biol.Chem. 2012 Sep 14;287(38):31804-12.
- Kleinlogel S, Feldbauer K, Dempski RE, Fotis H, Wood PG, Bamann C, Bamberg E. Ultra light-sensitive and fast neuronal activation with the Ca(2)+-permable channelrhodopsin CatCh. Nat. Neurosci. 2011 14:513-518.