Journal: bioRxiv

Article Title: All-viral tracing of monosynaptic inputs to single birthdate-defined neurons in the intact brain

doi: 10.1101/2021.10.18.464781

Figure Lengend Snippet: A) Schematic of experimental design and resulting histology 24 days after the rabies injection. Top left: a population of birthdate-matched (E14) cells in the hippocampus was targeted to express TVA and G by injecting an undiluted virus carrying Cre in utero and a large volume of the rabies helper virus carrying TVA and G in the adult hippocampus. A rabies virus carrying GCaMP6f was used to label cells providing monosynaptic input to this cell population. These inputs were then visualised via a prism implanted between the MEC (brain region marked in grey) and the cerebellum. Bottom left: confocal maximum intensity projection of the dorsal hippocampus showing cells expressing helper proteins and/or GCaMP6f. Image insets are single z-plane confocal images showing colocalization of antibody staining for a tag introduced by the helper virus and GCaMP6f introduced by the rabies virus in one example cell (i.e. a starter cell) and only GCaMP6f expression in a neighbouring cell (i.e. an input cell) highlighted with an arrow and a yellow dotted circle. Right: confocal maximum intensity projection showing input cells expressing GCaMP6f in the MEC. The white dotted line illustrates the impression made by the prism on the MEC. DG: dentate gyrus, Sub: subiculum. B) In vivo imaging example. Top left: imaging is performed with head-fixed mice under a two-photon benchtop microscope. Right: maximum intensity projection (across a 2-minute recording) of five cells in the MEC that provide monosynaptic input to the ipsilateral hippocampus 19 days after the rabies injection. Bottom left: ΔF/F traces of two cells with different activity onsets highlighted with corresponding colours in the image to the right.

Article Snippet: Mice were imaged with a custom two-photon benchtop microscope (Femtonics, Hungary) or two-photon miniscope ( Zong et al ., 2017, 2021 ; Obenhaus et al ., 2021 ).

Techniques: Injection, In Utero, Expressing, Staining, In Vivo Imaging, Imaging, Microscopy, Activity Assay