Specific gene expression in mouse cortical astrocytes is mediated by a 1740bp-GFAP promoter-driven combined adeno-associated virus2/5/7/8/9

• We designed a new GFAP promoter of 1740bp for transgene study in astrocytes.
• Combined AAV2/5/7/8/9 carrying our promoter specifically targeted astrocytes.
• Astrocytic EGFP expression stabilized 3–4 weeks after viral injection.

We sought to demonstrate the in vivo transduction efficiency and tropism range in astrocytes of a combined-serotype adeno associated virus (AAV2/5/7/8/9). To control expression of enhanced green fluorescent protein (EGFP), a 1740bp glial fibrillary acidic protein (GFAP) promoter was obtained and ligated into vectors of each AAV serotype (2/5/7/8/9). Purified AAVs were then injected into the somatosensory cortex of C57BL/6J mice. Cell-type specific antibodies and subsequent immunofluorescence were used to identify astrocytes (GFAP), neurons (neuronal nuclear antigen, NeuN), microglia (ionized calcium-binding adapter molecule 1, Iba1), and oligodendrocytes (myelin basic protein, MBP), whereby, EGFP expression was measured in each cell type at 1–4 weeks post-injection. Our results indicated that the majority of astrocytes expressed EGFP, while only a small number of neurons expressed EGFP. Both microglia and oligodendrocytes lacked EGFP expression after viral injection. Quantitative analyses revealed that the percentage of EGFP-positive astrocytes was about 98% after viral injection, while the EGFP-positive neuronal percentage was less than 2%. Thus, this study shows that using a combined-serotype AAV carrying a 1740bp GFAP promoter results in successful, cell-type specific infection of the central nervous system, with robust gene expression in murine astrocytes.