Viral Expression of Epigenome Editing Tools in Rodent Brain Using Stereotaxic Surgery Techniques

Abstract

Delivery of molecular tools for targeted epigenome editing in rodent brain can be facilitated by the use of viral vector-mediated gene transfer coupled with stereotaxic surgery techniques. Here, we describe the surgical protocol utilized by our group, which is optimized for herpes simplex virus (HSV)-mediated delivery into mouse brain. The protocol outlined herein could also be applied for delivery of adeno-associated viruses (AAV) or lentiviruses in both mice and rats. This method allows for efficient viral transgene expression and subsequent epigenome editing in rodent brain with excellent spatiotemporal control. Nearly any brain region of interest can be targeted in rodents at every stage of postnatal life. Owing to the versatility, reproducibility, and utility of this technique, it is an important method for any laboratory interested in studying the cellular, circuit, and behavioral consequences of in vivo neuroepigenome editing.

Keywords: Neuroepigenome editing; Rodent brain; Stereotaxic surgery; Virus-mediated gene transfer.

Fig. 1

Correct placement of rodent’s head within stereotaxic instrument and surgical procedure for viral delivery, (a) A cartoon depicting the fixation of animal’s head within the stereotaxic instrument. The ear bars are securely in place, preventing lateral movement of the skull. The incisor adapter restricts vertical movement, with the nose clamp is gently tightened into place, (b) Upon surgically exposing the stereotaxic landmarks on the skull, the stereotaxic coordinates are measured relative to bregma. Hamilton syringes are used to deliver the viral solution to desired regions within the animal’s brain via small burr holes in the animal’s skull

Fig. 2

Stereotaxic landmarks on the skull. The diagram above depicts the stereotaxic landmarks bregma and lambda on the exposed surface of the rodent’s skull

Fig. 3

Stereotaxic delivery of HSV to discrete brain regions. HSV expressing GFP under the control of the CMV promoter was stereotaxically injected into the nucleus accumbens (NAc) of a mouse to demonstrate the transduction efficiency and spread of the HSV viral vectors (image previously published [14]). These viral vectors are capable of co-expressing neuroepigenome editing constructs under the control of distinct promoters. The injection was performed at a 10° lateral angle at +1.6 anterior/posterior, +1.5 mediolateral, and −4.4 dorsal/ventral coordinate relative to bregma. Scale bar is 300 μm