Thy1 transgenic mice expressing the red fluorescent calcium indicator jRGECO1a for neuronal population imaging in vivo

Abstract

Calcium imaging is commonly used to measure the neural activity of large groups of neurons in mice. Genetically encoded calcium indicators (GECIs) can be delivered for this purpose using non-invasive genetic methods. Compared to viral gene transfer, transgenic targeting of GECIs provides stable long-term expression and obviates the need for invasive viral injections. Transgenic mice expressing the green GECI GCaMP6 are already widely used. Here we present the generation and characterization of transgenic mice expressing the sensitive red GECI jRGECO1a, driven by the Thy1 promoter. Four transgenic lines with different expression patterns showed sufficiently high expression for cellular in vivo imaging. We used two-photon microscopy to characterize visual responses of individual neurons in the visual cortex in vivo. The signal-to-noise ratio in transgenic mice was comparable to, or better than, mice transduced with adeno-associated virus. In addition, we show that Thy1-jRGECO1a transgenic mice are useful for transcranial population imaging and functional mapping using widefield fluorescence microscopy. We also demonstrate imaging of visual responses in retinal ganglion cells in vitro. Thy1-jRGECO1a transgenic mice are therefore a useful addition to the toolbox for imaging activity in intact neural networks.

Reversible Loss of Hippocampal Function in a Mouse Model of Demyelination/Remyelination

“…We used a recently developed transgenic line, Thy1-jRGECO1a line GP8.31, which expresses the state-of-theart red GECI jRGECO1a under the Thy1 promoter. jRGECO1a is expressed mostly in projection neurons across various brain regions, including the CA1 pyramidal and DG granular layers of the hippocampus (Dana et al, 2018). The enhanced imaging depth and high sensitivity achieved with jRGECO1a compared to green GECIs like GCaMP that we previously used for cortical imaging (Dana et al, 2016) enabled us to record, in six out of the seven mice used in this study, from the upper and lower blades of the DG down to 650 µm under the hippocampal surface using up to 120 mW of 1100 nm excitation light (Figures 2A-D).…”

“…Two-photon laser scanning microscopy (TPLSM) of the fluorescence signal from genetically encoded calcium indicators (GECIs) enables monitoring the activity of thousands of individual neurons in the rodent brain with micron-scale resolution and high signal-to-noise ratio (Chen et al, 2013;Dana et al, 2016Dana et al, , 2019. Moreover, state-ofthe-art GECIs provide the temporal dynamics and sensitivity that are necessary to allow detection of single APs over time scales of months, mainly by switching to stable transgenic expression strategies (Dana et al, 2014(Dana et al, , 2016(Dana et al, , 2018(Dana et al, , 2019Madisen et al, 2015;Wekselblatt et al, 2016). Therefore, this approach may enable the exploration of changes in brain activity following demyelination and remyelination with the required sensitivity and accuracy to detect changes in individual neurons over time.…”

Comparison between transgenic and AAV-PHP.eB-mediated expression of GCaMP6s using in vivo wide-field functional imaging of brain activity

“…The use of red fluorescent indicators can also be used to overcome hemodynamic confounds as well as to image deeper into the cortex. [46][47][48][49] The magnitude of the visually evoked response was significantly larger in the AAV-PHP.eB and Ai94 mice compared to the Thy1-GCaMP6s mice, suggesting differences in GCaMP expression in the responding neuronal population between mouse lines. Moreover, differences between mice were observed in the spatial organization of resting-state activity and absolute brightness.…”

Localized semi-nonnegative matrix factorization (LocaNMF) of widefield calcium imaging data

“…Data type (2). For this dataset we imaged adult Thy1-jRGECO1a mice (line GP8.20, purchased from Jackson Labs) [41]. In preparation for widefield imaging, a thinned-skull craniotomy was performed over the cortex, in which the mouse was anesthetized with isoflurane, had its skull thinned, and was implanted with an acrylic headpiece for restraint.…”