Visualization of neurons is indispensable for the investigation of neuronal circuits in the central
nervous system. Virus vectors have been widely used for labeling particular subsets of
neurons, and the adeno-associated virus (AAV) vector has gained popularity as a tool for
gene transfer. Here, we developed a single AAV vector Tet-Off platform, AAV-SynTetOff, to
improve the gene-transduction efficiency, specifically in neurons. The platform is composed
of regulator and response elements in a single AAV genome. After infection of Neuro-2a
cells with the AAV-SynTetOff vector, the transduction efficiency of green fluorescent protein
(GFP) was increased by approximately 2- and 15-fold relative to the conventional ... More
Visualization of neurons is indispensable for the investigation of neuronal circuits in the central
nervous system. Virus vectors have been widely used for labeling particular subsets of
neurons, and the adeno-associated virus (AAV) vector has gained popularity as a tool for
gene transfer. Here, we developed a single AAV vector Tet-Off platform, AAV-SynTetOff, to
improve the gene-transduction efficiency, specifically in neurons. The platform is composed
of regulator and response elements in a single AAV genome. After infection of Neuro-2a
cells with the AAV-SynTetOff vector, the transduction efficiency of green fluorescent protein
(GFP) was increased by approximately 2- and 15-fold relative to the conventional AAV vector
with the human cytomegalovirus (CMV) or human synapsin I (SYN) promoter, respectively.
We then injected the AAV vectors into the mouse neostriatum. GFP expression in the
neostriatal neurons infected with the AAV-SynTetOff vector was approximately 40-times
higher than that with the CMV or SYN promoter. By adding a membrane-targeting signal to
GFP, the axon fibers of neostriatal neurons were clearly visualized. In contrast, by attaching
somatodendritic membrane-targeting signals to GFP, axon fiber labeling was mostly suppressed.
Furthermore, we prepared the AAV-SynTetOff vector, which simultaneously
expressed somatodendritic membrane-targeted GFP and membrane-targeted red fluorescent
protein (RFP). After injection of the vector into the neostriatum, the cell bodies and dendrites
of neostriatal neurons were labeled with both GFP and RFP, whereas the axons in the
projection sites were labeled only with RFP. Finally, we applied this vector to vasoactive
intestinal polypeptide-positive (VIP+) neocortical neurons, one of the subclasses of inhibitory
neurons in the neocortex, in layer 2/3 of the mouse primary somatosensory cortex. The
results revealed the differential distribution of the somatodendritic and axonal structures at
the population level. The AAV-SynTetOff vector developed in the present study exhibits
strong fluorescence labeling and has promising applications in neuronal imaging.