New preprint: viral vectors for in vivo calcium imaging
We show that systemic injections of PHP.eB AAVs to express GECIs is a highly promising technique for imaging neural activity and circumvent the need for transgenic GECI expressing mouse lines. We also establish the use of novel soma-targeted GECIs that outperform current Ca2+ indicators using both systemic and local virus injections.
Grødem et al (preprint, 2021): doi: https://doi.org/10.1101/2021.05.14.443815
We have struggled to get GCaMP from systemic administration to work reliably, the signal was just not bright enough. So, after lots of failed experiments with various GECIs, we decided to do a more rigorous screening.
We tested a range of GCaMPs for suitability in two-photon imaging using retro-orbital and local injections of PHP.eb AAVs.
Ribo-jGCaMP8s also works with ROI but takes up to 6 weeks for viable imaging brightness. However, local injections of Ribo-jGCaMP8m and s give rise to incredible labeling density and highly improved brightness compared to previous versions
RO injections of GCaMP come with several advantages; no need for driver lines or intricate breeding, no injection surgery, and can be combined with transgenic lines. We demonstrate the latter by cell-type targeted chemogenetics combined with brain-wide GCaMP in PV-Cre mice.
All plasmids are currently in processing at Addgene and will be available soon. The original jGCaMP8 sensors from the Looger lab and the GENIE project are already available on Addgene @addgene @janeliagenie.