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

Nicholas J Michelson,Timothy H Murphy,Matthieu P Vanni

doi:10.1117/1.nph.6.2.025014

Nicholas J Michelson, Timothy H Murphy + Show 1 more

Open Access

https://doi.org/10.1117/1.nph.6.2.025014

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Journal: Neurophotonics	Publication Date: Jun 22, 2019
Citations: 17	License type: cc-by

Affiliation: University of British Columbia

Abstract

.We employ transcranial wide-field single-photon imaging to compare genetically encoded calcium sensors under transgenic or viral vector expression strategies. Awake, head-fixed animals and brief visual flash stimuli are used to assess function. The use of awake transcranial imaging may reduce confounds attributed to cranial window implantation or anesthesia states. We report differences in wide-field epifluorescence brightness and peak response to visual stimulation between expression strategies. Other metrics for indicator performance include fluctuation analysis (standard deviation) and regional correlation maps made from spontaneous activity. We suggest that multiple measures, such as stimulus-evoked signal-to-noise ratio, brightness, and averaged visual response, may be necessary to characterize indicator sensitivity and methods of expression. Furthermore, we show that strategies using blood brain barrier-permeable viruses, such as PHP.eB, yield comparable expression and function as those derived from transgenic mice. We suggest that testing of new genetically engineered activity sensors could employ a single-photon, wide-field imaging pipeline involving visual stimulation in awake mice that have been intravenously injected with PHP.eB.

Highlights

Mesoscale functional imaging is a powerful approach to monitor large-scale cortical activity and functional connectivity.[1,2,3,4] This imaging modality measures cortical neuronal activity directly through the use of fluorescent indicators, or indirectly through intrinsic optical signals
The results showed that, while the TIGRE mouse strategy provided the strongest basal fluorescent level and visual response signal-to-noise ratio (SNR), evoked signals and the spatial organization of spontaneous activity were comparable with tetracycline operator (tetO)-GCaMP6s and negative mice infected by associated virus (AAV)-PHP.eB-GCaMP6s
We conducted a head-to-head comparison of three transgenic models and one AAV-transduced model expressing GCaMP6s in cortical neurons using in vivo transcranial wide-field imaging

Summary

Introduction

Mesoscale functional imaging is a powerful approach to monitor large-scale cortical activity and functional connectivity.[1,2,3,4] This imaging modality measures cortical neuronal activity directly through the use of fluorescent indicators (e.g., calcium and neurotransmitter indicators or voltage-sensitive dyes), or indirectly through intrinsic optical signals. The use of ultrasensitive fluorescent indicators, such as calcium sensor, GCaMP6,8 or superfast indicators, such as glutamate sensor and iGluSnFR, can overcome these limitations.[9,10,11,12,13] Whatever the signal recorded, optical access to the entire dorsal cortex can be obtained through the intact skull in mice using a transcranial chronic window.[14,15]

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