A couple months ago the latest Cre-dependent optogenetic reporter mouse lines were published in a Nature Neuroscience paper. But one particular line, the GCaMP3 reporter strain, was missing at roll call. This line was published almost at the same time in the Journal of Neuroscience. In the February 29 issue of J. Neurosci, Zariwala et al. show that when crossed with Cre lines the Ai38 line yields stable GCaMP3 expression without the typical toxicity observed with AAV infections (which correlates with GCaMP3 diffusing into the nucleus and is observed as early as 4-6 weeks after infection). For a side-by-side comparison of GCaMP3 and Oregon Green BAPTA-1 (OGB-1), the authors looked at the visual cortex of anesthetized mice. GCaMP3-expressing pyramidal cells of the visual cortex (obtained using a Wfs1-Tg2-Cre line) showed preserved orientation selectivity to moving oriented gratings. Interestingly, the maximum ΔF/F achieved in GCaMP3-expressing neurons was substantially higher than with OGB-1. On the opposite, OGB-1 gave higher ΔF/F for low responder cells. One downside is that imaging from the Ai38 line required about 3 x more laser power than when using AAVs or OGB-1. But overall it looks like GcaMP reporter strains are on the right track and already experiment-ready. Now the question is will you get the Ai38 mouse from the Jackson Lab (#014538, link here) or will you wait for the GCaMP5 reporter strain which is announced for the summer?
- Original article by Zariwala et al.