Intracranial Injection of Adeno-associated Viral Vectors

Summary

Here we present the intracranial injection of AAV vectors for fluorescent labeling of neurons and glia in the visual cortex.

Abstract

Intracranial injection of viral vectors engineered to express a fluorescent protein is a versatile labeling technique for visualization of specific subsets of cells in different brain regions both in vivo and in brain sections. Unlike the injection of fluorescent dyes, viral labeling offers targeting of individual cell types and is less expensive and time consuming than establishing transgenic mouse lines. In this technique, an adeno-associated viral (AAV) vector is injected intracranially using stereotaxic coordinates, a micropipette and an automated pump for precise delivery of AAV to the desired area with minimal damage to the surrounding tissue. Injection parameters can be tailored to individual experiments by adjusting the animal age at injection, injection location, volume of injection, rate of injection, AAV serotype and the promoter driving gene expression. Depending on the conditions chosen, virally-induced transgene expression can allow visualization of groups of cells, individual cells or fine cellular processes, down to the level of dendritic spines. The experiment shown here depicts an injection of double-stranded AAV expressing green fluorescent protein for the labeling of neurons and glia in the mouse primary visual cortex.

Protocol

1. Virus Handling and Storage

1. Proper protection and handling techniques should be chosen based on the biosafety level of the virus to be used. These practices can be found in Biosafety in Microbiological and Biomedical Laboratories 5^th edition, available on the CDC website
   (http://www.cdc.gov/od/OHS/biosfty/bmbl5/bmbl5toc.htm). The use of AAV vectors is approved for Biosafety Level 1 (BSL-1). For the experiment shown here, a lab coat and gloves will be worn when handling the virus, in accordance with procedures for handling BSL-1 agents.
2. To preserve the activity o....

Discussion

Virally-mediated gene delivery holds great potential for the study of neurological processes and treatment of brain disorders^1,2,3. The great versatility of this technique can also be exploited to fluorescently label cells for imaging both in vitro and in vivo⁴. Here we demonstrate a detailed procedure for the transduction of neurons and glia in mouse visual cortex using a double-stranded adeno-association virus expressing enhanced green fluorescent protein.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
St–lting Mouse and Neonatal Rat Adaptor	Stoelting Co.	51625	Regular stereotax for securing animals for surgery may be substituted
Extra Fine Bonn Scissors, 8.5cm, straight tip, cutting edge 13mm	Fine Science Tools	14084-08
Eye Dressing Forceps, 10cm, tip width 0.5mm, curved	Fine Science Tools	11152-10
Dumont #5/45 Forceps- Dumoxel Standard Tip, 11cm, angled	Fine Science Tools	11251-35	Extra-fine tipped forceps for performing craniotomy
Standard Pattern Forceps, straight, 2.5mmx1.35mmtip, 12cm	Fine Science Tools	11000-12
Microtorque Control Box and Tech2000 handpiece	Ram Products, Inc.	TECH2000ON/OFF	Dental drill
Micro Drill Stainless Steel Burrs 1.4mm tip diameter	Fine Science Tools	19008-14
Wiretrol micropipettes, to deliver 1-5 Ul	VWR international	5-000-1001 or 53480-287
Mineral oil	VWR international	29447-338
Manual Micromanipulator and Tilting Base (right-handed)	World Precision Instruments, Inc.	M3301-M3-R	Used for determining stereotaxic co-ordinates
UltraMicroPump (UMP3) (one) with SYS-Micro4 Controller	World Precision Instruments, Inc.	UMP3-1
Sutures	VWR international	95056-952
P-97 Flaming/Brown Micropipette Puller	Sutter Instrument Co.	P-97
Tobradex			Available from your institution’s veterinary services