Systems Core

The current focus of the Systems Core is to develop and implement the use of neural viral tract tracers to define complete circuits within the same animal. Because of its genetic modifiability, we are using variants of the Pseudorabies virus (PRV), to create new and improved methods for these determinations of synaptic connectivity. In addition, in contrast to other possible viruses, we use the PRV because it is safe for humans.

The Systems Core is divided into two parts. Dr. Lynn Enquist of Princeton University heads the first part. Dr. Enquist is a virologist with a specialization in the development of viral tract tracers. Basically, we suggest to Dr. Enquist a particular type of application of the PRV, for example defining the autonomic connections of the brain to a peripheral target organ to be done using a reporter gene such that no immunocytochemistry is necessary. In this example, Dr. Enquist developed a PRV mutant that makes green fluorescent protein (GFP), he sends us a sample and we test it in the animal and target organ in question.

The second part of the Systems Core is within the laboratory of Dr. Timothy Bartness, at Georgia State University. Dr. Bartness tests the viruses developed by Dr. Enquist as part of experiments he is doing in his laboratory, or in conjunction with CBN members who have a particular application of the virus. Dr. Bartness receives the ideas and requests of the CBN members and then discusses with Dr. Enquist the feasibility of the request, time-line of development and implementation of the virus. In addition, Dr. Bartness or CBN-supported staff members train the CBN investigator on how to use the virus.

The virus works well in several species including rats, mice and several hamster species. At present, all PRV mutants only can be used to trace neural circuits in a retrograde direction (i.e., from the end of the circuit to its beginnings). This can be done by injection the virus into the peripheral target or within the brain itself. This means that the virus is not suitable, a t present, for anterograde tract tracing (i.e., from the beginning of the circuit to its end), nor for injections to label peripheral sensory neurons because the central projecting of part of these bipolar neurons would require an anterograde tracer.

Currently available viruses and applications include

Viruses

1. GFP
2. dsRED
3. native PRV
4. beta-galactosidase (PRV-BaBlu)

Current Applications

1. Retrograde tract tracing, especially peripheral injection sites for autonomic connections, but including central injections
2. Dual virus applications for localization of common neurons within circuits
3. Combination of PRV with immunocytochemistry for neurotransmitters, enzymes of synthesis or receptors
4. Combination of PRV with in situ hybridization for neurotransmitters, enzymes of synthesis or receptors

Presently there is no charge for:

1. Reasonable supplies of the PRV mutants
2. Training at a mutually convenient time

Note: We do not supply antibody for the standard PRV virus, but as a CBN member you are eligible for a discount for the PRV antibody from Applied BioSystems (ask for Phil Schwartz and identify yourself as a CBN member).

In development

Conditional viral reporter where the reporter turns on only when neurons of a specific neurochemical phenotype are encountered in a circuit (Ba2001 PRV).