These M72-IRES-ChR2-YFP mice express a ChR2(H134R)-EYFP fusion gene from the from the olfactory receptor 160 locus (Olfr160). Mice that are homozygous for the targeted mutation are viable and fertile. Only olfactory sensory neurons (OSN) expressing this specific odorant receptor, M72, express ChR2(H134R)-EYFP, rendering them light sensitive. Sensory neurons that express the modified allele express both ChR2-YFP as well as the intact M72 receptor and project axons to a medial and a lateral glomerulus on the dorsal surface of each olfactory bulb. Light directed at the glomerulus can elicit neuronal activity and drive odor guided behavior. These mutant mice thus allow precise, timed delivery of sensory input to the olfactory system. Homozygotes are viable and fertile. M72-IRES-ChR2-YFP mice are similar to STOCK Omptm1.1(COP4*/EYFP)Tboz/J mice (Stock No. 014173), which express ChR2(H134R)-EYFP all mature olfactory sensory neurons.
The ChR2(H134R)-EYFP fusion protein is composed of a Chlamydomonas reinhardtii-derived channelrhodopsin-2 that harbors a gain-of-function H134R substitution fused in-frame with an enhanced yellow fluorescent protein. The ChR2(H134R) is designed to cause larger stationary photocurrents compared to ChR2.
The bacterial opsins are retinal-binding proteins that combine a light-sensitive domain with an ion channel or pump; providing light-dependent ion transport, membrane potential alteration, and sensory functions to bacteria. This ChR2(H134R) functions as a blue light-driven cation channel that depolarizes the cell and causes action potentials. As such, illuminating ChR2(H134R)-expressing cells with blue light (450-490 nm) leads to rapid and reversible photostimulation of action potential firing activity in these cells.
