Selectively Imaging Cranial Sensory Ganglion Neurons Using AAV-PHP.S

Abstract

Because of their ease of use, adeno-associated viruses (AAVs) are indispensable tools for much of neuroscience. Yet AAVs have been used relatively little to study the identities and connectivity of peripheral sensory neurons, principally because methods to selectively target peripheral neurons have been limited. The introduction of the AAV-PHP.S capsid with enhanced tropism for peripheral neurons ( Chan et al., 2017 ) offered a solution, which we further elaborate here. Using AAV-PHP.S with GFP or mScarlet fluorescent proteins, we show that the mouse sensory ganglia for cranial nerves V, VII, IX, and X are targeted. Pseudounipolar neurons of both somatic and visceral origin, but not satellite glia, express the reporters. One week after virus injection, ≈66% of geniculate ganglion neurons were transduced. Fluorescent reporters were transported along the central and peripheral axons of these sensory neurons, permitting visualization of terminals at high resolution, and in intact, cleared brain using light sheet microscopy. Further, using a Cre-dependent reporter, we demonstrate by anatomic and functional criteria, that expression is in a cell type-selective manner. Finally, we integrate earlier neuroanatomical and molecular data with in vivo Ca 2+ imaging to demonstrate the sensory characteristics of geniculate ganglion auricular neurons, which were previously undocumented. Our analyses suggest that the AAV-PHP.S serotype will be a powerful tool for anatomically and functionally mapping the receptive fields and circuits of the expanding numbers of molecular subtypes of many somatosensory and viscerosensory neurons that continue to be defined via single-cell RNA sequencing.

Neural circuits for taste sensation

“…Simultaneously, the glossopharyngeal nerve, which innervates the taste buds of the foliate papillae and circumvallate papillae in the posterior tongue, possesses cell bodies in the petrosal ganglion. By expressing a GCaMP variant with transgenic mice ( Fowler and Macpherson, 2021 , Fowler et al, 2022 , Wu et al, 2015 ) or AAV vector ( Asencor et al, 2022 , Lee et al, 2017 ), the calcium activity in ganglion neurons was measured upon oral exposure to various tastants. Most ganglion neurons exhibit a narrow spectrum of profiles in response to specific modalities ( Fowler et al, 2022 , Lee et al, 2017 , Wu et al, 2015 ).…”

Fluorescence imaging of peripheral nerve function and structure

“…Chan et al used a technique they named CREATE (Cre recombinase-based AAV targeted evolution) to select capsids specific to different cell types, which gave rise to AAV-PHP.eB and AAV-PHP.S, which effectively transduced the central and peripheral nervous systems, respectively. 45 Based on these findings, Asencor et al systematically investigated and reported the neuroanatomical tracing results of AAV-PHP.S in peripheral nerves like the geniculate nerve (cranial nerves V, VII, IX, and X), illuminating for the first time the sensory properties of auricular neurons in the geniculate ganglion 46 [Fig. 3A].…”

“…By introducing particular peptides into the heparin-binding loop, Gowanlock et al created the retrograde tracer rAAV2-retro, which could be efficiently retrograde delivered to projection neurons in the mouse brain. 44 With its effective retrograde transport and 45 Based on these findings, Asencor et al systematically investigated and reported the neuroanatomical tracing results of AAV-PHP.S in peripheral nerves like the geniculate nerve (cranial nerves V, VII, IX, and X), illuminating for the first time the sensory properties of auricular neurons in the geniculate ganglion 46 [Fig. 3A].…”