Emerging role of viral vectors for circuit-specific gene interrogation and manipulation in rodent brain

Abstract

Over the past half century, novel tools have allowed the characterization of myriad molecular underpinnings of neural phenomena including synaptic function, neurogenesis and neurodegeneration, membrane excitability, and neurogenetics/epigenetics. More recently, transgenic mice have made possible cell type-specific explorations of these phenomena and have provided critical models of many neurological and psychiatric diseases. However, it has become clear that many critical areas of study require tools allowing the study and manipulation of individual neural circuits within the brain, and viral vectors have come to the forefront in driving these circuit-specific studies. Here, we present a surface-level review of the general classes of viral vectors used for study of the brain, along with their suitability for circuit-specific studies. We then cover in detail a new long-lasting, retrograde expressing form of herpes simplex virus termed LT-HSV that has become highly useful in circuit-based studies. We detail some of its current uses and propose a variety of future uses for this critical new tool, including circuit-based transgene overexpression, gene editing, and gene expression profiling.

Pubertal Testosterone Programs Adult Behavioral Adaptations to Sexual Experience through Infralimbic Cortex ΔFosB

“…AAV2/5 viral vectors were purchased from the University of North Carolina Viral Vector Core, and titres were ∼1.0 × 10 13 transducing particles per microliter. These AAV vectors reach maximal expression around 10 d and sustain expression indefinitely (Vialou et al, 2010; Eagle et al, 2015; Sarno and Robison, 2018). These vectors only infect neurons and are no more toxic than vehicle alone (Zachariou et al, 2006).…”

Delineating the Organization of Projection Neuron Subsets with Multi-fluorescent Rabies Virus Tracing Tool

“…Besides RV tracing virus, other retrograde viral tracers (such as canine adeno virus type 2 (CAV2), retrograde adeno associated virus (retro-AAV)) or traditional tracers (CTB, Fluorogold) are also utilized for tracing projection neurons to certain target regions [17,[40][41][42][43] . Compared with traditional tracers, viral tracers are more widely used to study the fine structural and functional properties of neural circuits due to their stronger signal, selectivity, genetic engineering convenience, especially trans-synaptic ability for higher order circuit tracing [9][10][11][12] . With the supply of RV glycoprotein by AAV virus to rRV-ΔG infected neurons, upstream neurons can also be labeled due to the rRV trans-synapse spreading [14,19,22,44] .…”

“…Deciphering brain connections has been largely dependent on effective circuit tracing, measuring, and manipulation techniques. Neurotropic virus-based tracers have been widely utilized to elucidate the organization and function of neural circuits owing to their stronger signal, selectivity, compatibility with exogenous genetic engineering methods, and trans-synaptic ability [9][10][11][12] . The insertion of exogenous genes such as optogenetic, chemogenetic, and Ca 2+ /voltage-sensitive genes in combination with a Cre/lox system allows for tracer viruses to be used for the monitoring, manipulation, and subsequent functional dissection, of specific neural circuits [13][14][15][16] .…”

Investigating Memory Updating in Mice Using the Objects in Updated Locations Task

“…Ideally, the compound can be delivered immediately after the update session to avoid potential disruptions in learning the update, performance during updating, or state‐dependent effects. This may not be possible for viral manipulations, which typically peak days (HSV) or weeks (AAV, lentiviruses) after infusion (Sarno & Robison, ). Viruses should be delivered 24 hr after the final training session to allow the original memory to consolidate before the manipulation is induced, and the update session should be performed when virus expression peaks.…”