Voltage imaging using transgenic mouse lines expressing the GEVI ArcLight in two olfactory cell types

Abstract

Genetically encoded voltage indicators (GEVIs) allow for cell-specific optical recordings of membrane potential changes in defined cell populations. One tool that would further their use in the in vivo mammalian brain is transgenic reporter animals that facilitate precise and repeatable targeting with high expression levels. The present literature on the development and use of transgenic mouse lines as vehicles for GEVI expression is limited. Here we report the first in vivo experiments using a transgenic reporter mouse for the GEVI ArcLight (Ai86(TITL-ArcLight)), which utilizes a Cre/tTA dependent expression system (TIGRE 1.0). Following pairing to appropriate Cre- and tTA transgenic mice, we report two mouse lines with ArcLight expression restricted to olfactory sensory neurons (OMP-ArcLight), and a subpopulation of interneurons that include periglomerular and granule cells (Emx1-ArcLight) in the olfactory bulb (OB). The ArcLight expression in these lines was sufficient for in vivo imaging of odorant responses in single trials. Odor responses were measured in the OB using epifluorescence and 2-photon imaging. The voltage responses were odor-specific and concentration-dependent, and confirmed earlier conclusions from calcium measurements. This study shows that the ArcLight Ai86(TITL-ArcLight) transgenic line is a flexible genetic tool that can be used to record neuronal electrical activity of a variety of cell types with a signal-to-noise ratio that is comparable to previous reports using viral transduction.

The Mammalian Olfactory Bulb Contributes to the Adaptation of Odor Responses: A Second Perceptual Computation Carried Out by the Bulb

“…Moreover, preliminary results measuring olfactory receptor neuron activity using the Genetically Encoded Voltage Indicator, ArcLight showed comparable adaptation responses as those measured here using calcium sensors ( Platisa et al, 2020 ). This strengthens the conclusion that the choice of optical sensor is unlikely to explain the measured differences between input and output.…”

“…Third, by demonstrating that the input measurements were similar regardless of the sensor used. Furthermore, olfactory receptor neuron adaptation measured using a voltage indicator gave similar results ( Platisa et al, 2020 ). Thus, it is unlikely that the reported differences between input and output are artifactual.…”

Stimulus Driven Functional Transformations in the Early Olfactory System

“…Calcium imaging offers an alternative approach for quantifying ORN responses in vivo . ORNs can be anatomically labeled with organic dyes (Friedrich and Korsching, 1997 ; Ma and Shepherd, 2000 ; Wachowiak and Cohen, 2001 ; Fried et al, 2002 ; Wachowiak et al, 2002 ; Korsching, 2005 ), and genetic targeting strategies have used the olfactory marker protein (OMP) promoter (Farbman and Margolis, 1980 ; Danciger et al, 1989 ) to generate transgenic mice expressing different reporters of neural activity in ORNs (Bozza et al, 2004 ; McGann et al, 2005 ; Albeanu et al, 2018 ; Dewan et al, 2018 ; Platisa et al, 2020 ).…”

Imaging sensory transmission and neuronal plasticity in primary sensory neurons with genetically-encoded voltage indicator, ASAP4.4-Kv

“…Transgenic animals should overcome these limitations as demonstrated by our studies using the Pirt promotor to selectively drive strong GCaMP3 expression in DRG neurons 4 . Currently, transgenic mouse lines expressing the GEVI have been reported for in vivo studies in olfactory cells 43 . Future engineering efforts could focus on transgenic GEVI mouse lines for selective expression in targeted tissues, which promise spatially homogeneous transgene expression and long-term time windows for GEVI imaging.…”