Cre-dependent adeno-associated virus preparation and delivery for labeling neurons in the mouse brain

Virus-mediated gene delivery is a powerful strategy for labeling and manipulating neurons in mammalian brains. A major drawback of this gene delivery method has been the lack of cell-type specificity. However, methods that combine Cre-knockin mice and Cre-activated adeno-associated virus (AAV) have now been developed to achieve high-level, stable, and cell-type-specific gene expression. Here, we describe a protocol for the design, production, and delivery of Cre-dependent AAVs. This method is simple and highly efficient, and allows chronic live imaging of defined classes of synapses in the mouse brain.